Installing and Administering OSI Transport Services

Chapter 2 75
Planning Your Network
General X.25 Questions
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:
• It defines a mechanism for conveying NSAPs in 1984 and 1988
X.25 CALL packets. OTS supports full 8878 by default.
• Defines a “special” mechanism, called SNDCP, which simulates
this behavior on 1980 X.25 networks. Many OSI implementations
do not support the SNDCP behavior.
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.