3Com Router User Manual

							Synchronous Serial Interface127
Level detection is enabled for the synchronous serial interface by default.
9Enable or disable data carrier detection
By default, when the system decides whether the synchronous serial interface is in 
UP status or DOWN status, it detects the DSR signal, DCD signal and whether the 
interface connects a cable at the same time. Only when the three signals are 
effective, will the system regard the interface is in UP status, otherwise, in DOWN 
status. If data carrier detection is disabled for the synchronous serial interface, the 
system will not detect the DCD signal.
Please use the following commands in the view of the synchronous serial 
interface.
Ta b l e 118   Enable or disable data carrier detection for the synchronous serial interface
Data carrier detection is enabled for the synchronous serial interface by default.
10Set the synchronous serial interface to work in full duplex or half duplex mode
To operate with some devices working in half-duplex mode, the synchronous serial 
interface can be configured to work in half-duplex mode.
Please make the following configurations in synchronous serial interface mode.
Ta b l e 119   Set the synchronous serial interface to work in full duplex or half duplex mode 
By default, the synchronous serial interface works in full duplex mode.
11Enable or disable internal loopback/external loopback
To perform special function test, the internal loopback/external loopback are 
enabled for the synchronous serial interface. 
Please use the following commands in the view of the synchronous serial 
interface.
Ta b l e 120   Enable/disable internal loopback/external loopback for the synchronous serial 
interface
The internal loopback/external loopback are disabled by default.
Enable level detection for the synchronous serial 
interface.detect dsr-dtr
Disable level detection for the synchronous serial 
interface.undo detect dsr-dtr
OperationCommand
Enable data carrier detection for the synchronous serial 
interface.detect dcd
Disable data carrier detection for the synchronous serial 
interface.undo detect dcd
OperationCommand
Set the synchronous serial interface to work in half 
duplex modereverse-rts
Set the synchronous serial interface to work in full 
duplex modeundo reverse-rts
OperationCommand
Enable the internal loopback/external loopback for 
the synchronous serial interface. loopback
Disable the internal loopback/external loopback 
for the synchronous serial interface. undo loopback 
						

							128CHAPTER 10: CONFIGURING WAN INTERFACE
12Configure 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.
Ta b l e 121   Set MTU of synchronous serial interface
The unit of mtu is byte, ranging between 128-1500, with 1500 as default.
13Configure 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.
Ta b l e 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. 
14Set the idle coding of synchronous serial interface
Perform the following configuration in serial interface view.
Ta b l e 123   Set the idle coding of synchronous serial interface
The idle coding of synchronous serial interface is 7E.
ISDN BRI InterfaceTechnical 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 
OperationCommand
Set MTU of synchronous serial interfacemtu size
Recover the default value of MTUundo mtu
OperationCommand
Set the time interval for sending keepalive packetstimer hold seconds
Disable keepalive packet sendingundo timer hold
OperationCommand
Set the idle coding of synchronous serial interface 
to FFidle-mark
Restore the idle coding of synchronous serial 
interface to 7Eundo idle-mark 
						

							ISDN BRI Interface129
equipment complying with relevant ISDN standard of ITU-T able to access ISDN 
easily.
User-network interface specification of ISDN:
In ITU-T I.411 recommendations, reference configurations for ISDN user-network 
interfaces are given according to concepts of function group (a group of functions 
required by users to access ISDN) and reference point (a point used to distinguish 
function groups), as shown in the following diagram.
Figure 47   Reference configuration of ISDN user-network interface
The function group includes:
■Network terminal 1 (NT1): It mainly fulfills functions of OSI layer 1 including the 
subscriber line transmission function, loop test and D channel contention. 
■Network terminal 2 (NT2): Also called intelligent network terminal, including 
layer 1-layer 3 of OSI. 
■Type-1 terminal equipment (TE1): Also called ISDN standard terminal, which is 
user equipment conforming to ISDN interface standard (such as digital phone 
set). 
■Type-2 terminal equipment (TE2): Also called non-ISDN standard terminal, 
which is user equipment not conforming to ISDN interface standard. 
■Terminal adapter (TA): It implements adaptation function, making TE2 to access 
ISDN standard interface. 
The reference point includes:
■R reference point: It is between non-ISDN equipment and TA
■S reference point: It is between user terminal and NT2.
■T reference point: It is between NT1 and NT2.
■U reference point: It is between NT1 and line terminal.
Preparations before Configuration
Be clear about the following items before the configuration:
TE2TA
TE1
S
S R
2345
NT2NT1
U T
1 
						

