Configure X.25 directory
Tasks list of X.25 configuration
configure
other X.25 interface parameter
configure
X.25 data transportation
Configure annex X.25 characters of transporting data message
configure
X.25-TCP switching parameter
configure
PVC switching among X.25 interfaces
configure
SVC switching among X.25 interfaces
configure
XOT switching among X.25 interfaces
configure
X.25-TCP switching gateway
monitor
and maintain LAPB and X.25
Examples of configurations of X.25 and LAPB
Example of typical configurations of LAPB
Example of typical configurations of X.25
This
chapter will introduce how to setup network link through LAPB and X.25.
X.25 is a credible data transportation protocol face to linking, it
mainly includes LAPB of OSI data link layer and X.25 of network layer.
X.25 defines two types of hosts: DTE and DCE. The router which use X.25 encapsulation can be used as DTE or DCE equipments, this is different from hardware DTE and DCE.
More details ,please refer to the chapter of “X.25 and LAPB commands” in “WAN commands references”. Other commands, please use command index.
LAPB of X.25 work in data link layer of OSI reference model.
LAPB defines ways to switch data(its unit is frame),detect no-order
frame, losing frame, re-transmitted frame, response frame on special link .
These parameters are fit for X.25 link because X.25 work on group layer of LAPB.
Table-5 Some parameters and their defaults
table 1:LAPB
parameter |
|||
command |
purpose (LAPB parameter) |
Parameter values |
default |
x25
mod modulus |
Set
module value |
8
or128 |
8 |
x25
k window-size |
Set
windows sizes(K) |
2~(module-1)frame |
7 |
x25
n1 bytes |
Set
max bytes of each frame(N1) |
137-1512 |
1500 |
x25
n2 tries |
Set
the counter of transmitting frame(N2) |
1-255
times |
16 |
x25
t1 seconds |
Set
re-transmitting timer (T1) |
1-64
seconds |
3 |
x25
t2 seconds |
Set
the timer of overtime receiving (T2) |
1-32
seconds |
0 |
l Module
value of LAPB and LAPB K—LAPB
decide operation mode. Module 8 is used widly because it accords all standard
LAPB and is enough for most links.
Module 128 can get bigger throughput on high speed link with low
error ratio through adding the numbers of transmittable frames before
transportation validate (configure by parameter K in LAPB window).
According to such a define, parameter K of LAPB can set 1 less than the value of operation value. Module 8 often transmit 7 frames before validate receiving frames. Module can set the value of K 127. If default, LAPB use the basic mode when the size of window is 7.
l LAPB
N1-when connectting X.25 network, user use N1 parameter set by network manager.
This parameter is the most bytes in LAPB frame, it decides the size of X.25
group.
Parameter N1 should be equal to the value of MTU through hired line. The value of N1 has limited effects on interface MTU. If it does not configure properly , it will leads link failure easy. The suggestion is to keep the default value.
l LAPB N2—the counter of transportation (N2) shows the retransmitted times before cutting link.
l LAPB T1- The counter of retransmitted (T1), it decides how long the transmitted frame can keep not to be validated before the router receive the validated frame. For X.25 network, the setting of retransmitted timer must match the configurations of network.
l LAPB T2— T2 value of DTE equipment can be different from the value of T2,but should note the opposite party. When T2 is up, DTE(DCE) must transmit validated frame, so that the opposite party can receive the validated frame before his T1 is up(T2<T1).
The configuration of T1 timer is very important for hired line,
because the design of LAPB assume that if the frame has not received before
T1,it had losed.
The configuration of the timer must be enough big to permit the biggest frame to come and back one time. If the timer is too small, the software will poll before validate to back, this will lead frame retransmitted and serious protocol problems. If the timer is too big, the software will wait longer than necessary time, this will reduce band- width.
An example to configure LAPB T1 timer, please refer to “examples of typical LAPB configurations”.
Tasks list of X.25 configurations
User should do as follows to configure X.25.
