Shepherd writeup

Shepherd template: (per RFC 4858, date 2/24/2012)

1) What type of RFC? 

Proposed standard, on the template header.

(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
   Segment Routing (SR) architecture allows a node to steer a packet
   flow through any topological path and service chain by leveraging
   source routing.  The ingress node prepends a SR header to a packet
   containing a set of segment identifiers (SID).  Each SID represents a
   topological or a service-based instruction.  Per-flow state is
   maintained only at the ingress node of the SR domain.

Working Group Summary
WG consensus is strong.  2 companies have implementations (rtbrick and cisco).  
The first WG call came at a bad time, but the subsequent call shows agreement:
Following the WGLC the AD returned the document with further comments. These 
were also discussed fairly extensively on the list:

Late changes included removal of the IPv6 SID TLV (which had gone unimplemented)
and several lesser things. 

Document Quality
  Existing Implementations of protocol: 2 companies,  4 implementations see:
Two rtg-dir QA early reviews
Chris Hopps:
Bruno Decraene

 Document Shepherds: Susan Hares, John Scudder
 AD:  Alvaro Retana 
 RTG-DIR review (1): Christian Hopps
 RTG-DIR QA review (2): 	Bruno Decraene
 SEC-DIR early reviiew (3): Brian Weis  

(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.

The document had careful read-throughs by both IDR co-chairs (who have
both shepherded the document at various times), with subsequent Q&A and
revision with the authors.

Note, this report covers draft-ietf-idr-bgp-prefix-sid-20.

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

No - between IDR and Spring RTG-DIR reviews, chair reviews and
implementations, the depth of the review seems appropriate. The multiple
WGLC and post-WGLC discussions show that a number of people reviewed the
document carefully.

(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.

The shepherd was concerned that secdir evaluate whether there were any
additional concerns about multidomain segment routing, over and above
those of BGP-enabled MPLS. The secdir review can be found at
which found the draft to be "ready with nits". The authors and chairs
discussed the nits with the reviewer, Brian Weis. Brian was satisfied
with the response:

(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.


(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.


Clarence Filsfils <>

Hannes Gredler:

Acee Lindem

Keyur Patel

Stefano Previdi (sprevidi)" <>

Saikat Ray <>

Arjun Sreekantiah

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


(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?   

Solid.  The link to MPLS and Spring has caused significant review. 

(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.) 

No appeals or discontent related to draft. 

(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

No nits other than a backdated reference that can be resolved by the
RFC Editor.

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


(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?

Most normative references are RFCs, but see answer to (15).

(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. 

There are normative dependencies on:
draft-ietf-spring-segment-routing-15 (in RFC Ed Queue)
and draft-ietf-spring-segment-routing-mpls-13. The SPRING chairs
say this one has been through a first WGLC, received additional AD
and other feedback, been revised, and soon will go through a second
WGLC. So it seems likely it will move forward promptly.

(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 changes.  It will create an additional IDR Attribute, but this is an
addition rather than a change to earlier IDR specifications. 

(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).


(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.


(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.

None needed.