WO2001001654A2 - Network latency recovery for internet gateways - Google Patents

Network latency recovery for internet gateways Download PDF

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Publication number
WO2001001654A2
WO2001001654A2 PCT/US2000/018160 US0018160W WO0101654A2 WO 2001001654 A2 WO2001001654 A2 WO 2001001654A2 US 0018160 W US0018160 W US 0018160W WO 0101654 A2 WO0101654 A2 WO 0101654A2
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Prior art keywords
network latency
modem
modem connection
connection
high speed
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PCT/US2000/018160
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French (fr)
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WO2001001654A3 (en
Inventor
Keith T. Chu
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Conexant Systems, Inc.
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Publication of WO2001001654A2 publication Critical patent/WO2001001654A2/en
Publication of WO2001001654A3 publication Critical patent/WO2001001654A3/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/32—Circuits or arrangements for control or supervision between transmitter and receiver or between image input and image output device, e.g. between a still-image camera and its memory or between a still-image camera and a printer device
    • H04N1/32609—Fault detection or counter-measures, e.g. original mis-positioned, shortage of paper
    • H04N1/32614—Fault detection or counter-measures, e.g. original mis-positioned, shortage of paper related to a single-mode communication, e.g. at the transmitter or at the receiver
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/66—Arrangements for connecting between networks having differing types of switching systems, e.g. gateways
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L47/00—Traffic control in data switching networks
    • H04L47/10—Flow control; Congestion control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L47/00—Traffic control in data switching networks
    • H04L47/10—Flow control; Congestion control
    • H04L47/28—Flow control; Congestion control in relation to timing considerations
    • H04L47/283—Flow control; Congestion control in relation to timing considerations in response to processing delays, e.g. caused by jitter or round trip time [RTT]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/40—Network security protocols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M11/00—Telephonic communication systems specially adapted for combination with other electrical systems
    • H04M11/06—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/00127—Connection or combination of a still picture apparatus with another apparatus, e.g. for storage, processing or transmission of still picture signals or of information associated with a still picture
    • H04N1/00204—Connection or combination of a still picture apparatus with another apparatus, e.g. for storage, processing or transmission of still picture signals or of information associated with a still picture with a digital computer or a digital computer system, e.g. an internet server
    • H04N1/00209—Transmitting or receiving image data, e.g. facsimile data, via a computer, e.g. using e-mail, a computer network, the internet, I-fax
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/00127—Connection or combination of a still picture apparatus with another apparatus, e.g. for storage, processing or transmission of still picture signals or of information associated with a still picture
    • H04N1/00281—Connection or combination of a still picture apparatus with another apparatus, e.g. for storage, processing or transmission of still picture signals or of information associated with a still picture with a telecommunication apparatus, e.g. a switched network of teleprinters for the distribution of text-based information, a selective call terminal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/00127—Connection or combination of a still picture apparatus with another apparatus, e.g. for storage, processing or transmission of still picture signals or of information associated with a still picture
    • H04N1/00281—Connection or combination of a still picture apparatus with another apparatus, e.g. for storage, processing or transmission of still picture signals or of information associated with a still picture with a telecommunication apparatus, e.g. a switched network of teleprinters for the distribution of text-based information, a selective call terminal
    • H04N1/00312—Connection or combination of a still picture apparatus with another apparatus, e.g. for storage, processing or transmission of still picture signals or of information associated with a still picture with a telecommunication apparatus, e.g. a switched network of teleprinters for the distribution of text-based information, a selective call terminal with a digital transmission apparatus, e.g. a switched network of teleprinters for the distribution of text-based information, SMS or ISDN device
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/32—Circuits or arrangements for control or supervision between transmitter and receiver or between image input and image output device, e.g. between a still-image camera and its memory or between a still-image camera and a printer device
    • H04N1/32609—Fault detection or counter-measures, e.g. original mis-positioned, shortage of paper
    • H04N1/32646—Counter-measures
    • H04N1/32683—Preventive counter-measures, e.g. using redundant hardware, or anticipating a fault
    • 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
    • H04L69/24—Negotiation of communication capabilities
    • 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
    • H04L69/28—Timers or timing mechanisms used in protocols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
    • H04N2201/0008—Connection or combination of a still picture apparatus with another apparatus
    • H04N2201/0015—Control of image communication with the connected apparatus, e.g. signalling capability
    • H04N2201/0024—Converting image communication control signals, e.g. group 3 facsimile protocol signals, to non-image communication control signals or vice versa
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N2201/00—Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof
    • H04N2201/0008—Connection or combination of a still picture apparatus with another apparatus
    • H04N2201/0015—Control of image communication with the connected apparatus, e.g. signalling capability
    • H04N2201/0025—Adapting an image communication to a non-image communication or vice versa, e.g. data rate-conversion

Definitions

  • the present invention generally relates to network latency, and more particularly to network latency recovery for Internet gateways.
