Design of Switch Architecture for the Geographical Cell Transport Protocol

by Gyawali, Umesh

The Internet is divided into multiple layers to reduce and manage complexity. The International Organization for Standardization (ISO) developed a 7 layer network model and had been revised to a 5 layer TCP/IP based Internet Model. The layers of the Internet can also be divided into top layer TCP/IP protocol suite layers and the underlying transport network layers. SONET/SDH, a dominant transport network, was designed initially for circuit based telephony services. Advancement in the internet world with voice and video services had pushed SONET/SDH to operate with reduced efficiencies and increased costs. Hence, redesign and redeployment of the transport network has been and continues to be a subject of research and development. Several projects are underway to explore new transport network ideas such as G.709 and GMPLS.

This dissertation presents the Geographical Cell Transport (GCT) protocol as a candidate for a next generation transport network. The GCT transport protocol and its cell format are described. The benefits provided by the proposed GCT transport protocol as compared to the existing transport networks are investigated. Existing switch architectures are explored and a best architecture to be implemented in VLSI for the proposed transport network input queued virtual output queuing is obtained. The objectives of this switch are high performance, guaranteed fairness among all inputs and outputs, robust behavior under different traffic patterns, and support for Quality of Service (QoS) provisioning. An implementation of this switch architecture is carried out using HDL.

A novel pseudo random number generation unit is designed to nullify the bias present in an arbitration unit. The validity of the designed is checked by developing a traffic load model. The speedup factor required in the switch to maintain desired throughput is explored and is presented in detail. Various simulation results are shown to study the behavior of the designed switch under uniform and hotspot traffic. The simulation results show that QoS behavior and the crossing traffic through the switch has not been affected by hotspots.