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Re: Gen-art review of draft-ietf-netlmm-proxymip6-10.txt

2008-02-19 13:48:58
Thanks Elwyn for the review. We will address each of these comments
and will propose the text, some time this week.

Regards
Sri

On Mon, 18 Feb 2008, Elwyn Davies wrote:


I have been selected as the General Area Review Team (Gen-ART)
reviewer for this draft (for background on Gen-ART, please see
http://www.alvestrand.no/ietf/gen/art/gen-art-FAQ.html).

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

Document: draft-ietf-netlmm-proxymip6-10.txt
Reviewer: Elwyn Davies
Review Date: 18 Feb 2008
IETF LC End Date: 20 Feb 2008
IESG Telechat date: 21 Feb 2008

Summary:
This document is well written and is in fairly good shape for submission to 
the IESG.
There are a number of minor issues which ought to be fixed.  I think that for 
a more general reader there are a number of points that are fully covered in 
the detail but when reading the introduction and protocol overview questions 
arise which aren't answered until later in the document, and I was left 
thinking whether the problem had been addressed until much later.  I have 
noted these items in the comments.  I believe it would only take a few 
sentences to lay these issues to rest and make the document easier to 
understand for those who are not immersed in netlmm.

Comments:

s3, paras just after fig 2:  The para after fig 2 claims that the LMA sets up 
the bidir tunnel; then the next para claims that the MAG 'establishes' the 
(same) tunnel.  Be clear which one has responsibility.

s3, p12:

    The local mobility anchor, being the topological anchor point for the
    mobile node's home network prefix, receives any packets that are
 sent by any correspondent node to the mobile node.

I think it should be made clear (assuming I understand correctly what is 
going on) that this 'correspondent' node does not require any of the MIPv6 
correspondent functionality and will not see any specialized MIPv6 messages. 
It is difficult to think of an alternative term, but this could be confusing.

s5.3.4, item 2:  Whether the tunnel is deleted is surely an implementation 
issue.  The LMA and MAG could agree to maintain the tunnel even if there are 
no MNs active on the MAG to save on setup costs.  I think this could be a 
MAY, leaving it up to implementers to optimize if desired. (This is actually 
discussed later in s5.6.1.. a forward pointer is needed here)

s6.1, bullet 2:  Does this make any assumptions about commonality of IID 
between addresses used by the interface?

s6.5: I thought it was said earlier that checking that the MN is entitled to 
mobility services was a MUST.  Does the SHOULD refer to the means of 
authenticating?

s8.2: The (M) flag is not added to the Binding Ack message by RFC 4140 (only 
to the Binding Update msg).

s10: The new registry for the Handoff Indicator values is not specified in 
the IANA Considerations.

Areas where some earlier explanation would make life easier for the general 
reader:

3:  I think it would be useful to explain how the LMA knows that the MN that 
has moved from p-MAG to n-MAG is the same MN.. and hence gets the same prefix 
somewhere here (the MN_identity, auth and policy I think).

s5.1, last para:  (it turns out that s5.2 and s6.3 give most of the answers 
but I was left worrying) States that the mobile node's address prefix would 
normally be the key for the binding cache entry.  This implies that it will 
be a unique key and hence every MN requires a different address prefix.  I 
think this is sort of implied earlier, but I think it could be stressed at 
the outset.  This raises a couple of more significant issues in my mind:
- A MAG using stateless address config will be advertising one prefix per 
attached MN:  if there are lots of them the RA's will be very large.  Is this 
an issue? (not if everything is a pt2pt link, but
- How does the MN know which prefix to use if it isn't a pt2pt link?
[s5.2 does not address these issues although it clarifies that the prefix per 
MN mode is used]  s6.3 states that it is assumed that links will be pt2pt and 
hence only one prefix on link.  This should be made clear earlier, probably 
in the protocol overview.

I think some additional notes on the Shared_prefix model case and what 
happens if the links are *not* pt2pt would be helpful:  There is a 
significant risk of the RAs getting very large if multiple prefixes need to 
be advertised - and it requires slightly different policy to make sure a MN 
can pick the right prefix if there is more than one prefix advertised.

s6.4: I think that explaining where the DHCPv6 server would be and how it 
would know what prefix to take the address out of would be useful.  (A few 
words plus a pointer to s6.11 would do.)

Editorial:

(idnits is happy with the document)

s2.2, MN-Identifier: Expand NAI and MAC acronyms.

s4.1: Associate PAD with Peer Authorization Database.

Fig 5: Provide key to various acronyms.

s5.1, bullet 1: 'enabled'/'turned off':   This reads as if the flag is 
sometimes present and sometimes not present.  Suggest using 'set'/'reset' or 
'true'/'false'.

s5.1, bullet 3: Define ALL_ZERO.

s5.2: The terms Per-MN-Prefix and Shared-Prefix model are not defined in this 
doc.  Are they imported from some other netlmm doc?

s5.3: Would be useful to put in a pointer to the message format descriptions 
here.

s5.4.1.1: use of == and != ... use of words is better than C programming 
language .







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