cheriton@PESCADERO.STANFORD.EDU ("David Cheriton") (11/14/88)
In response to some complaints about lack of activity on this mailing list, here's a brief comment on some of the work going on. A recent effort with V has been to extract the transport protocol techniques used to achieve fast network IPC performance and develop a high-performance general purpose protocol for consideration as a standard. For example, there is currently no protocol in the IP/TCP suite that properly supports RPC, multicast and other aspects of V-style RPC. The result of this effort is VMTP (see RFC1045), which has taken much greater effort and many more revisions (and insights) than ever anticipated at the begining. A Unix version of the software is now available and we are revising the V kernel to bring it up to the VMTP specification. A key intersting technique that has lead to significant simplifications in the protocol is recursion. In the original protocol there were special packet types for data copy operations, for acknowledgements, for message forwarding and even locating operations (GetPid()). VMTP now includes only two packet types (Request and Response). All the other operations are implemented in terms of these two types. To illustrate, the acknowledgement packets were replaced by datagram requests to the VMTP communication manager of the sender. (These techniques and more are described in a SIGCOMM'88 paper, ``Exploiting Recursion...'') The result has been to simplify the IPC implementation, the protocol specification and the hardware support for the VMTP, we are developing as part of another project (see Kanakia and Cheriton... SIGCOMM'88.) (These papers can be requested from nevena@pescadero, including your postal address.) VMTP is now evolving to a draft standard status in the Internet community (and will hopefully receive even wider acceptance.) We expect VMTP to provide the bases for experimentation with security, real-time, scaling, and possibly fault tolerance using V. The use of recursion seems like a powerful tool for structuring and simplifying the protocol. PS An announcement of the availability of VMTP for Unix should go out in the next week.