Nortel Networks 8000 - Manual (Page 212)

Nortel Secure Router 8000 Series
Configuration -WAN Access 7 LAPB and X.25 configuration
For Router A and Router D, the whole process of setting up and applying TCP connection is
transparent, and it does not matter whether the data is forwarded through the IP network or
X.25 network.
Features of the XOT in the SR8000
Implementing XOT in the SR8000 accords with RFC1613 recommendation and possesses the
following features:
• Supports SVC application. The two routers can dynamically set up a SVC by sending a
call packet, and the VC is automatically cleared when no data is transmitted.
• Supports PVC application. After the two routers configure a PVC, they directly enter the
data transmission status without the process of call creation. If no data is transmitted, the
VC is not cleared dynamically.
• Supports the Keepalive attribute of TCP. If Keepalive is not configured, TCP connection
is not cleared for a long time after the line is disconnected. If Keepalive is configured,
TCP checks the availability of the links, and automatically clears the TCP connection if
no reply is received from the opposite side for a certain number of times.
7.2 LAPB configuration
7.2.1 Establishing the configuration task
Applicable environment
As an independent link layer protocol, LAPB can carry IP protocols to transmit data in IP
network.
Preconfiguration tasks
None.
Data preparation
To configure LAPB, you need the following data.
No. Data
1 LAPB window parameter K
2 Frame numbering mode (also called modulo)
3 N1: the maximum bits of the I frame.
4 N2: the maximum retry that DCE or DTE sends a frame to DTE or DCE
successfully
5 Time of the system timers T1 and T2 and T3 in LAPB
Issue 5.3 (30 March 2009) Nortel Networks Inc. 7-9