Interface, data message transportation and route tasks is usually divided to parts by common characters and using frequency. We have discussed before that user can modify LAPB frame parameter to optimize X.25 operations.
configure
other X.25 interface parameter
configure
X.25 data transportation
Configure annex X.25 characters of transporting data message
configure
X.25-TCP switching parameter
configure
PVC switching among X.25 interfaces
configure
SVC switching among X.25 interfaces
configure
XOT switching among X.25 interfaces
configure
X.25-TCP switching gateway
monitor
and maintain LAPB and X.25
All these characters can exist in X.25 interface together.
Though X.25 has default parameters, user can change these settings to meet X.25 network, or supplier can change these parameters. D-Link also provides annex configurations to optimize X.25.
Note : If user connect the router to network by X.25 ,user must use the parameters that set by the network manager. These parameters are described in “configure X.25 interface” and “configure LAPB”. And user also should note that parameter of L2 of X.25 in ”configure LAPB” will affect operations on L3 of X.25. There is an example of configuring X.25 at the bottom of this chapter.
User should do as follows to configure X.25 interface:
l set the range of virtual circuit
l set default controlling values of flux
These tasks describe important parameters to X.25, the first task is necessary, others are demanded or optional, this is depended on the type of router link X.25.
User must encapsulate X.25 protocol in interface configuration mode before configure X.25
command |
purpose |
encapsulation
x25 |
Encapsulate X.25 |
The router using X.25 encapsulation can be use as DTE or DCE (up to supplier).
User need to use following commands to configure operation mode of appointed interface:
command |
purpose |
x25
interface
[dte|dce] |
Set X.25 operation mode |
The default operation mode is DTE.
There is an example of configuring X.25 DTE operation in the paragraph of “an example of typical X.25 configurations”.
set the range of virtual curcuit
X.25 maintain several connections on a physical link line between DTE nd DCE. These connections are called virtual circuit(VC) or logic circuit(LC).X.25 can maintain 4095 virtual circuits numbered from 1 to 4095. A annex virtual circuit can be signed by logic circuit nuber (LCN) or virtual circuit number(VCN) .
Many documents use VC, LC, VCN and LCN to express virtual circuit , each of them express the number of virtual circuit.
A important part of X.25 is the range of virtual circuit numbers. Virtual circuit numbers can be divides to two ranges:(list by value adding)
1. permanent virtual circuit
2. switching virtual circuit
SVC can be created by X.25 call, this is very like to telephone network to create switching voice circuit when creating call.
Note: in this manual, except to use ITU-T, or call received on interface is call-in, and call transmitted on interface is call-out.
Because X.25 need DTE and DCE have the same range of virtual circuit, when the interface is connecting, the change of the range limit will keep until X.25 restart group service.
User can use following commands to configure the range of X.25 virtual circuit:
command |
purpose |
range |
default |
x25
htc circuit-number |
Set the highest virtual circuit number |
1-4095 |
1024 |
x25
pvc circuit-number |
Set
the highest permanent virtual circuit number |
0-1024 |
0 |
User must keep the values of two terminals of X.25 link line same.
These values must be set to the values assigned by network.
If the range of PVC is equal to the top limit of VC, it is not necessary to use SVC. Besides the signed range, virtual circuit 0 can not be sed.
There is an example of configure the range of virtual circuit in “an example of the range of virtual circuit”.
If using the router as a X.25 switch, user does not need to configure X.121 address. If the router connect PDN, user must configure X.121 address of interface.
User can use following commands to configure X.121 address:
command |
purpose |
x25
address
x121-address |
configure X.121 address |
More details about configurations mode of X.25 interface’s address, please refer to ” an example of typical X.25 configuration”.
set default controlling values of flux
It is necessary to set the size of windows to control flux and data packet because X.25 suggest to use flux controlling protocol mightily. Because many networks use the default ,user can overlook this value easy. The mistook value of flux controlling may leads to X.25 local error.
