Switch/Router Architectures

8Architectures with Shared-Memory-Based Switch Fabrics: Case Study—Cisco Catalyst 3550 Series Switches

8.1 Introduction

The Cisco Catalyst 3550 Series are fixed configuration, stackable switches that employ a distributed shared memory switch fabric architecture. The architecture of the Catalyst 3550 is based on the older Catalyst 3500 XL Layer 2 (only) switch [CISC3500XL99]. The Catalyst 3500XL switch is one of the switches that belongs to the Catalyst “XL” family of switches that includes the Catalyst 2900XL and Catalyst 2900XL LRE. The XL family of switches are strictly Layer 2 switches, with no Layer 3 capabilities beyond the simple functions provided by the management interface (Telnet, SNMP, etc.).

The Catalyst 3550 switches are enterprise-class switches that support Layer 2 and 3 forwarding as well as quality of service (QoS) and security features required in many of today's networks. The Catalyst 3550 Series support a range of 100 Mb/s Ethernet and Gigabit Ethernet interfaces that allow them to serve as access layer switches for medium enterprise wiring closets and as backbone switches for medium-sized networks.

In the Catalyst 3550 [CISC3550DS05, CISC3550PRS03, CISCRST2011], all Layer 2 and 3 forwarding decisions are performed in network interfaces modules ASICs (referred to as satellite ASICs). The Layer 2 and 3 forwarding decisions in some cases involve processing Layer 4 parameters of the arriving packets. The network satellite ASICs manage either a group of 100 Mb/s ...