3Com PathBuilder S200 Series Owner's Manual page 105

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:
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.
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
T0008-16F
• Inefficient use of the WAN bandwidth
• Increased session timeouts
• Ongoing tuning of network parameters to fix session timeouts
LLC2
SNA
FEP
Keepalives/Acks
Before
SNA
FEP
LLC2
Keepalives/Acks
After
LLC2 Local Termination
CC
CC
LLC2
Keepalives/Acks
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Release 5.2M