RE: SCTP for CARD?

Hi all,

Just as a meta point - for interoperability, two option transports
will cause interoperability problems.  If there are two nodes
that both support different transport protocols, they will be unable
to communicate.

If you make one protocol a SHOULD and another a MAY - then there
needs to be some text about this problem, at least a warning.

John

> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]]On Behalf Of
> ext Eunsoo Shim
> Sent: 10 April, 2004 00:39
> To: James Kempf; Trossen Dirk (Nokia-NRC/Boston); [email protected];
> [email protected]
> Subject: Re: [Seamoby] SCTP for CARD?
> 
> 
> James,
> 
> Could we make SCTP an option rather than the required 
> transport protocol as
> suggested by Dirk?
> I am reluctant to bring in SCTP to test CARD at this moment.
> What do you think?
> 
> Eunsoo
> 
> > Dirk,
> >
> > We could specify that people can experiment with UDP (MAY), 
> but we don't
> > need to ask for an IANA port allocation. In the CTP draft, the new
> transport
> > section says SCTP is required but people are encouraged to 
> experiment with
> > ICMP or UDP to determine what is best. We could do the same 
> for CARD.
> >
> > How does that sound?
> >
> >             jak
> >
> >
> > ----- Original Message ----- 
> > From: "Dirk Trossen" <[email protected]>
> > To: <[email protected]>; <[email protected]>;
> > <[email protected]>; <[email protected]>
> > Sent: Friday, April 09, 2004 5:56 AM
> > Subject: RE: [Seamoby] SCTP for CARD?
> >
> >
> > > Hi James,
> > >
> > > excellent idea, in particular considering the 
> experimental status of
> > > CARD.
> > >
> > > One point though. What if an AR does not implement CTP? 
> It would still
> > > need an SCTP implementation for CARD which might be more overhead
> > > compared to UDP. So do we want to throw out UDP entirely 
> or define it as
> > > using UDP as minimal and have SCTP as optional extension, 
> in particular
> > > in combination with CTP?
> > >
> > > Dirk
> > >
> > >
> > >
> > > ))) Message sent using Nokia Access Mobilizer -- 
> > www.nokia.com/accessmobilizer (((
> > >
> > > --- Original Message ---
> > > From: ext James Kempf <[email protected]>
> > > To: [email protected], [email protected]
> > > Date: Thu Apr 08  16:11:10 EDT 2004
> > > Subject: [Seamoby] SCTP for CARD?
> > >
> > >
> > > Folks,
> > >
> > > While working to resolve the AD Review comments about 
> congestion and
> > > transport on CTP, it occured to me that the same comments 
> might apply to
> > > CARD for the interrouter protocol (Section 5.2.1), since the two
> protocols
> > > will be running inter-router in the same kinds of 
> networks. SCTP (RFC
> > 2960)
> > > has some very nice features that make it attractive for 
> this purpose,
> > > including a partial reliability mode (see 
> draft-ietf-tsvg-prsctp-03.txt,
> > now
> > > on the RFC Editor queue) which allows an application to 
> cause congestion
> > > retransmits to be cancelled if a realtime constraint is 
> not met. One
> > > difference is that the interrouter CARD presumably won't 
> have such a
> > > realtime constraint, because it won't be run when the MN 
> asks for the
> CARD
> > > information, but rather during updates of the caches on 
> both routers,
> due
> > to
> > > changes in the network configuration. The CARD spec is somewhat
> ambiguous
> > on
> > > this point, Section 4.4.2 seems to imply that it will be 
> run if the
> router
> > > has a cache miss and thus would have a realtime 
> constraint, while in
> > Section
> > > 4.2.2, it says that if the current AR doesn't have the 
> capabilities, it
> > > should return an error message to the MN, not poll all 
> the local CARs.
> The
> > > latter sounds more likely to be the better performer in 
> the end, but
> SCTP
> > > could accommodate either case.
> > >
> > > Another advantage of using SCTP is that we can use the 
> same port for
> both
> > > CARD and CTP and use the PPI to differentiate them. The PPI is the
> Payload
> > > Protocol Identifier that tells what protocol is in the 
> payload. This
> would
> > > allow us to address the Discuss from Ted Hardie and 
> Thomas Narten, about
> > > allocating scarce port resources to experimental protocols.
> > >
> > > Finally, since CARD is experimental, I think this would 
> be an excellent
> > > opportunity to try out SCTP in a real application, 
> without impacting
> > > anybody's product or deployment plans. If it doesn't 
> work, we can always
> > > revert to using UDP when and if CARD is taken to proposed 
> standard.
> > >
> > > So, I'd like to propose that we replace the current 
> somewhat ambiguous
> > > specification for UDP between ARs with SCTP, and 
> multiplex with CTP over
> > the
> > > same port.  There would be no change to the AR-MN transport.
> > >
> > > Comments? Please send them by next Thurs.
> > >
> > >             jak
> > >
> > >
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> >
> >
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> 
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