Subject: ITU-T Study Group 15 Question 21

From: Tom-PT Taylor <[email-masked]>
Date: Fri, 17 Sep 1999 12:36:38 -0500

ITU-T Study Group 15 studies transmission interfaces.  They have been
working for the last year on a new question (21/15), dealing with
transmission requirements for gateways between the SCN and IP networks.
This seems to go a bit beyond the basics, and people following Megaco may
wish to have a look at the work.  The following is an extract from a Study
Group 15 meeting report dated June/July 1999.  For further details, contact
Jerry Skene at Tellabs.  The next meeting of the group is Oct. 4-8 in the
Washington, D.C. area.
Mr. Jeremy SKENE
Tellabs Operations, Inc.
 45085 University Drive
Ashburn, VA 20147 USA
Tel.: +1 703 724 7302
Fax: +1 703 724 7202
email: [email-masked]

I'm not sure how material it is to their work, but I suspect from the
material below that their view of architecture may differ somewhat from that
of SIGTRAN.

3.6     Question 21/15 - Signal Processing Aspects of Networks Optimised for
Internet Protocol
3.6.1   Summary
The experts of Question 21/15 (Functionality and Interface Specifications
for GSTN Transport Network Equipment for Interconnecting GSTN and IP
Networks) met from 21-June - 2-July, 1999 in Geneva, under the
Rapporteurship of Mr. Jeremy Skene (Tellabs, Finland). The main objective
was to advance the study of GSTN Transport Network Equipment for
Interconnecting GSTN and IP Networks(TIGIN), Recommendation G.TIGIN.
Eleven incoming liaisons were reviewed and 5 liaisons were prepared to be
sent (Annex 8 to COM 15-R 38)..
The experts agreed that work would continue under the question in the next
Study Period. A draft text of the new question was prepared.
Two interim meetings were planned (Annex 6 to COM 15-R 38).
3.6.2   Agreements
The following agreements were made during the meeting:
EDH
Working methods for the Question were discussed. The Rapporteur indicated
that interim work will be conducted via a web-based technology provided by
the UTI-IT department, called WebBoard. This is a discussion group system
that allows participants to contribute to specific area of work carried out
by Q.21. To sign on to the board, it is first necessary to have a user ID
and password. Delegates interested in subscribing to this board should send
a request via email to the Rapporteur ([email-masked]).
The URL of the WebBoard is: http://wwwp.itu.int:8080/~itu.t/.
It was agreed that the Rapporteur will add the Q.21 mailing list itself to
the WebBoard user list, so that all Q.21 list members will receive email
notification of new messages.
TD20(GEN) was presented. This describes an update on EDH issues resulting
from the April 1999 meeting of TSAG.
TD11(PLEN) was presented. This describes EDH progress, including an
innovative method for cataloguing documents developed by Q.4/15. The Q.21/15
Rapporteur indicated that he would use this method for the next meeting if
possible.
General Topics
TD2(PLEN) was presented. This contained information from the Chairman of
SG15, including the date of the next SG15 meeting. This is to be held 3- 14
April, 2000, in Geneva.
Review of Interim Activities
TD18(WP2/15) was presented. This was the meeting report for the Q.21/15
meeting in San Francisco. A typographical error on page 6 was corrected,
changing reference from Q.TIGIN to G.TIGIN.
TD23(WP2/15) was presented. This is concerning the work of Q.9/11,
indicating that they are commencing work on echo control logic for VOIP
networks. It was noted that this work will affect the Media Gateway
Controller more than TIGIN equipment.
TD22(WP2/15) was presented. This is information concerning the work in ETSI
TIPHON group, informing us of their work on VOIP. This included an ETSI
document describing network architecture and reference configurations being
used in their work. This is relevant to the work being done in Q.21/15, and
it was used several times during our meeting as a reference document. It was
noted that Q.21/15 uses the decomposed gateway model described here.
Review of Incoming Liaisons
TD11(GEN) was presented. This is a liaison statement form SG12, describing
the work they are doing on the transmission performance impact of
introducing IP-based technology into the PSTN. It was noted that draft
Recommendation G.177 has relevance for Q.21/15's work, and Q.21 will follow
the progress of this work.
TD12(GEN) and TD13(GEN) were presented. These were liaison statement from
SG13, describing their work on GII and IP projects, respectively. TD12(GEN)
announced that SG 13 will convene an IP experts meeting in September. A
liaison statement was sent to the source of TD12(GEN), indicating that
several Q.21/15 delegates are interested in attending this meeting.
TD14(GEN) was presented. This is a liaison statement from SG13 requesting
information on work relevant to IP-related work performed in the IETF. It
was noted that IETF working groups relevant to Q.21/15 include the Media
Gateway Control Protocol (MEGACO) and Signalling Transport (SIGTRAN) groups
within the Transport Area. Information was sent to SG15 management
