Network service access point address
A network service access point address, defined in ISO/IEC 8348, is an identifying label for a service access point used in OSI networking.
These are roughly comparable to IP addresses used in the Internet Protocol; they can specify a piece of equipment connected to an Asynchronous Transfer Mode network. A specific stream, analogous to a TCP/IP port or socket, is specified by using a transport service access point. ATM can also use a presentation and session access point, but these may also be unspecified; this is up to the application.
Allocation and scope
NSAP addresses are allocated by the International Organization for Standardization, through a system of delegated authorities, which are generally national standards organizations. One of the schemes to generate NSAPs uses E.164 which is the addressing format describing telephone numbers.NSAP addresses do not specify where a network terminal is located. Routing equipment must translate NSAP addresses to subnetwork points of attachment to route OSI packets; virtual circuit identifier numbers are an example of a datalink layer SNPAs in ATM; when OSI packets are sent encapsulated in IP packets, the IP address is considered an SNPA.
Synchronous Digital Hierarchy/Synchronous Optical Networking networks are a major part of the network infrastructure, and NSAPs are used extensively. They are usually assigned by the network management/network operations centre personnel and agreed upon within an organization to be unique and are required before any operational connectivity is established at the commissioning stage.
NSAP addresses are used in the following OSI-based network technologies:
- ATM switched virtual circuit networks
- X.25
- Frame Relay
- IS-IS
- Synchronous Digital Hierarchy and Synchronous Optical Networking networks.