CA1208801A - Computer network system and its use for information unit transmission - Google Patents
Computer network system and its use for information unit transmissionInfo
- Publication number
- CA1208801A CA1208801A CA000448023A CA448023A CA1208801A CA 1208801 A CA1208801 A CA 1208801A CA 000448023 A CA000448023 A CA 000448023A CA 448023 A CA448023 A CA 448023A CA 1208801 A CA1208801 A CA 1208801A
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- Canada
- Prior art keywords
- session
- network
- node
- data
- host processor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
Abstract
Computer Network System And Its Use For Information Unit Transmission Abstract In a computer network a communication session established between a user node such as a data terminal and an application program in a host processor node defines the communication rules to be used and can be shared by a third user node without a new session establishment operation.
Session identifier information is stored in the host processor and in a communication controller when a session is established and this stored information is compared with session sharable fields in information units sent from the session sharing third user node to the application program in the host processor. When the session is established between a primary port of the communication controller and an application program in the host, it can be shared on transaction basis by a plurality of data terminals in a group of terminals operating as secondary ports in the network.
Session identifier information is stored in the host processor and in a communication controller when a session is established and this stored information is compared with session sharable fields in information units sent from the session sharing third user node to the application program in the host processor. When the session is established between a primary port of the communication controller and an application program in the host, it can be shared on transaction basis by a plurality of data terminals in a group of terminals operating as secondary ports in the network.
Description
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Computer network system and its use ~or information unit transmission.
The present invention relates to a computer network system where a plurality of user stations or data terminals are 5 attached over a data transmission network to one or a plurality of hcst processors.
An overview of the architecture used in computer networks is given in an article by S. Wecker, "Computer network ar-chitectures" Computer, September 1979. Another similar overview including a description of the SNA (Systems Network Architecture) network, is provided with an article by P E
Green '!An introduction to network architectures and pro-tocols" in IBM Systems Journal, ~ol. 18, No. 2, 1979. In these articles the various available computer networks such as SNA, DNA, ARPANET etc. are described by means of hi-erarchical architectural layers, where the lowest layer relates to the physical communication lines interconnecting the various user nodes of the network and where the highest level concerns the conversation per se between the various end users of the network.
Computer network systems have been subject to standard-ization work by the International Orginaization for Stand-ardization (ISO) and in a paper by ~lerbert Zimmerman "OSI.
~ Reference Model-The ISO Model of Architecture for Open ; 25 Systems Interconnlsction" IEEE Transactions on Communica-tions, April 1980, the architecture include seven layers:
physical t data link, network, transport, session, presen-tation and application layer. The present lnvention concerns mainly the session layer, which relates to the establish-ment, termination and control of a session between two end users of a network.
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Computer network system and its use ~or information unit transmission.
The present invention relates to a computer network system where a plurality of user stations or data terminals are 5 attached over a data transmission network to one or a plurality of hcst processors.
An overview of the architecture used in computer networks is given in an article by S. Wecker, "Computer network ar-chitectures" Computer, September 1979. Another similar overview including a description of the SNA (Systems Network Architecture) network, is provided with an article by P E
Green '!An introduction to network architectures and pro-tocols" in IBM Systems Journal, ~ol. 18, No. 2, 1979. In these articles the various available computer networks such as SNA, DNA, ARPANET etc. are described by means of hi-erarchical architectural layers, where the lowest layer relates to the physical communication lines interconnecting the various user nodes of the network and where the highest level concerns the conversation per se between the various end users of the network.
Computer network systems have been subject to standard-ization work by the International Orginaization for Stand-ardization (ISO) and in a paper by ~lerbert Zimmerman "OSI.
~ Reference Model-The ISO Model of Architecture for Open ; 25 Systems Interconnlsction" IEEE Transactions on Communica-tions, April 1980, the architecture include seven layers:
physical t data link, network, transport, session, presen-tation and application layer. The present lnvention concerns mainly the session layer, which relates to the establish-ment, termination and control of a session between two end users of a network.
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2 ~2~88~1 In an IBM Systems Network Architecture (SNA) network ~IBM is a registered trade mark of International Business Machines Corporation) a plurality of information units are circulating in the ne~work between pairs of end users when sessions have been established between such pairs. These information units are of various types and hierarchical levels according to the various layers they are representing. A description of such information units and their use in established sessions is provided in an article by James D. Atchins: "Path Control: The Transport Network of SNA" I~EE Transactions on Communications, April 1980.
The extensive growth and use of data networks in today's society has opened up a number of new possibilities in modern data communication technology.
On data networks there are many more parties, capable of communicating with one another than on networks built with leased lines.
There are also many applications, requiring communication between two parties only during a short interval of time, for example seat reservation and banking applications.
In this environment a large amount of computer resources would be required to perform the computer session establishment function for the individual pairs to communicate with one another. The Nordic Public Data Network, as described in the publication "The Public Data Networks in the Nordic Countries" published in March 1978 by the Swedish PTT, is an example of a computer network using switched lines ~circuit switching).
The present invention as claimed is intended to overcome the drawbacks of the known computer network systems.
According to a preferred embodimPnt of the present invention a plurality of independent terminals are grouped into one 12~
! unit, which is viewed and defined by a host computer in the network as a virtual terminal unit. A number of similar or different sessions are defined and established between applications in the host computer and the virtual ter-minal.
These sessions are shared by all physical terminal unit!; in the group.
According to another embodiment of the invention a session established between an end user at one node of the computer network and an application program in a host processor will be recorded as a shareable session which can be shared by a second end user at other nodes without a new session estab-lishment procedure.
Accordin~ to still another embodiment of the invention one lS or a plurality of sessions be-tween a host processor appli-cation program and data terminals are offered in host pro-cessor ports of a data network, to be shared by terminals operating as secondary port stations in the network.
An advantage of the invention is that time and resource consuming session establishment procedures in a computer network will be decreased.
Another advantage of the invention is that the response time for a data terminal calling a computer application program will be decreasec!.
`The present invention is especially advantagcous ln such environments where a large amount of short transaction type messages are circulating in a computer network between end users and where the session establishment time is consid-era~le as compared to the total processing time in a ses-sion.
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The invention will now be described in an environment which is substantially based upon the IBM SNA architecture, however, the invention is not restricted to any specific type of lletwork. A typical SNA network is described in the IBM Manual "Advanced Communication Functions for Virtual Telecommunications Access Method", GC27-0463-2, Februar~
1981.
A detailed description of the invention will now be given with reference to the accompanying drawings, wherein:
Fig. 1 discloses a block diagram of a computer network system according to the present in~ention.
Fig. 2 discloses architectural layers according to the present invention.
Fig. 3 discloses a basic link information unit.
Fig. 4 is a first example of a transmission header.
Fig. S discloses a second example of a transmission header.
Fiy. 6 is a block diagram of a computer network including switched lines.
Fig. 7 is a functional diagram for session establishment sequences for switched lines.
Fig. 8 discloses another embodiment of a computer network including switched lines.
Fig. 9 is a functional diagram for the operatlon o the network in fiy. 8.
Fig. 1 discloses a computer network including a host pro-cessor 1 in a domain A and a host p~ocessor 9 in a domain 8.
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A communication controller 2 is attached to the host 1 via a channel I6 and a local cluster controller 4 is attached over a channel 15 to the host. The communication controll~r ~ is connected to a remote cluster controller 5 over a SDLC
(synchronous data link control) link 21. The communication controller 2 is also connected over a link 25 to a remote communication controller 6 and by means of links 22-24 to terminals 31-33 forming a terminal group 3. A cross-domain link 26 connects the communication controller 2 with a remote communication controller 11 in the domain B. In the domain B thexe is also shown a communication controller 10 connected between the host processor 9 and -the remote communication controller 11.
The host processor 1 includes an operating system 17, a-plurality of application programs 13 and a Virtual Tele-communications Access Method (VTAM) 12 comprising a System Services Control Point (SSCP) component 14.
Each element in the network of fig. 1 that can send or receive data is assigned a network address and is known as a network addressable unit (NAU). The network address uniquely identifies the element, regardless of whether the element is a device, such as terminal or a terminal control unit, a program such as an application program in a cluster con~
troller or in a host processor, or a portion of an access method, such as a VTA~I. The network address contains the ' information necessary to route data to its des-tination.
Three types of network addressable units are defined: system ; services control point (SSCP), physical units (PU) and logical units (LUl.
The system services control point (SSCP) 14 in the host processor 1 is the component of VTAM that manages the network. The SSCP performs functions such as bringing up the network and shutting it down, assisting in establishing and -.
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terminating the communication between network addressable units, and reacting to network problems, such as ~ailuré of a link or a control unit. To perform these functions; tHe SSCP must be able to communicate with physical units and logical units in the network under its control.
A physical unit (PU) is shown in fig. 1 as an encircled P~.
It is a portion of a device, usually programming or cir-cuitry or both, that performs control functions for the device in which it is located and, in some cases, for ot~er devices that are attached to the device that contains the PU. For the devices under its control, the physical unit ~ takes action during activation and deactivation, during - error recovery and resynchronization, during testing, and during gathering of statistics on operation of the device.
Each device in the network is associated with a physical unit. In the local cluster controller 4 there is a physical unit 41 and in the remote cluster controller 5 there is a physical unit 51. There are also physical units in the local communication controller 2 and in the remote communication - 20 controller 6.
; A logical unit is a device or program by which an end user, a terminal operator or an input/output mechanism, gains access to the network. A logical unit can be built-in logic or programming associated with terminal subsystem or stan~- ~ 25 alone device, or an application program. To the networ~ a logical unit is l:he source of a request coming into the network. But a logical unit may or may not be the original source. The contents of the request of the information on which the request is based may have originated at a device controlled by the logical unit. Similarily, the network sees a logical unit as a destination o~ a request unit ~RU).
.
In fig. l a logical unit is shown as an encircled LU. In the host processor l there are shown a plurality of application '' ".~., .:
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7 i 2 ~8 ~ 1 program logical units 13. In the local cluster controller 4 there are two logical units 42 and 43 controlling the devices 44 and 45. In the cluster controller 5 there are logical units 52-54 controlling device loops 55-57. In a conventional terminal group 3 there are physical units and logical units ~or each terminal. These physical units are marked 34-36 and the logical units 37-39.
