Configuring PAD Service Directory of X25

Topology of Network

Application of PAD Model

Description

Application

The List of Configuration Tasks  

Examples

 

 This Chapter tells how to use PAD services to establish linkage with the equipment at remote terminal on X25 protocol.

The complete introduction of PAD commands can be referred to the chapter The Commands for Linking PAD and X25 in the book “The Reference for WAN Commands” If the location of other commands needs to be known, the master index for commamds shall be used or on-line search shall be conducted.

 

Topology of Network

PDA configuration is used to activate the X25 linkage between network equipments. PAD is a kind of equipment receiving character stream transmitted from one or multiple terminals. It divides the character stream into groups and transmitted the group data to host computer. PAD also can do its work reversely, that is, it can receive the data transmitted from network host and translate the data package into character stream acceptable to the terminal. PAD is defined on X3, X28 and X29 under the suggestion of CCITT.

Chart 1 demonstrates a X.25 user at remote terminal sets up calling with x.25 host computer at common data center.  through X.25 exchnage network and  internal PAD application program of 1700 router

Chart 1 Standard X. 25 Linkage between Dumb Terminal and X.25

PAD can be configured by changing the application program on protocol to make it work. In Chart 2, a computer at remote terminal sets up simulation modem calling with IP network, link to 1700 router and allow IP to divide data to achieve the conversion from IP to X.25 protocol. It first communicates with PAD equipments inside the router, then links to X.25 host computer.

Chart 2 Dialing up to X.25 Host Computer through protocol conversion

Application of PAD Model

    The following parts descripes how to use PAD user interface to set up X.25 PAD linkage

Description

Application

The List of Configuration Tasks  

Examples

Description

X.28 emulation is the standard user interface between DTE and PAD. The router of the Compnay offers X.28 user emulation model (PAD model), which enable uers to interchange with PAD and control PAD. During the periond of controlling information exchange, the message or command sent from DTE to PAD is called PAD command signal. The message sent from PAD to DTE is called PAD service signal. These signals and transmitted data are the coded character stream defined on IA5.

For the asynchronous devices of terminals accessible to X.25 network host or modem, they shall be grouped, installed or deinstalled in accordance with PAD equipment. When standard X.25 commands are used in PAD, the X.3 PAD parameters, resetting calling or clearing calling can be set. X.3 defines the various parameters used in X.25 network on the ITU-T suggestion. There are total 22 X.3 PAD parameters that meed to be configured. X.3 PAD parameters define the built-in variables of PAD operation. For instance, No.9 parameter is crpad parameter, it defines the added the byte number after entering <CR>. X.3 parameters can be set by X.25 host computer at remote terminal of X.29. (See Chart 3)

Chart 3 Dialing up to asynchronous device of X.25 host computer on X.25 Network

Application

PAD uses X.28 standard user interface to enable PAD system administrator to dial up to x.25 network or set PAD parameters. The interface is commonly used in many European countries. It complies with ITU-T standards for X.25.

PAD interface is designed for accessing the remote or local asynchronous device or the asynchronous device applied by asynchronous host computer through X.25. For example, dial-up application program uses X.28 interface to access remote X.25 host computer. Banks often employ X.28 PAD calling support, such as ATM, the background application of point of sale of authorizied equipments and alarming system. ATM can be linked to a alarming computer and a router in an asynchronous manner. After the alarm is trigged, the warner sends a alarming calling through router and X.28 PAD.

The PAD calling through router of the Company can be transmitted on public group network, Internet, special X.25 network, special network based on IP and FR network. It can be used to convert ptotocol. The protocol conversion and VTY asynchronous interface enable the users to use the PAD services and other protocols, such as the local area transmission of Digital Equipment Corporation (DEC) and Transmission Control Protocol (TCP), to access X. 25 application in both directions.

The List of Configuration Tasks

    This part describes the following optional tasks:

l        Setting up and Clearing Calling

l       Customizing Local X.3 Parameters

l        Mornitoring X.25 FAD Linkage

l        X. 25 PAD Access Limitations

 By using user’s command “EXEC”, pad accesses to X.28 model.. The pad model is accessible when Ctrl-p is pressed. The prompt of default PAD model is “pad” and “(>)”. When pad> appears, the standard user’s interface can be used and PAD can be configured under this model.

Setting up and Clearing Calling

   Manay function related to X.25 can be realized under PAD model, such as resetting and clearing calling. Table 20 lists the executable and usable command signals.

   Under PAD model, the various PAD command signals can be used, the standars can be selected or the command syntax can be expanded. For example, the command “clr” or “clear” is entered to clear calling. The commands designated on the standard command syntax are only the short ones of expanded command syntax. The role of these  two command syntaxes are same in essence.

Command

Functions

Clr

Clearing virtual call

Help

Showing help information

Int

Transmitting interrupted group data

par?

Par

Showing current value of local parameter values

Prof filename

Install a standard outline value

Reset

Resetting Calling

Set

Changing local parameter values

set?