							130CHAPTER 10: CONFIGURING WAN INTERFACE
■Whether the interface provided by telecom service provider is ISDN BRI U 
interface or ISDN BRI S/T interface: In ITU-T I.411 recommendation, the 
reference model of ISDN user-network interface is given. However, there is a 
worldwide dispute about the position of division point between the user and 
network. And U interface or S/T interface is used according to different nations. 
In this case, before purchasing the router, the user must ensure whether the 
interface provided by the telecom server is ISDN BRI U interface or ISDN BRI S/T 
interface.
■Whether digital service is provided: ISDN can provide integrated services like 
digital service or voice service. Since the router is to perform digital 
communication, the ISDN line that the user applies for t be realized.
■Whether to select Point-to-Point connection or Point-to-Multipoint connection 
(optional): ISDN supports semi-permanent connection function. If the user only 
uses ISDN to connect fixed points, ISDN dedicated line can be used. Otherwise, 
Point-to-Multipoint connection is required.
■Caller Identification function (optional): On ISDN with CID function, the caller 
number can be filtered, so that only a group of user lines can dial in this router, 
enhancing the security of the network.
Configure ISDN BRI 
InterfacePlease enter the view of the specified ISDN BRI interface with the following 
command in all views.
Ta b l e 124   Enter the view of the specified ISDN BRI interface
The ISDN BRI interface is used to dial up. Please refer to Dial-up for detail. 
CE1/PRI InterfaceAlong with the emergence of Pulse Code Modulation (PCM) technique in the 
1960s, Time Division Multiplexing (TDM) technique is eventually achieving broad 
applications in the digital communication systems. The TDM system is divided into 
two types: E1 system recommended by ITU-T and T1 system recommended by 
ANSI. The former one is widely applied in Europe and China, and the latter is 
mainly applied in North America and Japan (the J1 system adopted in Japan is 
similar to the T1 system and hence can be taken as T1 system).
CE1/PRI interface has two operating modes: E1 operating mode (also called 
non-channelized operating mode) and CE1/PRI operating mode (also called 
channelized operating mode).
When the CE1/PRI interface operates in E1 operating mode, it equals to an 
interface with the data bandwidth of 2 Mbps, on which no timeslots are divided. 
Its logic feature is the same as that of a synchronous serial interface. It supports 
the data link layer protocols such as PPP, Frame Relay, LAPB and X.25, and the 
network protocols such as IP and IPX.
When the CE1/PRI interface operates in CE1/PRI operating mode, it is physically 
divided into 32 timeslots numbered from 0 to 31. Timeslot 0 is used to transmit 
the synchronization information. This interface can be used as either a CE1 
interface or a PRI interface.
OperationCommand
Enter the view of the specified ISDN BRI interfaceinterface bri number 
						

