Subject: Last call on default router preferences

From: Suresh Krishnan <[email-masked]>
Date: Tue, 11 May 2004 23:55:11 -0400 (EDT)

Hi Folks,
	I have a couple of comments on this draft

Section 2.3 Route Information Option
* The length can be more tightly specified. For example if the prefix 
length is 0 the draft allows the length to be 1,2 or 3 while it is 
sufficient to specify 1 as the only valid value for the length. Is there 
a reason for this?
* Since the preference is in the middle of the octet (between the 
reserved fields) the host needs to do an arithmetic shift for this
 to be used. Is this necessary?
* The following statement 
"If a host processes a Router Advertisement carrying multiple Router 
Information Options with the same Prefix and Prefix Length, it MUST 
process one of the options (unspecified which one) and it MUST 
effectively ignore the rest."
implies that the host needs to keep state about the previously encountered 
route information options in the message. Does this need to be specified?

Section 3.5 Router Reachability Probing
When the better router becomes available again(say due to a system 
restart) it will send a new RA message which can trigger the switchover  
to the better router. Why is the probing needed at all?

Section 2.2 Changes to RA message:
This draft assumes the presence of the H bit in the RA message. The MIPv6 
spec which defines this is still a draft. Assuming that it becomes a
standard this draft still needs to mention MIPv6 as a normative reference. 

Section 5.2:
Router X and router Y are mixed up in paragraph 1 and 3.
para 1 mentions
"a multi-homed host is connected to the 6bone/internet via router X on
one link and to an isolated network via router Y on another link"
para 3 mentions
"For example, router X on the isolated network should advertise a Route 
Information Option for the isolated network prefix."

Section 6:
In the security considerations, the draft mentions that this draft is no 
worse than status quo. But it may not be so. With 2461 a router 
advertisement expires after a maximum of 18 hrs. But with this draft we 
can send a route information option with an infinite lifetime. Thus the 
effect of a misconfigured/malicious router can linger around for longer. 

Regards
Suresh

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