AIS user manual AI2524 Router Card User’s Manual, Configure a Lapb Datagram Transport

AI2524 Router Card User’s Manual

Configure LAPB You can use only LAPB as a serial encapsulation method if you hav a private serial line. You must use one of the X.25 packet-level encap- sulations when attaching to an X.25 network.

The LAPB standards distinguish between two types of hosts: Data Terminal Equipment (DTE), and Data Circuit-terminating Equipment (DCE). At Level 2, or the data link layer in the OSI model, LAPB al- lows for orderly and reliable exchange of data between a DTE and a DCE. A router using LAPB encapsulation can act as a DTE or DCE device at the protocol level, which is distinct from the hardware DTE or DCE identity.

Using LAPB under noisy conditions can result in greater throughput than HDLC encapsulation. When LAPB detects a missing frame, th router retransmits the frame instead of waiting for the higher layers to recover the lost information. This behavior is good only if the host tim- ers are relatively slow. In the case of quickly expiring host timers, however, you will discover that LAPB is spending much of its tim transmitting host retransmissions. If the line is not noisy, the lower overhead of HDLC encapsulation is more efficient than LAPB. When you are using long-delay satellite links, for example, the lock-step be- havior of LAPB makes HDLC encapsulation the better choice.

To configure LAPB, complete these tasks. The tasks in the first section are required; the remaining are optional.

zConfigure a LAPB Datagram Transport

zModify LAPB Protocol Parameters

zConfigure LAPB Priority and Custom Queuing

zConfigure Transparent Bridging over Multiprotocol LAPB

zMonitor and Maintain LAPB and X.25

Configure a LAPB Datagram Transport

Set the appropriate LAPB encapsulation to run datagrams over a serial interface. One end of the link must be DTE, the other must be DCE.

1.Specify a serial interface. interface serial number

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