Subject: [Idr] draft-ietf-idr-error-handling-03

From: <[email-masked]>
Date: Tue, 8 Jan 2013 09:38:23 +0000

Hi,

The draft proposes to correct some errors in received BGP attribute, at least for optional & transitive bits.

While this looks good, it looks dangerous to me. Indeed, when a router perceives an error in the message received from a peer, we never know if the perceived error is due to the sender, the receiver or the IETF specification. There is a tendency to believe that the error is on the sender side, because when I see an error, I tend to believe that I'm right and the other is wrong. While in fact, we just don't know.
So if I correct an error while _I_ (the receiver) was wrong, I introduce a new error in the message. The issue is that each router in this BGP network (e.g. Internet) having this implementation introduce an error. So the network has to handle N errors at the same time and this can have significant impact especially for downstream implementations using RFC 4271 error handling.
As an illustration of attribute correction/overwriting: let's change the attribute length of this attribute 99 that I received (cf the RIPE_Labs incident where the originator of the route was correct, but multiple propagators changed the attribute and introduced an error)

I'd rather propose to react to an error with treat as withdraw, rather than try to correct it.

In addition, for simplification (hence improved code reliability / easier testing) of the error handling code, I would tend to use treat as withdraw for all errors, rather than introducing "attribute discard" for a very few specific cases (hence very limited improvement).

Thanks,
Regards,
Bruno

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