Subject: RE: [Idr] Recommend Book on BGP

From: "john smith" <[email-masked]>
Date: Mon, 03 Oct 2005 04:04:19 +0000

The RFC seems fine,

perhaps something like "BGP is based on the Bellman-Ford algorithm" etc. 
would be a nice line to add....

>From: Jing Shen <[email-masked]>
>To: [email-masked]
>Subject: [Idr] Recommend Book on BGP
>Date: Fri, 30 Sep 2005 16:57:13 +0800 (CST)
>
>Hi,
>
>I'm sorry if this is off-topic.
>
>Would anybody recommend some book on BGP? Someone
>recommend Halabi's book, but it seems focusing on
>operational area. Is there any book discussing how BGP
>is designed and implemented?
>
>thanks
>
>Joe shen
>

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From: Curtis Villamizar <[email-masked]>
Date: Mon, 03 Oct 2005 01:04:42 -0400

> >is designed and implemented?

John,

The question seemed to be more focused on how to design and code a BGP
implementation, presumably one that will not fail when deployed in a
real network.  I sent Mr. Shen a private message indicating that there
was no really good book on BGP implementation.  The lessons learned
about BGP's behaviour in real networds and the implications for data
structures and algorithms used to implement BGP is not to my knowledge
available in any textbook.

There are plenty of anecdotal examples in IETF and NANOG archives of
things that weren't done right the first time in some implementations.
Even basic things like making writes non-blocking and properly
handling non-blocking writes have been missed by some implementations.
One prominent implementation at one time had a linked list of per
prefix policy statements despite the known poor search time for a
linked list.  An example of a misfeature is one vendors ill conceived
"optimization" of sending route deletes to all peers even if no route
announcement had been sent to a subset of those peers.  All of these
problems are corrected in today's major implementations.

Though not in any textbook, apparently this stuff is far enough from
obvious that it wouldn't hurt to be in one.  The reason it isn't may
be that the audience for such a book is too small or there is a lack
of people with the capabilty and time to write it.  

That sort of thing doesn't belong in the RFC and mentioning
Bellman-Ford doesn't come anywhere close to covering the topic.

Curtis

ps - History also has plenty of at one time deployed "how not to
design a router" problems that are not specific to BGP.

---

From: "john smith" <[email-masked]>
Date: Mon, 03 Oct 2005 05:41:11 +0000

>design a router" problems that are not specific to BGP.

Then there is no harm in writing code like this is there?

for(;P("\n"),R--;P("|"))for(e=C;e--;P("_"+(*u++/8)%2))P("|"+(*u/4) %2);

as stated here:
http://www.gdargaud.net/Humor/C_Prog_Debug.html

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