The purpose of the network according to fig. 1 is to es-tablish and control communication between two logical units in the network and the corresponding end users. As an example such communication could be established between the terminal 32 over the link 23, the communication controller 2, the channel 16, VTAM 12 and an application program 13 in the host processor 1.
Before the operation of fig. 1 will be further described, reference is made to the architectural layers disclosed in , fig. 2. According to the cited article "OSI Reference Model"
by Herbert Zimmermann a structure of seven layers is shown.
The highest layer is the application layer 71 followed by the presentation layer 72, the session layer 73, the trans-port layer 74, the network layer 75, the data link layer 76 and the physical layer 77. This layered structure 70 rep-resents one part amongst two communication partners com-municating over the network. A structure 80 includiny the~
corresponding layers 81-87 represent the second part o~ the communication. Two corresponding layers such as the pre-sentation layer 72 and the presentation layer 82 can be considered to communicate over a Peer-to Peer level 62.
Simi]arly thc (lata link layer 7G can ~c consldcrcd to communicate with the data link layer-86 over another Peer-to-Peer connection 66.
The meaning o~ the various layers can roughly be described as follows. The application layer relates to the conver-"~ ~
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sation per se between two end users. The presentation layer defines the type of presentation of data for such a con-versation, i.e. presentation such as display, print etcS The session layer relates to the establishment and control of a session between two end users for conversation purposes. The transport layer provides control from user node to user node across the network, whereas the network layer defines the control between two adjacent nodes within the network. The data link layer relates to the protocol used for data transfer over the link between two nodes whereas the phy-sical layer concerns the electrical characteristics and signalling needs required for a connection.
The present inven-tion concerns mainly the session layers 73 and 83 and their Peer-to-Peer protocols. According to the present invention session sharing will be used to reduce the access and response time in the network. When the network is working in a session sharing mode the session layer 73 will be split into a higher shared session layer 78 and a lower basic session layer 79.
i 20 The network of fig. 1 relates to the System Network Ar-chitecture (SNA) whereas the layered structure of fig. 2 relates to the ISO model. In the SNA architecture there are only six layers as follows: end user, presentation, trans-mission and data flow, path, data link, and physical. The functions of the session layer of -the ISO model are embedded partly in the transmission and data flow layer and partly in the path control layer of the SNA architecture.
The ~ata flow bctwccn vl~rious nodcs in thc nctwork of fig. 1 ls comprised o~ a plurality of information units as shown in fig. 3. The request-response unit (RU) 9~ and a request-response header (Rl{) 93 constitutes the basic information unit (BIU) travelling from one end user node to another end user node in the network. A transmission header (TH) 92 is .
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headed in front of the BIU for guiding the unit through the network. The transmission header comprises address infor-mation and other necessary information for transmission control. A request-response unit RU provided with a response request header (RH) and a transmission header TH is called a path information unit (PIU) 96. When such an informal:ion unit is sent from one node in the network over a data link to another node, a link header (LH) 91 is added in front,of the unit and a link trailer (LT) 95 is attached to the end of the unit~ This builds up a basic lin~ unit (BLU) as shown in fig. 3. A basic link unit comprises one or several PIUs.
Before the two doma.ins A and ~ of the networX in fig. 1 can be used the operator of the host processor 1 must start VTAM
12 of the domain ~ and the operator of the host processor 9 must start the corresponding access method oE the domain B.
Such an initialization of a domain with an operator command will activate some or all of the resources in the domain.
This means that sessions will be established between the SSCP 19 and the various PUs and various LUs in the domain.
It is assumed that an end user of the LU 52 in the cluster controller 5 in fig. 1 wants to communicate with an appli-~ cation program 13, say the application program 13a in the ', host processor 1. Before such a communication can be es~
; tablished a session must be established between the LU 52 in the`cluster controller 5 and the LU l~a in the host pro-cessor 1. The session establishment starts by the LU 52 sending a logon request over the link 21, the communication controller 2 and the channel 16 to the SSCP 1~ in the host r~roccssor 1. Such a rcqllcst contains nodc ldcnti~ication information and also a su~gestion of session parameters to be used for the comrnunication. Session parameters enable each end of the session to know what the other end will do in different communication situations. The session para-meters are a string of bit settings that indicate the rules i......
,., -` 10 ~LZ(~88(~1 to be followed in the session for such things as request and response sequences, resolution of contention, use of request chaining, use of brackets, and use of change-direction indicators. The host processor 1 might agree or might change the suggested session parameters. A logon mode table in VTAM
12 is used for checking session parameters. The host pro-cessor 1 will then send a "Bind" request from VTA~I 12, over the channel 16, the communication controller 2 and the link 21 to the LU 52 for the cluster controller 5, thus estab-~ 10 lishing a session between the LU 52 and the LU 13a in thehost processor 1. A session has now been established and the two end users of the two LUs can now communica-te request-response units of the type shown in fig. 3. When the com-munication is completed the session will be terminated by either side of the communication.
When a group 3 of terminals 31-33 are frequently exchanging short transactions with an application program such as the application program 13a in the host processor 1, the non-productive session establishment and session termination procedure between the terminal L~s and the application program LU will heavily load the host processor 1. According to the present invention such an unproductive overhead will be extensively reduced by assigning a group address to the terminal group 3. VTAM 12 will then view the terminal group
The extensive growth and use of data networks in today's society has opened up a number of new possibilities in modern data communication technology.
On data networks there are many more parties, capable of communicating with one another than on networks built with leased lines.
There are also many applications, requiring communication between two parties only during a short interval of time, for example seat reservation and banking applications.
In this environment a large amount of computer resources would be required to perform the computer session establishment function for the individual pairs to communicate with one another. The Nordic Public Data Network, as described in the publication "The Public Data Networks in the Nordic Countries" published in March 1978 by the Swedish PTT, is an example of a computer network using switched lines ~circuit switching).
The present invention as claimed is intended to overcome the drawbacks of the known computer network systems.
According to a preferred embodimPnt of the present invention a plurality of independent terminals are grouped into one 12~
! unit, which is viewed and defined by a host computer in the network as a virtual terminal unit. A number of similar or different sessions are defined and established between applications in the host computer and the virtual ter-minal.
These sessions are shared by all physical terminal unit!; in the group.
According to another embodiment of the invention a session established between an end user at one node of the computer network and an application program in a host processor will be recorded as a shareable session which can be shared by a second end user at other nodes without a new session estab-lishment procedure.
Accordin~ to still another embodiment of the invention one lS or a plurality of sessions be-tween a host processor appli-cation program and data terminals are offered in host pro-cessor ports of a data network, to be shared by terminals operating as secondary port stations in the network.
An advantage of the invention is that time and resource consuming session establishment procedures in a computer network will be decreased.
Another advantage of the invention is that the response time for a data terminal calling a computer application program will be decreasec!.
`The present invention is especially advantagcous ln such environments where a large amount of short transaction type messages are circulating in a computer network between end users and where the session establishment time is consid-era~le as compared to the total processing time in a ses-sion.
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The invention will now be described in an environment which is substantially based upon the IBM SNA architecture, however, the invention is not restricted to any specific type of lletwork. A typical SNA network is described in the IBM Manual "Advanced Communication Functions for Virtual Telecommunications Access Method", GC27-0463-2, Februar~
1981.
A detailed description of the invention will now be given with reference to the accompanying drawings, wherein:
Fig. 1 discloses a block diagram of a computer network system according to the present in~ention.
Fig. 2 discloses architectural layers according to the present invention.
Fig. 3 discloses a basic link information unit.
Fig. 4 is a first example of a transmission header.
Fig. S discloses a second example of a transmission header.
Fiy. 6 is a block diagram of a computer network including switched lines.
Fig. 7 is a functional diagram for session establishment sequences for switched lines.
Fig. 8 discloses another embodiment of a computer network including switched lines.
Fig. 9 is a functional diagram for the operatlon o the network in fiy. 8.
Fig. 1 discloses a computer network including a host pro-cessor 1 in a domain A and a host p~ocessor 9 in a domain 8.
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A communication controller 2 is attached to the host 1 via a channel I6 and a local cluster controller 4 is attached over a channel 15 to the host. The communication controll~r ~ is connected to a remote cluster controller 5 over a SDLC
(synchronous data link control) link 21. The communication controller 2 is also connected over a link 25 to a remote communication controller 6 and by means of links 22-24 to terminals 31-33 forming a terminal group 3. A cross-domain link 26 connects the communication controller 2 with a remote communication controller 11 in the domain B. In the domain B thexe is also shown a communication controller 10 connected between the host processor 9 and -the remote communication controller 11.
The host processor 1 includes an operating system 17, a-plurality of application programs 13 and a Virtual Tele-communications Access Method (VTAM) 12 comprising a System Services Control Point (SSCP) component 14.
Each element in the network of fig. 1 that can send or receive data is assigned a network address and is known as a network addressable unit (NAU). The network address uniquely identifies the element, regardless of whether the element is a device, such as terminal or a terminal control unit, a program such as an application program in a cluster con~
troller or in a host processor, or a portion of an access method, such as a VTA~I. The network address contains the ' information necessary to route data to its des-tination.
Three types of network addressable units are defined: system ; services control point (SSCP), physical units (PU) and logical units (LUl.
The system services control point (SSCP) 14 in the host processor 1 is the component of VTAM that manages the network. The SSCP performs functions such as bringing up the network and shutting it down, assisting in establishing and -.
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terminating the communication between network addressable units, and reacting to network problems, such as ~ailuré of a link or a control unit. To perform these functions; tHe SSCP must be able to communicate with physical units and logical units in the network under its control.
A physical unit (PU) is shown in fig. 1 as an encircled P~.
It is a portion of a device, usually programming or cir-cuitry or both, that performs control functions for the device in which it is located and, in some cases, for ot~er devices that are attached to the device that contains the PU. For the devices under its control, the physical unit ~ takes action during activation and deactivation, during - error recovery and resynchronization, during testing, and during gathering of statistics on operation of the device.
