EXP Computer PathBuilder S200 - Manual (Page 105)

Bridging 101
T0008-16F Release 5.2M
LLC2 Local Termination
Before Local
Termination 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
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
Termination 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.
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.
SNA
FEP CC
LLC2
Keepalives/Acks
Before
SNA
FEP CC
LLC2
Keepalives/Acks
LLC2
Keepalives/Acks
After