[e2e] overlay over TCP

Joe Touch touch at ISI.EDU
Wed Jan 19 20:38:29 PST 2005



Armando L. Caro, Jr. wrote:
> On Wed, 19 Jan 2005, Joe Touch wrote:
> 
> 
>>In particular, _if_ you're referring to PR-SCTP, please indicate where
>>in the PR-SCTP RFC its use for unreliable, out-of-order messages is
>>simply and clearly described. ;-)
> 
> For out-of-order messages, refer to Section 6.6 in RFC 2960. I think
> this section is fairly clear.
> 
> For unreliable messages, refer to Section in 3.5 and 3.6 in RFC 3758.  I
> think this section is clear, given that the reader is familiar with SCTP
> basics.

Greek is clear to a Greek as well. ;-)

Sec 3.5 and 3.6 are obscure, if the intent is to describe something that 
supports UDP-like semantics with TCp-like congestion control, such as is 
referred to in passing near the end of Sec 1 (item #3) of that RFC.

As to the full set of reasons for which DCCP is preferable to PR-SCTP, 
see sec 3.3.2 of the DCCP problem statement ID (where PR-SCTP is 
referred to as U-SCTP).

Note that item F2 in sec 3.5  of RFC 3758 also allows delaying outgoing 
chunks for aggregation; DCCP does not appear to do that (any DCCP 
experts like to chime in?)DCCP appers to correlate packets on the wire 
with application writes and reads; the same is not necessarily true with 
SCTP. There are substantial advantages to such correlation when 
tunneling network layer packets over transport protocols. I think that's 
what David Reed was referring to...

Joe
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