Design of multiported interfaces to improve local area network performance.

摘要

Networked applications, increasing in popularity and requiring more bandwidth with each software release, will generate ever-increasing traffic in a local area network. These networked applications' bandwidth requirements will continue to increase until they exceed existing transceiver technology. When bandwidth-limited by transceiver speeds, one deploys trunks (parallel communications channels) to increase the aggregate data rate between two directly connected entities.; The de facto standard local area network (LAN) is switched Ethernet. A switched Ethernet network is a LAN whose topology is created by interconnecting client machines directly to switches. Switches form the core of the network's infrastructure and are used to forward traffic from a source to a destination via category 5 twisted pair cabling. Since local area network switches are often constructed with twenty-four to forty-eight ports, trunking client machines would require installation of additional switches. A switched Ethernet network with N channel trunks does not scale—it requires N switch ports per client. Therefore, trunks will not be deployed in the local area because they do not scale in switched Ethernet. Since trunks will not be deployed in the local area, future networked applications will be bandwidth-limited by transceiver speeds.; This research proposes that multichannel local area networks (MLANs) should be used when client machines become bandwidth-limited. An MLAN is a local area network topology created by equipping client machines with multiported network interface cards. Each MLAN's client machine thus can transmit and receive data on multiple Ethernet segments. This work hypothesizes that a network architecture based upon MLANs could increase the aggregate data rate of client machines (as is used in trunking). The resultant network should scale in low-cost switched Ethernet networks without modifying the network's existing infrastructure (the switches or the wiring) by interconnecting multiple clients per switch port. The examination will assess the viability of the MLAN local area network architecture and determine its performance limitations.; An MLAN's performance is dependent upon the architecture of its client machine's multiported NIC. With multiple channels available to client machines, the work explores the performance of MLANs in comparison with equivalent switched Ethernet topologies constructed with traditional single ported NICs. This thesis shows how an MLAN's client machines should select a channel on which to transmit a packet with two currently relevant networked applications-web browsing and video. When transmitting web browser traffic, the focus of this research is how channel selection impacts file throughput; and, when transmitting video traffic, how channel selection impacts packet latency. Finally, extensions to the contention-based network protocol (Ethernet) are examined to improve application performance.; All experiments are conducted using discrete event simulation and show the following. When transmitting web browser traffic, the MLAN's file throughput is approximately a factor of three less than an equivalent single channel topology; and, when transmitting video traffic, an MLAN's average packet delay is approximately 10–30% higher than an equivalent single channel topology. Extensions to the Ethernet protocol decrease the rate with which packets are dropped for all MLAN's, however, the decrease is dependent upon a combination of the multiported NIC's architecture and traffic source. The rate of dropping packets ranges from no improvement to approximately a factor of 50.