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Using the X.25 Transport Protocol

The X.25 Transport Protocol (XTP) transports X.25 traffic over TCP/IP. XTP allows existing X.25 devices to communicate over a TCP/IP backbone and migrate from an X.25 network to a network of your choice.

This document provides an overview of XTP. It includes a diagram of how your network might look before using XTP and how the same network would look after using XTP. It also shows how to configure XTP and describes configuration and monitoring commands.

This document includes the following sections:

XTP Overview

Configuration Information

Displaying the XTP Prompts

Configuration Procedures

XTP Commands

XTP Overview

XTP is designed to work with X.25 devices that are located at multiple remote sites. In such environments, XTP can eliminate the use of X.25 packet switched networks for communicating with servers at one or more centralized locations.

To enable this, you use routers at the server and remote locations to encapsulate the data and deliver the X.25 packets between the clients and server via TCP/IP.

Figure 1 shows a typical network configuration before and after using XTP. In a typical configuration, the X.25 clients might be ATM banking machines.

Figure 1 XTP — Before and After

Configuration Information

X.25 recognizes an incoming call for XTP based on the node addresses configured for XTP. Therefore, in order to transport X.25 traffic between the X.25 nodes, you must configure X.25 to map to the Data Terminal Equipment (DTE) address and IP addresses of the routers to which the nodes are connected.

For example, in Figure 1, you must configure X.25 clients on the

Note: When configuring XTP, if a router is connected to an X.25 switch, it is considered to be DTE. If it is not connected to a switch, it is considered to be DCE. Refer to Figure 1 for examples.

To configure a router for XTP, you must define the following information from the XTP config> prompt and then restart the router.

For information on configuration and monitoring commands, see XTP Commands.

Local DTEs

Local DTEs are X.25 nodes connected to X.25 interfaces on the router. Use the X.121 address from your X.25 service provider to configure local DTEs.

Peer Routers

Peer routers are the routers you are communicating with over TCP/IP. Therefore, the peer router can differ depending on the point of view. For example, in Figure 1.

You designate the peer router by its internal IP address.

Remote DTEs

Remote DTEs are remote X.25 nodes to which the local X.25 nodes open connections and exchange data. Use the X.121 address from your X.25 service provider to configure remote DTEs.

You must configure a unique internal IP address for each peer router. For example, in Figure 1, the Concentrator router must know the unique IP address of each Remote router and each Remote router must know the IP address of the Concentrator router.

PVC

A Permanent Virtual Circuit (PVC) is a permanent channel that connects after X.25 restarts. These channels, because they are constant, are similar to leased telephone lines.

A PVC, in XTP context, is a PVC from a local X.25 DTE node to a remote X.25 DTE.

When you configure a router for PVCs, you must map the IP address of the peer router and the PVC number of the remote and local DTE.

Displaying the XTP Prompts

To display the XTP configuration prompt, enter protocol xtp at the Config> prompt.

Config> xtp
XTP config>
To display the XTP monitoring prompt, enter protocol xtp at the + prompt.

+protocol xtp
X.25 Transport Console
XTP>

Configuration Procedures

This section shows how to configure the network displayed in Figure 2.

Figure 2 Sample Configuration

This configuration shows three routers, the Concentrator router, Remote 1 router, and Remote 2 router. To get XTP up and running on this network, you need to perform the following steps for each of these routers.

Note: New configurations do not take effect until you restart the router.

Setting the Data Link

 Set the data-link protocol for each serial interface. The GTS 250 Series router in Figure 2 has three serial interfaces, two for X.25 and one for PPP.

You can enter list devices at the Config> prompt to see a list of configured interface numbers.

Config>set data-link X25 
Interface Number [0]? 1
Config>set data-link x25 
Interface Number [0]?2 
Config>set data-link ppp 
Interface Number [0]?3

Configuring IP

 Before you configure the Concentrator router for XTP, you must define the IP address for the IP interface and the router.

