Cisco Systems 8600 Series manual Virtual Switch Interfaces, BPX Switch VSI Interfaces

Tag Switching and the BPX 8650

Virtual Switch Interfaces

Figure 9-5shows how virtual switch interfaces are implemented by the BPX switch in order to facilitate tag switching. A virtual switch interface (VSI) provides a standard interface so that a resource in the BPX switch can be controlled by additional controllers other than the BPX controller card such as a tag switch controller.

The tag switch controller is connected to the BPX switch using ATM T3/E3/OC3 interfaces on the TSC device (a 7200 or 7500 series router) and on a BXM card. The ATM OC3 interface on the 7200 router is provided by an ATM port adapter, on the 7500 router by an AIP or a VIP with ATM Port Adapter, and for the BXM front card by an ATM OC3 4-port or 8-port back card.

Figure 9-5 BPX Switch VSI Interfaces

BPX 8650 Label Switch Router (LSR)

	BPX switch
		BXM 3
					ATM OC3 interface
	VSI slave
					VPI.VCI A (VSI master to slave I/F)
					VPI.VCI B (VSI master to slave I/F)
		Backplane
					VPI.VCI C (VSI master to slave I/F)
BXM 1			BXM 2	Note:
VSI slave			VSI slave
				Dotted lines indicate
				VSI to VSI slave I/Fs

Router

(7200 or 7500)

Tag

switch controller

VSI master

S6878

To ATM edge router or other ATM LSR (BPX 8650 or LS 1010)

A distributed slave model is used for implementing VSI in a BPX switch. Each BXM in a BPX switch is a VSI slave and communicates with the controller and other slaves, if needed when processing VSI commands. The VSI master sends a VSI message to one slave. Depending on the command, the slave either handles the command entirely by itself, or communicates with a remote slave to complete the command. For example, a command to obtain configuration information would be processed by one slave only. A command for connection setup would cause the local slave to communicate with the remote slave in order to coordinate with both endpoints of the connection.

Figure 9-6shows a simplified example of a connection setup with endpoints on the same slave (BXM VSI), and an example of a connection setup with endpoints on different slaves (BXM VSIs) is shown in Figure 9-7.

Tag Switching 9-9