Subject: RE: your mail

From: Shahram Davari <[email-masked]>
Date: Mon, 22 Jul 2002 09:16:00 -0700

To find the bottom of the stack you need parsing.

-Shahram

> -----Original Message-----
> From: Gray, Eric [mailto:[email-masked]]
> Sent: Tuesday, July 02, 2002 12:36 PM
> To: [email-masked]'
> Cc: Shahram Davari; [email-masked] '
> Subject: RE: your mail 
> 
> 
> Eric,
> 
> 	I'm guessing that some hardware implementations might be 
> optimized around the need to process at most K labels.  For any
> such implementation, being required to possibly look at the Nth
> label - where N is the number of labels in the stack and N may 
> be greater than K - may be virtually indistinguishable from 
> being required to parse the entire packet.
> 
> 	In such cases, the engineers have to take a hard look at
> what they might use as a fall back for the N > K case and then
> do some hard analysis about whether or not such a fall back is
> guaranteed to work in all cases.  Because the consequences of
> not getting the right answer after all this hard looking and
> analysis are systemic at the network level, it might be useful
> if this was hashed out publicly in a little more detail - don't 
> you think?  :-)
> 
> Eric W. Gray
> Systems Architect
> Celox Networks, Inc.
> [email-masked]
> 508 305 7214
> 
> 
> -----Original Message-----
> From: Eric Rosen [mailto:[email-masked]] 
> Sent: Tuesday, July 02, 2002 11:02 AM
> To: Shahram Davari
> Cc: 'Eric Osborne '; 'George Sheng '; [email-masked] '; 
> [email-masked] '
> Subject: Re: your mail 
> 
> 
> SD=> So you do more than one lookup- so what? so you need to 
> parse the whole
> SD=> packet in the core-so what? so you need to keep state in 
> the core,
> 
> Please pay attention. 
> 
> There is not  more than one lookup; doing the hash  does not 
> require looking
> anything up. 
> 
> Finding the bottom label does not involve parsing the whole packet. 
> 
> There is no state kept in the core. 
> 
> SD=> so you have no longer a simple label swap
> 
> It is true that the essence of  load balancing over equal 
> cost paths is that
> the outgoing interface  is not chosen solely on the basis  of 
> the top label.
> So? 
> 
> SD=> MPLS was  designed to have simple  forwarding. Hashing 
> takes  it to new
> SD=> levels of simplification never seen before.  
> 
> You might take a peek at section 3.12 of RFC 3031. 
>