Each device in the network is associated with a physical unit. In the local cluster controller 4 there is a physical unit 41 and in the remote cluster controller 5 there is a physical unit 51. There are also physical units in the local communication controller 2 and in the remote communication - 20 controller 6.
; A logical unit is a device or program by which an end user, a terminal operator or an input/output mechanism, gains access to the network. A logical unit can be built-in logic or programming associated with terminal subsystem or stan~- ~ 25 alone device, or an application program. To the networ~ a logical unit is l:he source of a request coming into the network. But a logical unit may or may not be the original source. The contents of the request of the information on which the request is based may have originated at a device controlled by the logical unit. Similarily, the network sees a logical unit as a destination o~ a request unit ~RU).
.
In fig. l a logical unit is shown as an encircled LU. In the host processor l there are shown a plurality of application '' ".~., .:
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7 i 2 ~8 ~ 1 program logical units 13. In the local cluster controller 4 there are two logical units 42 and 43 controlling the devices 44 and 45. In the cluster controller 5 there are logical units 52-54 controlling device loops 55-57. In a conventional terminal group 3 there are physical units and logical units ~or each terminal. These physical units are marked 34-36 and the logical units 37-39.
The purpose of the network according to fig. 1 is to es-tablish and control communication between two logical units in the network and the corresponding end users. As an example such communication could be established between the terminal 32 over the link 23, the communication controller 2, the channel 16, VTAM 12 and an application program 13 in the host processor 1.
Before the operation of fig. 1 will be further described, reference is made to the architectural layers disclosed in , fig. 2. According to the cited article "OSI Reference Model"
by Herbert Zimmermann a structure of seven layers is shown.
The highest layer is the application layer 71 followed by the presentation layer 72, the session layer 73, the trans-port layer 74, the network layer 75, the data link layer 76 and the physical layer 77. This layered structure 70 rep-resents one part amongst two communication partners com-municating over the network. A structure 80 includiny the~
corresponding layers 81-87 represent the second part o~ the communication. Two corresponding layers such as the pre-sentation layer 72 and the presentation layer 82 can be considered to communicate over a Peer-to Peer level 62.
Simi]arly thc (lata link layer 7G can ~c consldcrcd to communicate with the data link layer-86 over another Peer-to-Peer connection 66.
The meaning o~ the various layers can roughly be described as follows. The application layer relates to the conver-"~ ~
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sation per se between two end users. The presentation layer defines the type of presentation of data for such a con-versation, i.e. presentation such as display, print etcS The session layer relates to the establishment and control of a session between two end users for conversation purposes. The transport layer provides control from user node to user node across the network, whereas the network layer defines the control between two adjacent nodes within the network. The data link layer relates to the protocol used for data transfer over the link between two nodes whereas the phy-sical layer concerns the electrical characteristics and signalling needs required for a connection.
The present inven-tion concerns mainly the session layers 73 and 83 and their Peer-to-Peer protocols. According to the present invention session sharing will be used to reduce the access and response time in the network. When the network is working in a session sharing mode the session layer 73 will be split into a higher shared session layer 78 and a lower basic session layer 79.
i 20 The network of fig. 1 relates to the System Network Ar-chitecture (SNA) whereas the layered structure of fig. 2 relates to the ISO model. In the SNA architecture there are only six layers as follows: end user, presentation, trans-mission and data flow, path, data link, and physical. The functions of the session layer of -the ISO model are embedded partly in the transmission and data flow layer and partly in the path control layer of the SNA architecture.
The ~ata flow bctwccn vl~rious nodcs in thc nctwork of fig. 1 ls comprised o~ a plurality of information units as shown in fig. 3. The request-response unit (RU) 9~ and a request-response header (Rl{) 93 constitutes the basic information unit (BIU) travelling from one end user node to another end user node in the network. A transmission header (TH) 92 is .
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headed in front of the BIU for guiding the unit through the network. The transmission header comprises address infor-mation and other necessary information for transmission control. A request-response unit RU provided with a response request header (RH) and a transmission header TH is called a path information unit (PIU) 96. When such an informal:ion unit is sent from one node in the network over a data link to another node, a link header (LH) 91 is added in front,of the unit and a link trailer (LT) 95 is attached to the end of the unit~ This builds up a basic lin~ unit (BLU) as shown in fig. 3. A basic link unit comprises one or several PIUs.
Before the two doma.ins A and ~ of the networX in fig. 1 can be used the operator of the host processor 1 must start VTAM
12 of the domain ~ and the operator of the host processor 9 must start the corresponding access method oE the domain B.
Such an initialization of a domain with an operator command will activate some or all of the resources in the domain.
This means that sessions will be established between the SSCP 19 and the various PUs and various LUs in the domain.
It is assumed that an end user of the LU 52 in the cluster controller 5 in fig. 1 wants to communicate with an appli-~ cation program 13, say the application program 13a in the ', host processor 1. Before such a communication can be es~
; tablished a session must be established between the LU 52 in the`cluster controller 5 and the LU l~a in the host pro-cessor 1. The session establishment starts by the LU 52 sending a logon request over the link 21, the communication controller 2 and the channel 16 to the SSCP 1~ in the host r~roccssor 1. Such a rcqllcst contains nodc ldcnti~ication information and also a su~gestion of session parameters to be used for the comrnunication. Session parameters enable each end of the session to know what the other end will do in different communication situations. The session para-meters are a string of bit settings that indicate the rules i......
,., -` 10 ~LZ(~88(~1 to be followed in the session for such things as request and response sequences, resolution of contention, use of request chaining, use of brackets, and use of change-direction indicators. The host processor 1 might agree or might change the suggested session parameters. A logon mode table in VTAM
12 is used for checking session parameters. The host pro-cessor 1 will then send a "Bind" request from VTA~I 12, over the channel 16, the communication controller 2 and the link 21 to the LU 52 for the cluster controller 5, thus estab-~ 10 lishing a session between the LU 52 and the LU 13a in thehost processor 1. A session has now been established and the two end users of the two LUs can now communica-te request-response units of the type shown in fig. 3. When the com-munication is completed the session will be terminated by either side of the communication.
When a group 3 of terminals 31-33 are frequently exchanging short transactions with an application program such as the application program 13a in the host processor 1, the non-productive session establishment and session termination procedure between the terminal L~s and the application program LU will heavily load the host processor 1. According to the present invention such an unproductive overhead will be extensively reduced by assigning a group address to the terminal group 3. VTAM 12 will then view the terminal group
3 as one single node, as a virtual terminal in the network.
and will use the group address ~or communication with the terminals in the qroup.
The communication between the terminal group 3 and the application pro~ram 13a in thc host proccs.sor l is startcd by a conventional session establishment procedure between one terminal, say terminal 31 in the group and the appli-cation program 13a. When the session is initiated, the communication controller 2 storcs both thc group address of the group 3 and the terminal address of the terminal 31 and transmits the group address as an or~igin address over the ~' ` ~, ll ~Z~88~1 channel 16 to VTAM 12. When a session has been established between the terminal 31 and the application program 13a', another terminal such as the terminal 32 may join or~share this session. PIUs (fig. 3) e~changed between the terminals in the group 3 and the application program 13a are routed into one single buffer area for one single session in VT~
12. The PIUs received over the channel 16 from VTAM 12 to the comniunication controller 2 contains the group address in the transmission header 92 according to fig. 3, whereas the ' 10 terminal address is embedded into the request unit 94. The communication controller 2 will then distribute the in-formation units according to the terminal addresses.
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It is important that a session has been established between , the terminal group 3 and the application program 13a in the ,host processor 1 before session sharing can be used. If one terminal, say the terminal 33, is sending a request unit at a time when no session has been opened, VTAM 12 will anal~ze this request unit and finds that there is no session opened. '' VTAM 12 will then return a response unit having certain condition,indicators set, telling the terminal 33 that thbre i5 no session established. The terminal 33 will then ini-tiate a session by sending a conventional logon request, whereafter the other terminals might share this new session.
Session sharing is possible between the terminals in the group 3 only as long as the various terminals are using the same session parameters for the communication. If one ' terminal or if the application program wants to use another session parameters, a new session might be established.
Sincc VT~M ].2 sccs only OllC tcrminaJ in tl~c gr,oup 3, this 30 , means that the old session must be terminated be~ore the new session can be established. Another terminal might then share the new session by adapting its communication to the new session parameter conditions.
The session sharing procedure just described is transparent ,~
12 1 2~ ~ 8~'1 to VTAM 12 and is mainly handled on a lower level by the communication controller 2. According to another embodiment of the present invention session sharing is handled on VTAM
level. It is assumed as an exemple that LU 52 in the cluster controller has established a session with the application program 13a in the host processor 1. It is also assumed that a LU 61 attached to the remote communication controller 6 intends to join this session on a session sharing level. The data traffic between the host processor 1 and the LU 52 in the cluster controller 5 flows over the link 21, the com-munication controller 2 and the channel 16. The data traffic between the LU 61 and the application program in the host processor 1 flows over the remote controller 6, the link 25, the communication controller 2 and the channel 16. According to the SNA architecture a transmission header g2 for a path information unit (PIU) in fig. 3 passing the link 21 has a format FID 2 according to fig. 4. The transmission header of the format FID 2 discloses a format identification field 101, a destin~tion address field 102, an origin address field 103 and a sequence number field 104. A PIU travelling along the link 25 and along the channel 16 has a format FID
1 according to fig. ~. The transmission header of the format FID 1 includes a data count field 105.
