Editor's note: These minutes have not been edited.
Los Angeles IETF Proceedings
Transport Services Area
Minutes of the Transaction TCP BOF (ttcp)
Reported by: Bob Braden/USC Information Sciences Institute
This BOF was convened to discuss a set of TCP extensions for efficient transaction-mode communication, i.e., request-response mode, which is currently documented in an Experimental RFC [Braden, R., "T/TCP -- TCP Extensions for Transactions, Functional Specification", RFC-1644, ISI, July 1994]. There has recently been interest in using T/TCP, especially as a component of performance improvements for the World Wide Web. As a result, some have suggested starting a working group to create a standard.
This BOF was convened to discuss T/TCP and its possible standardization. The main speaker was Bob Braden, who developed T/TCP as an NSF-funded research project. This talk covered the history of early efforts to define an Internet standard transaction transport protocol, the development of TCP, a brief outline of the theory and features of T/TCP, and finally its advantages and disadvantages. See the slides following.
A number of interesting issues were raised.
* T/TCP optimizes transactions after the first between any
pair of hosts. However, some transaction-mode applications, e.g., the DNS, have the property that a given client makes individual transactions to a large number of different servers, in which case T/TCP will not provide much performance improvement over pure TCP.
To provide efficient transaction transport in that case, synchronized clocks are needed. It was suggested that one might consider synchronizing clocks for DNS server hosts, a small subset of all Internet hosts.
* More work may be needed on T/TCP congestion control. As a
a compatible extension of TCP, T/TCP includes all the normal TCP congestion control machinery, which comes into play as transactions become larger. However, it was observed that TCP has no congestion control on SYN segments, and if there is heavy use of T/TCP for minimal transactions, the Internet will be filled with SYN segments. It may be necessary to include some rate-based control over transactions, in addition to the normal byte-based congestion control of TCP.
* One view of T/TCP is that each request and each response is
a logical "record". In a stream of successive transactions between the same (client,server) pair, connection termination is effectivley being used as a record mark. An alternative way to get the record mark functionality would be to insert a "thin" protocol layer above TCP, a "session" layer", whose framing carries a record mark. This alternative is being explored for the World Wide Web.
* Christian Huitema recently proposed a TCP modification in which
each packet carries logical connection handle, to better support mobility and dynamic host configuration. Since T/TCP also introduces a logical connection handle, an incarnation number or "connection count", it may be possible to use the same handle for both.
The group consensus was that it would be useful to have a working group to consider standardization of T/TCP. Roughly a dozen people out of the 60 attendees indicated that they would participate in such a working group. The chair promised to report this to the Area Director.