General X.25 Questions

Is ISO 8878 behavior supported?

ISO 8878 defines how X.25 is to be used to provide CONS. Among other features:

The configurable parameter, "snet_allow_iso8878", in the file "ots_subnets" controls whether or not OTS will use the SNDCP when communicating over 1980 X.25.

What versions of X.25 will be used?

There are three versions of X.25 support: X.25 '80,'84, and '88. Each is effectively a superset of the previous. Sending X.25 '84 traffic to an X.25 '80 system may result in connection refusal. It is important to understand what systems support which protocol. OTS by default sends X.25 '84 packets and receives both X.25 '80 and '84.

What level of X.25 switch or PDN should I use?

If your switch or Public Data Network only supports X.25 '80, then systems connected through it must use X.25 '80. Otherwise '80, '84, and '88 are acceptable.

Is subaddressing supported?

HP recommends use of subaddressing in order to share the same physical card with various services. If subaddressing is not supported, then you will be restricted to configuring a single CONS and a single CLNS network through each card. For a discussion of the parameter see "snet_bind_by_pid" in the "ots_parms".

Are Protocol ID values used?

If the remote can accept calls using the NULL PID, then you can safely set the "tpcons_null_pid" parameter. OTS by default sends the PID. The parameter "tpcons_null_pid", in the file "ots_parms" can override this behavior.

By default, OTS will also accept call packets with either the OSI or NULL PID values. Setting the "snet_bind_by_pid" parameter in the "ots_subnets" file will prevent OTS from accepting CALL requests using the NULL. If set, OTS will refuse calls with a PID other than the OSI standard PID.

What Network layer protocols will be used (CONS, CLNS)?

The Connectionless Network Service (CLNS) has the advantage in that it can be used with routers and does not require the gateway facility provided by MSDSG in order to interconnect with CLNS/LAN subnetworks. However, CLNS does present more overhead because each packet sent contains addressing information, and Transport Class 4 must be used.

The Connection-Oriented Network Service (CONS) is currently more widely used than CLNS/X.25.