HP OpenVMS Systems Documentation

You cannot configure the X.25 CONS protocol stack on DECnet-Plus end system products using the configuration tools alone. To successfully configure the stack, you must understand NCL and the management entities in the X.25 CONS stack. Table 8-17 shows the management entities used at each layer of the protocol stack.

The X.25 and LAPB protocols allow many options that vary among X.25 networks. DIGITAL's products provide X.25 network profiles that contain all the pertinent network parameters for most PSDNs. For example, profiles contain the default value and permissible range for the X.25 window size. The system administrator specifies the profile name during system configuration. Typically, the profile name corresponds to the name of the PSDN.

The X.25 and X.25 Access software components follow instructions from both their user applications and their management entities. You cannot control the behavior of these components entirely by management. In some cases, X.25 and X.25 Access software ignore certain management parameters, depending on which functions an X.25 application uses.

Example Configuration

The following illustrated configuration and the examples that follow help clarify the interrelationships among management entities for outgoing and incoming calls using X.25 CONS. Assume the end system implementations NCOSI and SYBILL are connected to a local X.25 packet switch, which in turn is connected to an AT&T Accunet line, as shown in Figure 8-17.

Figure 8-17 Example Configuration

Accunet addresses are NTN-based, similar to PACNET. All addresses discussed in this section are based on conversion rules defined in international standards.

NCOSI is set up as the OSI application initiator, SYBILL as the responder. AT&T assigned a range of addresses to the line from 6171234500 to 6171234599.

The Accunet DNIC is 3134, and the international prefix is 0. NCOSI has a local subaddress of 40, and SYBILL has a local subaddress of 10. From these subaddresses, the remaining addresses are derived using the conversion rules explained in Section 8.8.2.1. Table 8-18 lists these addresses.

Outgoing Connections

Figure 8-18 shows the entity relationships for outgoing connections. The following actions occur during an outgoing call:

1. The OSI application initiator provides the full OSI stack specification of the destination along with the OSI transport template entity name to OSAK. (Note that no major OSAK management components are involved in outgoing connections; therefore, they are not shown in Figure 8-18.) OSAK passes the TSEL and NSAP on down to OSI transport.
2. OSI transport follows instructions in the OSI transport template to set up a connection over CONS. It uses the OSI transport CONS NSAP address for the source address.
3. X.25 and X.25 Access software follow instructions in the X25 access template to make the call. The nsap mappingattribute is true and the dte class attribute is null, forcing NSAP-to-X.25 network address conversions through X.25 access reachable addresses. The value in the local subaddress causes X.25 and X.25 Access software to provide a calling DTE address in the outgoing X.25 call packet.
4. X.25 and X.25 Access software select the X.25 access reachable address with the longest address prefix that matches the destination NSAP. X.25 access reachable addresses provide for two types of conversions. X.121 mapping converts an X.121-translatable NSAP to an X.121 address using the rules defined in Section 8.8.2.1. Manual mapping converts from any NSAP address directly to any specific X.25 network address. Most NSAPs in the transport/X.25 CONS stack are X.121-translatable and use X.25 access reachable address x121d. The dte class attribute indicates that the call may be placed on any X.25 protocol DTE line under X.25 access DTE class Accunet.
5. The X25 dte class entity defines how to translate X.121 addresses to the local X.25 network addresses. X.25 and X.25 Access software use these translation rules only when the original NSAP was converted through X.121 mapping.

Figure 8-18 Entity Relationships for Outgoing Connections

Incoming Connections

Figure 8-19 shows the entity relationships for incoming connections.

Figure 8-19 Entity Relationships for Incoming Connections

The following initialization actions take place before incoming connections can be accepted.

1. OSAK opens a port to OSI transport for every TSAP required by OSAK applications.
2. OSI transport activates any x25 access filter entities specified in the osi transport cons filters attribute.
3. X.25 and X.25 Access software open a channel to each LAPB link during initialization, and in turn, each LAPB link opens channels to their associated modem connect line entity.

