EXP Computer S200 Before Local, Well as network delays, Terminal session, causing, After Local

LLC2 Local Termination

Before Local	Without Local Termination, networks face significant problems with bandwidth
Termination	usage and session timeouts due to polling overhead between the host and terminal, as
	well as network delays.
	For example, Figure 49 shows a terminal session on a source route bridged Token
	Ring LAN connected to a host without Local Termination. During the terminal
	session, LLC2 polls, such as ACKs and keepalives, are exchanged between the host
	and the terminal session, causing:

• Inefficient use of the WAN bandwidth

• Increased session timeouts

• Ongoing tuning of network parameters to fix session timeouts

SNA

FEP

LLC2

Keepalives/Acks

Before

CC

Figure 49. Before Local Termination Example

You can increase timer values to reduce the number of session timeouts experienced on a network, but configuring large numbers of stations makes such a solution impractical. Moreover, it does not solve the problem with “keepalives” slowing down network traffic.

After Local	The best solution to such network traffic problems is to locally terminate the LLC2
Termination	session at the Token Ring interface, as shown in Figure 50.

SNA

FEP

LLC2

Keepalives/Acks

After

CC

LLC2

Keepalives/Acks

Figure 50. After Local Termination Example

Using LLC2 LT, you can spoof traffic on a Token Ring LAN, reducing the polling overhead by minimizing session timeouts. Ack and “keepalive” messages traverse the network between spoofers; they are controlled in frequency by the WAN parameters.

Bridging 101

T0008-16F Release 5.2M