User can do as follows to configure the parameters of flux controlling
l set the size of default window
l set the size of default frouping
User can use following commands to configure the values of X.25 flux controlling:
command |
purpose |
range |
default |
x25
psize size |
Set
the size of grouping(bytes) |
128,256,512,1024 |
128 |
x25
wsize packets |
Set the size of window |
2-(module-1) |
2 |
Note: X.25 needs DTE and DCE have default max sizes of windows and data grouping. When interface is connecting, it will restart the protocol if user change the mode.
configure other X.25 interface parameters
Some applications of X.25 do not work often, some parameters can use to modify X.25 protocol:
User need do as follows to configure other interface parameters of X.25:
User need to use following commands to configure timer:
command |
purpose |
x25
t20 seconds |
Set
DTE T20 restart request is over time, default is 180seconds. |
x25
t23 seconds |
Set
DTE T23 to clear over time request, default is 180 seconds. |
There is an example “an example of typical configurations of X.25”.
X.25 use X.121 defined by ITU-T to create SVC. The address of X.121 changes from 0-15 digit, because the importance of addresses created by call, there are some interface address characters to X.25.
User need to do as follows to configure X.25 address:
l understand normal X.25 address
l configure the byname address of interface
understand normal X.25 address
If it is X.25 call source or destination, use X.121 address on X.25 interface. The course of create call of X.25 appoint the addresses of source and X.121. When the interface is call source, the X.121 address of the interface is source address. If destination address matches the interface address, the interface is the destnation of the received call.
The X.25 module of the router can route X.25 call including
receiving and process call, but the router is not the source or destination of
call. Route X.25 will not change the addresses of source or destination, but
keep appointed address by source host. Route X.25 is just simply to connect
logic X.25 channels to finish switching among several X.25 connecting.
X.121 address byname is supported on a interface, this permit to treat the interface as destination host when the destination address of a call is not the interface address or null.
Local processing (like IP encapsulation) can only execute call-in. Its destination X.121 is match to the serial or the byname of the interface.
Use following commands to configure the bynames:
command |
purpose |
[no]
x25 alias [string] |
Use X.121 address byname on the
interface |
configure X.25
data transportation
Supporting X.25 is the most common configurations on X.25 network
to transport data. Data transportation work by co-operations among X.25 hosts.
It can transport data packet through creating map between the addresses of
remote hosts’ protocols and the address of local X.121.
User need to do as follows to finish X.25 configurations:
l map the address of the protocol to X.121 address
map the address of the protocol to X.121
address
This paragraph introduces map operations of X.25 protocol addresses, and introduces how to map X.121 address for a remote host.
Encapsulation is a co-operation course between X.25 host and the router. Because X.25 host arrives by the address of X.121, the router must map the host protocols and addresses to X.121 address.
Each encapsulation X.25 interface must configure corresponding data grouping parameters. For example, there is a IP address on the interface with X.25.
User need to use command”X.25 address “to configure X.121 address for the interface encapsulated X.25 protocol. This is source address of X.25 call; is also used as destination protocol address by destination hosts . Encapsulation virtual circuit need to create map on the interfaces between source and destination hosts.
For each X.25 interface, it need to map each destination host protocol to X.121 address.
If needed and the destination host has the ability, one host map must configure to support several protocols, and define a interface for each supported protocol.
Use following commands to create map:
command |
purpose |
[no]
x25 map ipaddress pvc pvc_no [broadcast] |
Add/delete
one permanent virtual circuit comparison |
[no]
x25 map ipaddress svc x121-address [broadcast][ebackup] |
Add/delete
one switching virtual circuit comparison
|
Ebackup expresses the address map is an enforced backup kind.
Note: multi-protocol map, especially with broadcast communication, can lead to big communication load, it needs bigger queque, windows or more virtual circuits. User can add “broadcast” to appoint the configurations of OSPF protocol. Refer to command map in “commands of X.25 and LAPB”.
map destination X.121 address to a logic virtual interface
This chapter will introduce how to configure a router to help remote
computers connect to LAN through X.25 network.