The following occurs upon receipt of an incoming call on an X.25 DTE:

1. X.25 and X.25 Access software use the protocol dte inbound dte class attribute to determine which X25 access DTE class applies to the call.
2. X.25 and X.25 Access software extract the NSAP address from the address extension facilities, if they exist. If the facilities do not exist, X.25 and X.25 Access software convert the X.25 network addresses to NSAP addresses using the x25 access dte class attributes.
3. X.25 and X.25 Access software search the X.25 access filters for a match with the attributes of the incoming call. If a match exists, X.25 and X.25 Access software pass the message up to the application that activated the filter.
4. OSI transport searches for an osi transport template entity with inbound characteristic = true, network service=cons, and cons template having the name of the X25 access filter. If found, OSI transport accepts the X.25 call with the X25 access template specified in the cons template attribute. With this procedure, the x25 access filter and x25 access template entities must use the same entity name.
5. OSI transport passes the message up to OSAK if the transport connect request PDU's called TSAP ID field matches the TSEL specified by OSAK during initialization step 2.
6. OSAK passes the message up to the OSI application if the SSEL and PSEL match those defined during initialization step 1. OSAK ignores the AP-Title and AE-Qualifiers.
   • OSAK invokes the OSI application responder using the command file defined in the osak application invocation entity prior to passing the message up.

The DECnet-Plus configuration procedure always configures the CLNS stack. You cannot use this procedure to configure the CONS stack alone.

By default, the DECnet-Plus for OpenVMS configuration procedure configures HDLC on WAN devices. This blocks X.25 access to the same devices. Use the advanced configuration procedure to override this default.

Manually add specific NCL commands to the configuration procedures to complete the configuration, as shown in the following examples.

All DECnet-Plus end system products support manual x25 access reachable addresses entities, allowing mapping of NSAPs to any X.25 network address. Set the default configuration to perform X.121 mapping without address extension facilities, as shown in this document. Use manual X.25 access reachable addresses only for destinations with non-X.121-based NSAPs.

X.25 and X.25 Access software provide controls to screen incoming calls with the x25 access filter and x25 access security filter entities. These mechanisms allow you to define access to the system based on call data such as source and destination addresses. The examples below do not use them. See X.25 documentation for more information.

The following subsections show examples from procedures used to configure OpenVMS Alpha and VAX systems. The procedures were performed on pristine systems that include only the base operating system and the minimum appropriate licenses. The system parameters are set as defined in the DECnet-Plus and X.25 documentation.

OpenVMS Alpha Configuration of OSI Transport Over X.25 CONS

Take the following steps to configure FTAM (and other OSI applications) with OSI Transport over X.25 CONS on an OpenVMS Alpha system. For more information on FTAM configuration, see the DECnet-Plus FTAM and Virtual Terminal Use and Management guide.

1. Install the DECnet-Plus base kit, as follows:

   $ PRODUCT INSTALL DECNET_OSI

2. Configure DECnet-Plus with WAN drivers and an additional OSI template for the CONS protocol stack. Do not configure WAN devices for routing.

   $ @NET$CONFIGURE ADVANCED

   
   Respond to the prompts as shown:
   • Do you want to configure Wide Area Devices? Y
   • Configure WANDD? Y
   • Configure built in serial port as synchronous? Y
   • Data Link protocol for ZRA0 (SSCC)? NONE
   • Do you want to create additional OSI templates? Y
   • Type of network service (CLNS/CONS/RFC1006)? CONS
   • Name of the OSI template? CONS
   • Transport classes to support? 0,2
   • Do you want to create additional OSI templates? N
3. Install X.25 for OpenVMS Alpha, as follows:

   $ PRODUCT INSTALL X.25

4. Configure and start X.25, as follows:

   $ @X25$CONFIGURE ADVANCED

   
   Respond to the prompts as shown:
   • Configuring WANDD...
   • Change your current configuration: N
   • Create a new configuration script (from menu)
   • Do you want to configure any Remote DTE Classes? N
   • Do you want to configure any synchronous lines? Y
   • X.25 Address: 61712345
   • Profile Name: ACCUNET
   • Outgoing Logical Channel Range: {[1..127]}
   • Do you want to use LLC2 communications? N
   • Do you want to create any applications? N
   • Do you want to set up additional filters? N
   • Do you want to set up additional templates? N
   • Do you want to specify reachable addresses? N
   • Allow all X.25 calls (from menu)
5. The configuration procedures in steps 2 and 4 do not account for local X.25 address formats. Modify the configuration by adding the following NCL commands to SYS$STARTUP:X25$EXTRA_SET.NCL:

   set lapb link link-0 sequence modulus 8 set x25 access dte class accunet internationalprefix 0 set x25 access dte class accunet dnic 3134 set x25 access dte class accunet strip dnic true set x25 access reachable address x121d dte class accunet set x25 access template "osi transport" local subadd 6171234540

