3com MSR 20-20 참조 매뉴얼

Use the sdlc modulo command to configure the modulus of the SDLC.

Use the undo sdlc modulo command to restore the default setting.

By default, the SDLC modulus is 8.

Like X.25, SDLC uses the modulus method to number frames. All frames sent are 
numbered incrementally and await an acknowledgment. When the frame number 
reaches the configured value (referred to as “modulus value”), subsequent frames 
are numbered from 1 again. For example, if the modulus value is set to 8, frames 
are numbered ...4, 5, 6, 7, 0, 1, ...

SDLC normally uses 8 as the modulus value.

# Restore the modulus value of SDLC to the default setting on Serial 2/0.

<Sysname> system-view

[Sysname] interface serial 2/0

[Sysname-Serial2/0] undo sdlc modulo 

sdlc sap-map local lsap sdlc-addr

undo sdlc sap-map local lsap sdlc-addr

Synchronous serial interface view

lsap: SAP address, in the range of 0x01 to 0xFE.

sdlc-addr: SDLC address, in the range of 0x01 to 0xFE.

Use the sdlc sap-map local command to configure the local SAP address to be 
used in SDLC-to-LLC2 frame format conversion.

Use the undo sdlc sap-map local command to restore the system default.

By default, the local SAP address used in SDLC-to-LLC2 frame format conversion is 
0x04.

When an SDLC frame is converted into an LLC2 frame, a SAP address is needed in 
addition to the MAC address.

Generally speaking, the SAP address used by the SNA protocol is 0x04, 0x08 or 
0x0C.

# Configure the SAP address to be used in SDLC-to-LLC2 frame format conversion 
on Serial 2/0.