Configuring XOT

XOT requires careful configuration of both the LayGO software and the Cisco routers and careful coordination between them.

Note: This manual does not provide detailed information on how to configure Cisco routers. Consult Cisco documentation or Cisco technical support for questions about configuring and operating Cisco routers.

Cisco Router Configuration

Each port (or interface to use Cisco's term) on a router which will be accessed via XOT must be properly configured to communicate with the X.25 device attached to it. In addition, the interface on which the XOT connections will come must be assigned an IP address. The procedures discussed here relate only to XOT routing.

For SVCs, 2 configuration entries are required. First the interface must be assigned an X.25 address with an entry of the form:

x25 address <address>

where <address> is a valid X.25 DTE/DCE address. Second, a corresponding entry must be made in the X.25 routing table:

x25 route ^<address> interface <interface>

where <interface> is the interface name, such as Serial0. X.25 call request packets with a called DTE address of <address> will then be routed to <interface>.

Finally, a routing table entry is required to route traffic from the X.25 interfaces to the XOT TCP/IP interface. That entry should be of the form:

x25 route .& xot <IP address>

where <IP address> is the IP address assigned to the XOT TCP/IP interface.

PVC configuration is done completely on the interface. The first entry establishes which X.25 Logical Channel Numbers (LCNs) will be allocated to PVCs:

x25 ltc <LCN>

where <LCN> is the LCN allocated for the first SVC. All lower LCNs greater than 0 automatically become allocated to PVCs. This means that <LCN> must be greater than 1 or no PVCs are allowed. Then, for each PVC on the interface, an entry is required of the form:

x25 pvc <local LCN> xot <IP address>
    interface Serial <interface id> pvc <remote LCN>


Note: The LayGO XOT Server requires that <local LCN> and <remote LCN> be the same. It automatically maps LCN N on the major device to LCN N on the remote interface.

We recommend that you set <interface id> to the same value as that of the interface on the router. For instance, if you are configuring interface Serial1/0 on the router, assign an <interface id> of 1/0 to the corresponding LayGO major device. The same interface id can be assigned to more than one LayGO major device. The LayGO XOT Server only uses <interface id> to form the character string for the initiator interface name during the XOT PVC call setup. For instance, if interface Serial1/0 is being configured on the router and <interface id> given as 1/0, the corresponding LayGO XOT session parameters will use Serial1/0 for both initiator and responder interface names. The default X.25 window and packet sizes for the interface on the router must also be entered in the LayGO XOT session parameters.

LayGO Software Configuration

There are 5 LayGO configuration components for XOT:

The Service Database

The service database used by the LayGO XOT Server and LayGO X.25 clients must contain one entry for each Return Layer service used for XOT. Remember that 2 Return Layer services are required for each X.25 Major Device which uses XOT. A detailed discussion of the service database can be found in the LayGO Configuration Manual. Return Layer service entries should have the form:

<service name>   9   <major device number>   0   null.cfg

For instance:

RTN0   9   0   0   null.cfg
RTN1   9   1   0   null.cfg
RTN2   9   2   0   null.cfg
RTN3   9   3   0   null.cfg

The Device Database

The device database used by the LayGO XOT Server must contain one entry for each Return Layer device used for XOT. A detailed discussion of the device database can be found in the LayGO Device Library. Return Layer device entries should have the form:

<device name>   <return service name>

For instance:


If the LayGO Device Library is also used by X.25 clients to manage the X.25 major device, one entry for each X.25 device is needed. For instance:

XOT0   RTN0   PKT0
XOT2   RTN2   PKT2

With these entries, the XOT Server would use devices XOT1 and XOT3. The X.25 clients would use XOT0 and XOT2.

.CFG Files

The LayGO RPC Server to which the LayGO XOT Server and X.25 clients will connect must be configured to provide the protocol services required by XOT. Complete details on LayGO stack configuration can be found in the LayGO Configuration Manual. Only details relevant to XOT are discussed here.

The System Stack configuration given to the RPC server at startup determines which protocols can be used. This is controlled by the "Numbers of X major devices" parameters where "X" is a protocol name. A value of 0 disables the protocol. A negative value creates one device for each physical line reported by the device driver. A positive value is the exact maximum number to create. 2 Return Layer devices and 1 X.25 Major Device are required for each XOT session. If no communications board is installed, the Emulation driver (board id 6) should be used and the number of X.21 bis devices can be set to 0. The "Maximum write buffers to queue on each CID" parameter should be set to a relatively high value, 16 or 32.

Note: Devices are always numbered 0 through N-1 where N is the number configured. For instance, if 8 Return Layer and 4 X.25 devices are configured, they will be devices 0-7 and 0-3 respectively. This means that for XOT, X.25 devices 0, 1, 2 and 3 would be stacked onto Return Layer devices 0, 2, 4 and 6, respectively.

The System Buffer Pool is a shared resource. It should be configured so that the largest buffer size will accommodate the largest maximum packet size required for any XOT session. XOT does not use any reference buffers.

Finally, the X.25 Major Device configuration should have the largest combined total of SVCs and PVCs required for any XOT session. The other parameters may have to be set on each device at runtime if the X.25 parameters are not the same for all sessions.

.XCL Files

Each X.25 SVC call request packet must contain a called DTE address which matches that assigned to the interface on the Cisco router to which the call will be directed. In addition, when using XOT, call request packets must contain optional facility parameters for packet and window sizes. LayGO supports the use of .xcl files to store encoded X.25 SVC call setup data including called and calling DTE addresses, optional facilities and user data. Complete details can be found in the LayGO Configuration Manual.

XOT Server Initialization Files

The LayGO XOT Server requires an initialization file which describes the parameters for each XOT session. The initialization file format is described elsewhere. The parameters given in this file must coincide with those of the other 3 components and of the Cisco router.