Re: 6man w.g. last call for <draft-ietf-6man-segment-routing-header-11.txt>

["Darren Dukes (ddukes)" <[e-mail]>]

Hi Joel, please see inline:

> On Mar 30, 2018, at 10:51 AM, Joel M. Halpern <[e-mail]> wrote:
> 
> I do not think this document is ready to be sent to the IETF and IESG for final approval.
> There are several kinds of problems.
> 
> ECMP1: The document asserts that entropy information is put into the flow label.   I wish this worked.  I helped bring this idea forward years ago, independent of SRH.  Unfortunately, there are two related problems.  First, adoption appears to be low.  Second, and more important, there are reports from the field that doing thi actually breaks other things and cause packet re-ordering under some circumstances.  As a result, vendors are suggesting that people turn it off even when it is available.
> ECMP2: If, with suitable analysis, we decide that this is actually safe to do, then the document needs to include both that analysis and clearly spelled out requirements that operators MUST verify that all their routers support this behavior and that they have enabled this behavior before turning on SRv6 usage.
> 
> Structure: The text in section 2.3 says "It is assumed in this document that the SRH is added to the packet by its source".  This is at best disingenuous.  It is very clear that the value of this behavior lies primarily in use by the network, not by the packet sources.  Claiming otherwise results in a document with minimal utility.  Even this document itself disagrees with this assertion.  Tucked into the very next section is text saying that "outer header with an SRH applied to the incoming packet".  If this behavior were a clearly spelled out requirement, rather than a "typically" and if the text in 2.3 were replaced with something realistic, then the document would at least be itnernally consistent and match the expected usages.

2.3 is clear, a packet source can add an SRH.  Since a source is the node in the node that owns the source address of a packet.  The source may be a host or a node encapsulating an inner packet in an outer IPv6 header.  There is nothing disingenuous about that.

> 
> Edge filtering: The text on edge filtering does not actually state that prevention of packets with SRH and a current DA of an internal node is mandatory.  Unless it is clearly stated, the security considerations text as currently written is significantly weakened.  If it is mandatory, then again the deployment section needs to note that an operator needs to verify that all of his edge devices support such filtering and have it properly enabled in order to use SRv6.

Please look up infrastructure ACLs.  This filtering has been common practice for a very long time and I believe is quite obvious to anyone operating a network.

> 
> Edge Filtering and hybrids: Other documents have talked about allowing external packets with SRv6 entries pointing to internal nodes (which means the DA upon arrival at the operator edge will be an internal node as I understand it).  It the intention is to permit that with appropriate security, then the edge filtering requirements need to be clear about the requirements for cryptographic validation at the edge.

This document is not defining any of what you mention in this comment.

> 
> Yours,
> Joel
> 
> On 3/29/18 4:30 PM, Bob Hinden wrote:
>> This message starts a two week 6MAN Working Group Last Call on advancing:
>>        Title           : IPv6 Segment Routing Header (SRH)
>>        Authors         : Stefano Previdi
>>                          Clarence Filsfils
>>                          John Leddy
>>                          Satoru Matsushima
>>                          Daniel Voyer
>> 	Filename       : draft-ietf-6man-segment-routing-header-11.txt
>> 	Pages          : 34
>> 	Date           : 2018-03-28
>>      https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header
>> as a Proposed Standard.  Substantive comments and statements of support
>> for publishing this document should be directed to the mailing list.
>> Editorial suggestions can be sent to the author.  This last call will
>> end on 12 April 2018.
>> An issue tracker will be setup to track issues raised on this document.
>> Thanks,
>> Bob & Ole
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