1. Display the IP config> prompt. 

Config>protocol ip
IP config>
2. Add an IP address for the IP interface (interface 3 in Figure 2). 

IP config>add address
Which net is this address for [0]? 3
New address [0.0.0.0]? 128.185.100.7
Address mask [255.255.0.0]? 255.255.255.1
3. Set the internal IP address of this router. Each router identifies its peer routers by the internal IP address of the peer routers. 

IP config>set internal-ip-address
Internal IP address [0.0.0.0]? 128.185.100.1
4. Exit the IP config> prompt. 

IP config>exit
Config>
In Figure 2, the IP interface is PPP. To configure PPP parameters, enter network 3 at the Config> prompt

Config>network 3                      
PPP interface configuration  
PPP config>
Note: This procedure does not include information on configuring PPP. See Configuring PPP.

Configuring X.25

Prior to configuring XTP, you must configure the X.25 parameters for each interface. This example configures the basic parameters for X.25, based on the topology in Figure 2.

The parameters you need to configure depend on your network topology. For details on the X.25 parameters, see X.25 Commands.

Interface 1

You would use the following instructions to configure interface 1, as defined in Figure 2.

1. At the Config> prompt, enter network followed by the number of the X.25 interface. In this example, it is interface 1. 

Config>network 1             
X.25 User Configuration 
X.25 Config>
2. Specify the network address by entering set address (X.25 node address). In Figure 2, the node address (DTE address) is 100. 

X.25 Config>set address 100
3. Enter set clocking followed by internal or external based on your router type. 

X.25 Config>set clocking internal
4. Enter set speed followed by the access rate (line speed). 

X.25 Config>set speed            
Access rate in bps  [9600]? 19200
5. Enter set equipment-type and specify whether the frame and packet levels act as DCE or DTE. 

X.25 Config>set equipment-type dce
6. Enter set pvc and define the lowest and highest PVC you are using. 

X.25 Config>set pvc low 1   
X.25 Config>set pvc high 1
7. Enter add pvc to define individual PVCs. 

X.25 Config>add pvc
Protocol [IP]? xtp
Packet Channel [1]?
Destination X.25 Address []? 101
Window Size [2]?
Packet Size [128]

Interface 2

 Use the following steps to configure interface 2, as defined in Figure 2.

1. At the Config> prompt, enter network followed by the number of the X.25 interface. In Figure 2, it is 2. 

Config>network 2             
X.25 User Configuration 
X.25 Config>
2. Use the procedures in the Interface 1 section to set the following parameters for interface 2:

3. Enter set svc and define the lowest and highest SVC you are using.

There are three types of SVCs: two-way, inbound, and outbound. The default is svc low-two-way = 1 and svc high-two-way = 64. All other SVC types default to 0. For further information on SVCs and PVCs, see X.25 Commands. 

X.25 Config>set svc low-inbound 0
X.25 Config>set svc high-inbound 0
X.25 Config>set svc low outbound 0
X.25 Config>set svc high outbound 0
X.25 Config>set svc low-two-way 1
X.25 Config>set svc high-two-way 1
4. Configure XTP to run over the X.25 interface. Enter add protocol at the X.25 Config> prompt. 

X.25 Config>add protocol
Protocol [IP]?xtp
Window Size [2]?
Default Packet Size [128]?
Maximum Packet Size [256]??
5. Exit the X.25 Config> prompt. 

X25 Config> exit
Config>

Setting the National Personality

 Each X.25 public network has its own standard configuration. The National Personality is a group of 28 variables that define the characteristics of the public data network. These variables provide the router with control information for packets transferred over the link.

To view the configuration values, enter list detailed at the X.25 Config> prompt. To set the default values for the national personality, enter set national-personality at the X.25 Config> prompt. For more information, see X.25 Commands.

Configuring XTP

After you have configured X.25 and defined the IP address, you are ready to configure XTP.

If you need further XTP command information, see XTP Commands.

