3Com 2000 TR manual How TR-in-FE Works

How TR-in-FE Works

Figure 2-1 shows a diagram of a basic TR-in-FE sys- tem. The illustration depicts three Switch 2000 TRs interfacing with a Switch 3000 through the Token Ring-in-Fast Ethernet Module. In this example, the Switch 3000 acts as an 800 Mbps point of aggrega- tion for this system with multiple FDX Fast Ethernet pipes feeding it.

Traffic that enters a port on the Token Ring switch and that is not destined for another port on the same switch is directed at the TR-in-FE Module. Subse- quently, the module puts a Fast Ethernet wrapper (see “Tunneling” section below) on the native Token Ring frame, and forwards the modified packet as a Fast Ethernet frame to the Switch 3000.

The Switch 3000 handles the frame as it would any other FE frame and forwards it to the appropriate port. If the destination address is another TR end sta- tion located on another switch, the destination TR-in-FE Module strips the frame of the Fast Ethernet information and sends the native TR frame to the appropriate destination port. If the destination is a Fast Ethernet attached server, the Fast Ethernet NIC with a TR-in-FE driver interprets the frame before pro- viding it to upper level applications. The fact that the application communicates using TR-in-FE is transpar- ent to the user.

How TR-in-FE Works 2-3

		II
	SuperStack			TR
	2000
	Switch
	II
	SuperStack		TX
	3000
	Switch
				Fiber
Fast	Ethernet			Copper
Server

Figure 2-1A Simple Token Ring-in-Fast Ethernet Configuration

Figure 2-2 illustrates another example of Token Ring-in-Fast Ethernet, but one on a scale more exem- plary of what a real user configuration looks like as part of an integrated system.