  • T.38 is an emerging International Telecommunications Union (ITU) standard for fax transmission over Internal Protocol (IP) networks.
  • ITU International Telecommunications Union
  • IP Internal Protocol
  • the standard defines how Group 3 end-to- end facsimile terminals can connect to each other through the Internet. Fax has traditionally been transmitted over standard telephone lines. Transmitting fax over a data network presents new opportunities for enhanced fax delivery, such as real time fax.
  • V.34 is a standard for modems operating at data signalling rates of up to 33,600 bit/s.
  • a communications system includes an internet protocol network, a calling modem and an answering modem configured to effectively handle network latency.
  • the calling modem includes a timer storing a network latency value.
  • the network latency value is compared to a network latency threshold. If the network latency value is less than the network latency value, then a high speed modem connection is continued. If the network latency value is greater than the network latency value, then the high speed modem connection is terminated. In place of the high speed modem connection, a low speed modem connection is established.
  • the calling modem is operable to transmit a modem connection selection signal for selecting a high speed modem connection or a low speed modem connection.
  • the answering modem is operable to receive the modem connection selection signal.
  • Figure 1 is a diagram showing exemplary signalling between a calling side and an answering side of a communications system with an acceptable network latency
  • Figures 2A-2B provide a flow chart of an exemplary network latency recovery process in accordance with the signalling and communications system of Figure 1 ;
  • Figure 3 is a diagram showing exemplary signalling between a calling side and an answering side of the communications system of Figure 1 with an unacceptable network latency;
  • Figure 4 is a block diagram of a calling modem in a calling gateway of Figures 1 and 3.
  • FIG. 1 shows a communications system C including end-point facsimile terminals Fl and F2 and Internet T.38 gateways Gl and G2.
  • Fl and Gl constitute the calling side of the system C
  • F2 and G2 constitute the answering side of the system C.
  • the gateway GI includes a calling modem
  • the gateway G2 includes an answering modem.
  • the facsimile gateways Gl and G2 allow for the facsimile terminals Fl and F2 to communicate transparently through an internet protocol (IP) network such as the Internet. Communication between the gateways Gl and G2, for example, can include transmitting a facsimile.
  • IP internet protocol
  • the calling gateway Gl encodes the fax signals into IP fax packets for transmission, and the answering gateway G2 decodes the transmitted IP fax packets back into fax signals.
  • FI and GI can be embodied in an Internet-aware facsimile device, and F2 and G2 can be embodied in another Internet-aware facsimile device.
  • Fl is shown sequentially providing a CNG signal sequence, a CM signal sequence, and a CJ signal sequence
  • Gl is shown sequentially providing an ANSam signal sequence and a JM signal sequence
  • G2 is shown sequentially providing a CNG signal sequence, a CM signal sequence, and a CJ signal sequence
  • F2 is shown sequentially providing an ANSam signal sequence and a JM signal sequence.
  • the design and operation of these signal sequences are understood in the art.
  • the CNG, CM, CJ, and JM signals are defined and described in the ITU V.8 Recommendation.
  • the signalling between the calling or emitting side and the answering or receiving side includes signals to accomplish network latency recovery.
  • the standard T.38 signals shown between the gateways Gl and G2 are t30- data(JM, info), t30-data(CM, info), and t30-indicator(CNG).
  • the T.38 signals added for network latency recovery are a t30-indicator(CNG sent) signal and a t30- indicator(DoV.8/Dolowspeed) signal.
  • Certain signals are designated "t30" to reflect that the terminals FI and F2 communicate during a T.30 session. The nature of a T.30 session is understood in the art. The designation also relates to the type of message in the particular signal.
  • the t30-indicat ⁇ r (DoV.8/Dolowspeed) signal is shown as the t30-indicator(DoV.8) signal in Figure 1 and is shown as the t30-indicator(Dolowspeed) signal in Figure 3.
  • the t30- indicator(CNG sent) signal is used to indicate to Gl if a CNG response has been transmitted by G2.
  • the t30-indicator(DoV.8/Dolowspeed) signal is used to indicate whether a V.8 modem connection should continue or if a Group 3 modem connection should be established.
