Recently, the application space of interconnection networks has started
expanding to areas such as IP router fabrics and I/O interconnects (e.g. the
Avici TSR and InfiniBand). Unlike traditional processor-memory
interconnection, the worst-case throughput of an interconnection network becomes
an important design consideration. For example, in the IP router
application, little can be said about the arrival process of incoming packets. At the
same time, there is no path to quickly apply backpressure to slow this flow of
packets. So, if the incoming packet rate exceeds the worst-case throughput
of the router, packets may be dropped. Obviously, a system designer would
like to be able to characterize this worst-case behavior.
In this work, we develop a polynomial-time algorithm to find the exact
worst-case throughput for most oblivious routing functions on an
arbitrary network topology. An oblivious routing function is one in which
a packet's path through the network depends only on its source and
destination. We show several key results using this algorithm:
 |
Our algorithm offers a significant increase in
accuracy over existing techniques for characterizing the worst-case throughput. |
 |
Traditional believes about
routing function design, such as increased route diversity leads to higher
throughput, do not always hold when considering the worst-case. |
Publications:
 |
Towles,
Brian and Dally, William J.
, "Worst-case
Traffic for Oblivious Routing Functions," (preliminary version) ACM Symposium on Parallel Algorithms and Architectures
(SPAA), Winnipeg, Manitoba, Canada, August, 2002. |
 |
Towles,
Brian and Dally, William J.
, "Worst-case
Traffic for Oblivious Routing Functions", Computer Architecture
Letters, Vol. 1, Feb. 2002. |
 | Towles,
Brian, "Finding
Worst-case Permutations for Oblivious Routing Algorithms,"
Concurrent VLSI Architecture Technical Report 121, December 2001. |
Back to main page |