A Service Access Point (SAP) is an identifying label for network endpoints used in
Open Systems Interconnection (OSI) networking.
The SAP is a conceptual location at which one OSI layer can request the services of another OSI layer. As an example, PD-SAP or PLME-SAP in
IEEE 802.15.4 can be mentioned, where the
medium access control (MAC) layer requests certain services from the
physical layer
In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer; The layer most closely associated with the physical connection between devices. This layer may be implemented by a PHY chip.
The ...
. Service access points are also used in
IEEE 802.2 Logical Link Control in
Ethernet and similar
data link layer protocols.
When using the OSI
Network system
Network, networking and networked may refer to:
Science and technology
* Network theory, the study of graphs as a representation of relations between discrete objects
* Network science, an academic field that studies complex networks
Mathematics
...
(
CONS or
CLNS), the base for constructing an address for a network element is an
NSAP address
A Network Service Access Point address (NSAP address), defined in ISO/IEC 8348, is an identifying label for a Service Access Point (SAP) used in OSI
OSI may refer to:
Places
* Osijek Airport (IATA code: OSI), an airport in Croatia
* Ősi, a vil ...
, similar in concept to an
IP address. OSI protocols as well as
Asynchronous Transfer Mode (ATM) can use Transport (TSAP), Session (SSAP) or Presentation (PSAP) Service Access Points to specify a destination address for a connection. These SAPs consist of NSAP addresses combined with optional transport, session and presentation selectors, which can differentiate at any of the three layers between multiple services at that layer provided by a network element.
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OSI protocols