Gateway link measurements @ UMass Amherst

These pages document the gateway link measurement efforts at UMass Amherst,  and provide access to the collected traces and post-processing tools for the traces.

Measurement Environment:

The UMass Amherst campus is connected to the Internet through a commerical ISP and Internet 2. Both of these are Gigabit Ethernet links. We have installed a passive monitoring infrastructure that sniffs on the packets on the commercial Gigabit Ethernet, link strips off the packet headers, and after anonymization of the address fields, archives the header-records on disk. The monitoring infrastructure consists of passive taps that redirect the signal from the underlying Gigabit fiber link. The tapped signal passes through regeneration equipment and is finally fed into an Endace DAG card in a special-purpose PC. The DAG cards strips off the TCP/IP headers of the packets, affixes an accurate timestamp on the header-record and writes it to a file. The DAG record is described here .

Access to traces:

Some of the collected and archived traces can be collected from here:

Collecting traces:

If you are an authorized UMass user, then follow this link to get information about how to configure a DAG card, collect and archive packet traces.

Post-processing tools:

After you have downloaded/collected a trace, here are some tools that can be of use:

1. parse.c: This program takes a trace file as an input and dumps out the fields of every record as ASCII text.
2. tcpflows: tcpflows is a tool that reconstructs TCP sessions from the trace and tracks performance statistics such as end-end retransmission, reordering rates, RTT, and other connection characteristics such as TCP sender window size, congestion control flavor etc.

Please contact Kyoungwon Suh (k w s u h A_T cs.umass.edu) for any queries regarding these measurement efforts.