RE: [PWE3] BFD for MPLS PWs

Tom and all,
Please see some comments inline below.
I've snipped parts of the original thread to make it readable.

Regards,
                   Sasha

> -----Original Message-----
> From: Thomas D. Nadeau [mailto:tnadeau@cisco.com]
> Sent: Monday, July 31, 2006 10:48 PM
> To: Rahul Aggarwal
> Cc: Yaakov Stein; pwe3@ietf.org
> Subject: Re: [PWE3] BFD for MPLS PWs
> 
> 
> 
> > Hi Tom,
... snipped ...
> 
> 	The reasons that were explained during the meeting:
> 
> 	1) sending the IP/UDP header is redundant
> 		for SH PWs because the labels or outer l2tpv3 header
> 		ID the VCCV payload.
>
[Sasha] This is only correct if the PW uses a CW. Not all of them do.
> 
> 	2) If you include the 127/ dest. address, then it is 
> useless other
> 		than it prevents errant routing if the PW header
> 		is inadvertently stripped.  However, skipping the
> 		IP header altogether obviates both problems. It
> 		also makes each VCCV/BFD packet shorter.
>
[Sasha] Can you please explain how skipping the IP header  solves
the problem of the PW label being popped in an inappropriate place?
>
> 	2) sending the IP/UDP header is useless for MH PWs because
> 		the MH PW addressing scheme will not fit into
> 		an IPv4 address.  Instead, the outer PW encapsulation
> 		identifies the destination.
>
[Sasha] IMHO Nothing in the IP/UDP proposal prevents you from using IPv6 headers/addresses as
IPv4 and IPv6 packets are easily discriminated using the Version field.
To the best of my recollection, the IPv4 and IPv6 addressing schemes are explicitly
allowed for MS-PWs, and I have not seen any realistic alternative proposals.
I also do not think that the "outer PW encapsulation" defines the packet destination
in MS-PWs.
> 
> 	3) the secondary routing header lookup/processing is
> 		a waste of processing cycles since it should
> 		always result in the receiving PE. The outer
> 		header identifies the PW packet already.
>
[Sasha] Can you please explain how to you see LSP-Ping being used in VCCV without IP/UDP headers?
> 
> 	Conversations with everyone except yourself (I couldn't
> find you after PWE3) that objected to the removal of the UDP/IP
> header at the meeting, all agreed that this was okay assuming that
> we add two new CV types to explicitly identify when the header
> is and is not included for BFD messages so that we can support
> older implementations. I will have the text for this shortly
> and will send it out.
> 
> 	--Tom
> 
> 
> 
> > rahul
> >
> >> 	--Tom
> >>
> >>
> >>
> >>> Y(J)S
> >>>
> >>>
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