Re: Multiple BFD sessions over one path

[Dave Katz <dkatz at juniper.net>]

But the point is that, the way 1hop is specified, there is *no* way to  
demultiplex the initial packet--thus the requirement.

The only mechanism for multiple sessions is to have multiple paths,  
with one session per path.  A "path" ends up with the somewhat  
reflexive definition of "something you can demultiplex by."

As such, I believe that the language in the two drafts is proper.

--Dave

On Sep 19, 2009, at 2:07 AM, Mach Chen wrote:

> Hi Dave,
>
> Thanks for your response!
>
> Based on your explanation, the point is whether there is a way to  
> demultiplex the initial patcket, if there is, means no need to limit  
> the BFD sesion. So, IMHO, it's better to clarify this in 1hop(since  
> the draft is still in IESG review state, seems not too late to do  
> it:-).
>
> Have a good weekend!
>
> Best regards,
> Mach
>
>
> --------------------------------------------------
> From: "Dave Katz" <dkatz at juniper.net>
> Sent: Saturday, September 19, 2009 2:39 PM
> To: "Mach Chen" <mach at huawei.com>
> Cc: <rtg-bfd at ietf.org>
> Subject: Re: Multiple BFD sessions over one path
>
> > The point of the text in 1hop is that there isn't any use in  
> > having  more than one session over a "path", and in any case it  
> > can't be done  because there would be no way to demultiplex the  
> > initial packet of  multiple sessions on the same "path" (because  
> > the first packet carries discriminator 0).
> >
> > But diffserv is essentially a tunnel of sorts;  each service level  
> > has potentially different forwarding characteristics, so it may be  
> > useful  to run BFD over more than one level (and the sessions can  
> > be  demultiplexed because they are contextualized by the diffserv  
> > level).
> >
> > Essentially, each diffserv service level is considered to be a   
> > separate path, not unlike GRE or IPsec or what have you.
> >
> > Implementors are free to do as they please;  the point of the text  
> > is  to not preclude creative use of BFD where it can be useful.
> >
> > --Dave