Implementers Guide for H.248 Sub-Series of Recommendations1

Implementers Guide for H.248 Sub-series of Recommendations1

Summary

This document is a compilation of reported defects identified in the ITU-T H.248 sub-series of Recommendations currently in force. It must be read in conjunction with the Recommendations to serve as an additional authoritative source of information for implementers. The changes, clarifications and corrections defined herein are expected to be included in future versions of affected H.248 sub-series Recommendations.

This revision contains all updates submitted up to and including those at Study Group 16 meeting in May 2003.

This document was approved by ITU-T Study Group 16 on 30 May 2003 and obsoletes the earlier version of this Implementors Guide approved on 25 October 2002.

Implementers Guide for H.248 Sub-series of Recommendations1

Change Log

(All changes that were included in H.248.1 v1 (03/02) are omitted here.)

V10 (Bruges, June 2002)

Changed references to H.248 Amendment 1 to H.248.1 and added new sections for changes common to H.248.1 v1 and v2 and sections exclusively for H.248.1v2, renumbering the existing sections and IG item numbers.

New:

6.1Specify types for rtp/jit and rtp/delay in Annex E.12.4

6.2 Define the ‘#’ symbol in INEQUAL in text encoding

6.3Empty Descriptor Syntax

6.4Define the symbol for NULL Context in text encoding

6.5Corrections to Appendix A example statistics

6.6Corrections to Package Guidelines for Statistics in 12.1.5

6.7Specification of the meaning of automatic in E.13 tdm package

V11 (Geneva, October 2002)

Modification:

6.7 Added additional changes to gain

New:

6.8Protocol Version Negotiation

6.9Statistics and Move

6.10Incorrect reference

6.11Additional Codepoint for Annex C

6.12Wildcarding Principles

11.1Additional error codes (this is a new section for H.248.8 and renumbers all higher IG sections)

V12 (San Jose, February 2003)

Modification:

11.1Package-defined Error Codes (Section renamed – no other changes)

New:

6.13 Wildcarding in the Topology Descriptor

6.14 Binary Value for Packetization Time (Annex C)

10.3Announcement Package Editorial Error

11.2Additional Error Code

V13 (Geneva, May 2003)

New:

6.15Modification of Terminations by MGCs

6.16Optional Command in an Action

6.17Ordering of Transactions

6.18Replies to Actions with no Commands

Contact Information

Table of Contents

1Scope

2Introduction

3Defect Resolution Procedure

4References

5Nomenclature

6Technical and Editorial Corrections to H.248.1 Version 1 (03/2002)

6.1Specify types for rtp/jit and rtp/delay in Annex E.12.4

6.2Define the ‘#’ symbol in INEQUAL in text encoding

6.3Empty Descriptor Syntax

6.4Define the symbol for NULL context in text encoding

6.5Corrections to Appendix A example statistics

6.6Corrections to Package Guidelines for Statistics in 12.1.5

6.7Specification of the meaning of automatic in E.13 tdm package

6.8Protocol Version Negotiation

6.9Statistics and Move

6.10Incorrect Reference in v2

6.11Additional Codepoint for Annex C

6.12Wild Carding Principles

6.13Wildcarding in the Topology Descriptor

6.14Binary Value for Packetization Time (Annex C)

6.15Modification of Terminations by MGCs

6.16Optional Commands in an Action

6.17Ordering of Transactions

6.18Replies to Actions with no Commands

7Technical and Editorial Corrections to H.248.2 (2000)

7.1Package ID of Text Telephone Package in H.248.2 shall be 0x0010

7.2Value of NAK

7.3Correction in parameter values in Call Type Discrimination package in H.248.2

7.4Correction in parameter values in Call Type Discrimination package in H.248.2

7.5Missing Keywords in H.248.2 Clause 8.1.2 (ex-F.8.1.2)

7.6Duplicated propertyID in H.248.2 Clause 8.1 (ex-F.8.1)

7.7Inconsistencies in Fax Transport property in H.248.2 Clause 9.1 (ex- F.9.1)

7.8Duplicated PropertyID in H.248.2 Clause 10.1 (ex-F.10.1)

8Technical and Editorial Corrections to H.248.3 (2000)

8.1Correct Binary PropertyIDs in Soft Key Package

8.2Correct Binary DigitMap Completion EventID in Keypad Package

9Technical and Editorial Corrections to H.248.4 (2000)

9.1SCTP Streams

10Technical and Editorial Corrections to H.248.7 (2000)

10.1Superfluous information

10.2Announcement Playing Clarification

10.3Announcement Package Editorial Error

11Technical and Editorial Corrections to H.248.8 (2002)

