Measurement infrastructures

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.