Shepherd writeup

(1) What type of RFC is being requested (BCP, Proposed Standard, Internet Standard, Informational, Experimental, or Historic)? Why is this the proper type of RFC? Is this type of RFC indicated in the title page header?

Proposed Standard.
This is the appropriate RFC type given the protocol extensions defined within the document.

(2) The IESG approval announcement includes a Document Announcement Write-Up. Please provide such a Document Announcement Write-Up. Recent examples can be found in the "Action" announcements for approved documents. The approval announcement contains the following sections:

Technical Summary:

This document extends Automatic Multicast Tunnelling (AMT, RFC 7450) to allow the relay discovery process to use a new AMTRELAY DNS resource record for discovering source-specific multicast channels.  This allows a set of AMT relays that can receive and forward multicast traffic from a sender to be advertised via reverse IP entries in DNS, hence the DNS Reverse IP AMT Discovery or DRIAD name.  

Working Group Summary:

There was no particular controversy in the WG process, and consensus was good.

Document Quality:

The document is well written, explaining the basic mode of operation clearly, and including many example use cases. 


The document shepherd is Tim Chown (, and the responsible AD is Warren Kumari.

(3) Briefly describe the review of this document that was performed by the Document Shepherd. If this version of the document is not ready for publication, please explain why the document is being forwarded to the IESG.

I have read the draft, reviewed recent WG list discussion, and am happy that it is ready overall to be advanced to the IESG.

(4) Does the document Shepherd have any concerns about the depth or breadth of the reviews that have been performed?


(5) Do portions of the document need review from a particular or from broader perspective, e.g., security, operational complexity, AAA, DNS, DHCP, XML, or internationalization? If so, describe the review that took place.


(6) Describe any specific concerns or issues that the Document Shepherd has with this document that the Responsible Area Director and/or the IESG should be aware of? For example, perhaps he or she is uncomfortable with certain parts of the document, or has concerns whether there really is a need for it. In any event, if the WG has discussed those issues and has indicated that it still wishes to advance the document, detail those concerns here.

I am happy overall with the document.

I would suggest that the text in 2.3.1 on applying a Happy Eyeballs algorithm where there are multiple choices for the relay be expanded; it is very vague at present.  I presume that this may result in multiple unicast AMT streams coming in to a given gateway, and all but one of these would be pruned back, but some specifics on that, and how the preferred stream is retained, would be useful. This also needs to be set against the proposed active/active failover mode described in 2.4.3.

While maximising the multicast portion of the path will avoid data duplication over unicast tunnels, using a relay close to the source (and known to the source such that it can be added to the DNS reverse zone) has some management benefits.  It’s an interesting trade-off.  The document proposes mechanism(s) to discover topologically close relays; with hindsight perhaps this, and aspects such as handling active/active failover, should have been covered in a separate document to a basic DNS RR specification that assumes a single gateway and single relay near the source.

(7) Has each author confirmed that any and all appropriate IPR disclosures required for full conformance with the provisions of BCP 78 and BCP 79 have already been filed. If not, explain why?

Yes. See

(8) Has an IPR disclosure been filed that references this document? If so, summarize any WG discussion and conclusion regarding the IPR disclosures.


(9) How solid is the WG consensus behind this document? Does it represent the strong concurrence of a few individuals, with others being silent, or does the WG as a whole understand and agree with it?

Consensus is good, with no opposition to publication, but mboned is a relatively small WG with a generally low attendance at meetings.  The WGLC in June passed but needed a prod from the WG chairs and another poke from Warren as the AD to get additional responses - see

Those who did comment were favourable, for example - “This is a very useful addition to the AMT toolkit, which should encourage the deployment of multicast services.  I therefore support its adoption enthusiastically.” - William Atwood.

(10) Has anyone threatened an appeal or otherwise indicated extreme discontent? If so, please summarise the areas of conflict in separate email messages to the Responsible Area Director. (It should be in a separate email because this questionnaire is publicly available.)


(11) Identify any ID nits the Document Shepherd has found in this document. (See and the Internet-Drafts Checklist). Boilerplate checks are not enough; this check needs to be thorough.

I ran a nits check on the -08 version.  See
The two warnings about IPv4 literal and multicast addresses appear to be spurious.  This was discussed by the author at
It looks like the nit checker needs a tweak for SSM?
Otherwise, the document passes all nit checks.

(12) Describe how the document meets any required formal review criteria, such as the MIB Doctor, media type, and URI type reviews.

No such reviews are required.

(13) Have all references within this document been identified as either normative or informative?


(14) Are there normative references to documents that are not ready for advancement or are otherwise in an unclear state? If such normative references exist, what is the plan for their completion?

No, all references are at RFC status.

(15) Are there downward normative references (see RFC 3967)? If so, list these downward references to support the Area Director in the Last Call procedure.

None apparent.

(16) Will publication of this document change the status of any existing RFCs? Are those RFCs listed on the title page header, listed in the abstract, and discussed in the introduction? If the RFCs are not listed in the Abstract and Introduction, explain why, and point to the part of the document where the relationship of this document to the other RFCs is discussed. If this information is not in the document, explain why the WG considers it unnecessary.

No. Though it does update RFC 7450 by providing a specific DNS-based mechanism for AMT relay discovery.

(17) Describe the Document Shepherd's review of the IANA considerations section, especially with regard to its consistency with the body of the document. Confirm that all protocol extensions that the document makes are associated with the appropriate reservations in IANA registries. Confirm that any referenced IANA registries have been clearly identified. Confirm that newly created IANA registries include a detailed specification of the initial contents for the registry, that allocations procedures for future registrations are defined, and a reasonable name for the new registry has been suggested (see RFC 5226).

The IANA Considerations are covered in Section 5.
The document requests a new DNS Resource Record Type of type 260.
This type is already listed at, the reservation of which appears consistent with the document.
There is a sub-registry for the Relay Type field, for which four of 256 possible values are defined.

(18) List any new IANA registries that require Expert Review for future allocations. Provide any public guidance that the IESG would find useful in selecting the IANA Experts for these new registries.

The Relay Type field may potentially have additional values assigned in the future; as above four of 256 values are defined, the rest (4-255) are unassigned.  The document states that Expert Review would be required for these, as per Section 4.6 (policy of Specification Required) of RFC 8126.

(19) Describe reviews and automated checks performed by the Document Shepherd to validate sections of the document written in a formal language, such as XML code, BNF rules, MIB definitions, etc.