11.1Package-defined Error Codes

11.2Additional Error Code

12Technical and Editorial Corrections to RFC-3015

12.1Typographical Errors in the ASN.1 in RFC3015

13Implementation Clarifications for H.248.1 Version 1 (03/2002)

14Implementation Clarifications for H.248.4 (2000)

14.1MTP3 Interworking

Annex: H.248 RecommendationSub-series Defect Report Form

Implementers Guide for H.248 Sub-series of Recommendations1

Revised Implementers Guide for the
H.248 Sub-series of Recommendations

1Scope

This guide resolves defects in the following categories:

• editorial errors
• technical errors, such as omissions and inconsistencies
• ambiguities

In addition, the Implementors' Guide may include explanatory text found necessary as a result of interpretation difficulties apparent from the defect reports.

This Guide will not address proposed additions, deletions, or modifications to the Recommendations that are not strictly related to implementation difficulties in the above categories. Proposals for new features should be made through contributions to the ITU-T.

2Introduction

In order to give a clearer understanding of the text components and versions of Recommendation H.248, the Recommendation, including its annexes, has been renumbered into a sub-series according to the table below.

Renumbering table for Recommendation H.248

Title

The H.248 Implementors’ Guide is a compilation of reported defects for all versions of the H.248.x sub-series of Recommendations. In this edition of the Guide, reported defects identified as of 05/2003 are given for:

–H.248.1 version 1 (06/2000 plus corrections and editorial modifications of 03/2002)

–H.248.2 (11/2000)

–H.248.3 (11/2000)

–H.248.4 (11/2000)

–H.248.7 (11/2000)

–RFC3015

The Guide must be read in conjunction with the H.248.x sub-series of Recommendations to serve as an additional source of information for implementors. The changes, clarifications and corrections defined herein are expected to be included in future versions of affected H.248.x Recommendations.

3Defect Resolution Procedure

Upon discovering technical defects with any components of the H.248.x sub-series Recommendation, please provide a written description directly to the editors of the affected Recommendations with a copy to the Q.3/16 Rapporteur. The template for a defect report is located at the end of the Guide. Contact information for these parties is included at the front of the document. Return contact information should also be supplied so a dialogue can be established to resolve the matter and an appropriate reply to the defect report can be conveyed. This defect resolution process is open to any interested party. Formal membership in the ITU is not required to participate in this process.

4References

This document refers to the following H.248.x sub-series Recommendations:

–ITU-T Recommendation H.248.1 Version 1 (03/2002), Media Gateway Control Protocol

–ITU-T Recommendation H.248.1 Version 2 (05/2002), Media Gateway Control Protocol

–ITU-T Recommendation H.248.2 (2000), Facsimile, Text Conversation and Call Discrimination packages

–ITU-T Recommendation H.248.3 (2000), User interface elements and action packages

–ITU-T Recommendation H.248.4 (2000), Transport over Stream Control Transmission Protocol (SCTP)

–ITU-T Recommendation H.248.7 (2000), Generic Announcement Package

–ITU-T Recommendation H.248.8 (2002), Error Code and ServiceChange Reason Descriptions

5Nomenclature

In addition to traditional revision marks, the following marks and symbols are used to indicate to the reader how changes to the text of a Recommendation should be applied:

6Technical and Editorial Corrections to H.248.1 Version 1 (03/2002)

6.1Specify types for rtp/jit and rtp/delay in Annex E.12.4

E.12.4 Statistics

[Begin Correction]

Jitter

StatisticID: jit (0x0007)

Requests the current value of the interarrival jitter on an RTP stream as defined in IETF RFC 1889. Jitter measures the variation in interarrival time for RTP data packets.

Type: double

Possible Values: any 64 bit integer

Delay

StatisticID:delay (0x0008)

Requests the current value of packet propagation delay expressed in timestamp units. Same as average latency.

Type: double

Possible Values: any 64 bit integer

[End Correction]

6.2Define the ‘#’ symbol in INEQUAL in text encoding

B.2 ABNF Specification

[Begin Correction]

INEQUAL = LWSP (">" / "<" / "#" ) LWSP; “#” means ‘not equal’

[End Correction]

6.3Empty Descriptor Syntax

B.2 ABNF Specification

[Begin Correction]

signalsDescriptor = SignalsToken [ LBRKT [ signalParm

*(COMMA signalParm)] RBRKT ]

[End Correction]

[Begin Correction]

auditReturnParameter = (mediaDescriptor / modemDescriptor /

muxDescriptor / eventsDescriptor /

signalsDescriptor / digitMapDescriptor /

observedEventsDescriptor /

eventBufferDescriptor /

statisticsDescriptor / packagesDescriptor /

errorDescriptor / auditReturnItem)

auditReturnItem = (MuxToken / ModemToken / MediaToken /
DigitMapToken / StatsToken /
ObservedEventsToken / PackagesToken )