							CE1/PRI Interface131
■When the interface is used as a CE1 interface, all the timeslots except timeslot 
0 can be divided into multiple channel sets at will, and each group can be used 
as an interface upon timeslot binding. Its logic feature is the same as that of a 
synchronous serial interface. It supports the data link layer protocols, such as 
PPP, Frame Relay, LAPB and X.25, and the network protocols such as IP and IPX.
■When the interface is used as a PRI interface, timeslot 16 will be used as a D 
channel to transmit signaling. Therefore, only a group of timeslots except the 
timeslots 0 and 16 can be chosen as the B channels. These timeslots can be 
bound together with timeslot 16 to form a pri set to be used as an interface. 
The logic feature of this interface will be the same as that of an ISDN PRI 
interface. It will support the data link layer protocol PPP and network protocols, 
such as IP and IPX, and can be configured with parameters such as BDR 
(Dial-on-Demand Routing).
Configure CE1/PRI 
InterfaceCE1/PRI interface configuration includes:
■Enter the view for a specified interface
■Set the interface operating mode
■Bind the interface to be channel sets
■Bind the interface to be a pri set
■Set the line code format
■Set line clock
■Set frame format
■Enable/disable internal loopback/external loopback
1Enter the view for a specified interface
In system view, use the following command to enter the view of a specified 
CE1/PRI interface.
Ta b l e 125   Enter the view of a specified interface
2Set the interface operating mode
CE1/PRI interface has two operating modes: E1 operating mode and CE1/PRI 
operating mode
Perform the following configurations in CE1/PRI interface view.
Ta b l e 126   Set the operating mode of CE1/PRI interface
By default, the CE1/PRI interface operates in CE1/PRI operating mode.
After enabling the CE1/PRI interface to operate in E1 mode using the using e1 
command, the system will automatically create a serial interface numbered serial 
number:
0. This interface owns the same logic feature as that of a synchronous 
serial interface, and can be treated as a synchronous serial interface for further 
configurations.
Perform the following configuration in all views.
OperationCommand
Enter the view of CE1/PRI interfacecontroller e1 number
OperationCommand
Set the CE1/PRI interface to operate in E1 modeusing e1
Set the CE1/PRI interface to operate in CE1/PRI modeusing ce1 
						

							132CHAPTER 10: CONFIGURING WAN INTERFACE
Ta b l e 127   Enter the synchronous serial interface view
The following are to be set:
■Operating parameters of data link layer protocol, such as PPP, Frame Relay, 
LAPB or X.25.
■IP address
■The operating parameters of the standby center need to be set when the 
interface serves as the main interface or standby interface of the standby 
center. 
■The rules for address translation or packet filtering need to be set if the firewall 
is to be set up on the interface.
For more details, refer to the related sections of this manual.
3Bind the interface to be channel sets
Perform the following configurations in CE1/PRI interface view.
Ta b l e 128   Bind the interface to be channel sets
The timeslots can be bind to form up to 31 channel sets on a CE1/PRI interface.
The CE1/PRI interface can be bound to be channel sets only when it is enabled to 
operate in CE1/PRI mode through the using ce1 command.
Only one timeslot binding mode is supported on one CE1/PRI at one time, that is, 
the interface can only be bound into either channel sets or a pri set in that period.
After binding the interface to be channel sets, the system will automatically create 
a Serial interface numbered serial number:set-number. This interface has the 
same logic feature as that of a synchronous serial interface, and can be treated as 
a synchronous serial interface for further configurations.
Perform the following configuration in all views.
Ta b l e 129   Enter the synchronous serial interface view
The following is to be set:
■Operating parameters of data link layer protocol, such as PPP, Frame Relay, 
LAPB or X.25.
■IP address
■The operating parameters of the standby center need to be set when the 
interface serves as the main interface or standby interface of the standby 
center.
OperationCommand
Enter the synchronous serial interface viewinterface serial number:0
OperationCommand
Bind the timeslots of CE1/PRI interface to a 
channel setchannel-set set-number 
timeslot-list range
Remove binding timeslots to form channel 
setsundo channel-set set-number
OperationCommand
Enter the synchronous serial interface viewinterface serial 
number:set-number 
						

