EXP Computer S200 Manuel D’Utilisation

Bridging 

101

T0008-16F

Release 5.2M

Without Local Termination, networks face significant problems with bandwidth 
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

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.

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

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.

SNA

FEP

CC

LLC2

Keepalives/Acks

SNA

FEP

CC

LLC2

Keepalives/Acks

LLC2

Keepalives/Acks