Subject: RE: CT reliability model was RE: [seamoby] [Issue] Support for Mu lti- Phase CT

From: "Gary Kenward" <[email-masked]>
Date: Wed, 11 Jul 2001 10:42:33 -0400

Phil:

 There is a technical reason for "polyphasic" ct (although I 
don't really like the term) and I believe it was offered up on
the list. Interestingly enough, the phases reverse themselves
for pct and rat:

   - proactive ct: it *may* be advantageous to transfer all the
     "static" context early; the dynamic, or state dependent 
     context can be transferred early on, but then there is the
     real likelihood that the state context at the old AR will 
     change and the state context at the new AR will have to
     be synchronize; OR, ctp could wait until the handover begins
     to happen to transfer the dynamic context.

   - reactive ct: the situation is somewhat reversed (although it
     is too simplistic to say the two phases of context transfer
     are in reverse order); it *may* be possible to provide a 
     close to seamless forwarding of the traffic quickly by 
     transferring critical forwarding context immediately and 
     deferring the transfer of context that is not critical to 
     forwarding; the selection of critical/non-critical is the
     tricky bit, and probably contentious.

  Of course, if all the context is easily extracted at the old
AR and fits into one MTU, then the whole rationale for two phase
ct disappears.

Gary

> -----Original Message-----
> From: Phillip Neumiller [mailto:[email-masked]]
> Sent: Wednesday, July 11, 2001 9:58 AM
> To: 'Pat Calhoun'
> Cc: Kenward, Gary [WDLN2:AN10:EXCH]; [email-masked]
> Subject: RE: CT reliability model was RE: [seamoby] [Issue] 
> Support for
> Mu lti- Phase CT
> 
> 
> > Glad to hear you like FMIPv6++, but I still don't see much of a
> > benefit in combining CT within the MIP message.
> 
> I have not heard one technical reason why NOT.  This is just YOUR
> opinion Pat.  In fact I DONT like your poly-phasic idea and I have
> stated technical reasons why.  Why don't you give me a "technical"
> reason why rather than "I don't see much of a benefit" stuff?
> 
> BTW, I have not seen any real support for your polyphasic CT on
> the list but it remains a requirement in your mind for some reason.
> 
> Thanks,
> 
> Phil
>

---

From: Pat Calhoun <[email-masked]>
Date: Wed, 11 Jul 2001 07:41:45 -0700

> AR and fits into one MTU, then the whole rationale for two phase

I think that two phases are needed, regardless of the MTU size. I
believe that in order to achieve a seamless handoff, it is necessary
to transfer time sensitive context blobs as soon as possible (e.g.
header compression, L2 keying info, L3 SAs). These are necessary
in order to exchange packets with the mobile, but there may be other
time sensitive blobs that I haven't thought of as well. Non-time sensitive
blobs (e.g. accounting session id) are not needed to send/receive packets
and therefore do not need to be sent right away.

Mind you, if you have a platform (or service) where these blobs can be
sent in a single transmission really fast, then multi-phasic may not
be desirable, and shouldn't be mandatory. Even if multi-phasic exists,
the protocol should allow for all blobs to be sent in the first
transmission.

PatC