  • Network latency is here defined as the time between transmission of the t30-indicator(CNG) signal and reception of the t30-indication(CNG sent) signal.
  • Gl responds with the t30-indicatior(DoV.8) signal (Fig. 1). If network latency is unacceptable, then Gl responds with the t30-indicator(Dolowspeed) signal (Fig. 3). Normally, G2 and F2 have up to 4 seconds to respond with a V.8 signal, so it is proper to allow G2 to continue with CNG until G2 receives the t30-indicator(DoV.8/Dolowspeed) signal.
  • step 200 Fl transmits a CNG to Gl.
  • step 202 Gl detects the CNG and in response sends the t30-indicator(CNG) signal to G2. G2 is thereby informed to start transmitting CNG.
  • step 204 Gl starts its timer 400 (Fig. 4).
  • step 206 it is determined by Gl if a CNG sent signal has been received from G2. Control remains in step 206 until the CNG sent signal is received from G2.
  • step 208 Gl stops its timer 400. Based on the starting time and stopping time of the timer 400, Gl now stores a network latency timer value 408 (Fig. 4). When the network latency timer value 408 is too long, the high speed modem connection (in this case, a V.8 connection) fails. Until the CNG sent signal is received, Gl holds off transmission of an ANSam signal.
  • step 210 it is determined if the timer value 408 is below an acceptable latency threshold 404 (Fig. 4). If so, then control passes to step 212 where Gl transmits the t30-indicator(DoV.8) signal to G2. Next, in step 213, Gl continues transmitting ANSam since the timer value 408 was below an acceptable latency threshold 404. From step 213, control proceeds to step 214 where G2 ceases CNG transmission and transmits CM based upon the CM contents of F 1. Next, the network latency recovery process is completed in step 216.
  • the communications system C and associated signalling is shown for an unacceptable network latency.
  • the Fl is shown sequentially providing two CNG signal sequences and a DCS signal sequence;
  • Gl is shown sequentially providing a CED signal sequence and a DIS sequence;
  • G2 is shown sequentially providing two CNG signal sequences and a DCS signal sequence;
  • F2 is shown sequentially providing an ANSam signal sequence and a DIS signal sequence.
  • steps 210-214 are specific to Figure 3. Steps 200-10 are applicable to both Figure 1 and Figure 3.
  • step 210 if the timer value 408 is above the acceptable latency threshold 404, then control passes to step 218 where Gl transmits the t30-indicator(Dolowspeed) signal to G2 (Fig. 3).
  • step 220 Gl transmits CED, instead of ANSam, forcing Fl to use V.17 (a standard for data signalling rates up to 14,400 bit/s) and lower procedures.
  • a switch from one modem version to a previous modem version has generally been termed a "fallback.”
  • Gl continues to send CED while the timer value 408 is above the acceptable latency threshold 404.
  • step 222 control passes to step 222 where G2 continues with its CNG transmission, forcing F2 to use V.17 and lower procedures.
  • the network latency recovery process is then completed in step 216.
  • exemplary components of a calling modem M in the calling gateway Gl is shown.
  • the modem M includes a comparison block 402 coupled to a timer 400, a latency threshold 404, and a modem connection (or modulation mode) selection block 406.
  • the timer 400 stores the network latency value 408 described above.
  • the comparison block 402 compares the network latency value 408 to the network latency threshold 404 described above. Based on the result of that comparison, the modem connection selection block 406 generates either the t30-indicator(DoV.8) signal or the t30-indicator(Dolowspeed) signal.
  • the modem connection selection block 406 If the network latency value 408 is less than the latency threshold 404, then the modem connection selection block 406 generates a t30-indicator(DoV.8) signal. If the network latency value 408 is greater than the latency threshold 404, then the modem connection selection block 406 generates the t30-indicator(Dolowspeed) signal. It should be understood that the illustrated components can be implemented in a variety of ways (hardware or software).
  • a high speed modem connection is bypassed for a low speed modem connection.
  • the high speed modem connection for example, can be a V.8 modem connection, and the low speed modem connection can be a Group 3 modem connection. Also, the high speed modem connection can be a V.34 half-duplex connection.
  • the network latency recovery techniques described herein are applicable to a variety of modem connections or modulation modes.
  • network latency recovery is described in a modem context, it should be understood that the network latency recovery techniques described herein are applicable to other communication devices with similar structure and/or operation. Other ways of suspending or terminating a high speed modem connection based on current network latency are possible. Likewise, other ways of selectively operating a high speed modem connection and a low speed modem connection based on current network latency are possible.

