OSI/AS Configuration and Management Manual

NSAP Addressing

OSI/AS Configuration and Management Manual—424119-001

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SNPA Addresses Over X.25 WANs

In X.25 networks, the SNPA address is the DTE address plus the port number, if any.

The SNPA address is assigned by the X.25 network addressing authority, described in

“X.25 1980 Versus 1984 Addressing.”.

X25AM does not provide an SNPA address parameter that the TSP process can use.

Conceptually, however, the SNPA address can be described as follows:

In the OSI/AS subsystem, the local SNPA ENTRY object only represents an internal

number, not the real, local SNPA address. The real address is specified by the

SRCADDR and X25PORT attributes. The remote SNPA ENTRY object also represents

an internal number, not the real, remote SNPA address. The real remote address is

specified by the X25DESTADDR attribute.

For more information on SNPA addresses in X.25 environments, see the X.25 Access

Method (X25AM) Manual.

LSAP Selectors

An LSAP (link layer service access point) selector is used by the Data Link Layer to

identify the Network Layer user of its service. A system, therefore, can run multiple

protocols on the same controller by assigning each protocol (such as OSI) to a separate

LSAP. (LSAPs are sometimes called protocol identifiers.) In a LAN environment, an

LSAP selector is the hexadecimal string FE described in IEEE and ISO specifications.

In X.25 WAN environments, LSAP selectors are not applicable.

WAN (X.25) SNPA Address

Consists of... Local SNPA address:

SRCADDR parameter of the X25AM line

followed by the X25PORT parameter

(the port or subaddress of a subdevice)

Remote SNPA address:

X25AM subdevice (includes the remote

DTE address and possibly the port number)

(NOTE: The X.25 line address itself is not

configured in an OSI/AS subsystem.)

Configured Using SCF... X25DESTADDR attribute, X25PORT

attribute