Clarification of Byte Range Object Repair

[tlohmar]

Problem description

The operation of Byte Range Object Repair is not clear for MBS User Services:

• eMBMS (TS 26.346) uses the FDT Instance elements Alternate-Content-Location-1 and Alternate-Content-Location-2 to provide the URLs to the CDN for unicast repair.
• In TS 26.517, there is a NOTE in Clause 6.2.1:

The use of Alternate-Content-Location-1 and Alternate-Content-Location-2 is not supported.

• TS 26.502 CR0014r2 defines the "Object repair base URL" parameter for provisioning Object Repair in the MBSTF, but there is no description of how the MBS Client should construct URLs for Object Repair.

Suggested solution

Extend clause 6.2.1 in TS 26.517, adding more information about Object Repair URL construction.

Alternatively, extend clause 5.6 in TS 26.502, giving some high-level (stage 2) hints on URL construction.

[rjb1000]

I favour fixing this in TS 26.517 by specifying stage 3 procedures for Object Repair. A simple improvement to clause 6.2.1 could be:

Replace:

In order to fetch missing portions of an object, the MBS Client may use the Object Repair services. The Object Repair service is realized as a Byte-Range based File Repair, as specified in clause 9.3.6.2 of TS 26.346 [7].
NOTE: The use of Alternate-Content-Location-1 and Alternate-Content-Location-2 is not supported.

with:

In order to fetch missing portions of an object, the MBS Client may use the Object Repair service provided by the MBS AS at reference point MBS-4-UC, using the MBS User Service Announcement parameters specified in clause 5.2.8 to identify its endpoint address. The Object Repair service is realized as a Byte-Range based File Repair, as specified in clause 9.3.6.2 of TS 26.346 [7].
NOTE: The use of Alternate-Content-Location-1 and Alternate-Content-Location-2 to advertise the Object Repair parameters in the FLUTE FDT is not supported in the present document.

However, I'm not sure that clause 9.3.6.2 of TS 26.346 is entirely the correct reference. There may be differences in the procedure that need to be documented directly in TS 26.517, in which case an entirely new clause 6.3 should be added and referenced from here instead.

[tlohmar]

The current stage 3 (TS 26.517) does not support the parameters Object repair base URL and Object distribution base URL. Thus, more changes are needed.

[rjb1000]

@tlohmar has started drafting a CR to TS 26.517 in S4aI230060.

[rjb1000]

Ericsson CR contributed to SA4#123-e:

• TS 26.517 CR0009 "[5MBP3] Correction of parameter usage for Byte Range Object Repair" in S4-230507

[rjb1000]

Change Request revised and endorsed at SA4#123-e:

• TS 26.517 CR0009r1 "[5MBP3] Correction of parameter usage for Byte Range Object Repair" in S4-230688.

This is a candidate for merging into CR0001 at SA4#124 Berlin. @haudiobe to take care of this.

[rjb1000]

Late contribution from @tlohmar at SA4#124 (Berlin) was endorsed as the basis for further work:

• TS 26.517 CR0009r2 "[5MBP3] Correction of parameter usage for Byte Range Object Repair" in S4-231001

This contribution is to be merged into TS 26.517 CR0001 at the next meeting.

[rjb1000]

TS 26.517 CR0009r2 has been merged into the following ad hoc contribution:

• TS 26.517 CR0001r11 "[5MBP3] General Updates and Corrections" in S4aI230117.

[rjb1000]

No notable progress at SA4#125.

Latest draft CR contributed by @haudiobe was endorsed:

• TS 26.517 Rel-17 CR0001r13 "General Updates and Corrections" in S4-231394.

Pushing on to SA4#126.

[rjb1000]

No notable progress at SA4#126.

Latest draft CR contributed by @haudiobe was endorsed:

• TS 26.517 Rel-17 CR0001r14 "General Updates and Corrections" in S4-231882.

Offline editing in progress.

Pushing on to SA4#127.

[rjb1000]

Post-session object repair has been specified by @haudiobe in the run up to SA4#127 (Sophia Antipolis) and the new text was endorsed at this meeting as the way forward:

• TS 26.517 Rel-17 CR0001r18 "General Updates and Corrections" in S4-240413.

Further offline editing to occur after this meeting with power granted to SA4 ad hoc meeting to agree a revision of CR0001 to be sent to SA#103 (Maastrict) for agreement.

[rjb1000]

Result of offline editing after SA4#127:

• TS 26.517 Rel-17 CR0001r21 "General Updates and Corrections" in S4aI240019.

Power granted to SA4 ad hoc meeting to agree a revision to be sent to SA#103 (Maastricht) for agreement.

[rjb1000]

Following online editing, Change Request agreed by ad hoc meeting:

• TS 26.517 Rel-17 CR0001r22 "General Updates and Corrections" in S4aI240026.

This has agreed status in SA4:

• TS 26.517 Rel-17 CR0001r23 "General Updates and Corrections" in S4-240533

Sent to SA#103 (Maastricht) for approval in CR Pack SP-240272.