First, remote computers connect PSDN network( or connect X.25 directly )
by a normal dialing way, the network providers transfer call to X.25 network
through PAD. PAD help to finish creating call.
At that time, the course of throwin experience the transferring from
asychronism to synchronization and leads to PPP over X.25 dialing way.
If the local router has configured the map from destination X.121
address to a logic virtual interface, it will accept call, and
turn call to PPP dial-in service to finish authentication, accounting,
authorization and so on. After passing authentication, the remote computer can
access LAN.
Use
following commands:
command |
function |
[no]
translate x25 x121-address virtual-template virtual-template-interface-number |
add/delete
one map from X.121 to virtual circuit. |
the following is basic configuration chart:
chart 1 an typical configuration chart mapping X.121 address
to virtual interface
Configure annex X.25 characters of transporting data message
The software of the router permit to configure annex X.25 characters of transporting data message, the grouping include many user characters for x.25 call.
Use following parameters to configure:
Do as follows to configure optional parameters, user and other characters:
l configure virtual circuit leisure time encapsulation
l configure X.25 negotiation parameters
configure virtual circuit leisure time
encapsulation
The router can clear switching virtual circuits after a leisure time.
Use following commands to set this time:
command |
purpose |
x25
idle seconds |
set
leisure time to clear virtual circuits. Range(0-214783647), default is 100
seconds. |
More details ,refer to “an example of typical X.25 configurations”.
configure X.25
negotiation parameters
The software of X.25 supports to configure x.25 negotiation parameters. It permits to use the functon of D byte location, the function to negotiate the length of grouping, the function to negotiate the size of grouping windows, the function to take main call address in X.25 call request grouping.
Use following commands to set supported X.25 negotiation parameters:
command |
purpose |
[no]
x25 dbit |
set
to whether permit D byte location or not |
[no]
x25 nps |
open /close the function of negotiation
the length of grouping |
[no]
x25 nws |
Open/close the function to negotiate the size
of grouping windows |
[no]
x25 cwla |
the function to take main call address in X.25
call request grouping. |
configure X.25-tcp switching paramters
Use following commands:(only limited to part tested versions)
command |
purpose |
[no]
x25 tcp user-data line |
set user
data used by X.25-tcp on the interface |
[no]
x25 tcp pkt-format [rfc1006|transparent|user]
|
set
the message format of switching |
[no]
x25 tcp iso-address line |
set
iso extensible address used by X.25-tcp on this interface |
configure PVC switching among X.25 interfaces
This router can be used as X.25 switch. This include PVC switching and SVC switching. The two interfaces used as PVC switching must have PVC which is not used yet.
Use following commands in configuration mode:
command |
Purpose |
[no]
x25switch connect port1 port1_pvc_no port2 port2_pvc_no |
configure
PVC switching |
When to configure switch table, the two connecting interfaces must save to effective permanent virtual circuit.
configure SVC switching among X.25 interfaces
The sizes of windows and groupings of two sides’ hosts can be different through switch, it will be set to the smaller one through switch module.
Use following commands in configuration mode:
command |
Purpose |
[no]
x25switch destination [x121addr/default] port |
Configure a SVC interface addressing |
configure XOT switching among X.25 interfaces
It can switch X.25 message on TCP/IP through the router.
Use following commands in configuration mode:
command |
Purpose |
[no]
x25switch xot pvc local-interface local-pvc
remote-interface remote-pvc remote-ip-address [source interface] |
configure one PVC XOT interface addressing |
[no]
x25switch xot svc x.121-address remote-ip-address [source
interface] |
configure one SVC XOT interface addressing |
configure X.25-TCP switching gateway
It can switch messages between X.25 and TCP through the router.
Use following commands in configuration mode:
command |
Purpose |
[no]
translate tcp ip ip-address svc intr1 x121address1
lport locport rport remport [backup
intr2 x121address2] |
configure
a map from source IP address to destination X.121 address, and TCP
interception interface of local and remote
|
[no]
translate tcp ip ip-address pvc intr1 pvc#1
lport locport rport remport [backup
intr2 pvc#2] |
configure a map from source IP address to destination PVC address, and TCP interception interface of local and remote |
monitor and maintain LAPB and X.25
To monitor and maintain X.25 and LAPB, use following commands in management mode:
command |
Purpose |
clear
x25 port vc-number |
Clear SVC |
show
interface serial number |
show running statistics information on the interface |
show
x25 |
show X.25 interface address map table |
show
x25switch |
show
X.25 switching table inforamtion |
[no]
debug lapb [iframes|sframes|uframes|raw]serial |
debug all kinds of frame by LAPB |
[no]
debug x25 [events|normal|raw|xot]serial |
debug X.25 internal events and messages |
[no]
debug x25 xot |
debug XOT setup cources |
[no]
debug x25 tcp [data|event|list] |
debug events, data receiving and transmitting , status of link line of X.25-TCP |
Examples
of configurations of X.25 and LAPB
Some examples to help to understand how to configure LAPB and X.25.
Example of typical configurations of LAPB
In the following example, the size of frame N1, the size of windows K and the max retransmit parameter N2 keep their defaults.Command “Encapsulation” make DCE to load a independent protocol (default is IP protocol). Command “X.25” set the retransmit timer to 4 seconds, use to long delay of DTE or slow connecting.
Router_config# interface s1/0
Router_config_s1/0#encapsulation x25
Router_config_s1/0#x25 interface dce
Router_config_s1/0#x25 t1 4
Example of typical configurations of X.25
This chapter will introduce you an example of typical configurations of x.25 to help you to understand related tasks and contents of X.25 of D-Link series routers. In this chapter, the content behind “!” is note, it can not be input in commands.
To connect two routers through back-to-back serials simply
(1)network
requirements
If you only want to connect two routers back-to-back simply, encapsulate X.25 between serials and load IP data message to transport, you just need to configure two routers as follows.
(2)network chart
chart 2 two routers connect directly through serials
(3)configuration steps
! configure Router A:
! choose interface
Router#config
Router_config#interface s1/0
! appoint IP address for the interface
Router_config_s1/0#ip address 202.38.160.1 255.255.255.0
! encapsulate this interface to X.25 interface and make it work in DTE mode
Router_config_s1/0#encapsulation x25
! appoint X.121 address of this interface
Router_config_s1/0#x25 address 20112451
! appoint the address map to the opposite terminal
Router_config_s1/0#x25 map 202.38.160.2 svc 20112452
!configure Router B:
! choose interface
Router#config
Router_config#interface s1/0
! appoint IP address for the interface
Router_config_s1/0#ip address 202.38.160.2 255.255.255.0
!set interface speed
Router_config_s1/0#physical-layer speed 64000
! encapsulate this interface to X.25 interface and make it work in DCE mode
Router_config_s1/0#encapsulation x25
Router_config_s1/0#x25 interface dce
! appoint X.121 address of this interface
Router_config_s1/0#x25 address 20112452
! appoint the address map to the opposite terminal
Router_config_s1/0#x25 map 202.38.160.1 svc 20112451
connect
the router to X.25 public grouping network
(1)network requirements
Router A, router B and router C are connected to the same X.25 network :
requirements
:IP addresses of serial 1/0 of three routers are 168.173
The X.121 addresses of three routers assigned by network are 30561001,30561002,30561003;
The size of standard window supported by sub-network: receiving window is 5 and transmitting window is 5;
standard max grouping length: max receiving grouping length is 512 and max transmitting grouping length is 512;
Channel range: 1—32.