							CE1/PRI Interface133
■The rules for address translation or packet filtering need to be set if the firewall 
is to be set up on the interface.
For more details, refer to the related sections of this manual.
4Bind an interface to be a pri set
Perform the following configurations in CE1/PRI interface view.
Ta b l e 130   Bind the interface to be a pri set
Timeslots on a CE1/PRI interface can be bound to be only one pri set.
When binding an interface to be a pri set, timeslot 16 on a CE1/PRI interface is 
used as the D channel and the other timeslots are used as B channels. As for the 
CE1/PRI interface, timeslot 0 will be excluded since it is used to transmit the 
synchronous information. If no timeslots are specified to be bound, all the 
timeslots will be bound to form an interface similar to an ISDN PRI interface of 
30B+D. If only timeslot 16 is bound, the binding activity will fail.
The CE1/PRI interface can be bound to be a pri set only when it is enabled to 
operate in CE1/PRI mode through the using ce1 command.
Only one timeslot binding mode is supported on one CE1/PRI interface at one 
time, that is, the interface can only be bound into either channel sets or a pri set.
After the interface is bound to be a pri set, the system will automatically create a 
Serial interface numbered serial number:15. This interface is logically equivalent 
to an ISDN PRI interface, and hence you can further configure it.
Perform the following configuration in all views.
Ta b l e 131   Enter the ISDN interface view
The following is to be set:
■BDR operating parameters
■Encapsulate the data link layer protocol PPP, its authentication parameters and 
etc.
■IP address
■The operating parameters of the standby center need to be set when the 
interface serves as the main interface or standby interface of the standby 
center.
■Configure the firewall if necessary.
For more details, refer to the related sections of this manual.
5Set the line code format
A CE1/PRI interface supports two types of line code formats: ami format and 
hdb3 format.
Perform the following configurations in CE1/PRI interface view.
OperationCommand
Bind the timeslots of CE1/PRI interface to be a 
pri setpri-set [ timeslot-list range ]
Remove binding timeslots to be a pri setundo pri-set
OperationCommand
Enter the ISDN interface view interface serial number:15 
						

							134CHAPTER 10: CONFIGURING WAN INTERFACE
Ta b l e 132   Set the line code format on the CE1/PRI interface
By default, the line code format on the CE1/PRI interface is hdb3.
6Set line clock
When the CE1/PRI interface operates as DCE, you should choose the internal 
clock, that is, master clock mode. When it operates as DTE, you should choose 
the line clock, that is, slave clock mode.
When the CE1/PRI interfaces on two routers are directly connected, the two ends 
will respectively operate in line clock mode (slave) and internal clock mode 
(master). When the CE1/PRI interfaces on routers are connected to a switch, the 
switch will operate as DCE which provides clock signal, the interfaces on the 
routers will operate in line clock mode (slave).
Perform the following configurations in CE1/PRI interface view.
Ta b l e 133   Set the line clock of the CE1/PRI interface
By default, the line clock of CE1/PRI interface is slave clock.
7Set the frame format of interface
When the CE1/PRI interface operates in CE1/PRI mode, it supports two types of 
frame formats: crc and no-crc4. The frame format crc4 supports the 4-bit Cyclic 
Redundancy Check (CRC) on physical frames, whereas the frame format no-crc4 
does not.
Perform the following configurations in CE1/PRI interface view.
Ta b l e 134   Set the frame format of CE1/PRI interface
By default, the frame format of CE1/PRI interface is no-crc4.
8Enable/disable internal loopback/external loopback
The interface needs to be set to internal loopback or external loopback when 
during the test on some special functions.
Perform the following configurations in CE1/PRI interface view.
Ta b l e 135   Enable/disable the internal loopback/external loopback
OperationCommand
Set the line code format on the CE1/PRI interfacecode { ami | hdb3 }
Restore the line code format on the CE1/PRI 
interfaceundo code
OperationCommand
Set the line clock of the CE1/PRI interface clock { master | slave }
Restore the line clock of the CE1/PRI interface 
to the default valeundo clock
OperationCommand
Set the frame format of CE1/PRI interfaceframe-format { crc4 | no-crc4 }
Restore the frame format of CE1/PRI interfaceundo frame-format
OperationCommand
Enable the internal loopback/external loopback of 
the CE1/PRIloopback
Disable the internal loopback/external loopback of 
the CE1/PRIundo loopback 
						

