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Question 7/15 - Voice gateway equipment

(Continuation of Questions 8 and 21/15 and part of Question 5/15)

Background and justification

This Question deals with the General Switched Telephone Network (GSTN)/Internet Protocol (IP) gateway equipment known as TIGIN (Transport Network Equipment for Interconnecting the GSTN to networks optimized for Internet protocol and ATM Networks). Circuit switched systems and equipment have traditionally transported voice and voice-band traffic in international networks. With the advent of networks using Internet Protocol and ATM, and as a result of the considerable growth in these types of networks, more and more speech traffic is expected to be carried over these transport networks.

For the next several years, much of this voice traffic will pass through equipment interconnecting the GSTN and networks optimized for internet protocol and/or ATM networks. For this reason, there is a need to ensure a high quality of service for speech carried in part or wholly via networks optimized for Internet Protocol or ATM networks. Recommendations for protocols exist or are being developed for converting and transporting GSTN originated voice and voice-band data over packet and cell-based networks. The interworking of these is covered by other Recommendations. It is the purpose of this Question to encompass these recommendations under various equipment specifications and to include performance requirements and tests that will help ensure that the correct and appropriate functionality is present in this equipment. It is not proposed to redefine these existing protocols or define new ones.

This Question will be responsible for the G.799 series of Recommendations and the parts of G.766 series Recommendations that deal with TIGIN operation.


  • What functionality, interfaces, performance requirements and functional tests need to be specified and recommended for Transport network equipment for Interconnecting GSTN and networks optimized for Internet protocol and/or ATM Networks (TIGIN) to provide good performance in the network?
  • What impact do speech-processing issues related to this TIGIN equipment have on overall network performance?
  • What management interfaces should be recommended for TIGIN gateways?

Study items

Study items to be considered include:

  • Overall TIGIN functionality
  • Interfaces to GSTN, ATM and networks optimized for internet protocol
  • Protocols and Internet interworking functions to be supported
  • Control and operation interfaces
  • Level offset, echo return loss and background noise issues
  • Functionality to ensure minimal end-to-end delay
  • Effects of placing TIGINs in tandem and methods of minimize the impact of these effects
  • Degradation caused by low bit rate coders and other non-linearities, and Recommendations to minimize the impact of these degradations
  • Impact of evolving terminal equipment such as modems, fax, wireless and multimedia terminals
  • Impact of cell-loss on voice/voice-band/audio performance and therefore its impact on the facility and performance thresholds recommended for ATM/B-ISDN transmission
  • Impact of packet-loss on voice/voice-band/audio performance and its impact on the facility and performance thresholds recommended for IP networks
  • Interface from ATM networks and networks optimized for internet protocol interface to other voice systems such as packetized and non-packetized multiplication systems, especially those used in mobile and cellular environments
  • Study of possible optimization of TIGIN gateway functionality to take advantage of the way in which ATM networks and networks optimized for internet protocol transport voice and voice-band data traffic ;
  • Study methods of utilizing the principles learned in DCME and PCME to efficiently utilize bandwidth in a TIGIN gateway
  • Determine the requirements of using various speech coding algorithms for transport over networks optimized for internet protocol and ATM networks
  • Determine method of supporting T.38 facsimile traffic

Specific tasks

  • Revise Recommendation G.799.1 to include items listed as for further study
  • Develop an expanded version of G.799.1 to include support of ATM networks
  • Update G.776.1 as necessary


  • ITU-T SG4 on TMN
  • ITU-T SG 7 on Data Protocols
  • ITU-T SG 8 on facsimile
  • ITU-T SG 11 on Signalling
  • ITU-T SG 12 on performance
  • ITU-T SG 13 on architectures
  • ITU-T SG 16 on protocols
  • ITU-R TG 8/1 on IMT-2000
  • IETF SIGTRAN and MEGACO Working Groups on interface protocols
  • ETSI TIPHON on architectures
  • ATM Forum VMOA group on Protocols
  • IMTC – VoIP Activity Group on Protocols
  • ITU-R SG4 WP4B on voice on mixed terrestrial/satellite networks


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Updated : 2004-10-21