indicating these relationships, as part of an outgoing liaison statement.
TD19(GEN) was presented. This contained information on guidelines for
ISOC/IETF collaboration.
TD21(GEN) was presented. This contained information on procedures for prompt
transmittal of liaison statements.
TD23(GEN) was presented. This contained guidelines on TSB Patent Policy.
TD25(GEN) was presented. This contained information on voice over XDLS from
the ADSL forum. It was noted that TIGIN gateway equipment will not initially
include specifications for direct connection to DSL facilities.
TD34(GEN) was presented. This was a response from SG4 to a liaison from SG13
on the ITU-T IP project.
TD6(WP2/15) was presented. This informed us of a new Recommendation, I.380
on performance parameters for IP packet transfer. This Recommendation will
be studied to determine its relevance to Q.21/15's work. A liaison statement
was sent to WP4/13, informing them of the work being done in our question,
and requesting guidance on the performance requirements of TIGIN gateways.
TD12(PLEN) was presented. This was a report on recent IETF activities
related to optical transmission.
G.TIGIN
WD 21-5 was presented. This is a statement of the workplan for the Question.
It was agreed to change in the first item the term voice coding to signal
processing, and to add the items OA&M, bearer control, and signalling
translation. Contributions are requested on text defining bearer control as
separate from call control.
It was agree to add a new item addressing the issue of tandem free
operation. It was noted that in many instances calls will be placed from a
mobile network, routed through an IP network, and terminated on a mobile
network. In order to realize acceptable speech quality, it will be necessary
to minimize the number of transcoders used in such a call. Contributions are
requested on text for G.TIGIN on this topic.
A study item will be added concerning the physical integration of a TIGIN
gateway with an MGC. Requirements and test on the combined equipment need to
be described.
A study item on availability will be included. Contributions are requested
on requirements and tests for this.
A typographical error was corrected, changing DCEM to DCME. The term N-ISDN
was changed to B-ISDN.
TD27(GEN) was discussed. It was agreed that echo control logic would be
performed within the MGC, and not within a TIGIN gateway. It was agreed that
any discussion of echo control logic in G.TIGIN would refer to Q.115, as
updated by Q.9/11 for inclusion of echo control logic for IP networks.
TD28(GEN) was presented. This is the revision 2 draft text of a subset of
G.TIGIN. Changes made include:
*       change reference to DS1, DS3 to the actual bit rate, followed by
reference to G.704, throughout the document
*       in section 2, change the figure 1 reference to be a figure 2.1
reference, remove reference to gatekeeper, add TDM interface, IP interface,
change speech compression/decompression to signal processing
*       it was agreed to add separate paragraphs following figure 2.1
briefly describing the main block shown in the figure.
*       Figure 2.1 was changed as follows: text on TDM and IP interfaces was
removed, boxes echo canceller & voice features were combined into a box
labelled signal processing, a box labelled signalling gateway was added,
with the note that is was optional, reference to PCC protocol, TMN, SNMP was
removed, LAN was changed to Network Interface
*       It was agreed to add text to section 2 describing the fact that a
TIGIN gateway may need to support some signalling gateway functions when TDM
channel associated signalling is used.
*       In section 3, figure 3.1 was changed as follows: a new line labelled
'Facility Associate Signalling' was added between the GSTN cloud and
G.TIGIN, the term 'Media Gateway' will be changed to 'TIGIN Gateway' (here
and throughout the document), 'TDM Transport Interface' and associated
recommendations with be changed to 'TDM Bearer Interface', 'IP Transport
Interface' and associated recommendations will be changed to 'IP Bearer
Interface', a new line connection G.TIGIN to MGC will be added, labelled
'signalling over IP', a label 'signalling over IP' will be added to the line
connecting SC to MGC, the SC box will be moved to the left of the MGC box,
indicating that signalling entering this box from the outside originates
with the TDM network
*       It was agreed that more than one figure, similar to figure 3.1 would
be useful, to illustrate the various scenarios possible with different TIGIN
configurations.
*       It was stated that if a single network management/call control
interface was used and large volumes of network management traffic were
present, then call control bandwidth would suffer. It was therefore agreed
to add a new section on network interface performance requirements.
Contributions on this section are requested.
*       text to be included in section 3.1 stating that at least one of the
stated interfaces need to be supported
*       a defined list of IP bearer interfaces to be supported, including a
layered description of these (provided by Matt Holdrege), follows:
Layer 3         IP
Layer 2         PPP     FR      ATM
Layer 1         G.704, G.707, G.703, G.957
handling of IP over PPP to be defined as in IETF RFC 1661
handling of IP over Frame Relay to be defined as in IETF RFC 2427
handling of IP over ATM to be defined as in IETF RFC 1483 or MPLS
(contribution on IP/ATM to come)
handling of IP over SDH to be defined as in IETF RFC xxxx (approved, but
number not yet assigned.
*       Text to be included in section 3.2, stating that at least one of the
stated interfaces needs to be supported. Dario Parola of Lucent agreed to
provide a list of GSTN TDM bearer interfaces to be included here.
*       In Section 3.3 it was agreed to break section 3.3.1 up into two
subsections, 3.3.1.1 - Upper layers for PCC, and 3.3.1.2, lower layers for
PCC. Upper layer will be as defined in draft Recommendation H.GCP (to be
determined in September 1999), and the lower layers will be as defined in
section 3.1, and will include reference to common LAN interfaces.
*       There was discussion on how or if a TIGIN gateway would determine or
set packet size. Contributions are requested on this. A liaison was sent to
Q.13/16 requesting guidance on this.
*       A new, optional, section 3.4 will be added, tentatively titled TDM
Signalling Interface. This section will describe the method by which the
TIGIN gateway extracts and passes on facility associated signalling (FAS),
if required. It was noted that a TIGIN gateway must include a Signalling
Gateway if it is to support FAS. Subsections on FAS methods were agreed to
as follows, for placeholder purposes. Contributions on each item, including
the specific method in which each signalling method is to be supported and
the correct method of referencing the subject standards documents, are
requested. It is noted that if a TIGIN gateway makes use solely of SS7
signalling, then compliance with this section is not required.
*       SS7 Facility Associated Signalling
*       Q.931
*       R1 - Q.2
*       R2 - Q.400
*       placeholder for Q.SIG (ECMA)
*       placeholder for V 5.2 (G.965)
*       placeholder for GR-303 (Telcordia)
*       Channel Associated as per G.704
*       In section 4.1, it was agree to change the title 'voice features' to
'signal processing features'. This section will be broken into two sections,
one containing mandatory items, and one optional items. A mandatory coder
will be G.711.
*       It was agreed to remove section 4.4, titled 'Codec Characteristics'.
*       It was agreed that a section on reliability and performance would be
added, covering such items as redundancy, safety, reliability, etc.
Reference will be made to existing Recommendations covering international
switching equipment where relevant. Contributions are requested on this
section.
*       No changes were made to section 4.8 - Network Management.
Contributions are requested on this section.
*       Version 3 of G.TIGIN will be the output of this meeting is
reproduced in COM 15-R 46 and will be posted on the WebBoard by 23-July-99.
TD29(GEN) was presented. This is section 1.1 of the now decomposed draft
Recommendation G.TIGIN, containing the scope of G.TIGIN. It was agreed to
change the words 'transcoding protocols' to 'transcoding' in the first
paragraph.
TD30(GEN) was presented. This is section 1.2, 1.3 and 1.4 of G.TIGIN draft
Recommendation, describing References, Terms and Definitions, and
Abbreviations. A typographical error was changed in the Abbreviation
section, changing the term 'GSTN' used in the definition of GTSN to 'PSTN'.
Matt Noah of ADC Telecommunications has graciously agreed to be editor of
these sections. Q.21 participants are encouraged to send any requested
changes to these sections to the WebBoard
(http://wwwp.itu.int:8080/~itu.t/).
D.511 was presented. This delayed document contained requirements and
suggestions for Recommendation G.TIGIN, including a suggested breakdown of
items within the Recommendation, updated references, and specific
suggestions for text for several sections. Several specific changes were
made to the G.TIGIN draft (TD28(GEN)) as a result of this contribution.
These have been included in the discussion on TD28(GEN).
D.542 was presented. This delayed document contains guidelines on forming
Experiment Groups to improve the quality of the standards.
Outgoing Liaisons
Q.21/15 generated 5 outgoing liaisons (see Annex 8 to COM 15-R 38).
3.6.3   Future Work
Two interim meetings were planned as shown in Annex 6 to COM 15-R 38.
Representatives of SG15 will be attending the IP Experts Meeting hosted by
SG13 in September.

Tom Taylor
Advisor -- IPConnect Standards
E-mail: [email-masked] (internally, Tom-PT Taylor)
Phone and FAX: +1 613 736 0961

---

From: Matt Holdrege <[email-masked]>
Date: Fri, 17 Sep 1999 15:07:49 -0700

>material below that their view of architecture may differ somewhat from that

The ITU architecture doesn't differ from SIGTRAN at all. In fact, it is
totally aligned and once the SIGTRAN architecture document becomes an RFC,
it will very likely be an informative reference to the documents that this
ITU group produces.