AIS AI2524 user manual Example Typical Lapb Configuration, Modify Lapb Protocol Parameters

Chapter 12: AI2524 X.25 Configuration Steps

2.In interface configuration mode, select an encapsulation and pro- tocol if using a single protocol or select the multiple protocol op- eration by performing one or more of these tasks:

zEnable encapsulation of a single protocol on the line using DCE operation.

encapsulation lapb dce [ protocol]

zEnable encapsulation of a single protocol on the line using DTE operation.

encapsulation lapb [dte] [ protocol]

zEnable use of multiple protocols on the line using DCE opera tion.

encapsulation lapb dce multi

zEnable use of multiple protocols on the line using DTE opera- tion.

encapsulation lapb [dte] multi

Single protocol LAPB defaults to IP encapsulation. Multiprotocol LAPB does not support source-route bridging or TCP/IP header com- pression, but does support transparent bridging. Only protocols sup- ported by a single protocol encapsulation are supported by multiprotocol LAPB encapsulation.

Example: Typical LAPB Configuration

In this example, the frame size (N1), window size (k), and maximum retransmission (N2) parameters retain their default values. The en- capsulation interface configuration command sets DCE opera- tion to carry a single protocol, IP by default. The lapb t1 interfac configuration command sets the retransmission timer to 4,000 milli- seconds (4 seconds) for a link with a long delay or slow connecting DTE device.

interface serial 3 encapsulation lapb dce lapb t1 4000

Modify LAPB Protocol Parameters

X.25 Level 2 or LAPB operates at the data link layer of the OSI refer- ence model. LAPB specifies methods for exchanging data (in units called frames), detecting out-of-sequence or missing frames, retrans mitting frames, and acknowledging frames. Several protocol parame-

August 1997	Page 12-49
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