Abstract

A communications system (C) includes an internet protocol network, a calling modem (M) and an answering modem configured to effectively handle network latency. The calling modem (M) includes a timer (400) storing a network latency value (408). The network latency value (408) is compared to a network latency threshold (404). If the network latency value (408) is less than the network latency threshold (404), then a high speed modem connection is continued. If the network latency value (408) is greater than the network latency threshold (404), then the high speed modem connection is terminated. In place of the high speed modem connection, a low speed modem connection, a low speed modem connection is established. The calling modem (M) is operable to transmit a modem connection selection signal for selecting a high speed modem connection or a low speed modem connection. The answering modem is operable to receive the modem connection selection signal.

Description

NETWORK LATENCY RECOVERY FOR INTERNET GATEWAYS
The present invention generally relates to network latency, and more particularly to network latency recovery for Internet gateways.
T.38 is an emerging International Telecommunications Union (ITU) standard for fax transmission over Internal Protocol (IP) networks. The standard defines how Group 3 end-to- end facsimile terminals can connect to each other through the Internet. Fax has traditionally been transmitted over standard telephone lines. Transmitting fax over a data network presents new opportunities for enhanced fax delivery, such as real time fax.
The ITU-T T.38 recommendation indicates that support for V.34 is for further study. V.34 is a standard for modems operating at data signalling rates of up to 33,600 bit/s.
Briefly, a communications system includes an internet protocol network, a calling modem and an answering modem configured to effectively handle network latency. The calling modem includes a timer storing a network latency value. The network latency value is compared to a network latency threshold. If the network latency value is less than the network latency value, then a high speed modem connection is continued. If the network latency value is greater than the network latency value, then the high speed modem connection is terminated. In place of the high speed modem connection, a low speed modem connection is established. The calling modem is operable to transmit a modem connection selection signal for selecting a high speed modem connection or a low speed modem connection. The answering modem is operable to receive the modem connection selection signal.
A better understanding of the present invention can be obtained when the following detailed description of the preferred embodiment is considered in conjunction with the following drawings, in which: Figure 1 is a diagram showing exemplary signalling between a calling side and an answering side of a communications system with an acceptable network latency;
Figures 2A-2B provide a flow chart of an exemplary network latency recovery process in accordance with the signalling and communications system of Figure 1 ; Figure 3 is a diagram showing exemplary signalling between a calling side and an answering side of the communications system of Figure 1 with an unacceptable network latency; and
Figure 4 is a block diagram of a calling modem in a calling gateway of Figures 1 and 3.
Turning now to the drawings, Figure 1 shows a communications system C including end-point facsimile terminals Fl and F2 and Internet T.38 gateways Gl and G2. Fl and Gl constitute the calling side of the system C, and F2 and G2 constitute the answering side of the system C. The gateway GI includes a calling modem, and the gateway G2 includes an answering modem. The facsimile gateways Gl and G2 allow for the facsimile terminals Fl and F2 to communicate transparently through an internet protocol (IP) network such as the Internet. Communication between the gateways Gl and G2, for example, can include transmitting a facsimile. With respect to facsimile communications, the calling gateway Gl encodes the fax signals into IP fax packets for transmission, and the answering gateway G2 decodes the transmitted IP fax packets back into fax signals. FI and GI can be embodied in an Internet-aware facsimile device, and F2 and G2 can be embodied in another Internet-aware facsimile device. Fl is shown sequentially providing a CNG signal sequence, a CM signal sequence, and a CJ signal sequence; Gl is shown sequentially providing an ANSam signal sequence and a JM signal sequence; G2 is shown sequentially providing a CNG signal sequence, a CM signal sequence, and a CJ signal sequence; and F2 is shown sequentially providing an ANSam signal sequence and a JM signal sequence. The design and operation of these signal sequences are understood in the art. The CNG, CM, CJ, and JM signals are defined and described in the ITU V.8 Recommendation.