Note: When configuring your network for XTP, remember that the peer routers are always the routers you are communicating with over TCP/IP. Therefore, the peer router can differ depending on the point of view. In Figure 2, the peer router to Remote 1 router and Remote 2 router is the Concentrator router.

1. To access the XTP config> prompt, enter protocol xtp at the Config> prompt.

2. Add interface 1 to the XTP configuration. Enter add local-dte at the XTP Config> prompt. 

XTP config>add local-dte
Interface number [0]? 1
DTE address []? 101
DTE address []?
3. Add interface 2 to the XTP configuration. Enter add local-dte at the XTP Config> prompt. 

XTP config>add local-dte
Interface number [0]? 2
DTE address []? 201
DTE address []?
4. Add Remote 1 router (as the peer router). Enter add peer-router and enter the IP address of this router. 

XTP config>add peer-router
Router's internal IP Address [0.0.0.0]? 128.185.100.2
5. Add the remote DTE for Remote 1 router. Enter add remote-dte and enter the IP and DTE address of this DTE. 

XTP config>add remote-dte
Peer router's internal IP Address [0.0.0.0]? 128.185.100.2 
DTE address []? 301                                          
DTE address []?
6. Add Remote 2 router (as the peer router). Enter add peer-router and enter the IP address of this router. 

XTP config>add peer-router
Router's internal IP Address [0.0.0.0]? 128.185.100.3
7. Add the remote DTEs for Remote 2 router. Enter add remote-dte and enter the IP and DTE addresses of this DTE. 

XTP config>add remote-dte
Peer router's internal IP Address [0.0.0.0]? 128.185.100.3 
DTE address []? 401                                          
DTE address []? 402
DTE address []? 403                                          
DTE address []? 404
DTE address []?

Script for Configuring the Remote Routers

 The following is a copy of the script used to configure Remote 1 router and Remote 2 router. The process is the same as that defined in the section, Configuration Procedures.

Remote 1 Router

*config

Config>set data-link x25 1
Config>set data-link ppp 2
Config>network 1
X.25 Config>set address 300
X.25 Config>set clocking internal
X.25 Config>set speed 19200
X.25 Config>set equipment-type dce
X.25 Config>set pvc low 1
X.25 Config>set pvc high 1
X.25 Config>add pvc
	Protocol [IP]? xtp
	Packet Channel [1]? 1
	Destination X.25 Address []? 301
Window Size [2]? 
	Packet Size [128]? 
X.25 Config>exit
Config>
Config>protocol ip
IP config>add address
	Which net is this address for [0]? 2
	New address [0.0.0.0]? 128.185.100.8
	Address mask [255.255.0.0]? 255.255.255.0

IP config>set internal-ip-address
Internal IP address [0.0.0.0]? 128.185.100.2
IP Config>exit
Config>

Config>protocol xtp
XTP config>add local-dte
Interface number [0]? 1
DTE address []? 301
DTE address []?

XTP config>add peer-router
Router's IP address? 128.185.100.1

XTP config>add remote-dte
Peer router's internal IP Address [0.0.0.0]? 128.185.100.1
DTE address []? 101
DTE address []?

Remote 2 Router

*config

Config>set data-link x25 1
Config>set data-link ppp 2

Config>network 1
X.25 Config>set address 400
X.25 Config>set clocking external
X.25 Config>set speed 19200
X.25 Config>set equipment-type dte
X.25 Config>set svc low-inbound 0
X.25 Config>set svc high-inbound 0
X.25 Config>set svc low-outbound 0
X.25 Config>set svc high-outbound 0
X.25 Config>set svc low-two-way 1
X.25 Config>set svc high-two-way 64
X.25 Config>add protocol
	Protocol [IP]? xtp
	Window Size [2]? 
	Default Packet Size [128]? 
	Maximum Packet Size [256]? 
X.25 Config>exit

