RE: [PWE3] Proposed new 5.4.3 for arch draft

[Sasha Vainshtein <Sasha at AXERRA.com>]

Alia and all,
I agree that checksum is a valid method of verification (even if
occasionally it could fail). My understanding has been, however,
that we do not want to use it, and tried to block a possible
loophole.
Regards,
                      Sasha

-----Original Message-----
From: Alia Atlas
To: Sasha Vainshtein
Cc: 'Stewart Bryant '; 'pwe3@ietf.org '
Sent: 3/3/2004 4:09 AM
Subject: RE: [PWE3] Proposed new 5.4.3 for arch draft

At 08:52 PM 3/2/2004, Sasha Vainshtein wrote:
>Stewart and all,
>Basically fine, please see a couple of minor comments inline (marked
>[Sasha]).
>
>Regards,
>                  Sasha.
>... snipped ...
>
>5.4.3. PW Packets Aliasing IP Packets
>
>To allow accurate packet inspection in an MPLS PSN, and/or to operate
>correctly over MPLS PSNs that have deployed equal-cost multiple-path
>load-balancing (ECMP), a PW packet must not alias an IP packet.
>[Sasha] IMO it should be MUST NOT or, probably, SHOULD NOT.
>IP packets are carried in MPLS label stacks without any protocol
>identifier. The method of packet discrimination must therefore
>be based on some unique characteristic of the IP packet header,
>which PWE3 must not mimic.
>[Sasha] I honestly believe no one will ever propose verifying the
cheksum
>[Sasha] of the first 20 bytes after the bottom label as "the unique
>[Sasha] characteristic of the IP packet header". But worse things have
>[Sasha] happened, so maybe we should explicitly block this.

The checksum is legitimate to consider as a verification, if one doesn't

want to depend on just the first nibble.

Alia

>This is the subject of work in progress.
>
>-----------------------------------------------------
>
>
>9.  IANA considerations
>
>     IANA considerations will be identified in the PWE3 documents that
>     define the PWE3 encapsulation, control and management protocols.
>
>
>
>
>
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