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The LU 61 is enabled to share an active session between the LU 52 in the cluster controller 5 and the LU 13a in the host ` processor l b~ modifying the transmission header FID 1 in fig. 4. A session identifier field 106 is used for the LUS2-LU13a session and is added to the transmission header. This field includes a flag bit 1~7, which when set, indicates th~t tl!e tran-;missio~ hcadcr rcprcsents a sharab]c scssion information unit. The other bits in the SSID field 106 uniquely define and name the established session between the LU 52 and the LU 13a. VTAM 12 stores the session identifier field 106 in a session identifier table (138, fig. 6). When the LU 61 joins this previously established session, mod-i .~ ~
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13 ~Z~88~1 ified transmission headers of the type shown in fig. 4, i.e.FID IM must be used with the field 106 marked with the same bits as for the established main session between LUS2 and LU13a. When such a PIU is received by VT,~M 12 from LU 61, the destination address field 102 is the same as for the main session initiated by the LU 52, i.e. the address of the application program LU 13a. The origin field 103 is, how-ever, different, it is the address of the LU 61. VTAM 12 then looks into the field 106 and finds the session sharing bit 107 to be on. It will then compare this field 106 with stored information in the session identifier table and will find a corresponding session identifier for the session originated in the LU 52. Therefore a request unit trans-mitted with such a PI~ will be passed to -the same receiving buffer queue in VTAM as if it would have been received from the original LU 52.
The invention will now be described in more detail with re~erence to the figures 5, 6 and 7 for a switched data network, such as the Nordic Public Data Network.
In fig. 6 there is shown a terminal group 3 including terminals 31, 32 and 33, each connected to a corresponding port 171, 172 and 173. These ports are preferably stand-ardized X21 ports, according to the CCITT recommendation, to be connected over a switched data network 160 to other existing X21 ports 161, 162 and 163. Another terminal or terminals 175 w:Lth its port 174 represent other terminals of the network which do not belong to the group 3. It is assumed that terminals 3]-33 and 175 are provided with automatic calling units. Thc tcrmi.nals 3l-33 and ]75 with the ports 171-174 represent the secondry side of the network whereas the primary side is represented by the ports 161-163 con-nected to the communication controller 2.
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A session can be established between a secondary terminal 31 and a primary application program 13a for changing path '` information units (PIU) between the two end users of such a session. A path will then exist between the terminal 31 and the application program 13a as follows: terminal 31, the port 171, a link 22, a port 161, a line 164, a line 165 in a scanner 156 in the communication controller, a buf~er 155 in the controller, a link control 154 in the controller, a path control 153 in the controller, a connection point manager 152 in the controller, a channel adapter 151 in the con-troller, a channel 16, buffer pools 133 in the host pro-cessor 1, interface 136 between the buffer pools 133 and the application program 13a and a buffer 137 in the application program 13a.
lS A PIU sent from a terminal 31 towards the application program 13a is provided with a transmission header 92 according to fig. 3 and has a format as shown in fig. 5.
Such a transmission header is of a format type FID 3 and includes a format identifier field 101 similar to the field 101 in fig. 4. It also includes a local session identifier field 111 which uniquely identifies the terminal 31 to the communication controller 2. According to the present in-vention the conventional transmission header FID 3 used in SNA architecture is modified by the field 112 comprising a shared session identifier field. This field includes a bi~
which is on when shared session facility is used. It also includes information about the main session which is shar-able.
Whcn a PIU sent rorn th~ tcrmina~ 31 has passed the network 160, the scanner 156, the buffers 155 and the link control 15~ in the co~munication controller, it will reach the path control 153 and further the connection point manager 152 in the communication controller. The path control 153 will change the transmission header of this PIU from the modified -; ~
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format FID 3M in fig. 5 to ti~e modified format FID 1~1 in ~ig. 4 whereby the contents of the fieId 112 in FID 3M will be transferred to the fie~d 106 in FID lM. This new trans-mission header FID lM will enable VTAM 12 to route the PIU
coming from the channel adapter 151 and the channel 16 to the host processor. This routing is performed by a trans-mission subsystem component 132 in VTAM 12.
When VTAM 12 is started in a domain such as in the domain A
in fig. 1, a number of sessions will be established between the system se~vices control point (SSCP) 1~ and the various PUs and LUs in the domain. These sessions are established by ~ means of VTAM requests such as "Activate PU" and "Activate ; LU". An activated LU might then establish a session with an application program LU in the host processor as described in connection with fig. 1. This is, however, not true ~or resaurces such as terminals which are connected over switched lines to the host processor. Such terminals are not ac-tivated during the domain initialization time. A session initialization between a terminal over a switched line with a host application program is therefore much more compli-cated and time consuming that session initialization over leased lines.
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Fig. 7 is a schema-tic diagram for a session establishment procedure in a switched data network shown in fig. 6.
The operation starts with the network operator issuing a "Vary" command from the operator console in the host pro-cessor 1. The "Vary" command will be processed by the SSCP
component 131 in VT~1 12. SSCP 131 will then send an "~c-tivate link" request (RU) to the communication controller 2.
Communication controller 2 answers by a "Definite response"
RU to the SSCP ]31. SSCP 131 then sends an "Activate connect in" RU to the communication controller 2 which answers with a "Definite response" RU. The communication controller 2 is 1.~
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now ready for receiving incoming calls from the terminals over the network 160.
It is assumed that the terminal 31 in the group 3 in fig. 6 '; wants to establish a session with an application program 13a in the host processor 1. It will then use its auto~atic calling unit to call one of the ports of the communication controller 2, say the port 161. ~ connection link 22 will ~ - then be established between the secondary port 171 of the terminal 31 and the primary port 161 of -the communication controller 2. Such an incoming call is shown in fig. 6 and 7 a~ coming from the physical unit 34 of the terminal to the communication controller 2. The incoming call is answered by the communication controller 2 by a "Station Identification ` Re~uest" RU "XID Who are you?", which will be sent to the physical unit 34. The physical unit 34 answers by sending its identification "XID response" to the communication Gontroller 2.
A conversation will now start between the communication controller 2 and the SSCP 131 in the host processor 1~
Communication controller 2 will send a "Request contact"
which is an off-hook RU to the SSCP. The SSCP answers with a "Set Control Vector" RU to the communication controller 2.
- This RU defines certain conditions for the session to be established between the PU 34 and the SSCP 131. The com- .
munication controller 2 answers by a definite response to the SSCP 131. SSCP 131 then sends a "Contact" RU to the c:ommunication controller 2. The communication controller 2 answers with another "DeEinite response" followed by a "Contacted" ~U.
SSCP`131 will now send an "~ctivate Physical Unit" RU to the physical unit 34 which activates this unit. The physical unit 34 will return a "Definite response" to the SSCP 131.
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Next SSCP 131 sends an "Assign network address" RU to the communication controller 2, which answers by a definite response. The SSCP then sends a "Set Control Vector" RU to the communication controller which answers with a "Definite response". This control vector is for the LU 37 in the terminal 31. The SSCP 131 proceeds to send an "Activate - Logical Unit" RU to the logical unit LU 37 in the terminal 31. This activates the logical unit in the terminal 31 which answers with a "Definite response" RU to the SSCP. This ends the procedure or establishing a session between the system services control point 131 in VTAM 12 and the physical unit 34 and another session between the SSCP 131 and the logical unit 37 in the terminal 31. A session might now be estab~
lished between the LU 37 and an application program such as the application program 13a in the host processor 1 as if the terminal 31 would have been attached to the host pro-cessor over non-switched lines.
A session is initiated by the logical unit 37 sending a "Lo~on" Rtl to the SSCP 131. This logon request includes a set of parameters suggested to be used for the session to be established. The SSCP will send a "Control Initate" (Cinit) request to the application program 13a, which will act as a primary LU in the session. The primary LU 13a answers by issuing a macro instruction "OPNDST" to the SSCP 131. When this macroinstruction is executed by VTA~I 12, the session ' parameters provided by the logon request will be checke`d against a logon mode table (LMT) 135 in a table area 134 in VTAM 12 in fig. 6. A number of control blocks in a control block area 140 will be establishetl, such as a node l~lentifier control b~ock (NIU) 1~3, WhiCIl ;d~nti~ies tlle secondary node of the session to bc cstablished, i.c. the LU 37. ~ session identifier control block (SIB) 142 defining the current session will also be established and a function management ` control block (FMB) 141 for this session.
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i, SSCP 131 will send a "Bind" P~U to the secondary logical unit 37. This Bind RU might contain the same session parameters as the original logon request or it might contain s~ssion parameters which have been changed by VTAM 12. The secondary LU 37 will then send a response accepting or rejecting these session parameters. If the session parameters are-accepted, the SSCP 131 will send a "Start Data Traffic" RU to the secondary LU 37. A session has now been established between ~i a secondary LU 37 and a primary LU 13a.
'' ~4 '' When a PIU having a transmission header of type FID 3 according to fig. 5 is received by the path control 153, ~ fig. 6, from the terminal 31, it will change the trans-; mission header to the format FID 1 according to fig. 4, as described previously. This PIU will be sent over the channel 16 to the host processor 1 and is routed by the transmission subsystem component 132 to a specific buffer area in the buffer pools 133 defined by the FMR block 141. The RU 94 of the PIU 96 (fig. 3) will then be transferred from the VTAM
buffer 133 to the application program buffer 137. Similarly a RU from the application program buffer 137 will be trans-ferred to the VTAM buffer 133 assigned by the FMB block 141 and will be built into a PIU by the TSC component 132 adding a transmission header 92. The TSC component 132 will then route this PIU to the communica-tion controller 2 and to its connection point manager 152 and further to the path control 153. The path control 153 will then change the transmi~sion header of the format FID 1 into the format FID 3 for further transfer to the terminal 31.
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Tllc? session cstablishment prccc(l~lre dcscribccl can be uscd for establishing a session bctween a host applicatlon program and a group of terminals 3 in fig. S. This means ' that when a session is established between the termlnal 31 and the application program 13a the content of the session ~; sharing identifier field 112 in the modified transmission , ! . ' . ." ` . .
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~Z~88(:1 1 r header FID 3M in fig. 5 will he stored in a Session Sharing Control Table (SSCT) 158 in the connection point manager 152 of the communication controller 2. Another terminal 32 ~ay then share this established session by using the same SSID
-;~ 5 information 112 in its transmission header when it sends a PIU to the application program 13a. This SSID information is compared to data stored in the SSCT 158 for routing the PIU
to the same destination as for the main session. Such a session sharing is made on the communication controller level. The PIUs exchanged between the communication con-troller 2 and the host processor 1 will use the group address for the terminal group 3 in the origin address field 103 (fig. 4) of their transmission headers 92 ~fig. 3).
When a station outside the group 3, such as a terminal 175, 15 is sharing an established session, the SSID information in the field 106 of a transmission header for the main session, say terminal 31-application program 13a, must be stored in a session sharing table SST 138 in VTAM 12. A PIU travelling from the terminal 175 along a shared session towards the 20 application program l3a will be routed to its destination buffer in VTAM 12 by the transmission subcomponent 132 comparing the SSID information in the PIU with stored f information in the table 138. If there is a list entry ~ defining a main sessionr the RU part of this PIU is queued into the VTAM b~uffer 133 assigned previously to the corresponding main session.
Fig. 8 and fig. 9 disclose another embodiment of the present invention.
According to fig. 8 a host processor 1 is attached over a channel 16 to a com~unication controller 2. ~ plurality of terminals 281-284 are eacll attached to corresponding sec-ondary ports 271-274 in a switched data networ~ 260, such as i .
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~, ';r IZ~18~1 the Nordic Public Data Network. A plurality of primary ports 261-263 of the network 2~0 are attached to primary ports 251-253 of the communication controller. The ports 261-263 are preferable standardized X21 ports.
An examT~le of the communication controller 2 is the IB~ type ; 3705 controller described in the ~lanual "IB~ 3704 and 3705 Communications Controllers Principle of operations" GC30 3004-6, October 1979.
An example of the terminals 281-284 is the IB~I type 3275 terminal described in the IBM ~lanual ~n introduction to the IBM 3270 Information Display System GA27-2739-14, February 1982.
It is assumed that the terminals 281-284 represent a large number of terminals to be used for communication with an application program 213 in the host processor 1 on trans-action basis. The transactions to be sent over the net~ork are rather short messages, however, the frequency of trans-action occurances is high. In a conventional data network such a transaction traffic would need an extremely high amount of session establishments and terminations resulting in a very high host processor overhead time as compared to the useful processing time of the transactions. The solution to such a traffic problem will be a session sharing syste~
according to the present invention.
A plurality of parallell sessions 241-243 will be estab-lished between primary half .se~ssio-l.s ~tl-c primary part of a session) 201-203 oF tlle alT~]icatit)n program 213 and sec-ondary half sessions (the secondary part of a session) 231-233 for the communication controller ports 251-253. These sessions will be enabled by sessions 341-343 established between the System Services Control Point (SSCP) 294 in the host processor and physical units 221-223 for the ports 251-253 in the communication controller 2 and similar sessions * Regi-stered trade mark ,~
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; ~~ 21 1ZG8~1 between the SSCP 294 and the logical units 231-233 for these ports, Each half session on the primary side for the appli-~ cation program 213 will include a node identifier block (NIB) 291-293. In the example of fig. 8 there are shown three parallell sessions 241-243 between the application ,~ program 213 and three ports 251-253 in the communication controller. It is of course obvious for a man skilled in the art that any other number of parallell sessions and ports, can be used.
An example of sessions established between communication controller output ports and a host processor application program is shown in the IBM Manual "IB~I X.25 NCP Packet Switching Interface" GC30-3080-1, June 1982.
The terminals 281-284 are viewed as a terminal group 203 where all terminals are oE a similar type and are using the same session parameters. The terminals 281-284 and their secondary ports 271-274 are to be connected to the primary ports 261-263 by using a group dial number. This means that the terminal 281 for the port 271 will dial a group number for connection establishment to a primary port, which might lead to a connection 276 between the ports 271 and 262. If the port 262 would be occupied, say by a connection 277, the port 271 might succeed to be connected to the port 261, which is attached over the line 264 to the communication .
controller port 251.
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The data traffic between one terminal, say the terminal 281 in fig. 8 ànd the host processor 1 will now be described witll reference to ~ig. 9. ~ t.5 ass-lm~d that the terminal ; 281 is calling the communication controller 2 over the network 260 using the gro~-p dial number for the ports 261-; 263 and that it succeeds to reach the port 262 over the connection link 276. Such an "Incoming Call" in fig. 9 is i t i'` ' ~:.
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answered by the communication controller by a station identifier request XID "Who are you". The terminal will then - respond with an "XID Response", which will identify its station address to the communication controller and further to the application program 21~, usiny the session 242 previously established between the application program 213 and the port 252 in the communication controller 2. The application program in the host will then send a "What can I
do for you" request whereafter the terminal answers with a "Request Transaction ID". This transaction request includes an identification information such as password. The request will be answered by the application program by an acknow-` ledgement or rejection of the transaction. In case theacknowledgement is positive a data exchange will start between the terminal 281 an~ the application program 213 using the previously established session between the appli-cation program 213 and the port 252, which session is shown as the session 242 in fig. 8. ~hen the transaction is completed the terminal will send an "End Transaction"
message to the application program 213 which answers with an "Acknowledgement". ~he terminal 281 will then brake the connection 276 after it has sent an "End Contact" request to the application program in the host.
~s an example the data network system according to fig. 8 and fig. 9 can be used for a banking application. The application program 213 in the host processor 1 is attached to a data base and the terminals in the terminal group 203 are communicating with such a data base on a transaction bases via the application program 213.
When the network operator starts the network in the morning of a working clay, the host processor will first establlsh the three parallell sessions 241-243 between the application program 213 and the communication controller ports 251-253.
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~Z~88~1 This means,tllat the terminal group 203 is viewed by VTAM 12 in the host processor as three physical uni-ts 221-223, three ~ logical units 231-233 and three links 251-253 instead of as one physica] unit and one loc~ical unit for each terminal in the group 203. VTAM 12 will also assign network addresses to these three physical and logical units in the communication controller 2.
It should be understood that the system according to fig. 8 and fig. 9 will substantially reduce the session estab-,10 lishment and termination overhead as compared to conven-tional session housekeeping for switched connections~ It should be understood that the physical units 221-223 and the `J logical units 231-233 in the communication controller will be activated in a conventional manner when the network is started by the network operator in the host processor 1 in the morning of a working day. This will establish the sess,ions 341-343 between the SSCP 294 and said physical and logical units. The parallell LU-LU sessions 241-243 can then be established preferably from the primary host processor side..In such a session establishment procedure the session parameters are negotiatable, as in a conventional system, and a conventional "~ind" request is used to decide which f~ session parameters should be used. It can therefore be said ~, that the sessions 241-243 are not fixed but they can be adapted to the type oE applications needed for servicing the terminals in the group 203. It is, however, important that ~r all the three s~ssions 241, 242 and 243 are using the same session parameters at the same time because the terminals in the group 203 are randomly connected to the three ports 261-263.
30~ The duration time T for a session, such as the sessions 241-243, is up to several hours. The time Tl for a session est`ablishment operation is of the order of hundreds of , milliseconds. The duration time t for a transaction is preferably a few seconds whereas the~actual processing .
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time tl for a transaction in the host processor is only a few milliseconds. This means that t is at least a magnitude less than T and that tl is at least a magnitude less'than Tl.
The present invention reduces the overall response time for the calling terminals because no session establishment time Tl is needed in the processor l for each transaction.
The present invention is not restricted to SNA architect~re with a strictly centralizecl control system using a System Services Control Point 294. The control sessions 341-343 could therefore be substitu-ted by some other kind of network contr~l system. The essential inventive concept is that one or a plurality of sharable sessions, preferably established according to negotiatable session parameter rules, are used for serving a plurality of user stations or terminals.
The present invention is also not restricted to the em-hodiments described. It is, for instance within the scope of the invention to establish several parallel sessions 242-l, 242-2, 242-3 ... in fig. 8 between a primary LU202 and a seoondary LU232 Eor a port 252. These sessions would be ¢ established with different session parameters thus enabling terminals using different session parameters to be connected to the same port. ~ccording to such a modification a calling terminal 281-284 should identify his session type, i.e.
which parameters and which session amongst the ~lurality of sessions 242-1 to 242-3 should be used, preferably by a session identi~ier ~ie1cl 1ll or 1]2, see fitl. 5, in its ~ransmissio~ e.~dcr rot cat,ll r~ c rsscntla] inventivc idea is that one established session is shared by two or a plurality of users.
It is also within the scope of the present invention to~
establish a pluralitY of p~rallel sessions between each ~. .;7 ~, ~v ~ y v I ~ U. . Cl 1 .L G . ::~ G ;~ 1 .LV11:~ V~ ~, W
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lZ~88~1 primary port and a plurality of application programs 13 respectively. This means that all terminals 281-284 may use any port 261-263 for a connection to any application program 13. Such a system is the most general mode of session and ' ' 5 port sharing in the data network.
' In such a system each application program 13 amongst a first plurality of application programs would have one session ' established to each primary port of a second plurality of primary ports 251-253. Each one of a third plurality of secondary data terminals 281-284 are then adapted to call any primary port for transaction exchange with any appli-' 'cation program. The network 260 interconnecting the sec-' ond'ary terminal ports 271-274 with the primary ports 261-263 might be either a circuit switching network or a packet swltching network. It is only important that an in~ormation unit, a PIV reaching a primary port 261-263 from a secondary port 271-274 connected to a secondary terminal 281-284, is provided with session identi.fier information 111, 112 or ", 106, fig. 4 and 5, in order for the communication controller 2 to route such a PIU into the selected session amongst the sessions branching out from that port, in order to reach the ' desired application program 13. ~, , Examples of various types of session parameters to be used for various types of sessions is given in the IBM manual ~
"System Network Architecture Reference Summary" GA27-3136-4, ~r January l9~1.
' " While the invention has been particularly shown and descri'bed with reference to preferred embodiments thereof, other changes in form and details may be made therein without departing from th~ spirit,and scope of the invention.
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and will use the group address ~or communication with the terminals in the qroup.
The communication between the terminal group 3 and the application pro~ram 13a in thc host proccs.sor l is startcd by a conventional session establishment procedure between one terminal, say terminal 31 in the group and the appli-cation program 13a. When the session is initiated, the communication controller 2 storcs both thc group address of the group 3 and the terminal address of the terminal 31 and transmits the group address as an or~igin address over the ~' ` ~, ll ~Z~88~1 channel 16 to VTAM 12. When a session has been established between the terminal 31 and the application program 13a', another terminal such as the terminal 32 may join or~share this session. PIUs (fig. 3) e~changed between the terminals in the group 3 and the application program 13a are routed into one single buffer area for one single session in VT~
12. The PIUs received over the channel 16 from VTAM 12 to the comniunication controller 2 contains the group address in the transmission header 92 according to fig. 3, whereas the ' 10 terminal address is embedded into the request unit 94. The communication controller 2 will then distribute the in-formation units according to the terminal addresses.
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It is important that a session has been established between , the terminal group 3 and the application program 13a in the ,host processor 1 before session sharing can be used. If one terminal, say the terminal 33, is sending a request unit at a time when no session has been opened, VTAM 12 will anal~ze this request unit and finds that there is no session opened. '' VTAM 12 will then return a response unit having certain condition,indicators set, telling the terminal 33 that thbre i5 no session established. The terminal 33 will then ini-tiate a session by sending a conventional logon request, whereafter the other terminals might share this new session.
Session sharing is possible between the terminals in the group 3 only as long as the various terminals are using the same session parameters for the communication. If one ' terminal or if the application program wants to use another session parameters, a new session might be established.
Sincc VT~M ].2 sccs only OllC tcrminaJ in tl~c gr,oup 3, this 30 , means that the old session must be terminated be~ore the new session can be established. Another terminal might then share the new session by adapting its communication to the new session parameter conditions.
The session sharing procedure just described is transparent ,~
12 1 2~ ~ 8~'1 to VTAM 12 and is mainly handled on a lower level by the communication controller 2. According to another embodiment of the present invention session sharing is handled on VTAM
level. It is assumed as an exemple that LU 52 in the cluster controller has established a session with the application program 13a in the host processor 1. It is also assumed that a LU 61 attached to the remote communication controller 6 intends to join this session on a session sharing level. The data traffic between the host processor 1 and the LU 52 in the cluster controller 5 flows over the link 21, the com-munication controller 2 and the channel 16. The data traffic between the LU 61 and the application program in the host processor 1 flows over the remote controller 6, the link 25, the communication controller 2 and the channel 16. According to the SNA architecture a transmission header g2 for a path information unit (PIU) in fig. 3 passing the link 21 has a format FID 2 according to fig. 4. The transmission header of the format FID 2 discloses a format identification field 101, a destin~tion address field 102, an origin address field 103 and a sequence number field 104. A PIU travelling along the link 25 and along the channel 16 has a format FID
1 according to fig. ~. The transmission header of the format FID 1 includes a data count field 105.
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The LU 61 is enabled to share an active session between the LU 52 in the cluster controller 5 and the LU 13a in the host ` processor l b~ modifying the transmission header FID 1 in fig. 4. A session identifier field 106 is used for the LUS2-LU13a session and is added to the transmission header. This field includes a flag bit 1~7, which when set, indicates th~t tl!e tran-;missio~ hcadcr rcprcsents a sharab]c scssion information unit. The other bits in the SSID field 106 uniquely define and name the established session between the LU 52 and the LU 13a. VTAM 12 stores the session identifier field 106 in a session identifier table (138, fig. 6). When the LU 61 joins this previously established session, mod-i .~ ~
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13 ~Z~88~1 ified transmission headers of the type shown in fig. 4, i.e.FID IM must be used with the field 106 marked with the same bits as for the established main session between LUS2 and LU13a. When such a PIU is received by VT,~M 12 from LU 61, the destination address field 102 is the same as for the main session initiated by the LU 52, i.e. the address of the application program LU 13a. The origin field 103 is, how-ever, different, it is the address of the LU 61. VTAM 12 then looks into the field 106 and finds the session sharing bit 107 to be on. It will then compare this field 106 with stored information in the session identifier table and will find a corresponding session identifier for the session originated in the LU 52. Therefore a request unit trans-mitted with such a PI~ will be passed to -the same receiving buffer queue in VTAM as if it would have been received from the original LU 52.
The invention will now be described in more detail with re~erence to the figures 5, 6 and 7 for a switched data network, such as the Nordic Public Data Network.
In fig. 6 there is shown a terminal group 3 including terminals 31, 32 and 33, each connected to a corresponding port 171, 172 and 173. These ports are preferably stand-ardized X21 ports, according to the CCITT recommendation, to be connected over a switched data network 160 to other existing X21 ports 161, 162 and 163. Another terminal or terminals 175 w:Lth its port 174 represent other terminals of the network which do not belong to the group 3. It is assumed that terminals 3]-33 and 175 are provided with automatic calling units. Thc tcrmi.nals 3l-33 and ]75 with the ports 171-174 represent the secondry side of the network whereas the primary side is represented by the ports 161-163 con-nected to the communication controller 2.
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A session can be established between a secondary terminal 31 and a primary application program 13a for changing path '` information units (PIU) between the two end users of such a session. A path will then exist between the terminal 31 and the application program 13a as follows: terminal 31, the port 171, a link 22, a port 161, a line 164, a line 165 in a scanner 156 in the communication controller, a buf~er 155 in the controller, a link control 154 in the controller, a path control 153 in the controller, a connection point manager 152 in the controller, a channel adapter 151 in the con-troller, a channel 16, buffer pools 133 in the host pro-cessor 1, interface 136 between the buffer pools 133 and the application program 13a and a buffer 137 in the application program 13a.
lS A PIU sent from a terminal 31 towards the application program 13a is provided with a transmission header 92 according to fig. 3 and has a format as shown in fig. 5.
Such a transmission header is of a format type FID 3 and includes a format identifier field 101 similar to the field 101 in fig. 4. It also includes a local session identifier field 111 which uniquely identifies the terminal 31 to the communication controller 2. According to the present in-vention the conventional transmission header FID 3 used in SNA architecture is modified by the field 112 comprising a shared session identifier field. This field includes a bi~
which is on when shared session facility is used. It also includes information about the main session which is shar-able.
Whcn a PIU sent rorn th~ tcrmina~ 31 has passed the network 160, the scanner 156, the buffers 155 and the link control 15~ in the co~munication controller, it will reach the path control 153 and further the connection point manager 152 in the communication controller. The path control 153 will change the transmission header of this PIU from the modified -; ~
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format FID 3M in fig. 5 to ti~e modified format FID 1~1 in ~ig. 4 whereby the contents of the fieId 112 in FID 3M will be transferred to the fie~d 106 in FID lM. This new trans-mission header FID lM will enable VTAM 12 to route the PIU
coming from the channel adapter 151 and the channel 16 to the host processor. This routing is performed by a trans-mission subsystem component 132 in VTAM 12.
When VTAM 12 is started in a domain such as in the domain A
in fig. 1, a number of sessions will be established between the system se~vices control point (SSCP) 1~ and the various PUs and LUs in the domain. These sessions are established by ~ means of VTAM requests such as "Activate PU" and "Activate ; LU". An activated LU might then establish a session with an application program LU in the host processor as described in connection with fig. 1. This is, however, not true ~or resaurces such as terminals which are connected over switched lines to the host processor. Such terminals are not ac-tivated during the domain initialization time. A session initialization between a terminal over a switched line with a host application program is therefore much more compli-cated and time consuming that session initialization over leased lines.
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Fig. 7 is a schema-tic diagram for a session establishment procedure in a switched data network shown in fig. 6.
The operation starts with the network operator issuing a "Vary" command from the operator console in the host pro-cessor 1. The "Vary" command will be processed by the SSCP
component 131 in VT~1 12. SSCP 131 will then send an "~c-tivate link" request (RU) to the communication controller 2.
Communication controller 2 answers by a "Definite response"
RU to the SSCP ]31. SSCP 131 then sends an "Activate connect in" RU to the communication controller 2 which answers with a "Definite response" RU. The communication controller 2 is 1.~
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now ready for receiving incoming calls from the terminals over the network 160.
It is assumed that the terminal 31 in the group 3 in fig. 6 '; wants to establish a session with an application program 13a in the host processor 1. It will then use its auto~atic calling unit to call one of the ports of the communication controller 2, say the port 161. ~ connection link 22 will ~ - then be established between the secondary port 171 of the terminal 31 and the primary port 161 of -the communication controller 2. Such an incoming call is shown in fig. 6 and 7 a~ coming from the physical unit 34 of the terminal to the communication controller 2. The incoming call is answered by the communication controller 2 by a "Station Identification ` Re~uest" RU "XID Who are you?", which will be sent to the physical unit 34. The physical unit 34 answers by sending its identification "XID response" to the communication Gontroller 2.
A conversation will now start between the communication controller 2 and the SSCP 131 in the host processor 1~
Communication controller 2 will send a "Request contact"
which is an off-hook RU to the SSCP. The SSCP answers with a "Set Control Vector" RU to the communication controller 2.
- This RU defines certain conditions for the session to be established between the PU 34 and the SSCP 131. The com- .
munication controller 2 answers by a definite response to the SSCP 131. SSCP 131 then sends a "Contact" RU to the c:ommunication controller 2. The communication controller 2 answers with another "DeEinite response" followed by a "Contacted" ~U.
SSCP`131 will now send an "~ctivate Physical Unit" RU to the physical unit 34 which activates this unit. The physical unit 34 will return a "Definite response" to the SSCP 131.
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Next SSCP 131 sends an "Assign network address" RU to the communication controller 2, which answers by a definite response. The SSCP then sends a "Set Control Vector" RU to the communication controller which answers with a "Definite response". This control vector is for the LU 37 in the terminal 31. The SSCP 131 proceeds to send an "Activate - Logical Unit" RU to the logical unit LU 37 in the terminal 31. This activates the logical unit in the terminal 31 which answers with a "Definite response" RU to the SSCP. This ends the procedure or establishing a session between the system services control point 131 in VTAM 12 and the physical unit 34 and another session between the SSCP 131 and the logical unit 37 in the terminal 31. A session might now be estab~
lished between the LU 37 and an application program such as the application program 13a in the host processor 1 as if the terminal 31 would have been attached to the host pro-cessor over non-switched lines.