Config>protocol ip
IP config>add address
	Which net is this address for [0]? 2
	New address [0.0.0.0]? 128.185.100.9
	Address mask [255.255.0.0]? 255.255.255.0

IP config>set internal-ip-address
Internal IP address [0.0.0.0]? 128.185.100.3
IP Config>exit
Config>
Config>protocol xtp
XTP config>add local-dte
Interface number [0]? 1
DTE address []? 401
DTE address []? 402
DTE address []? 403
DTE address []? 404
DTE address []?		
XTP Config>add peer-router
	Router's IP address? 128.185.100.1
XTP config>add remote-dte
Peer router's internal IP Address [0.0.0.0]? 128.185.100.1
DTE address []? 201
DTE address []?
XTP config>exit
Config>

XTP Commands

This section describes the XTP commands.

Not all parameters apply to all router platforms. Press Space twice after you type a command to display the available parameters for each command for your router. Enter help for information about using the command line interface.

[C] means the command is available at the XTP config> prompt.

[M] means the command is available at the XTP> prompt.

Table 1 XTP Commands

Command Function
Add [C] [M] Adds an interface, peer router, remote DTE or PVC definition.

Delete [C] [M] Deletes an interface, peer router, remote DTE or PVC definition.

Disable-XTP [C] De-activates the XTP forwarder.

Enable-XTP [C] Activates the XTP forwarder.

Exit [C] [M] Returns to the previous prompt.

List [C] [M] Lists interfaces, peer routers, remote DTEs and PVC definitions.

Set [C] Sets the keepalive timer.

Add [C] [M]

Adds an interface, a peer router, a remote X.25 node with corresponding routers, or a PVC from a local X.25 node to a remote X.25 node.

Syntax: add

local-dte
peer-router
remote-dte
pvc

local-dte

Adds the X.25 DTE addresses, or the X.25 node(s), that communicate with the router on the specified interface.

If the interface is DCE, you can configure only one local X.25 node. If the interface is DTE, you can configure multiple local nodes.

Example: add local-dte 

Interface number [0]? 1  
DTE address []? 101      
DTE address []?

peer-router

Adds a peer router. Enter the internal IP addresses of the routers to which the remote X.25 nodes are connected. You can use these IP addresses to open TCP connections and transport X.25 packets that contain connection requests and X.25 data.

Example: add peer-router 

Router's internal IP Address [0.0.0.0]? 128.185.100.2

remote-dte

Adds remote X.25 nodes and corresponding routers. You can connect remote nodes with local X.25 nodes so they can exchange data. You must configure a unique IP address for each remote X.25 node you configure. Any request or data sent to this remote node goes to the router. The router then uses one of its local X.25 interfaces to forward the data to the X.25 node.

Example: add remote-dte 

Peer router's internal IP Address [0.0.0.0]? 128.185.100.2
DTE address []? 301                                          
DTE address []?

pvc

Adds a PVC from a local X.25 node to a remote X.25 node. You cannot add a PVC from the monitoring prompt (XTP>).

Three things need to exist in order to activate a PVC configuration:

Example: add pvc

Local PVC Number [1]? 1
Local X.25 DTE address []? 100
Remote PVC Number [1]? 1
Remote X.25 DTE address []? 301
Note: When you add PVCs to the XTP configuration, you must also configure the PVC in X.25. See X.25 Commands.

Delete [C] [M]

Deletes an interface, peer router, remote DTE, or PVC from the XTP configuration.

Syntax: delete

local-dte
peer-router
remote-dte
pvc

local-dte

Deletes specific local interfaces from the XTP configuration.

Example: delete local-dte 

Interface number [0]? 1     
DTE address []? 101           
Record deleted

peer-router

Deletes specific peer routers from the XTP configuration.

Example: delete peer-router 

Router IP Address [0.0.0.0]? 128.185.100.2  
Record deleted

remote-dte

Deletes specific remote DTEs from the XTP configuration.

Example: delete remote-dte 

DTE address []? 401

pvc

Deletes PVC definitions from the XTP configuration.

