[PWE3] Re: Header Compression over MPLS & Allison's DISCUSS Comment on PWE3 IANA Allocation Draft

Hi, Jerry,

> Carsten Bormann made a comment on RFC1144 problems at IETF-63 [in
> the context of the avt document header compression over mpls], but I wasn't
> aware that cRTP and IPHC were also in the "problem" category.  In
> particular, cRTP is widely deployed and IMO should be supported for
> Header Compression over MPLS.

The IETF consensus on CRTP is reflected in ECRTP, RFC 3545 (and
also explained as the text goes on).  Here's the statement:

   CRTP was designed for reliable point to point links with short
   delays.  It does not perform well over links with high rate of packet
   loss, packet reordering and long delays.

   ...this document defines modifications and extensions
   to CRTP to increase robustness to both packet loss and misordering
   between the compressor and the decompressor

   ...The enhanced CRTP, as
   defined in this document, is thus suitable for many applications in
   the scenarios discussed above, e.g., tunneling and other virtual
   circuits.

Not that MPLS has a high rate of packet loss, or necessarily long
delays, but it is definitely a tunnel, and the kind of environment
that ECRTP, but *not* CRTP was defined for.  Just because a protocol
is widely deployed does not mean it should be viewed as applicable in
all environments.

Although the document for AVT is not baked yet, and could be changed,
we can see the in-WG review by Carsten that you mention as the Expert Review, so
I'll trade you, I'll support leaving in the registrations for ROHC and eCRTP,
if the others are left out.  (And the registrations for the PW types
need to be removed from the AVT doc; I'd missed them being there).

As I said about IPHC in my Discuss, I just don't know.  eCRTP uses it,
but it's a framework.  Used by itself, I'm not sure it's very robust.

Allison

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