Subject: [shim6] Comments on the draft-ietf-shim6-multihome-shim-api-08

From: Varjonen Samu <[email-masked]>
Date: Thu, 28 May 2009 11:53:54 +0300

Hi,

Some comments on the draft-ietf-shim6-multihome-shim-api-08.

Section 1. Introduction. I would prefer "network layer" instead of 
"IP-layer" (2 instances in introduction and 1 in fig. 1).

Shim is explained as a sub-layer in network layer and is referred as 
"shim sub-layer" and "shim layer" through out the document. I would just 
use one form uniformly through out the document. Sub-layer one would be 
my choice and it would rule out any ambiguity from the text as some 
parts talked about shim like it would have been its own layer.

Section 1. Introduction (second paragraph) tells that locator changes 
should be hidden from upper layer protocols. In general this is true but 
how about protocols/applications based on location awareness?

Section 4. Requirements. To me it looks like the requirements is missing 
one important case. Application may want to set used addresses 
(SHIM_LOC_*_RECVs and SHIM_LOC_*_SENDs). The current version looks like 
applications only need to obtain the information from shim sub-layer.

Section 5. Socket Options...
In descriptions on most options that have "o" in get and set just say 
"request" (get) or "inform" (set) or "specify" (set) while it is 
possible to get and set the information. I think this should be "Get or 
set the option" for all "get and settable" in this list. Same goes for 
the sections 5.*. Some of them start "can be set" and then later in 
example it is mentioned that it can also be obtained.

Section 5.4 has double specify in the first sentence.

In sections 7.2 and 7.3 the explanations of reserved fields, in my 
opinion, should be unified to say "Must be initialized to zero and must 
be ignored by the receiver"

The document left me puzzled on the situation if I deferrer the ctx 
setup and start off with plain IP and then upgrade to shim. Does the 
shim handshake start simultaneously with the plain IP communication or 
after some timer or can the implementor trigger it (with SHIM_DONTSHIM 
set to 1 in the middle of the communication?) and can I turn shim off 
during the communications? To my knowledge shim6 does not have any close 
procedures, so to me it looks like I would have to abandon the ctx for 
garbage collection by closing the socket.

BR,
Samu Varjonen
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