Example: delete pvc

Local DTE address []? 401
Remote DTE address []?
Record deleted

Disable-XTP [C]

De-activates the XTP forwarder.

Syntax: disable-xtp

Example: disable-xtp

Enable-XTP [C]

Activates the XTP forwarder.

Syntax: enable-xtp

Example: enable-xtp

Exit [C] [M]

Returns the previous prompt.

Syntax: exit

Example: exit

Config>

List [C] [M]

 You can use list at both the configuration and monitoring prompts, as described in the next sections.

List [C]

Lists the interfaces, peer routers, remote DTEs, or PVCs.

Syntax: list

all
xtp-status
local-dtes
peer-routers
remote-dtes
pvcs
keep-alive-timer

all

Displays the complete XTP configuration.

Example: list all 

Local DTEs:
Interface        DTE Addr
   1             101
   2             201
                            
Peer Routers:
128.185.100.2
128.185.100.3
                                                                          
Remote DTEs:
DTE Address      Peer Router
    301         128.185.100.2
    401         128.185.100.3
    402         128.185.100.3
    403         128.185.100.3
    404         128.185.100.3
   
PVCs:
Local PVC      Local DTE      Remote PVC      Remote DTE
 Number          Address        Number          Address
  1                100              1             301

xtp-status

Displays whether XTP is enabled or disabled.

Example: list xtp-status 

STATUS: XTP-ENABLED

peer-routers

Displays all the peer routers configured for XTP.

Example: list peer-routers 

Peer Routers:
128.185.100.2
128.185.100.3

remote-dtes

Displays all the remote DTEs configured for XTP.

Example: list remote-dtes 

Remote DTEs:
DTE Address      Peer Router
    301         128.185.100.2
    401         128.185.100.3
    402         128.185.100.3
    403         128.185.100.3
    404         128.185.100.3

pvcs

Displays all the PVCs configured for XTP.

Example: list pvcs 

PVCs:


Local PVC      Local DTE      Remote PVC      Remote DTE
 Number          Address        Number          Address
  1                100              1             301

keep-alive-timer

Displays the configuration of the keepalive timer, set using the set keep-alive-timer command.

Example: list keep-alive-timer

KEEP-ALIVE-TIMER: 10 seconds

List [M]

Displays the current active interfaces, peer routers, remote DTEs, PVCs and/or SVCs.

Syntax: list

all
xtp-status
local-dtes
peer-routers
remote-dtes
pvcs
pvc-detailed
pvcs-all-detailed
pvcs-queues
svcs
svc-detailed
svcs-all-detailed
svcs-queues

all

Comprehensively displays the output of all the list command options.

Example: list all

LIST OF LOCAL DTES
------------------
Interface     Local
  No           DTE
  1            101
  2            201
                                                                           LIST OF PEER ROUTERS
--------------------
 Router             CNN   Number         Received              Sent
                   State  of  Ckts      Pkts     Bytes   Pkts     Bytes
128.185.100.3     ACTIVE     15           60      1533    12       142
128.185.100.2     ACTIVE     12           63      1620    10       130
                                                                         
LIST OF REMOTE DTES
-------------------
      Remote        Router
       DTE            IP
       404          128.185.100.3
       403          128.185.100.3
       402          128.185.100.3
       401          128.185.100.3
       301          128.185.100.2
                                                       
LIST OF PVCS                                     
------------                                     
Index     Int    PVC        Local       Remote      
 No        No   State        DTE          DTE       
 1         1     ACTIVE      100          301    
                                                 
LIST OF SVCS                                     
------------                                     
Index     Int    SVC        Local       Remote   
 No        No   State        DTE          DTE    
  1         1     ACTIVE     200          401   
  1         1     ACTIVE     200          402
  1         1     ACTIVE     200          403   
  1         1     ACTIVE     200          404

xtp-status

Displays whether XTP is enabled or disabled.