(2)network char
chart 3 to connect the router to X.25 public grouping netwrok
(3)configure steps
configure router A:
! configure interface IP address
Router#config
Router_config#interface s1/0
Router_config_s1/0#ip address 168.173.24.1 255.255.255.0
! connect to public grouping network, let the router be DTE:
Router_config_s1/0#encapsulation x25
Router_config_s1/0#x25 address 30561001
Router_config_s1/0#x25 htc 32
Router_config_s1/0#x25 map 168.173.24.2 svc 30561002
Router_config_s1/0#x25 map 168.173.24.3 svc 30561003
configure router B:
! configure interface IP address
Router#config
Router_config#interface s1/0
Router_config_s1/0#ip address 168.173.24.2 255.255.255.0
! connect to public grouping network, let the router be DTE:
Router_config_s1/0#encapsulation x25
Router_config_s1/0#x25 address 30561002
Router_config_s1/0#x25 htc 32
Router_config_s1/0#x25 map 168.173.24.1 svc 30561001
Router_config_s1/0#x25 map 168.173.24.3 svc 30561003
configure router C:
! configure interface IP address
Router#config
Router_config#interface s1/0
Router_config_s1/0#ip address 168.173.24.3 255.255.255.0
! connect to public grouping network, let the router be DTE:
Router_config_s1/0#encapsulation x25
Router_config_s1/0#x25 address 30561003
Router_config_s1/0#x25 htc 32
Router_config_s1/0#x25 map 168.173.24.1 svc 30561001
Router_config_s1/0#x25 map 168.173.24.2 svc 30561002
configure
the range of virtual circuit
After executing following commands, serial 1/0 of the router
will be encapsulated X.25, and the range of virtual circuit is : permanent
virtual circuit is [1,8],switching virtual circuit is [9,64].
Router#config
Router_config#interface s1/0
Router_config_s1/0#encapsulation x25
Router_config_s1/0#x25 htc 64
Router_config_s1/0#x25 pvc 8
chart 4 XOT configurations chart based on PVC
configure router B1:
Router_config_s1/1#ip address 8.0.0.1 255.0.0.0
Router_config_s1/1#enc x25
Router_config_s1/1#x25 interface dce
Router_config_s1/1#x25 pvc 2
Router_config_s1/1#x25 map 8.0.0.10 pvc 1
configure router C1:
Router_config_f0/0#ip address 192.168.20.92 255.0.0.0
Router_config_s1/0#ip address 8.0.0.2 255.0.0.0
Router_config_s1/0#enc x25
Router_config_s1/0#x25 pvc 2
Router_config#x25switch xot pvc serial 1/0 1 serial 1/1 1
192.168.20.22
configure router C2:
Router_config_f0/0#ip address 192.168.20.22 255.0.0.0
Router_config_s1/1#ip address 8.0.0.11 255.0.0.0
Router_config_s1/1#enc x25
Router_config_s1/1#x25 pvc 2
Router_config#x25switch xot pvc serial 1/1 1 serial 1/0 1
192.168.20.92
configure router B2:
Router_config_s1/0#ip address 8.0.0.10 255.0.0.0
Router_config_s1/0#enc x25
Router_config_s1/0#x25 interface dce
Router_config_s1/0#x25 pvc 2
Router_config_s1/0#x25 map 8.0.0.1 pvc 1
The following is configuration chart and commands:
chart 5 X.25-TCP configurations chart
configure router B1:
ROUTER-CONFIG#translate
tcp ip 192.168.20.130 svc s1/0 111 lport 2000 rport 2000
ROUTER-CONFIG-S1/0#
encapsulation x25
ROUTER-CONFIG-S1/0#
x25 address 222
ROUTER-CONFIG-S1/0#
x25 tcp user-data 03010100
ROUTER-CONFIG-S1/0#
x25 tcp pkt-format RFC1006
ROUTER-CONFIG-S1/0#
x25 tcp iso-address 000fc909103600001111cb09103600002222
ROUTER-CONFIG-F1/0#
ip address 192.168.20.131 255.255.255.