Fall Colloquium Series presents Professor Neil Spring.
Title: Underspecified Network Protocols Complicate Research
Date: Monday September 20, 2010
Location: CSIC Building, Room 1115
Network protocols are well-specified where it matters: features necessary for interoperation. For other behaviors, such as heuristics or corner cases, standards are silent or ignored. I describe two research efforts that, at the start, seemed to be straightforward but became interesting because of varied implementation choices in routers and in wireless interfaces.
Maranello is our modification of the ARQ (acknowledgment) component of 802.11 to support partial retransmissions. The potential increase in throughput provided by Maranello depends on the aggressiveness of the underlying implementation: how it performs backoff and how it selects fallback rates. I will describe our exploration of these heuristics and show how well Maranello works when interfaces are well-behaved.
Discarte is our Internet mapping technique that uses the record route IP option to complement the traditional traceroute method. Having two methods to measure the same features exposes weaknesses of each, which in turn makes it possible to use clever techniques to correct errors. I will describe our application of disjunctive logic programming to scalably analyze measurements to derive maps with few errors.