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128 CHAPTER 10: CONFIGURING WAN INTERFACE
12 Configure MTU
MTU of synchronous serial interface affects the fragmentation and reassembling
of IP network protocol message on this interface.
Please use the following commands in the view of the synchronous serial
interface.
Table 121 Set MTU of synchronous serial interface
The unit of mtu is byte, ranging between 128-1500, with 1500 as default.
13 Configure the time interval for sending keepalive packets
The serial interface will send keepalive packets to the opposite end at every
keepalive interval to check if the link is in normal state or not.
Perform the following configuration in serial interface view.
Table 122 Set the time interval for sending keepalive packets
The time interval for sending keepalive packets is 10 seconds by default.
CAUTION: When the serial interface is encapsulated with HDLC protocol, the
keepalive interval set on both ends of the link must be the same.
14 Set the idle coding of synchronous serial interface
Perform the following configuration in serial interface view.
Table 123 Set the idle coding of synchronous serial interface
The idle coding of synchronous serial interface is "7E".
ISDN BRI Interface Technical Background
Integrated Services Digital Network (ISDN) is a new technology developed from
the 1970’s. It can provide all-digital services from terminal user to terminal user
and fulfill an all-digital transmission mode integrating services such as voice, data,
graphics and video.
ISDN is different from conventional PSTN. In conventional PSTN, information is
sent to the switch via analog user loop, converted to digital signal through A/D
conversion and then resumed to analog signal when reaching the destination user.
ISDN realizes the digital transmission of user loop to implement digital end-to-end
communication. This will enable various digital and analog information to transmit
via the standard digital interface. Besides, ITU-T standardizes ISDN services and
formulates such recommendations as I.430, Q.921 and Q.931 to make any
Operation Command
Set MTU of synchronous serial interface mtu size
Recover the default value of MTU undo mtu
Operation Command
Set the time interval for sending keepalive packets timer hold seconds
Disable keepalive packet sending undo timer hold
Operation Command
Set the idle coding of synchronous serial interface
to "FF"
idle-mark
Restore the idle coding of synchronous serial
interface to "7E"
undo idle-mark