[End Correction]

[Begin Correction]

;at-most-once, and DigitMapToken and PackagesToken are not allowed

;in AuditCapabilities command

auditItem = ( auditReturnItem / SignalsToken /
EventBufferToken / EventsToken )

auditItem = ( MuxToken / ModemToken / MediaToken /

SignalsToken / EventBufferToken /

DigitMapToken / StatsToken / EventsToken /

ObservedEventsToken / PackagesToken )

[End Correction]

6.4Define the symbol for NULL context in text encoding

B.2 ABNF Specification

[Begin Correction]

;The values 0x0, 0xFFFFFFFE and 0xFFFFFFFF are reserved,

;“-“ is used for NULL context.

ContextID = (UINT32 / "*" / "-" / "$")

[End Correction]

6.5Corrections to Appendix A example statistics

Appendix A.1.1 step 22

[Begin Correction]

From MG2 to MGC:

MEGACO/1 [125.125.125.111]:55555

Reply = 50009 {

Context = 5000 {

Subtract = A5555 {

Statistics {

nt/os=45123, ; Octets Sent

nt/or=45123, ; Octets Sent

nt/dur=40000 ; in milliseconds

}

},

Subtract = A5556 {

Statistics {

rtp/ps=1245, ; packets sent

nt/os=62345, ; octets sent

rtp/pr=780, ; packets received

nt/or=45123, ; octets received

rtp/pl=10, ; % packets lost

rtp/jit=27,

rtp/delay=48 ; average latency

nt/dur=38000 ; in millisec

}

}

}

}

[End Correction]

6.6Corrections to Package Guidelines for Statistics in 12.1.5

12.1.5 Statistics

[Begin Correction]

Statistics defined by the package, specifying:

Statistic name: only descriptive.

StatisticID: Is an identifier

StatisticID is used in a StatisticsDescriptor

Description

Units: unit of measure, e.g. milliseconds, packets

Type: One of:

Boolean

String: UTF-8 string

Octet String: A number of octets. See Annex A and Annex B.3 for encoding

Integer: 4 byte signed integer

Double: 8 byte signed integer

Character: Unicode UTF-8 encoding of a single letter.

Could be more than one octet.

Enumeration: One of a list of possible unique values (See 12.3)

Sub-list: A list of several values from a list. The type of sub-list SHALL also be specified. The type

shall be chosen from the types specified in this section (with the exception of sub-list). For example, Type: sub –list of enumeration. The encoding of sub-lists is specified in Annexes A and B.3.

Boolean

Possible Values:

A package must indicate the unit of measure, e.g. milliseconds, packets, either here or along with the type above, as well as indicating any restriction on the range.

[End Correction]

6.7Specification of the meaning of automatic in E.13 tdm package

C.1 General media attributes

[Begin Correction]

[End Correction]

E.13.1 Properties

[Begin Correction]

Gain Control

PropertyID: gain (0x000a)

Gain control, or usage of of signal level adaptation and noise level reduction is used to adapt the level of the outbound signal. However, it is necessary, for example for modem calls, to turn off this function. When the value is set to “automatic”, the termination serves as an automatic level control (ALC) with a target level provisioned on the MG and the direction being outward.

Type: integer

Possible values:

The gain control specifies the gain in decibels (positive or negative), with the maximum positive integer, 214748646 (0x7fffffff), reserved to represent "automatic".parameter may either be specified as "automatic" (0xffffffff), or as an explicit number of decibels of gain (any other integer value). The default value is provisioned in the MG.

Defined in: LocalControlDescriptor

Characteristics: read/write

[End Correction]

6.8Protocol Version Negotiation

11.3 Negotiation of protocol version

[Begin Correction]

A ServiceChange command from a MG that registers with an MGC shall contain the version number of the protocol supported by the MG in the ServiceChangeVersion parameter. Regardless of the version placed in the ServiceChangeVersion parameter the message containing the command shall be encoded as a version 1 message. Upon receiving such a message, if the MGC supports only a lower version, then the MGC shall send a ServiceChangeReply with the lower version and thereafter all the messages between MG and MGC shall conform to the lower version of the protocol. If the MG is unable to comply and it has established a transport connection to the MGC, it should close that connection. In any event, it should reject all subsequent requests from the MGC with Error 406  Version Not Supported.

If the MGC only supports higher version(s) than the MG, it shall
reject the association with Error 406 Version Not Supported.