 
Summary: Optimal Node Routing
Yossi Azar # Yoel Chaiutin +
Abstract
We study route selection for packet switching in the competitive throughput model. In
contrast to previous papers which considered competitive algorithms for packet scheduling, we
consider the packet routing problem (output port selection in a node). We model the node
routing problem as follows: a node has an arbitrary number of input ports and an arbitrary
number of output queues. At each time unit, an arbitrary number of new packets may arrive,
each packet is associated with a subset of the output ports (which correspond to the next
edges on the allowed paths for the packet). Each output queue transmits packets in some
arbitrary manner. Arrival and transmission are arbitrary and controlled by an adversary. The
node routing algorithm has to route each packet to one of the allowed output ports, without
exceeding the size of the queues. The goal is to maximize the number of the transmitted packets.
In this paper, we show that all nonrefusal algorithms are 2competitive. Our main result is an
almost optimal e
e1 # 1.58competitive algorithm, for a large enough queue size. For packets
with arbitrary values (allowing preemption) we present a 2competitive algorithm for any queue
size.
1 Introduction
Overview: A general network consists of nodes (routers) and communication links through which
