Chapter 2. Planning for SX.25

Planning an SX.25 host configuration involves identifying the communications ports on the system and deciding on the services that each port will provide (see Chapter 1 for an explanation of available SX.25 services). It is also necessary to collect information that must be provided during the configuration process. This chapter contains these sections to help you with configuration planning:

Port Naming Conventions

When the SX.25 application starts, it requests a hardware inventory (see the hinv(1M) reference page) of the number of communications ports that are installed on the system. SX.25 automatically assigns a name to each port that the inventory reports.

The maximum number of serial ports on a Silicon Graphics system varies with the bus architecture used on different system models. Table 2-1 lists the bus type and model of each Silicon Graphics system, the maximum number of communication ports that each model can contain, and the name that SX.25 software assigns to each port:

Table 2-1. Port Numbering on Silicon Graphics Systems

Bus Type

Model

Maximum Ports

Distribution of Ports

Port Name

GIO

Indy

 

 

 

Indigo

CHALLENGE S

4

 

 

 

4

4

Slot 1, 2 ports

 

Slot 2, 2 ports

 

Same as Indy

Same as Indy

wan00

wan01

wan10

wan11

Same as Indy

Same as Indy

EISA

Indigo 2

 

 

 

 

 

 

 

CHALLENGE M

8

 

 

 

 

 

 

 

8

Slot 1, 2 ports

 

Slot 2, 2 ports

 

Slot 3, 2 ports

 

Slot 4, 2 ports

 

Same as Indigo2

wan00

wan01

wan10

wan11

wan20

wan21

wan30

wan31

Same as Indigo2

VME

CHALLENGE L

16

Slot 1, 4ports

 

 

 

Slot 2, 4ports

 

 

 

Slot 3, 4 ports

 

 

 

Slot 4, 4 ports

wan00

wan01

wan02

wan03

wan10

wan11

wan12

wan13

wan20

wan21

wan22

wan23

wan30

wan31

wan32

wan33

 

CHALLENGE XL

16

Same as CHALLENGE L

Same as CHALLENGE L


Evaluating SX.25 Parameter Files

SX.25 software includes a collection of files that set parameters for link-level and packet-level protocols to values used by the vast majority of PDNs. In most cases, these values are appropriate for your port connections, and you can establish X.25 WAN and LAN connections using SX.25 parameter files. However, if you are using SX.25 for the first time, it is important to evaluate the suitability of the as-shipped files for connecting to your particular network and to identify any adjustments that might be needed. You can check factory-shipped parameter settings by opening the files with gx25adm (see “The Open Button” in Chapter 4).

If you are unsure of the operating requirements for a network to which you are connecting, discuss your questions with your network service provider.

Collecting Information for Port Configurations

If you plan to use SX.25 protocol parameter files, be prepared to supply this information during the configuration procedure:

  • A subnet ID for the port. This ID identifies the protocol stack to the SX.25 daemon.

  • A DTE address for the port. Ask your network service provider to supply addresses. See “X.121 Addresses” in Appendix A if you need detailed information.

  • The names of the ports to be configured. See Table 2-1 for the list of SX.25 port names.

  • Whether ports will operate as a DTE or DCE and the X.25 recommendation to which the port must conform (1980, 1984, or 1988).

  • The link procedure to be used on each port: LAP, LAPB, or LAPB with extended addressing for WAN ports; LLC1 or LLC2 for LAN ports.

Additional Information for Custom Protocol Files

If you plan to create custom parameter files, be prepared to substitute settings in the X.25 parameter files for settings that are required by your network service.

You might need to reset one or several of the packet-level parameters listed below to operate on the network to which you subscribe:

  • The extended address for any ports on which you plan to use OSI NSAP or other extended addressing.

  • The modulo number (8 or 128) used for packet sequencing

  • The type of logical channels that you will use and their numbers. (See “Logical Channels” in Chapter 1 and Figure 7-3.) Include PVCs if you plan to use them.

  • The default maximum size of packets and windows on local and remote DTEs, and the maximum size of the network service data unit (NSDU). (See Figure 7-4.)

  • Settings for packet-level timers, counters, and delays. (See Figure 7-5, Figure 7-6, and Figure 7-7.)

  • Throughput class boundaries. (See Figure 7-8.)

  • The types of negotiation that are supported: packet size, window size, and throughput class

  • If you belong to a closed user group (CUG), the conventions that are followed. (See Figure 7-9.)

  • The optional facilities to which you subscribe. (See Figure 7-10.)

  • Conventions for handling international calls, priority requests, addresses in outgoing calls, and diagnostic packets. (See Figure 7-11.)

  • Conventions for handling D-bits. (See Figure 7-12.)

You might need to reset one or several of the link-level parameters listed below to operate on the network to which you subscribe:

Additional Information for IP Connections

If you plan to configure IP on any connections (see “IP Network Connections” in Chapter 1), plan to supply this information during the configuration procedure (also see Figure 5-1):

  • For each network to which the SX.25 host is connecting, a local Internet address for the SX.25 host, the subnetwork mask of the network, the version of X.25 run on the network, and the addressing scheme that the network uses (CCITT or DDN)

  • Whether to allow broadcast packets

  • The high-water mark for data concatenation (if higher than 576 octets)

  • Maximum idle and minimum connection time for virtual circuits

  • Mode of operation, CCITT or DDN

  • How to handle reset and expedited data requests

  • PVC channel ranges, if you plan to use PVCs

  • Listen information for applications using the connection

If you plan to create an IP/IXE map, which allows users to designate hosts by their name rather than by their address, you need to supply this information:

  • The address or name of the IP hosts to which the SX.25 host will connect. If you plan to use a hostname, it must be listed in SX.25 hosts file (/etc/hosts).

  • The maximum packet and window size to be used in connections

Additional Information for PAD and PADD Connections

If you plan to use the PAD map (see “PAD and PADD Connections” in Chapter 1), plan to supply this information:

  • The name of the X.25 hosts to which local users will connect and any aliases by which these hosts are known (see Figure 5-6 and Figure 5-9)

  • The address of the X.25 hosts to which users will connect for PAD sessions. For WAN connections, the address is an X.121 address; for LAN connections, it is an LSAP address. Address information must include an extension for any host that is using extended addressing.

  • The X.29 version used on the remote host and any call user data (CUD) that is required in a connection request

  • The incoming and outgoing packet and window sizes on the remote host, whether it uses fast select, and whether it accepts reverse call charges (see Figure 5-7)

  • The closed user group (CUG) number and whether the CUG is bilateral or multilateral. If calls are routed by means of a recognized private operating agency (RPOA), the RPOA numbers (Figure 5-8).

If you plan to offer PADD services (see “PAD and PADD Connections” in Chapter 1), plan to supply this information:

  • Any CDU that is required in incoming calls

  • The addresses of hosts from which calls will be accepted

  • Whether CDU and address data must match exactly or in part

  • Whether the addresses are X.25 DTE (WAN connections) or X.25 NSAP (LAN connections)