[Gen-art] Review: draft-garcia-shim6-applicability-03

["Joel M. Halpern" <[e-mail]>]

I am the assigned Gen-ART reviewer for this draft. For background on 
Gen-ART, please see the FAQ at 
<http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>.

Please resolve these comments along with any other Last Call comments 
you may receive.

Document: draft-garcia-shim6-applicability-03
     Applicability Statement for the Level 3 Multihoming Shim Protocol
                                 (Shim6)
Reviewer: Joel M. Halpern
Review Date: 18-Feb-2012
IETF LC End Date: 14-March-2012
IESG Telechat date: N/A

Summary: This document is almost ready for publication as an information rfc

Major issues:
     The third paragraph of the introduction makes assertions about PI 
based multihoming being "not generally available to end sites due to a 
strict policy of route aggregation in the DFZ."  As far as I know, this 
is simply not the case.  RIRs sell IPv6 PI for reasonable fees.  Most 
operators accept PI advertisements from customers.  And those 
advertisements are passed on to other ISP, and accepted.  I would 
recommend removal of the first sentence of this paragraph.  Instead, it 
needs to be noted that PI based multihoming can be done with IPv6, and 
then point to the scaling concerns.


Moderate Issues:
     I am unable to understand the sentence "Shim6 has no means to 
enforce neither host nor network forwarding for a given locator to be 
used as source address."  I presume that what it is intended to 
communicate is simply a fact about shim6.  Please rewrite.

     If I am reading section 7.1.1 on MobileIPv6/Shim6 interaction, it 
looks like you are describing a scenario in which the mobile node uses 
multiple HOAs as locators with a correspondent node.  I would suggest 
that this section would be clearer if the communicating parties were 
identified.  I suspect that the intended behavioral assumption is that 
the mobile node will register its CoA multiple times, once with each 
home address.  But this does not seem to be stated explicitly.


Minor issues:
     In th long comparative paragraph in the introduction, "The Shim6 
approach is thought to have better scaling properties with respect to 
the state held in the DFZ than the IPv approach." Could "IPv 4 approach 
be replaced with "PI approach"?

     In section 7.7 on the interaction with NPT66, I think it would be 
helped by a bit more discussion of when certain shim6 messages are 
exchanged, and which fields are validated.  Specifically, I can not tell 
if it is ever possible to get a shim6 ULID-pair option through an NPT66 
which is rewriting the one of the addresses prefixes in the packet.  I 
suspect not.  If indeed it just won't work, this needs to be stated MUCH 
more clearly.

Yours,
Joel M. Halpern


Nits/editorial comments: