The All-New Switch Book: The Complete Guide to LAN Switching Technology, Second Edition

Chapter 17. Make the Switch!

Up to now, we have considered the various facets of switch operation only in isolation; that is, the issues related to flow control, Multicast Pruning, VLANs, Priority Operation, and so on, were treated independently of one another. This chapter shows how many of the concepts and mechanisms that have been discussed can be integrated into a complete switch architecture. Because the operation of these switch functions has already been discussed in depth in earlier chapters, no detail is provided here. This chapter focuses on how the various functional elements are combined in practical switches.

The approach taken is to walk through a hypothetical switch from input port to output port. At each stage, we look at the operations that must be performed, and in particular, the order in which actions must be taken to achieve the desired end results. To get the maximum benefit from this process, we assume that our switch is fully featured; that is, in addition to the basic functionality of a transparent switch, we consider the implications of:

• IEEE 802.3x Flow Control

• IEEE 802.3ad Link Aggregation

• IEEE 802.1p Multicast Pruning

• IEEE 802.1Q Virtual LAN support

• IEEE 802.1p/Q Priority Operation

• Network management

Of course, many switches implement only a subset of these capabilities, either for the switch as a whole or for particular ports (for example, not every switch port will be part of an aggregation). Those functions that are not implemented just simplify ...