Subject: Re: [MEXT] RE: Reliability of sending BRR by the HA?

From: Brian Haley <[email-masked]>
Date: Tue, 08 Jan 2008 10:52:15 -0500

Sorry for the late response, see inline.

Alexandru Petrescu wrote:
> marcelo bagnulo braun wrote:
>> Hi,
>>
>> i am trying to understand the impact of this in rfc3775 update
>>
>> I don't think that whether it is a good idea to use BRR from the HA is 
>> relevant for the discussion of RFC3775 update (it is of course 
>> relevant for the mext ml but not imho for this particular process of 
>> updating rfc3775)
>>
>> what imho is relavnt for the discussion of updating rfc3775 is whether 
>> rfc3775 is clear enough about whether HAs should send BRR or not

I don't think HA's have to support sending BRRs since they can't ever 
delete the MN binding, it really should only be useful for a CN that 
implements a cache-replacement policy that purges old bindings.

>> From the text of rfc3775 that Alex sent in his original posting, it 
>> seems that only CNs should send BRR and BE and not by the HA, so, is 
>> there any text in rfc3775 that can possibly create confusion about HAs 
>> using BRR or BEs? Does anyone has interpreted rfc3775 in the way that 
>> HAs should send BRR and BEs?
> 
> I will invite other implementers express whether it's clear or not who 
> sends BRR and BErr.
> 
> For my reading, there are some occurences about the possibility of HA
> being a CN, for example section 10.3.1 "Primary Care-of Address
> Registration" in 10.3 "Processing Bindings" in 10 "HA Operation":
> 
> rfc3775:
> [...]
>> To begin processing the Binding Update, the home agent MUST perform 
>> the following sequence of tests:
>>
>> o  If the node implements only correspondent node functionality, or 
>> has not been configured to act as a home agent,[...]
> 
> The 'node' (the home agent) can thus implement only CN functionality.

That was my understanding as well - the HA is also a CN.  HP's 
implementations will send a Binding Error if either HA or CN - I saw no 
reason to special case that code to limit it to one or the other.

I did not implement BRR since we don't have a cache replacement policy 
to delete old entries - memory is cheap :)

-Brian

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