Sally Floyd: Questions

• ROUND-TRIP TIMES (HOPS, NUMBER OF ASes) OF PACKETS?
  For packets on a particular link, each packet could be assigned an estimated round-trip time, a number of ASes for the end-to-end path, etc, based on the IP source and destination addresses for that packet. For packets on a particular link, what can we say about the distribution of round-trip times, or of the number of hops traversed, or the number of ASes traversed, or number of continents traversed, or (this is harder) the number of congested links traversed?

  [Example: For link X, can we say that most packets/bytes stay on that continent? Or that most packets have a minimum round-trip time of at least S seconds? Or that most packets on that link during this period of time traverse more than one congested link on their path from source to destination?]

• Andre Broido's presentation on Invariance of Internet RTT Spectrum at the SMA Oct 2002 Workshop looks at properties of distributions of round-trip times.
• Hao Jiang and C. Dovrolis's 2002 paper on Passive Estimation of TCP Round-Trip Times estimates the distribution of roundtrip-times, by connection and by byte, from several 2001 tcpdump traces.
• Constantinos Dovrolis reports on distributions of RTTs, from 1999, for the OC-3 link between UCSD and CERFnet.
• Mark Allman's A Web Server's View of the Transport Layer looks at path properties and TCP and HTTP protocol behavior from clients to a particular web server. The paper looks at the range of round-trip times, packet sizes, and other issues.
• The paper on TCP Behavior of a Busy Internet Server: Analysis and Improvements has packet trace data from the 1996 Olympic Web server. The lower quartile, median, and upper quartile of the distribution of round-trip times are 115 ms, 338 ms, and 778 ms, respectively.
• Ping Pan gave some pointers for data on:
  • Average hop counts
  • Merit Network's Statistics and Daily Reports on the routing table and routing problems.
• Andras Veres has raw data on the time delay between the first TCP SYN and the ACK.