The TCP/IP Implementor's Working Group met in Munich, on Monday, August 11th, at 7:30 PM. Steve Alexander presented an overview of recent changes that have been made to the "Known Problems" I-D. There were two, namely: - a discussion of keepalive problems was added - the "significance" category now includes a description of environments in which the problem is significant Steve Parker then gave an overview of the current status of the "Testing Tools" I-D. For each tool listed, the document provides information on: - name - category - availability - description - an overview of how automated the tool is - other references Currently the following tools are described: - dummynet, netperf, orchestra, packet shell, tcpanaly, tcptrace, tcplook, treno Feedback from the audience suggested two additions: - sock (Rich Stevens' test program); Kent Malave agreed to provide a description of this - SPINS, a protocol verification package The next item on the agenda was an overview of proposed changes to RFC 2001. 2001 is being revised to allow implementations which implement the required algorithms in an acceptable manner, but which may differ slightly from 4.3-BSD-Reno to be considered conformant to RFC 2001. At the same time, it is proposed that the initial slow-start window should be increased to two segments. There is an internet draft written by Floyd/Allman/Partridge, which discusses some additional proposed changes. Craig Partridge gave an overview of terms: - IW; initial congestion window - RW; restart congestion window after idle - LW; congestion window used after a loss Sally Floyd indicated that more research was needed to ensure that the correct trade-offs are made between good scenarios and bad. Craig Partridge asserted that no simulations done to date showed any problems with raising IW to two segments, but agreed that more cross-traffic simulation is probably a good idea. Allyn Romanow pointed out that not all of the changes in the Floyd/Allman/ Partridge draft were being considered for the RFC 2001 update; only increasing IW to two segments. Van Jacobson gave a historical overview of the reasons for the IW being one segment initially, namely a very early ethernet card that could only buffer a single frame on receive. Van also pointed out that dropped SYNs were a large problem with current web traffic. It was pointed out that if the congestion window oscillated between one segment and two, that this might be less bursty than with four. Matt Mathis pointed out that the current spec (2001) isn't completely up-to-date with all of the latest TCP congestion control enhancements. Craig agreed that more simulation should be done to ensure that fairness issues are handled correctly. Van pointed out that timing is really used for congestion control. He explained that the RTT est. is not really used to estimate round trip time, but rather as a clock to determine when it is likely that a packet has left the network. Van suggested that using the max rtt might be better than using the single RTT, which is a lower bound. Craig Partridge volunteered to write up the RTO algorithm (Karn's) as an RFC, since it is not currently documented in the RFC series. Bob Braden mentioned that the reason that a lot of Van's early work is not explained in RFC 1122 is that the 1122 working group didn't think that they could explain it as well, and that it provided an incentive to read the paper and get the whole story. It was suggested that Van should convert the paper into an RFC; Van seemed amenable. After the congestion control discussion ended, a list of outstanding problems for the "Known Problems" I-D was presented, and again, volunteers were solicited to contribute text to the I-D. Bernard Volz mentioned a new problem, namely implementations that only send a FIN after all outstanding data has been ACKed; this should be added to the I-D. A discussion of the IRTF End2end group's position on research vs. engineering was skipped. This was because the summary had been posted to the mailing list but generated little interest. The meeting then adjourned. Action items: - Kent Malave, write up description of 'sock' - Ian Heavens, write up issues around half-duplex close - Van Jacobson, possibly write up latest SIGCOMM paper as RFC - Craig Partridge, write I-D on Karn's algorithm -- Steve Alexander, Vern Paxson