6. Install FTAM and the other OSI applications so that you can actually use OSI transport over CONS, as follows:

   $ PRODUCT INSTALL OSAK, FTAM, VT

7. Configure FTAM, as follows:

   $ @OSIF$CONFIGURE

8. Add FTAM service aliases to the OSI applications database, as follows:

   $ EDIT/EDT SYS$SYSTEM:ISOAPPLICATIONS.DAT

9. Start OSAK and FTAM, as follows:

   $ @SYS$STARTUP:OSAK$START $ @SYS$STARTUP:OSIF$STARTUP

10. Manually enter the following NCL commands:

    NCL> ADD OSI Transport CONS NSAP Addresses {/103631346171234540 } NCL> SET OSI Transport Template CONS Loc NSAP/103631346171234540 NCL> SET OSI Transport Template CONS Classes {0, 2 }

OpenVMS VAX Configuration of OSI Transport Over X.25 CONS

Take the following steps to configure FTAM (and other OSI applications) with OSI Transport over X.25 CONS on OpenVMS VAX systems. For more information on FTAM configuration, see the DECnet-Plus FTAM and Virtual Terminal Use and Management guide.

1. Register the OpenVMS operating system in POLYCENTER. Specify your actual OpenVMS operating system version in the /VER= switch, as follows:

   $ PRODUCT REG PROD VMS /VER=V7.0 /SOURCE=SYS$UPDATE:

2. Install DECnet-Plus base kit with the X.25 Access software, as follows:

   $ PRODUCT INSTALL DECNET_OSI

3. Configure DECnet-Plus with WAN drivers and an additional OSI template for the CONS stack. Do not configure WAN devices for routing.

   $ @NET$CONFIGURE ADVANCED

   
   Respond to the prompts as shown:

   Do you want to configure Wide Area Devices? Y Do you wish to use WANDRIVER? Y Will you use DEC HDLC? N Will you use LAPB/E? Y Do you have any soft-loadable microcode devices on this system? Y Do you want asynchronous datalink support? N Data Link protocol for DSV-0-0 (DSV-11)? NONE Data Link protocol for DSV-0-1 (DSV-11)? NONE Do you want to create additional OSI templates? Y Type of network service (CLNS/CONS/RFC1006)? CONS Name of the OSI template? CONS Transport classes to support? 0,2 Do you want to create addional OSI templates? N

4. Configure and start X.25 Access software, as follows:

   $ @PSI$CONFIGURE ADVANCED

   
   Respond to the prompts as shown:

   Type of VAX P.S.I. configuration? Native Do you want to configure any synchronous lines? Y Select a line speed for your DTE: 9.6 X.25 DTE Address: 61712345 Logical Channel Ranges: [[1..127]] Profile Name: ACCUNET Do you wish to set up any PVCs? N Do you wish to create any Closed User Groups? N Do you wish to use LLC2 communications? N Do you wish to set up any applications? N Do you wish to set up additional templates? Y Template Name: "OSI Transport" DTE Class: ACCUNET Call Data: %x03010100 Charging Information: NO Local Subaddress: 40 NSAP Mapping: YES Do you want X.25 or X.29 programs to specify filter names in $QIO calls? YES Do you want IO$_ACPCONTROL calls issued by your programs to name any static filters? YES Filter Name: "OSI Transport" Call Data Value: %x03010100 Call Data Mask: %xFFFFFFFF Do you want to set up X.25 Security? NO Do you wish to create an NCL script now? Yes

5. The configuration procedures in steps 3 and 4 do not account for local X.25 address formats. Modify the configuration by adding the following NCL commands to the SYS$STARTUP:PSI$ENABLE_DECNET_CLIENTS.NCL file:

   create x25 access reachable address x121d address prefix /36 set x25 access reachable address x121d mapping x.121 set x25 access reachable address x121d dte class accunet set x25 access reachable address x121d address extensions true add osi transport cons nsap addresses {/103631346171234540 }