A session is initiated by the logical unit 37 sending a "Lo~on" Rtl to the SSCP 131. This logon request includes a set of parameters suggested to be used for the session to be established. The SSCP will send a "Control Initate" (Cinit) request to the application program 13a, which will act as a primary LU in the session. The primary LU 13a answers by issuing a macro instruction "OPNDST" to the SSCP 131. When this macroinstruction is executed by VTA~I 12, the session ' parameters provided by the logon request will be checke`d against a logon mode table (LMT) 135 in a table area 134 in VTAM 12 in fig. 6. A number of control blocks in a control block area 140 will be establishetl, such as a node l~lentifier control b~ock (NIU) 1~3, WhiCIl ;d~nti~ies tlle secondary node of the session to bc cstablished, i.c. the LU 37. ~ session identifier control block (SIB) 142 defining the current session will also be established and a function management ` control block (FMB) 141 for this session.
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i, SSCP 131 will send a "Bind" P~U to the secondary logical unit 37. This Bind RU might contain the same session parameters as the original logon request or it might contain s~ssion parameters which have been changed by VTAM 12. The secondary LU 37 will then send a response accepting or rejecting these session parameters. If the session parameters are-accepted, the SSCP 131 will send a "Start Data Traffic" RU to the secondary LU 37. A session has now been established between ~i a secondary LU 37 and a primary LU 13a.
'' ~4 '' When a PIU having a transmission header of type FID 3 according to fig. 5 is received by the path control 153, ~ fig. 6, from the terminal 31, it will change the trans-; mission header to the format FID 1 according to fig. 4, as described previously. This PIU will be sent over the channel 16 to the host processor 1 and is routed by the transmission subsystem component 132 to a specific buffer area in the buffer pools 133 defined by the FMR block 141. The RU 94 of the PIU 96 (fig. 3) will then be transferred from the VTAM
buffer 133 to the application program buffer 137. Similarly a RU from the application program buffer 137 will be trans-ferred to the VTAM buffer 133 assigned by the FMB block 141 and will be built into a PIU by the TSC component 132 adding a transmission header 92. The TSC component 132 will then route this PIU to the communica-tion controller 2 and to its connection point manager 152 and further to the path control 153. The path control 153 will then change the transmi~sion header of the format FID 1 into the format FID 3 for further transfer to the terminal 31.
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Tllc? session cstablishment prccc(l~lre dcscribccl can be uscd for establishing a session bctween a host applicatlon program and a group of terminals 3 in fig. S. This means ' that when a session is established between the termlnal 31 and the application program 13a the content of the session ~; sharing identifier field 112 in the modified transmission , ! . ' . ." ` . .
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~Z~88(:1 1 r header FID 3M in fig. 5 will he stored in a Session Sharing Control Table (SSCT) 158 in the connection point manager 152 of the communication controller 2. Another terminal 32 ~ay then share this established session by using the same SSID
-;~ 5 information 112 in its transmission header when it sends a PIU to the application program 13a. This SSID information is compared to data stored in the SSCT 158 for routing the PIU
to the same destination as for the main session. Such a session sharing is made on the communication controller level. The PIUs exchanged between the communication con-troller 2 and the host processor 1 will use the group address for the terminal group 3 in the origin address field 103 (fig. 4) of their transmission headers 92 ~fig. 3).
When a station outside the group 3, such as a terminal 175, 15 is sharing an established session, the SSID information in the field 106 of a transmission header for the main session, say terminal 31-application program 13a, must be stored in a session sharing table SST 138 in VTAM 12. A PIU travelling from the terminal 175 along a shared session towards the 20 application program l3a will be routed to its destination buffer in VTAM 12 by the transmission subcomponent 132 comparing the SSID information in the PIU with stored f information in the table 138. If there is a list entry ~ defining a main sessionr the RU part of this PIU is queued into the VTAM b~uffer 133 assigned previously to the corresponding main session.
Fig. 8 and fig. 9 disclose another embodiment of the present invention.
According to fig. 8 a host processor 1 is attached over a channel 16 to a com~unication controller 2. ~ plurality of terminals 281-284 are eacll attached to corresponding sec-ondary ports 271-274 in a switched data networ~ 260, such as i .
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~, ';r IZ~18~1 the Nordic Public Data Network. A plurality of primary ports 261-263 of the network 2~0 are attached to primary ports 251-253 of the communication controller. The ports 261-263 are preferable standardized X21 ports.
An examT~le of the communication controller 2 is the IB~ type ; 3705 controller described in the ~lanual "IB~ 3704 and 3705 Communications Controllers Principle of operations" GC30 3004-6, October 1979.
An example of the terminals 281-284 is the IB~I type 3275 terminal described in the IBM ~lanual ~n introduction to the IBM 3270 Information Display System GA27-2739-14, February 1982.
It is assumed that the terminals 281-284 represent a large number of terminals to be used for communication with an application program 213 in the host processor 1 on trans-action basis. The transactions to be sent over the net~ork are rather short messages, however, the frequency of trans-action occurances is high. In a conventional data network such a transaction traffic would need an extremely high amount of session establishments and terminations resulting in a very high host processor overhead time as compared to the useful processing time of the transactions. The solution to such a traffic problem will be a session sharing syste~
according to the present invention.
A plurality of parallell sessions 241-243 will be estab-lished between primary half .se~ssio-l.s ~tl-c primary part of a session) 201-203 oF tlle alT~]icatit)n program 213 and sec-ondary half sessions (the secondary part of a session) 231-233 for the communication controller ports 251-253. These sessions will be enabled by sessions 341-343 established between the System Services Control Point (SSCP) 294 in the host processor and physical units 221-223 for the ports 251-253 in the communication controller 2 and similar sessions * Regi-stered trade mark ,~
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; ~~ 21 1ZG8~1 between the SSCP 294 and the logical units 231-233 for these ports, Each half session on the primary side for the appli-~ cation program 213 will include a node identifier block (NIB) 291-293. In the example of fig. 8 there are shown three parallell sessions 241-243 between the application ,~ program 213 and three ports 251-253 in the communication controller. It is of course obvious for a man skilled in the art that any other number of parallell sessions and ports, can be used.
An example of sessions established between communication controller output ports and a host processor application program is shown in the IBM Manual "IB~I X.25 NCP Packet Switching Interface" GC30-3080-1, June 1982.
The terminals 281-284 are viewed as a terminal group 203 where all terminals are oE a similar type and are using the same session parameters. The terminals 281-284 and their secondary ports 271-274 are to be connected to the primary ports 261-263 by using a group dial number. This means that the terminal 281 for the port 271 will dial a group number for connection establishment to a primary port, which might lead to a connection 276 between the ports 271 and 262. If the port 262 would be occupied, say by a connection 277, the port 271 might succeed to be connected to the port 261, which is attached over the line 264 to the communication .
controller port 251.
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The data traffic between one terminal, say the terminal 281 in fig. 8 ànd the host processor 1 will now be described witll reference to ~ig. 9. ~ t.5 ass-lm~d that the terminal ; 281 is calling the communication controller 2 over the network 260 using the gro~-p dial number for the ports 261-; 263 and that it succeeds to reach the port 262 over the connection link 276. Such an "Incoming Call" in fig. 9 is i t i'` ' ~:.
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answered by the communication controller by a station identifier request XID "Who are you". The terminal will then - respond with an "XID Response", which will identify its station address to the communication controller and further to the application program 21~, usiny the session 242 previously established between the application program 213 and the port 252 in the communication controller 2. The application program in the host will then send a "What can I
do for you" request whereafter the terminal answers with a "Request Transaction ID". This transaction request includes an identification information such as password. The request will be answered by the application program by an acknow-` ledgement or rejection of the transaction. In case theacknowledgement is positive a data exchange will start between the terminal 281 an~ the application program 213 using the previously established session between the appli-cation program 213 and the port 252, which session is shown as the session 242 in fig. 8. ~hen the transaction is completed the terminal will send an "End Transaction"
message to the application program 213 which answers with an "Acknowledgement". ~he terminal 281 will then brake the connection 276 after it has sent an "End Contact" request to the application program in the host.
~s an example the data network system according to fig. 8 and fig. 9 can be used for a banking application. The application program 213 in the host processor 1 is attached to a data base and the terminals in the terminal group 203 are communicating with such a data base on a transaction bases via the application program 213.
When the network operator starts the network in the morning of a working clay, the host processor will first establlsh the three parallell sessions 241-243 between the application program 213 and the communication controller ports 251-253.
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~Z~88~1 This means,tllat the terminal group 203 is viewed by VTAM 12 in the host processor as three physical uni-ts 221-223, three ~ logical units 231-233 and three links 251-253 instead of as one physica] unit and one loc~ical unit for each terminal in the group 203. VTAM 12 will also assign network addresses to these three physical and logical units in the communication controller 2.
It should be understood that the system according to fig. 8 and fig. 9 will substantially reduce the session estab-,10 lishment and termination overhead as compared to conven-tional session housekeeping for switched connections~ It should be understood that the physical units 221-223 and the `J logical units 231-233 in the communication controller will be activated in a conventional manner when the network is started by the network operator in the host processor 1 in the morning of a working day. This will establish the sess,ions 341-343 between the SSCP 294 and said physical and logical units. The parallell LU-LU sessions 241-243 can then be established preferably from the primary host processor side..In such a session establishment procedure the session parameters are negotiatable, as in a conventional system, and a conventional "~ind" request is used to decide which f~ session parameters should be used. It can therefore be said ~, that the sessions 241-243 are not fixed but they can be adapted to the type oE applications needed for servicing the terminals in the group 203. It is, however, important that ~r all the three s~ssions 241, 242 and 243 are using the same session parameters at the same time because the terminals in the group 203 are randomly connected to the three ports 261-263.
