Subject: Extending AS_PATH attribute length en route

From: "Michael C. Cambria" <[email-masked]>
Date: Tue, 10 Sep 2002 09:48:25 -0400

Hi,

The draft doesn't say what an implementation should do when the total
length of the path attribute used up.  (i.e. the entire 1 or 2 octect
field is used up.)  When propergating to a peer, if the addition of
another AS would overflow the total length of the attribute, what should
be done?

Could a solution be to let an implementation change a received
unextended AS_PATH attribute length, when propergating, from 0 to
1 so that the total length of the attribute can hold greater than 255
octets?

Regardless, what to do when the (1 or 2 octet) length is used up should 
be specified.

MikeC

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From: Jeffrey Haas <[email-masked]>
Date: Tue, 10 Sep 2002 10:29:24 -0400

> Regardless, what to do when the (1 or 2 octet) length is used up should 

The more general overflow case is what you're talking about here.

It *might* not be appropropriate to deal with this since each
implementation may choose to do deal with this in its own way.

For the mandatory attributes, you have to be able to deal with
overflows.  But if you're getting an AS Path that big, something
has gone insane.

For optional attributes, you may be able to discard some of them -
for example, communities.

-- 
Jeff Haas 
NextHop Technologies

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From: "Michael C. Cambria" <[email-masked]>
Date: Tue, 10 Sep 2002 10:34:41 -0400

> The more general overflow case is what you're talking about here.

Yes (adding another path segment is quite clear).

> overflows.  But if you're getting an AS Path that big, something

If the received path attribute total was only 1 octet,

When implemeting, automated tools test for edge conditions.  So in the 
QA lab, we _will_ see full path attributes, log this fact and then ?

MikeC

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From: Jeffrey Haas <[email-masked]>
Date: Tue, 10 Sep 2002 11:06:56 -0400

> QA lab, we _will_ see full path attributes, log this fact and then ?

IMO, do not propagate the route since you can't.

-- 
Jeff Haas 
NextHop Technologies