In addition to the standard T.38 signals, the signalling between the calling or emitting side and the answering or receiving side includes signals to accomplish network latency recovery. The standard T.38 signals shown between the gateways Gl and G2 are t30- data(JM, info), t30-data(CM, info), and t30-indicator(CNG). The T.38 signals added for network latency recovery are a t30-indicator(CNG sent) signal and a t30- indicator(DoV.8/Dolowspeed) signal. Certain signals are designated "t30" to reflect that the terminals FI and F2 communicate during a T.30 session. The nature of a T.30 session is understood in the art. The designation also relates to the type of message in the particular signal. The t30-indicatυr (DoV.8/Dolowspeed) signal is shown as the t30-indicator(DoV.8) signal in Figure 1 and is shown as the t30-indicator(Dolowspeed) signal in Figure 3. The t30- indicator(CNG sent) signal is used to indicate to Gl if a CNG response has been transmitted by G2. The t30-indicator(DoV.8/Dolowspeed) signal is used to indicate whether a V.8 modem connection should continue or if a Group 3 modem connection should be established. Network latency is here defined as the time between transmission of the t30-indicator(CNG) signal and reception of the t30-indication(CNG sent) signal. If network latency is acceptable, then Gl responds with the t30-indicatior(DoV.8) signal (Fig. 1). If network latency is unacceptable, then Gl responds with the t30-indicator(Dolowspeed) signal (Fig. 3). Normally, G2 and F2 have up to 4 seconds to respond with a V.8 signal, so it is proper to allow G2 to continue with CNG until G2 receives the t30-indicator(DoV.8/Dolowspeed) signal.
Referring to Figures 2A-2B, a flowchart of an exemplary network latency recovery process in accordance with the signalling and communications system C of claim 1 is shown. The process begins in step 200 where Fl transmits a CNG to Gl. Next, in step 202, Gl detects the CNG and in response sends the t30-indicator(CNG) signal to G2. G2 is thereby informed to start transmitting CNG. From step 202, control proceeds to step 204 where Gl starts its timer 400 (Fig. 4). Control next proceeds to step 206 where it is determined by Gl if a CNG sent signal has been received from G2. Control remains in step 206 until the CNG sent signal is received from G2. When the CNG sent signal is received, control proceeds to step 208 where Gl stops its timer 400. Based on the starting time and stopping time of the timer 400, Gl now stores a network latency timer value 408 (Fig. 4). When the network latency timer value 408 is too long, the high speed modem connection (in this case, a V.8 connection) fails. Until the CNG sent signal is received, Gl holds off transmission of an ANSam signal.
Next, in step 210, it is determined if the timer value 408 is below an acceptable latency threshold 404 (Fig. 4). If so, then control passes to step 212 where Gl transmits the t30-indicator(DoV.8) signal to G2. Next, in step 213, Gl continues transmitting ANSam since the timer value 408 was below an acceptable latency threshold 404. From step 213, control proceeds to step 214 where G2 ceases CNG transmission and transmits CM based upon the CM contents of F 1. Next, the network latency recovery process is completed in step 216.
Referring to Figure 3, the communications system C and associated signalling is shown for an unacceptable network latency. The Fl is shown sequentially providing two CNG signal sequences and a DCS signal sequence; Gl is shown sequentially providing a CED signal sequence and a DIS sequence; G2 is shown sequentially providing two CNG signal sequences and a DCS signal sequence; and F2 is shown sequentially providing an ANSam signal sequence and a DIS signal sequence. The design and operation of these signal sequences are understood in the art. In terms of Figure 2, steps 210-214 are specific to Figure 3. Steps 200-10 are applicable to both Figure 1 and Figure 3. In step 210, if the timer value 408 is above the acceptable latency threshold 404, then control passes to step 218 where Gl transmits the t30-indicator(Dolowspeed) signal to G2 (Fig. 3). Next, in step 220, Gl transmits CED, instead of ANSam, forcing Fl to use V.17 (a standard for data signalling rates up to 14,400 bit/s) and lower procedures. A switch from one modem version to a previous modem version has generally been termed a "fallback." Gl continues to send CED while the timer value 408 is above the acceptable latency threshold 404. From step 220, control passes to step 222 where G2 continues with its CNG transmission, forcing F2 to use V.17 and lower procedures. The network latency recovery process is then completed in step 216. Referring to Figure 4, exemplary components of a calling modem M in the calling gateway Gl is shown. The modem M includes a comparison block 402 coupled to a timer 400, a latency threshold 404, and a modem connection (or modulation mode) selection block 406. The timer 400 stores the network latency value 408 described above. The comparison block 402 compares the network latency value 408 to the network latency threshold 404 described above. Based on the result of that comparison, the modem connection selection block 406 generates either the t30-indicator(DoV.8) signal or the t30-indicator(Dolowspeed) signal. If the network latency value 408 is less than the latency threshold 404, then the modem connection selection block 406 generates a t30-indicator(DoV.8) signal. If the network latency value 408 is greater than the latency threshold 404, then the modem connection selection block 406 generates the t30-indicator(Dolowspeed) signal. It should be understood that the illustrated components can be implemented in a variety of ways (hardware or software).
