(Enlarged continuation of Question 18/12 studied in 1997-2000)

Type of question

Task-oriented leading to a new ITU-T Recommendation and to revision of Recommendations in the G.100 series.

Background

Still, many of the Recommendations in the G.100-Series are presently based on configurations where the national part of an international connection is usually terminated by a single analogue telephone set or by a digital terminal. Consequently, these Recommendations may not explicitly consider PABXs (Private Automatic Branch Exchange) or networks like private ones or the Internet as a possible termination. However, modern private networks, mainly those of large size and/or using new technologies, will contribute in a specific, possibly significant amount to the overall transmission quality.

• Recommendations G.107, G.108 and G.109 - which are based on the E-model - provide the means for a flexible end-to-end approach to planning of speech transmission quality, whereas other Recommendations in the G.100 series still focus on allocation of single parameters to national or international segments of a connection.
• Recommendation G.175 (09/99) deals with the digital interconnection of public ISDN/PSTN and private networks. The primary application is to the overall quality of speech transmission for 3.1 kHz handset telephony using handsets, independent of all other types of services (e.g. facsimile and voice-band data) provided by those networks. The intention is to give guidance for transmission planning purposes, not only for a given network operator, but also for negotiations between the involved network operators. For the purpose of this Recommendation, only call paths between the private network and other networks (private or public) including telephone sets or other speech terminals are considered.

Consequently, the case of one network providing through-connections between two of it's interfaces to other networks (when this network is part of a concatenation of multiple networks) has not been considered up to now.

NOTE 1 - The term "private network" is used here to cover a wide range of large private networks (several intermeshed PABXs), serving customers like banks with branch offices, mainly in metropolitan areas, but also in some cases extending over the whole national geographical area.

NOTE 2 - The term "public network" is used here for any network providing transmission and switching functions as well as features which are available to the general public, not restricted to a specific user group. In this context, the word "public" does not imply any relation to the legal status of the network operator.

Text of the question

The main Question is what guidance can be provided in transmission planning for the interconnection of the public PSTN/ISDN with multiple other networks (e.g. private networks, Internet) including the cases of multiple concatenated public networks, based on a flexible allocation of transmission impairments in contrary to a rigid partitioning of parameter values?

Which transmission impairments are most important in a modern digital environment and should be considered during planning for calls that are handled to a great extent by other networks?

Is it possible to define a planning principle which enables the planner of a network which is part of an interconnection of the public PSTN/ISDN with multiple other networks (e.g. private networks, Internet) including the cases of multiple concatenated public networks to perform planning using an end-to-end consideration via the public ISDN/PSTN, resulting in a value for the expected speech transmission quality?

Study items

It is proposed that the case of concatenation of multiple networks involving both the PSTN/ISDN and other networks should be studied.

• What consequences must be taken into account with respect to multiple operators in the public network area, new services like virtual private networks, the Internet and new signalling systems?
• Are revisions of ITU-T G-Series Recommendations necessary, to take care of concatenation of the public PSTN/ISDN with multiple other networks (e.g. private networks, Internet) including the cases of multiple concatenated public networks?

Objectives and schedule

• New ITU-T Recommendation giving guidance for transmission planning using the E-Model in cases of concatenation of the public PSTN/ISDN with multiple other networks (e.g. private networks, Internet) including the cases of multiple concatenated public networks.
• Revision of other ITU-T G-Series Recommendations as indicated above.
• Provide educational support to projects in that area, e.g. ETSI EP TIPHON

Relationship with other activities

• With other ITU-T Recommendations: Under study
• With other ITU-T Study Groups:
  SG 2 (Network operation)
  SG 11 (Signalling Aspects)
  SG 13 (ITU-T I.300-Series of Rec.'s)
  SG 15 (System Specification)
  SG 16 (Speech coding)
• With other Bodies: ETSI EP TIPHON, ETSI TC STQ