3Com MSR 50, MSR 30 manual Lapb max-frame, Syntax lapb max-frame n1-value Undo lapb max-frame, 433

433

tcp peer ip: 10.1.1.1, peer port: 1998

tcp local ip: 10.1.1.2, local port: 1024

socket keepalive period: 5, keepalive tries: 3

come interface name: Serial1/0-10.1.1.1-1024

go interface name: Serial1/0

lapb max-frame

Syntax lapb max-frame n1-value

undo lapb max-frame

View Interface view

Parameter n1-value: N1 value of the LAPB parameter in bits, in the range 1096 to 12104. It is the maximum value of a frame expected from the DTE or DCE, 8 times the value of MTU plus the protocol header.

Description Use the lapb max-framecommand to configure the LAPB N1 parameter.

Use the undo lapb max-framecommand to restore the default.

The default value of N1 is calculated according to the MTU, upper layer protocol and modulo, as shows below:

Table 64 Difference between N1 and MTU (in bytes) versus upper layer protocol and modulo

		Difference between N1 and
Upper layer protocol	Modulo	MTU (bytes)
IP/IPX	8	4
IP/IPX	128	5
Multiprotocol	8	6
Multiprotocol	128	7
X.25	8	7
X.25	128	8

The default value of N1 varies with MTU and modulo.

For example, upon system initialization, the upper layer protocol is IP, modulo 8 and MTU 1500, so the default value of N1 is (1500+4)*8 = 12032. If the modulo is set to 128, then the default value of N1 is (1500+5)*8 = 12040. You can use the undo lapb max-framecommand to restore the new default. For the same reason, N1 changes with the change of MTU.

Example # Set the LAPB N1 parameter to 1160 on Serial 2/0.

<Sysname> system-view

[Sysname] interface serial 2/0

[Sysname-Serial2/0] lapb max-frame 1160