3 4
that data traffic having large frames did not consume DETAILED DESCRIPTION OF THE
more ring bandwidth than the system administrator PREFERRED EMBODIMENT configured for the multimedia traffic.
Referring now to FIG. 1, there is illustrated a typical
SUMMARY OF THE INVENTION 5 hardware configuration of a workstation with a central
A system and method is provided to complement use processing unit 10, and a number of other units inter
of priority for reserved traffic in multimedia computer- connected via a system bus 12. The workstation shown
ized data communication networks, to insure that the in mG }includes aIa^f ^ccessJmTMy ^ «}
opportunity for transmitting large, unreserved data read ^ memo^ <*°M>.16' and I/O adapter 18 for
frames is constrained. In accordance with a preferred 10 connecting peripheral devices such as disk units 20 to
... * * *x. ■ -r r * J the bus, a user interface adapter 22 for connecting a
embodiment of the invention, lf frames transmitted k ^ ... % louds Peaker 28> micr0phone 32,
when the server releases a token tend to be small then m&/m ^ usgr ... deyices tQ the bus> a com.
the server will capture a larger portion of the band- munication adapter 34; for connecting the workstation
width, e.g. if the server only obtains fifty percent of the 15 t0 a data processing network, and a display adapter 36
tokens and the remaining stations obtain fifty percent, for connecting the bus to a display device 38.
the server will obtain up to eighty percent of the ring yiG. 1 depicts a typical "intelligent" workstation,
bandwidth if its frames, on average, are nominally four however, the workstation may in fact be a "dumb"
times the size of the lower priority frames. terminal with only a limited processing capability under
In accordance with the invention, a short bandwidth 20 control of a host processor. Alternatively, the worksta
reservation acknowledgement is transmitted onto the tion may be a simple digital device for presenting audio
ring by the client for selected frames which it receives. or video streams. This is made clear in connection with
This bandwidth reservation acknowledgement, how- FIG. 2.
ever, differs from other communication acknowledge- FIG. 2 illustrates a data processing system compris
ments in that it is not addressed to any station on the 25 ing a number of workstations (here, three workstations
ring, but rather is simply transmitted at a non-zero pri- 200> 220> and 230) interconnected by a pair of data net
ority less than the server's priority. In a preferred em- works 210 md 240, so as to permit communication
bodiment, the criteria which is employed by the client between the workstations. It is assumed that the date
for such bandwidth reservation acknowledgement is processing system shown in FIG. 2 is of a type which
that the sender will send a bandwidth reservation ac- 30 PfTM* concurrent real-time communication between
knowledgement only when the IEEE 802.5 AC field is 'he u,sers; The network operates according to a conven
. , . .„ , / , * r tional network protocol, such as the token ring protocol
set, but will do so for a fixed amount of time or for a , ,. ~, , D. „ , . ,.. , „
_ , , . . , . .. described m Token Ring Network Architecture reference,
fixed number of received frames. This criteria provides SC30-3374 IBM 1989
an optimization reducing overall ring utilization, since 35 FIG 2 depicts'only one possible hardware configurathe bandwidth reservation acknowledgement is only tion for a data processing netWork. Other configurasent when the nng is congested. Such congestion is tions ^ possible. For example, the data processing deduced from the fact that the server had to make a system could be based upon a star network, or a host reservation to receive the token, and the AC field re- processor connected to a plurality of dumb terminals, or fleets this condition. 40 could further be based upon a plurality of remote proIn accordance with the foregoing, a communication cessors connected by a communication network. The network is disclosed which transmits an unsolicited networks could also be based upon a telephone netacknowledgement at non-zero priority for each non- work, an ISDN network, or any other "dial up" netzero priority frame received, such system thereby being works. Moreover, the workstations could be located independent of the communication protocol employed 45 within the single workspace or within a local area, or by the network station. could be remote from one another. A source for detailing technical planning information for configuring a BRIEF DESCRIPTION OF THE DRAWINGS network of workstations in accordance with the invenFIG. 1 is block diagram showing the configuration of tion> « the IBM Extended Services for OS/2 Example a typical workstation in accordance with the subject 50 Scenarios Manual, 1991.
invention- Multimedia computing is the processing of various
FIG. 2 is an illustration of a data processing system media, such as video, waveform audio, musical instru
including three workstations interconnected by a net- men{.ntferface (MIDI) streams animation,
work- graphics, and text. Such processmg includes the cap
_' , . ^ ^. - , , 55 ture, authoring (editing) and playback of media streams
FIG. 3 is a representation of a layered open systems „ .,0 v, . ° ■ ,. .. ,, ...
y , , . ^_ , A. ,. - as well as other data processmg applications. Multime
interconnection model showing the relationship of com- dia documents which ^ stored ^ some non.volatile
ponents of the subject invention to the layers; ra^mm, such as a disk, are referred to as recorded
FIG. 4 is a simplified schematic illustration of a work- multimedia applications. There are also live multimedia
station network employing multiple servers and clients ^ ... in which two or more people communicate
m a token ring configuration; witn each other at the same time using a computer. Live
FIG. 5 illustrates the fields of a typical token ring multimedia applications are normally conducted across
frame; space and time indicating that live multimedia is inher
FIGS. 6A-D illustrate priority reservation occurring ently distributed. Even recorded multimedia applica
on a token ring in accordance with the subject inven- 65 tions require distributed file system services to share
tion; large volumes of stored media, such as video disk, audio
FIG. 7 is a flow diagram detailing the program logic information, or computer-generated images. Thus, it is
in accordance with the subject invention. critical that a prioritizing scheme in accordance with
