"Paul E. Jones" wrote: ...
I am definitely giving consideration to using a modified Annex E/H.323.
Taking a broader view, I think that a connectionless approach is the right solution. I am considering both how Annex E or SCTP might satisfy the requirements .
Similat to TCP or SCTP, Annex E achieves its data reliability by means of sequence numbering and retransmission of lost messages. This requires both sides initialize sequencing and retransmission state and keep tracking those state during data transfer. From this view, Annex E can hardly be categorized as connectionless when used for reliable data transport.
I guess you were probably more referring to the "fast set-up" feature of Annex E, ie., you can send a user message to a new destination without explicitly going through a set-up procedure (while the sender and receiver stack will still internally go through set-up to allocate resource for the state information of this new connection and start tracking the sequence number, etc). This can be done with SCTP by piggy-backing the first user message with the INIT and INIT-ACK. The problem with this approach (the same is true to Annex E) is that you will lose most of the security protection on the destination end. People may argue that you can always run Annex E over IPSEC to get the protection, but IPSEC session is connection-oriented; before you can deliver the first user message, the IPSEC itself will need to establish an security association between the two endpoints.
-Qiaobing