Thus, when network latency is greater than an acceptable value, a high speed modem connection is bypassed for a low speed modem connection. The high speed modem connection, for example, can be a V.8 modem connection, and the low speed modem connection can be a Group 3 modem connection. Also, the high speed modem connection can be a V.34 half-duplex connection. It should be understood that the network latency recovery techniques described herein are applicable to a variety of modem connections or modulation modes. In addition, while network latency recovery is described in a modem context, it should be understood that the network latency recovery techniques described herein are applicable to other communication devices with similar structure and/or operation. Other ways of suspending or terminating a high speed modem connection based on current network latency are possible. Likewise, other ways of selectively operating a high speed modem connection and a low speed modem connection based on current network latency are possible.

Claims

1. A communications system including an internet protocol network, the system characterized by: a calling modem (M) coupled to the internet protocol network, the calling modem (M) including a timer (400), the timer (400) being operable to store a network latency value (408), the calling modem (M) being operable to compare the network latency value (408) to a network latency threshold (404), to transmit a low speed modem connection selection signal if the network latency value (408) is greater than the network latency threshold (404), and to transmit a high speed modem connection selection signal if the network latency value (408) is less than the network latency threshold (404); and an answering modem coupled to the internet protocol network, the answering modem being operable to receive the low speed modem connection signal and the high speed modem connection signal.
2. The communications system of claim 1, further comprising: a calling facsimile terminal (Fl) coupled to the calling modem; and an answering facsimile terminal (F2) coupled to the answering modem.
3. The communications system of claim 1, wherein a calling gateway (Gl) includes the calling (M) modem and an answering gateway (G2) includes the answering modem.
4. The communications system of claim 1, wherein the high speed modem connection comprises a V.8 modem connection.
5. The communications system of claim 1, wherein the low speed modem connection comprises a Group 3 connection.
6. The communications system of claim 1, wherein the high speed modem connection comprises a V.34 half-duplex connection.
7. A calling modem characterized by: a timer (400) to store a network latency value (408); a comparison block (402) compare the network latency value (408) and a network latency threshold (404); and a modem connection selection block (406) to transmit a low speed modem connection selection signal if the network latency value (408) is less than the network latency threshold (404) and to transmit a high speed modem connection signal if the network latency value (408) is greater than the network latency threshold (404).
8. The calling modem of claim 7, wherein the high speed modem connection comprises a V.8 modem connection.
9. The calling modem of claim 7, wherein the low speed modem connection comprises a Group 3 connection.
10. The calling modem of claim 7, wherein the high speed modem connection comprises a V.34 half-duplex connection.
11. A method of handling network latency, comprising by the steps of: storing a network latency value (408); comparing the network latency value (408) to a network latency threshold (404); transmitting a low speed modem connection signal if the network latency value (408) is less than the network latency threshold (404); and transmitting a high speed modem connection selection signal if the network latency value (408) is less than the network latency threshold (404).
12. The method of claim 1 1, wherein the high speed modem connection selection signal selects a V.8 modem connection.
13. The method of claim 1 1, wherein the low speed modem connection selection signal selects a Group 3 connection.
14. The method of claim 11, wherein the high speed modem connection selection signal selects a V.34 half-duplex connection.
15. A method of handling network latency, the method including the step of operating a high speed modem connection, the method comprising the steps of: measuring network latency; comparing the network latency to a network latency threshold (404); continuing operation of the high speed modem connection if the network latency is less than the network latency threshold (404); and terminating the high speed modem connection if the network latency is greater than the network latency threshold (404).
16. The method of claim 15, further comprising the step of: establishing a low speed modem connection if the network latency is greater than the network latency threshold (404).
17. The method of claim 16, further comprising the step of: providing a low speed modem selection signal if the network latency is greater than the network latency threshold (404) to indicate to perform the establishing a low speed modem connection step.
18. The method of claim 16, wherein the low speed modem connection comprises a Group 3 connection.
19. The method of claim 15, wherein the high speed modem connection comprises a V.8 modem connection.
20. The method of claim 15, further comprising the step of: providing a high speed modem selection signal to indicate to perform the continuing operation step if the network latency is less than the network latency threshold (404).
21. The method of claim 15, wherein the high speed modem connection comprises a V.34 half-duplex connection.
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