Changing then reading parameter values

Stat

Request the state of linkage

Quit

Quiting PAD linkage

Setting up Calling

   To set up calling with another X.25 information destination, X.121 address shall be designated and enter “command” under user’s mode or management mode.

pad svc address [profile-number [r|w]]

Dialing up remote interface address through SVC. If dial-up succeeds, X.28 mode is avaible and the prompt “>” appears

pad pvc interface pvc# [profile-number [r|w]]

 Dialing up remote interface address through PVC. If dial-up succeeds, X.28 mode is available and the prompt “>” appears.

Clearing Calling

After the linkage to the remote X.25 equipment is set up, the following command can be used to clear the linkage,

Steps

Command

Function

1

ctrl-p

Retreating from remote host computer to local router PAD model.

2

Clr

Clearing virtual calling 

Customizing Local X.3 Parameters

X.3 PAD parameters is set at the local terminal and the following commands are used under user’s mode or management mode:

Steps

Command

Function

1 .

pad svc address

Entering X.28 model

2

Ctrl-p

Retreating from X.28 model to PAD model.

2 .

par

Showing current X.3 PAD parameters

3 .

set parameter-number: new-value 

Changing parameter value

4 .

par

Verifying the PAD parameters are correctly set.

Mornitoring X.25 FAD Linkage 

To show the information of current open linkage, the following command shall be used under the management mode:

Command

 Function

Show x25

Showing the information of current open X.25 linkage

The information includes the current state of virtual circuit

X. 25 PAD Access Limitations

The configuration can limit the access to source X.121 address of router

Command 

  Function

X25 map pad x121addr

 Configuring static PAD-accessible source X121 address of router

X25 pad-access

Starting the access limitation of PAD and examing the access limitation through list item configured by the previous command. If there is no configuration, all the PAD access will be prohibited.

 

Examples

The examples provided are as follows:

l        PAD Signal Demonstration

l        Demonstration of Customizing X.3

l       Demonstration of X.3 Outline Value

l       Demonstration of Obtaining Help

l        Demonstration of Monitoring X.25 Network

PAD Signal Demonstration

    The following demonstration tells that the calling is set up with remote X.25 host computer through serial circuit. The interface address of remote host computer is 123456.RouterA. By using command “EXEC”, pad 123456 calls routerB.

Route A#pad svc 123456

COM

router-B> exit

CLR(cause=0x0,diag=0x0)

Router A#

The following example shows that the linkage to remote X.25 host computer is cleared. The command “clr” under X.28 model is used to disconnect the linkage between rounter A and router B.

router-A# pad svc 123456

COM

router-B>Ctrl-p

pad>clr

CLR CONF

Pad>

Demonstration of Customizing X.3

The following example changes the value of No.9 parameter. The value is changed from 0 to 1. A byte is added to the back of <CR> after entering. This configuration is executed at the local terminals through PAD command signal of set parameter-number: new-value.

Router A# pad svc 12345678

Router B>ctrl-p

pad>par

PAR 1:1 2:1 3:126 4:0 5:1 6:2 7:2 8:0 9:0 10:0 11:14 12:1 13:0 14:0 15:0 16:127 17:24 18:18 19:2 20:0 21:0 22:0 

pad> set 9:1

pad> par

PAR 1:1 2:1 3:126 4:0 5:1 6:2 7:2 8:0 9:1 10:0 11:14 12:1 13:0 14:0 15:0 16:127 17:24 18:18 19:2 20:0 21:0 22:0 

pad>

 

Demonstration of X.3 Outline Value

The following example shows that the existing outlook value of X..25 PAD parameter is amended and loaded. It accesses to the existing PAD outline value ppp, chnages padout parameter (the designated value is 9) into 2 and uses the command “par” of PAD model to display new parameter.

router-A# pad 3333

router-B>ctrl-p

pad>prof 0

pad>par

PAR 1:1 2:1 3:126 4:0 5:1 6:2 7:2 8:0 9:2 10:0 11:14 12:1 13:0 14:0 15:0 16:127 17:24 18:18 19:2 20:0 21:0 22:0

Note: If X.29 outline value is default value, this outline value will ba applicable to all X.25 calling, including the calling used for protocol conversion.

Demonstration of Obtaining Help

    The brief description of usable parameters is available by using command “help”.

pad> help

CLR - clear X.25 connection

HELP - this help

INT - send interrupt packet over X.25 connection

PAR? - show X.3 parameters as wanted

PROF - use X.3 profile 0 or 1

QUIT - quit PAD and clear connection

RESET - send RESET packet over X.25 connection

SET - set X.3 parameters

SET? - set X.3 parameters and show it

STAT - show X.25 connection status

Demonstration of Monitoring X.25 Network

The following example is the output of demostration of command “show X. 25”

router A# pad  svc 123456789

COM

Router B> ent

Router B#show x25

X.25/IP state

Serial1/0=UP

=====================================================================

No.Port       VC   I/O   State    X.121addr    IPaddr      hostname

=====================================================================

01 Serial1/0  16   in    work     1111

Router B#