Subject: [Gen-art] Gen-ART review of draft-ietf-mip6-hiopt-11.txt

From: Suresh Krishnan <[email-masked]>
Date: Wed, 26 Mar 2008 16:10:36 -0400

I am the assigned Gen-ART reviewer for
draft-ietf-mip6-hiopt-11.txt

For background on Gen-ART, please see the FAQ at
<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.

Summary: This draft is on the right track but there are a few issues 
that need to be fixed.

Meta-comment
============

* I did not personally like the way the document flows. I would have 
much preferred having the current section 4 before the current section 
3. The  way the document is currently written, I go through option 
formats before I have any clue what they would be used for and how they 
would be used.

* There does not seem to be a way for a MN to request a SPECIFIC piece 
of information from the DHCP server. e.g. How does the MN request just 
the home agent address and nothing else? If this is intentional please 
state so in the draft.

* There is no discussion regarding the interactions between information 
stored in the DHCP server and that provided by the relay. What is the 
DHCP server supposed to do with these two (potentially conflicting) 
pieces of information when it responds?

Substantial
===========

* Section 3.1.1

Prefix-len is described as "The length of the following IPv6 Home 
Network Prefix in bits". If I have the value 64 in here does it mean 
that the following IPv6 HNP is 8 octets in length? If not, I think this 
is ambiguous and misleading. If yes, the packet format has to be redrawn 
  since the picture shows the IPv6 Home Network Prefix to be 16 octets 
(fixed) in length. I suggest the following replacement text.

"The Prefix-len contains the number of leading bits in the IPv6 Home 
Network Prefix that are valid."

* Section 4.1

The term "Home Network information" has been overloaded in the document 
and hence it is hard to figure out which of the contexts is being used. 
e.g. The following text in section 4.1

"When provided with more than one home network information, the mobile 
node is required to have a selection mechanism to determine which one to 
use for establishing a Mobile IPv6 session."

I could understand this as either

a) "when there are multiple HNI options (say Id-Types 0,1,2)"
b) "when there are multiple sub-options for the same HNI option" - The 
sub-option data is ALSO referred to as "Home Network Information" in the 
packet format

Can we rename b) to something else, say "sub-option specific data".

* Section 4.1

"However, there SHOULD not be more than one Home Network Information 
option with Id-type 0 nor more than one Home Network Information option 
with Id-type 2 in the request."

Why is this a SHOULD and not a MUST. I have difficulty seeing any case 
that is an exception to this SHOULD.

* Section 4.3 Bullet C

"include all sub-options in one or more than one Home network
Information option(s) with Id-type 1 or 2 in the reply."

Did you mean "1 or 0" instead? (Because "1 or 2" is not very useful)

Cheers
Suresh
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