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In contrast, wide-area measurement infrastructures, such as NIMI and
Surveyor, deploy measurement software at both the sender and the
receiver to correctly measure one-way network characteristics
[Pax96,PMAM98,Alm97]. Such approaches are technically ideal for
measuring packet loss because they can precisely observe the arrival
and departure of packets in both directions. The obvious drawback is
that the measurement software is not widely deployed and therefore
measurements can only be taken between a restricted set of
hosts. Our work does not eliminate the need for such infrastructures,
but allows us to extend their measurements to include parts of the
Internet that are not directly participating. For example, access
links to Web servers can be highly congested, but they are not
visible to current measurement infrastructures.
Finally, there is some promising work that attempts to derive per-link
packet loss rates by correlating measurements of multicast traffic
among many different hosts [CDH+99]. The principle benefit of
this approach is that it allows the measurement of N2 paths with
O(N) messages. The slow deployment of wide-area multicast
routing currently limits the scope of this technique, but this situation may
change in the future. However, even with universal multicast routing,
multicast tools require software to be deployed at many different
hosts, so, like other measurement infrastructures, there will likely
still be significant portions of the commercial Internet that can not
be measured with them.
Our approach is similar to ICMP-based tools in that it only requires
participation from the sender. However, unlike these tools, we
exploit features of the TCP protocol to deduce the direction in which
a packet was lost. In the next section we describe the algorithms
used to accomplish this.
Next: Loss deduction algorithm
Up: Measuring packet loss
Previous: ICMP-based tools
Stefan Savage
8/31/1999