Installing and Administering OSI Transport Services

Chapter 1 39

HP OTS/9000 Resources

How OTS/9000 Uses the X.25 Network

OTS/9000 uses the X.25 address to conﬁgure a logical mapping of the

NSAP. For X.25 implementations using the 1984 speciﬁcation or later,

the NSAP is passed in the Extended Address (EA) facilities ﬁeld in the

X.25 call packets, if conﬁgured; the NSAP is the calling address. If the

X.25 switch or X.25 network does not support the 1984 X.25 protocol, or

the extended address facility is not conﬁgured, OTS/9000 will use the

X.25 address as the calling address.

X.25 offers several connection management facilities. OTS/9000 can be

conﬁgured to support the Reverse Charge (through osiadmin) and Closed

User Group (through customization) facilities. Refer to the HP X.25

documentation for a description of these facilities.

Using Protocol Identiﬁers (PIDs) and

Subaddresses

A single X.25 link is capable of supporting many applications, including

OTS. Different applications, including multiple attachments to the same

link by OTS, are differentiated from each other by the use of

subaddresses and Protocol Identiﬁers (PIDs).

If the underlying X.25 subnetwork supports subaddressing, the easiest

way to differentiate applications is to assign each one a unique

subaddress without regard to PIDs. However, if subaddressing is not

supported or not desired, the NULL subaddress must be used. If NULL

subaddressing is used, then unique PIDs must be assigned to

differentiate each application.

By default, OTS does not use a PID for X.25 subnetworks (it uses a

NULL PID). This allows for the greatest degree of interoperability with

remote OSI systems. If differentiation by PID is required, then OTS

must be conﬁgured to use the standard OSI PIDs.

To conﬁgure OTS to use the standard OSI PID, use an editor to modify

the active ots_subnets ﬁle. Change the snet_bind_by_pid parameter for

the affected subnetwork(s) to yes (1). This change will take effect the

next time the stack is started. Other related parameters are dest_pid in

the ots_dests ﬁle and tpcons_null_pid in the ots_parms ﬁle.