Status Report for SLAC/DOE IEPM Project

For November & December 1998

SLAC Home Page


Internation Telecommunication Union

Les attended the ITU meeting in Orlando Florida and made an invited presentation on Internet QoS Measurements. He was also a member of a panel on QoS. The ITU is particularly interested in Internet telephony, so prior to the meeting, we captured and analyzed Internet telephony packet streams and read up on the protocols. We also studied what performance metrics are critical to Internet telephony and what reasonable thresholds values are, and started to define and make some measurements on jitter.


Provided assistance to Colorado State and ESnet to understand the performance between Colorado State and SLAC in light of some chages in peering.


Les & Warren attended a voice conference of the XIWT. One topic was running UDP-echo servers at XIWT sites to compare with ping echo. After some discussion with security folks SLAC decided to look for another mechanism to compare with ping-echo. The goal is to see whether ping-echos are being deprecated (e.g. by traffic shaping of ICMP).


Our poster paper submission to the organizers of the INET'99 conference to be held in San Jose in June 1999, was accepted.


Les & Warren met with Chris Jones of CERN/Roche and two others from Roche pharmeceuticals to discuss details of Internet performance and to provide help with PingER.



Warren completed the work on remaking the PingER code. It calculates values for the 5 metrics (loss, response, quiescence, unreachability and unpredictability) fo 100 and 1000 byte packets for all nodes and all sites (nodes at the same site are aggregated in the latter case). The results are also split up into daily reports with hourly ticks, monthly reports with daily ticks and summary reports with monthly ticks. He has also added a new metric that we are calling the "jitter". It is the IQR of the RTT of the 10 packets.


Warren updated to allow selection of all the new options. The user can now select the metric, the monitoring site group, the remote site group, the packet size, the tick type, whether to do by site or by node, to exclude groups and to show beacon sites only. Occasionally it times out before all the page is completed.


Warren has been monitoring the icmp-seq order of the packets in our ping sample to find the magnitude of out of order packets. This can have a significant effect on Internet telephony. So far it appears roughly 1 in 10,000 samples has an out of order packet. This small effect should have no noticeable effect on Internet telephony or video conferencing. See for more information.


In order to try and understand the impact of setting IP precedence bits we are placing a monitoring machine behind a router running a new release of the Cisco IOS that can set precedence bits.

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Revised 23 December 1998
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