6. Install FTAM and the other OSI applications, as follows:

   $ PRODUCT INSTALL OSAK, FTAM, VT

7. Configure FTAM, as follows:

   $ @OSIF$CONFIGURE

8. Add FTAM service aliases to the OSI applications database, as follows:

   $ EDIT/EDT SYS$SYSTEM:ISOAPPLICATIONS.DAT

9. Start OSAK and FTAM, as follows:

   $ @SYS$STARTUP:OSAK$START $ @SYS$STARTUP:OSIF$STARTUP

Dynamically-assigned circuits are used for making infrequent connections to destinations outside the routing domain of your DECnet-Plus system. (A routing domain is a collection of systems that automatically configure to each other and exchange network topology information using consistent Network layer protocols.) Dynamically-assigned circuits are established upon arrival of data and are cleared when no more data is transmitted or received during a specified time (idle time).

8.8.3.1 Addressing Issues for Dynamically Assigned Circuits

When using dynamically-assigned X.25 routing circuits, the sending and receiving nodes must be in separate routing domains. The routing domain is defined with a unique AFI, IDI, and PreDSP combination in the NSAP address (see Figure 8-16). The format of the CLNS address must conform to that described in the DECnet-Plus Planning Guide.

The requirement for separate routing domains places two restrictions on addressing:

• The NSAP address used at the Routing layer for the source and destination can be any CLNS address except ones beginning with AFI 49.
• DECnet Phase IV network traffic cannot span dynamically-assigned X.25 routing circuits. Phase IV address translations apply only within a single routing domain.

If your DECnet-Plus system is isolated from the network and uses the dynamically-assigned X.25 routing circuit for communication, you may find it convenient to assign an NSAP address to your system that is based on your X.25 network address. If you do this, you must use the binary format of an X.121 address (AFI 37 or 53), as opposed to the decimal format described in Section 8.8.2.1 for X.25 CONS configurations. Section 8.4.1.6 explains how to use manual network entity titles to define the NSAP address for your system.

For each dynamically-assigned X.25 routing circuit, you must configure one or more reachable addresses. A reachable address defines a mapping between network service access points (NSAPs) and data terminal equipment (DTE) addresses used in X.25. An NSAP identifies a system in the network and is used by both the Network and Transport layers of DECnet-Plus. X.25 uses a DTE address to identify the end point of an SVC. Reachable addresses identify which NSAP or group of NSAPs should be sent over a particular X.25 circuit.

Consider the following example of two systems connected by an X.25 network:

The reachable address on System A specifies that if the destination NSAP matches the value 43:15082267643:0045:08002B16DE4F:21, then an X.25 circuit should be created by connecting to the DTE address 18628935742674. This example is a case of one-to-one NSAP-to-DTE mapping. The reachable address could also be set up such that any NSAP with the initial digits 43:15082267643 should be sent over that X.25 circuit, which would potentially cause many different NSAPs to be mapped to that particular X.25 circuit.

The NCL commands to create and initialize reachable addresses are created in the SYS$STARTUP:NET$OSI_TRANSPORT_STARTUP.NCL script (for OSI transport using CONS) and the SYS$STARTUP:NET$ROUTING_STARTUP.NCL script (for Routing using X.25).

The following example shows how to manually create a reachable address for routing using NCL. For more information on configuring routing, see Section 8.4.

ncl> create routing circuit x25_circuit-1 reachable address ughh_v -
_ncl> address prefix /4145418715004108002b0ed41e

ncl> set routing circuit x25_circuit-1 reachable address ughh_v -
_ncl> dte address { 2267643 }

ncl> set routing circuit x25_circuit-1 reachable address ughh_v -
_ncl> mapping manual

ncl> enable routing circuit x25_circuit-1 reachable address ughh_v

Specify the address prefix when you create the routing circuit entity. You cannot modify this attribute with the setcommand.

The X.25 configuration procedure automatically creates the following two X25 Access reachable addresses:

• X121 with address prefix 37:
• X121D with address prefix 36: