Switch Architecture

Let consider with a line card from a Nexus 7000 switch. In this example,  an approximation of silicon pathways inside a single M1 N7K-M108X2-12L series line card from a Nexus 7000 from a Cisco Live 2012 presentation showing the module architecture which approximates the internal silicon:

What They Do ?

Supervisor 2T White Paper

The Cisco Catalyst 6500 Supervisor Engine 2T is the latest addition to the Catalyst 6500 & 7600 family of Multi-Layer Switching Supervisor Engines. It offers much higher levels of forwarding performance, increases the scalability of many previously supported features, and introduces a host of new hardware-enabled functions beyond all previous Catalyst 6500 & 7600 Supervisor models.

This white paper will provide an architectural overview of the new Supervisor 2T. It will explore the physical layout of the Supervisor 2T, provide details about its updated hardware components, and give an overview of its newly introduced features.

High-Level Description of Supervisor 2T

The Supervisor 2T is made up of four main physical components:

●   The baseboard

●   The 5^th generation Multi-Layer Switching Feature Card (MSFC5)

●   The 4^th generation Policy Feature Card (PFC4)

●   The 2 Tbps Switch Fabric

Диагностика проблем Switch Fabric

Introduction

What is Switch Fabric?

The switch fabric is essentially the backplane for all ports and modules on the switch module. When a connection is made from a port on one module to a port on another module, it is made across the switch fabric. Physically, it is the combination of silicon, plastic, and metal that enables ports to connect and pass traffic between themselves.

The switch fabric can be blocking or non-blocking. Non-blocking fabric ensures that the total bandwidth of all ports that use the switch fabric do not exceed its capacity. What this means is that the density of the ports on the switch are such that their total capacity will never be greater than that of the switch fabric. Switches operating in non-blocking mode ensure that congestion will never occur on the switch, nor will ports ever want for bandwidth between each other.

A blocking switch has a port density capacity that exceeds the total capacity of the switch fabric. Control is possible by blocking traffic flow when the switch fabric capacity is exceeded or otherwise not available.

The switch fabric resides on the SE. When a port has to communicate with another port, it has the supervisor check its tables (Content Addressable Memory [CAM] for Layer 2 addresses and Ternary CAM [TCAM] for Layer 3 addresses) to determine what slot and port it needs. The supervisor then establishes the connection between the ports.The switch fabric can also reside on its own module (such as the Switch Fabric Module 2 (WS-X6500-SFM2) and the Switch Fabric Module (WS-C6500-SFM for the Catalyst 6500 Series), which enables the available capacity to be expanded without replacing the SE, or to expand beyond the capacity of the SE.

Архитектура Cisco Catalyst 6500

Multilayer Switch Feature Card (MSFC)

 Multilayer Switch Feature Card is the Layer 3 switching engine that sites on the Catalyst Supervisor as a daughter card. The MSFC is an integral part of the Supervisor Engine, providing high performance, multilayer switching and routing intelligence. On the MSFC daughter card, the route processor (RP) is located on the MSFC itself. Equipped with a high performance processor, the MSFC runs layer 2 protocols on one CPU and layer 3 protocols on the second CPU. These include routing protocol support, layer 2 protocols (Spanning Tree Protocol and VLAN Trunking Protocol for example), and security services.

 The control plane functions in the Cisco Catalyst 6500 are processed by the MSFC and include handling Layer 3 routing protocols, maintaining the routing table, some access control, flow initiation, and other services not found in hardware. Performance of the control plane is dependent on the type and number of processes running on the MSFC. The MSFC3 can support forwarding rates up to 500Kpps. The MSFC provide a means to perform Multilayer Switching (MLS) and interVLAN routing.

The MSFC builds the Cisco Express Forwarding information Base (FIB) table in software and then downloads this table to the hardware Application-specific-integrated circuits (ASICs) on the PFC and DFC (if present) that make the forwarding decisions for IP unicast and multicast traffic.

Role of MSFC 

1. Provide IOS based multi-protocol routing using a variety of routing protocols.
2. Work with the PFC for implementing layer 3 switching & traditional router based input/output ACL's. Note, PFC can implement ACL's without requiring a MSFC.
3. Provide other SW based features (like NAT, Policy Routing, Encryption etc) which are not supported in PFC hardware.