30~ The duration time T for a session, such as the sessions 241-243, is up to several hours. The time Tl for a session est`ablishment operation is of the order of hundreds of , milliseconds. The duration time t for a transaction is preferably a few seconds whereas the~actual processing .
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time tl for a transaction in the host processor is only a few milliseconds. This means that t is at least a magnitude less than T and that tl is at least a magnitude less'than Tl.
The present invention reduces the overall response time for the calling terminals because no session establishment time Tl is needed in the processor l for each transaction.
The present invention is not restricted to SNA architect~re with a strictly centralizecl control system using a System Services Control Point 294. The control sessions 341-343 could therefore be substitu-ted by some other kind of network contr~l system. The essential inventive concept is that one or a plurality of sharable sessions, preferably established according to negotiatable session parameter rules, are used for serving a plurality of user stations or terminals.
The present invention is also not restricted to the em-hodiments described. It is, for instance within the scope of the invention to establish several parallel sessions 242-l, 242-2, 242-3 ... in fig. 8 between a primary LU202 and a seoondary LU232 Eor a port 252. These sessions would be ¢ established with different session parameters thus enabling terminals using different session parameters to be connected to the same port. ~ccording to such a modification a calling terminal 281-284 should identify his session type, i.e.
which parameters and which session amongst the ~lurality of sessions 242-1 to 242-3 should be used, preferably by a session identi~ier ~ie1cl 1ll or 1]2, see fitl. 5, in its ~ransmissio~ e.~dcr rot cat,ll r~ c rsscntla] inventivc idea is that one established session is shared by two or a plurality of users.
It is also within the scope of the present invention to~
establish a pluralitY of p~rallel sessions between each ~. .;7 ~, ~v ~ y v I ~ U. . Cl 1 .L G . ::~ G ;~ 1 .LV11:~ V~ ~, W
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lZ~88~1 primary port and a plurality of application programs 13 respectively. This means that all terminals 281-284 may use any port 261-263 for a connection to any application program 13. Such a system is the most general mode of session and ' ' 5 port sharing in the data network.
' In such a system each application program 13 amongst a first plurality of application programs would have one session ' established to each primary port of a second plurality of primary ports 251-253. Each one of a third plurality of secondary data terminals 281-284 are then adapted to call any primary port for transaction exchange with any appli-' 'cation program. The network 260 interconnecting the sec-' ond'ary terminal ports 271-274 with the primary ports 261-263 might be either a circuit switching network or a packet swltching network. It is only important that an in~ormation unit, a PIV reaching a primary port 261-263 from a secondary port 271-274 connected to a secondary terminal 281-284, is provided with session identi.fier information 111, 112 or ", 106, fig. 4 and 5, in order for the communication controller 2 to route such a PIU into the selected session amongst the sessions branching out from that port, in order to reach the ' desired application program 13. ~, , Examples of various types of session parameters to be used for various types of sessions is given in the IBM manual ~
"System Network Architecture Reference Summary" GA27-3136-4, ~r January l9~1.
' " While the invention has been particularly shown and descri'bed with reference to preferred embodiments thereof, other changes in form and details may be made therein without departing from th~ spirit,and scope of the invention.
.~,
Claims (17)
1. Computer network system for data communication between a plurality of addressable nodes comprising a plurality of links interconnecting the nodes and at least one host processor for establishing a session between a first and a second node in the network for exchanging information units between said two nodes in accordance with session parameters defined during a session establishment operation, characterized by means for storing session identifier information and means for comparing said stored session identifier information with a session identifier field in an information unit sent by a third node to the second node without session establishment between the second node and the third node, whereby an established session between two nodes is shared by a third node.
2. A network according to claim 1, wherein said session identifier storing means comprises a shared session table located in a communication controller attaching the second and third node to the first node located in the host processor.
3. A network according to claim 1, wherein said session identifier storing means comprises a shared session table located in a virtual transmission access method of the host processor.
4. A network according to claim 1, wherein said session identifier field is located in a transmission header of an information unit travelling through the network,
5. A network according to claim 4, wherein said session identifier field comprises a session sharing mode indicator.
6. A network according to any one of claims 1, 2 or 3, wherein the first node is an application program in the host processor, the second and third nodes are data terminals attachable over switched lines to a communication controller and further to the application program using one shared session.
7. A network according to claim 2 , wherein an information unit sent from one data terminal to the communication controller comprises a first type of a transmission header including a local session identifier field and a shared session identifier field, said transmission header being changed in the communication controller into a second type of a transmission header including an origin address and a destination address whereby the origin address is the network address of a group of session sharable data terminals.
8. A method for transferring information units in a computer network system including establishing a first session between a first addressable node in a host processor and a second addressable node in a station attached to the network, the session establishment procedure including defining a set of session parameters amongst a plurality of parameters to be used in the session, said parameters defining the communication rules to be followed by both ends of the session, characterized by sharing the established first session with a third addressable node for exchanging information units between the first node and the third node without establishing a second session and identifying to the system each information unit sent or received by the third node in the shared session as an information unit related to the established first session.
9. A method according to claim 8, wherein the identification of an information unit is made by comparing session identifier data in a transmission header of the information unit with stored session identifier data.
10. A method according to claim 8, wherein the identification of an information unit is based upon the location of the third node in the network.
11. A method for transferring information units in a computer network system comprising at least one host processor, a number of addressable primary network ports connected to the host processor and a plurality of secondary network ports each attached to a corresponding data terminal and each connectable over a switched line to a primary port, including establishing at least one session between at least one primary port and an addressable node in the host processor, said session establishment procedure including defining a set of session parameters amongst a plurality of parameters to be used in the session, characterized by maintaining the established one session between said one primary port and the host node a time T, connecting a first secondary port to said one primary port over a switched line by a call from a corresponding terminal, starting a data conversation between said terminal and the host node for a transaction using the previously established one session, braking the line connection after the transaction is completed, the duration time t for the transaction being a magnitude smaller than the duration time T for said one session, and connecting another data terminal via its secondary port to said one primary port before said one session is terminated, for another transaction, whereby a plurality of secondary terminals are sharing one session.
12. A method according to claim 11, wherein the primary ports are located in a communication controller.
13. A method according to claim 12, wherein a plurality of sessions each defined by a different set of session parameters are established between one primary port and an addressable node in the host processor.
14. A method according to claim 13, wherein a session identifier field in a transmission header of an incoming information unit for a primary port is used to identify which session amongst a plurality of parallel sessions should be used for a transaction.
15. A method for transferring information units between a first plurality of application programs in a host computer and a second plurality of data terminals over a third plurality of primary ports of a data network, characterized by establishing parallel sessions between each application program and all primary ports respectively and providing session identifier information in each information unit travelling between an application program and a data terminal via said data network.
16. A method according to claim 15 wherein the data network is a circuit switched network.
17. A method according to claim 15 wherein the data network is a packet switched network.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE8301192A SE448919B (en) | 1983-03-04 | 1983-03-04 | METHOD FOR TRANSFERING INFORMATION DEVICES IN A COMPUTER NETWORK, AND COMPUTER NETWORK FOR IMPLEMENTATION OF THE METHOD |
| SE8301192.4 | 1983-03-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1208801A true CA1208801A (en) | 1986-07-29 |
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ID=20350260
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000448023A Expired CA1208801A (en) | 1983-03-04 | 1984-02-22 | Computer network system and its use for information unit transmission |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4586134A (en) |
| EP (1) | EP0118037B1 (en) |
| JP (1) | JPS59210754A (en) |
| CA (1) | CA1208801A (en) |
| DE (1) | DE3482891D1 (en) |
| DK (1) | DK121884A (en) |
| FI (1) | FI81227C (en) |
| NO (1) | NO166604C (en) |
| SE (1) | SE448919B (en) |
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| US7831204B1 (en) | 1981-11-03 | 2010-11-09 | Personalized Media Communications, Llc | Signal processing apparatus and methods |
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| US4736369A (en) * | 1986-06-13 | 1988-04-05 | International Business Machines Corp. | Adaptive session-level pacing |
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| US4914619A (en) * | 1987-10-19 | 1990-04-03 | International Business Machines Corporation | Apparatus and method for interconnecting an application of a transparent services access facility to remote source |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4458311A (en) * | 1981-10-09 | 1984-07-03 | International Business Machines Corporation | Text processor having an interactive display terminal which alternately functions as a data processing terminal |
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1983
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1984
- 1984-02-03 JP JP59017260A patent/JPS59210754A/en active Granted
- 1984-02-03 DE DE8484101100T patent/DE3482891D1/en not_active Expired - Fee Related
- 1984-02-03 EP EP84101100A patent/EP0118037B1/en not_active Expired
- 1984-02-15 US US06/580,576 patent/US4586134A/en not_active Expired - Fee Related
- 1984-02-22 CA CA000448023A patent/CA1208801A/en not_active Expired
- 1984-02-24 FI FI840761A patent/FI81227C/en not_active IP Right Cessation
- 1984-02-27 NO NO840740A patent/NO166604C/en unknown
- 1984-02-28 DK DK121884A patent/DK121884A/en not_active Application Discontinuation
Also Published As
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|---|---|
| NO840740L (en) | 1984-09-05 |
| US4586134A (en) | 1986-04-29 |
| FI81227C (en) | 1990-09-10 |
| NO166604C (en) | 1991-08-14 |
| SE8301192D0 (en) | 1983-03-04 |
| DK121884A (en) | 1984-09-05 |
| SE8301192L (en) | 1984-09-05 |
| FI840761A (en) | 1984-09-05 |
| DK121884D0 (en) | 1984-02-28 |
| FI81227B (en) | 1990-05-31 |
| EP0118037A2 (en) | 1984-09-12 |
| DE3482891D1 (en) | 1990-09-13 |
| EP0118037B1 (en) | 1990-08-08 |
| JPH0576817B2 (en) | 1993-10-25 |
| NO166604B (en) | 1991-05-06 |
| SE448919B (en) | 1987-03-23 |
| JPS59210754A (en) | 1984-11-29 |
| FI840761A0 (en) | 1984-02-24 |
| EP0118037A3 (en) | 1987-06-16 |
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