							CT1/PRI Interface135
By default, the functions of internal loopback and external loopback are disabled 
on the CE1/PRI interface.
Display and Debug 
CE1/PRI InterfacePerform the following configurations in all views to display the status and related 
information of the CE1/PRI interface, so as to monitor and maintain it.
Ta b l e 136   Display and debug CE1/PRI interface
Generally, CE1/PRI interface is applied to the dedicated line and dial-up services. 
For the typical configuration example and troubleshooting, refer to the 
configurations of protocols at each layer and dialing configurations in this manual.
CT1/PRI InterfaceAlong with the emergence of Pulse Code Modulation (PCM) technique in the 
1960s, Time Division Multiplexing (TDM) technique is eventually achieving broad 
applications in the digital communication systems. The TDM system is divided into 
two types: T1 system recommended by ANSI and E1 system recommended by 
ITU-T. The former one is mainly applied in North America and Japan (the J1 system 
adopted in Japan is similar to the T1 system and hence can be taken as T1 system), 
and the latter is widely applied in Europe and China.
T1 line is comprised of 24 multiplexed channels. In other words, one T1 primary 
frame DS1 contains 24 DS0 (64kbps) timeslots, each of them has 8 bits, and other 
1 bit is taken as the framing bit. As a result, each primary frame has 193 bits. This 
value can be got as follows: 24 x 8 + 1=193 bits. Since 8000 frames can be sent 
per second, the transmission speed of DS1 is 193 x 8K = 1.544 Mbps.
The CT1/PRI interface can only operate in channelized operating mode. It is used 
in the following two ways:
■When the interface is used as a CT1 interface, all the timeslots from 1 to 24 
can be divided into multiple groups at will, and each group can be bound to 
form a channel set. Upon the binding of each group of timeslots, the system 
automatically generates an interface which logically equals to a synchronous 
serial interface. It supports the data link layer protocols such as PPP, Frame 
Relay, LAPB and X.25, and the network protocols such as IP and IPX.
■When the interface is used as a PRI interface, timeslot 24 will be used as a D 
channel to transmit signaling. Therefore, only a group of timeslots except the 
timeslot 24 can be chosen as the B channels. These timeslots can be bound 
together with timeslot 24 to form a pri set which acts as an interface. The logic 
feature of this interface will be the same as that of an ISDN PRI interface. It will 
support the PPP data link layer protocol and network protocols, such as IP and 
IPX, and can be configured with parameters, such as BDR.
Configure CT1/PRI 
interfaceCT1/PRI interface configuration includes:
■Enter the view for a specified interface
■Bind the interface to be channel sets
OperationCommand
Display the operating status of the CE1/PRI 
interface display controller e1 
interface-number
Display the operating status of the channel set 
or pri setdisplay interfaces serial 
interface-number:number 
						

							136CHAPTER 10: CONFIGURING WAN INTERFACE
■Bind the interface to be a pri set
■Set the length/attenuation of the transmission cable
■Set the line code format
■Set line clock
■Set frame format
■Enable/disable internal loopback/external loopback
1Enter the view for a specified interface
In system view, use the following command to enter the view of a specified 
CT1/PRI interface.
Ta b l e 137   Enter the view of a specified interface
2Bind the interface to be channel sets
Perform the following configurations in CT1/PRI interface view.
Ta b l e 138   Bind the interface to be channel sets
The timeslots can be bind to form up to 24 on a CT1/PRI interface.
The CE1/PRI interface can be bound to be channel sets only when it is enabled to 
operate in CE1/PRI mode through the using ce1 command.
Only one timeslot binding mode is supported on one CT1/PRI interface at one 
time, that is, the interface can only be bound into either channel sets or a pri set in 
that period.
After binding the interface to be channel sets, the system will automatically create 
a Serial interface numbered serial number:set-number. This interface has the 
same logic feature as that of a synchronous serial interface, and can be treated as 
a synchronous serial interface for further configurations.
Perform the following configuration in all views.
Ta b l e 139   Enter the synchronous serial interface view
The following is to be set:
■Operating parameters of data link layer protocol, such as PPP, Frame Relay, 
LAPB or X.25.
■IP address
■The operating parameters of the standby center need to be set when the 
interface serves as the main interface or standby interface of the standby 
center.
OperationCommand
Enter the view of CT1/PRI interfacecontroller t1 number
OperationCommand
Bind the timeslots of CT1/PRI interface to a 
channel setchannel-set set-number 
timeslot-list range [ speed { 56 | 
64 } ]
Remove binding timeslots to form channel 
setsundo channel-set set-number
OperationCommand
Enter the synchronous serial interface viewinterface serial 
number:set-number