Example: list xtp-status 

Status:  XTP-ENABLE

local-dtes

Displays all the interfaces configured for XTP.

Example: list local-dtes

 LIST OF LOCAL DTES
------------------
Interface     Local
  No           DTE
  1            101
  2            201

peer-routers

Displays all the peer routers configured for XTP.

Example: list peer-routers

LIST OF PEER ROUTERS                                                       
--------------------                                                       
Router             CNN   Number            Received          Sent
                   State  of  Ckts      Pkts     Bytes   Pkts     Bytes
128.185.100.3     ACTIVE     15           60      1533    12       142
128.185.100.2     ACTIVE     12           63      1620    10       130

remote-dtes

Displays all the remote interfaces configured for XTP.

Example: list remote-dtes

LIST OF REMOTE DTES                   
-------------------                   
     Remote        Router
       DTE            IP
       404          128.185.100.3
       403          128.185.100.3
       402          128.185.100.3
       401          128.185.100.3
       301          128.185.100.2

pvcs

Displays all the PVCs configured for XTP.

Example: list pvcs

LIST OF PVCS                                        
------------                                        
Index     Int    PVC        Local       Remote      
 No        No   State        DTE          DTE       
 1         1    ACTIVE       100          301

pvc-detailed

Displays detailed information for a specific PVC definition. For a listing of Index numbers, enter list all at the XTP> prompt.

Example: list pvc-detailed

PVC Index Number [1]? 1                                                   
                                                                          
PVC  1 IN DETAIL                                                          
----------------                                                          
Int    PVC         Received              Sent               Dropped       
 No   State      Pkts     Bytes      Pkts     Bytes      Pkts     Bytes   
 1     ACTIVE    55       3220       35        2350       15      1870

pvcs-all-detailed

Displays detailed information for all PVC definitions.

Example: list pvcs-all-detailed

                                                                             
LIST OF PVCS                                                                 
----------------                                                          
Int    PVC         Received              Sent               Dropped       
 No   State      Pkts     Bytes      Pkts     Bytes      Pkts     Bytes   
 1    ACTIVE     55       3220        35      2350        15      1870

pvcs-queues

Displays

Example: list pvcs-queues

Queue status of PVCs
--------------------
Index  Int    PVC          Hold Queue
 No    No     State           Count   
  1     1     ACTIVE           10

svcs

Displays all the SVCs definitions.

Example: list svcs

LIST OF SVCS                                     
------------                                     
Index     Int    SVC        Local       Remote   
 No        No   State        DTE          DTE    
  1         1     ACTIVE     200          401   
  1         1     ACTIVE     200          402
  1         1     ACTIVE     200          403   
  1         1     ACTIVE     200          404

svc-detailed

Displays information for specific SVC definitions.

Example: list svc-detailed 

SVC Index Number [1]? 1
SVC  1 IN DETAIL                                                         
----------------                                                         
Int    SVC         Received            Sent            Dropped      
 No   State      Pkts     Bytes    Pkts     Bytes   Pkts     Bytes
 1	   ACTIVE      75       4220     55       3350    20       870

svcs-all-detailed

Displays information for all the SVC definitions.

Example: list svcs-all-detailed

LIST OF SVCS                                                                
------------                                                                
Index     Int    SVC         Received        Sent          Dropped
No        No   State      Pkts    Bytes   Pkts    Bytes   Pkts    Bytes
1	   ACTIVE      75        4220       55        3350        20    870
1   ACTIVE      55        3220       40        2350        15     970
1   ACTIVE      63        4003       50        3892        13     111
1   ACTIVE      78        4967       58        4167        12     800

svcs-queues

Displays

Example: list svcs-queues

Queue status of SVCs
--------------------
Index  Int    SVC          Hold Queue
 No    No     State           Count

Set [C]

Sets the keepalive timer.

Syntax: set keep-alive-timer

Example: set keep-alive-timer

Keep Alive Timer in seconds [10]?

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