Media Access Control: Wikis


Note: Many of our articles have direct quotes from sources you can cite, within the Wikipedia article! This article doesn't yet, but we're working on it! See more info or our list of citable articles.


From Wikipedia, the free encyclopedia

The Internet Protocol Suite
Application Layer
BGP · DHCP · DNS · FTP · GTP · HTTP · IMAP · IRC · Megaco · MGCP · NNTP · NTP · POP · RIP · RPC · RTP · RTSP · SDP · SIP · SMTP · SNMP · SOAP · SSH · Telnet · TLS/SSL · XMPP · (more)
Transport Layer
TCP · UDP · DCCP · SCTP · RSVP · ECN · (more)
Internet Layer
IP (IPv4, IPv6) · ICMP · ICMPv6 · IGMP · IPsec · (more)
Link Layer
ARP/InARP · NDP · OSPF · Tunnels (L2TP) · PPP · Media Access Control (Ethernet, DSL, ISDN, FDDI) · (more)

The Media Access Control (MAC) data communication protocol sub-layer, also known as the Medium Access Control, is a sublayer of the Data Link Layer specified in the seven-layer OSI model (layer 2). It provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multi-point network, typically a local area network (LAN) or metropolitan area network (MAN). The hardware that implements the MAC is referred to as a Medium Access Controller.

The MAC sub-layer acts as an interface between the Logical Link Control (LLC) sublayer and the network's physical layer. The MAC layer emulates a full-duplex logical communication channel in a multi-point network. This channel may provide unicast, multicast or broadcast communication service.

OSI Model
7 Application Layer
6 Presentation Layer
5 Session Layer
4 Transport Layer
3 Network Layer
2 Data Link Layer
1 Physical Layer
Circuit mode
(constant bandwidth)
Polarization multiplexing
Spatial multiplexing (MIMO)
Statistical multiplexing
(variable bandwidth)
Packet mode · Dynamic TDM
Related topics
Channel access methods
Media Access Control (MAC)


Addressing mechanism

The MAC layer addressing mechanism is called physical address or MAC address. A MAC address is a unique serial number. Once a MAC address has been assigned to a particular piece of network hardware (at time of manufacture), that device should be uniquely identifiable amongst all other network devices in the world. This guarantees that each device in a network will have a different MAC address (analogous to a street address). This makes it possible for data packets to be delivered to a destination within a subnetwork, i.e. a physical network consisting of several network segments interconnected by repeaters, hubs, bridges and switches, but not by IP routers. An IP router may interconnect several subnets.

An example of a physical network is an Ethernet network, perhaps extended by wireless local area network (WLAN) access points and WLAN network adapters, since these share the same 48-bit MAC address hierarchy as Ethernet.

A MAC layer is not required in full-duplex point-to-point communication, but address fields are included in some point-to-point protocols for compatibility reasons.

Channel access control mechanism

The channel access control mechanisms provided by the MAC layer are also known as a multiple access protocol. This makes it possible for several stations connected to the same physical medium to share it. Examples of shared physical media are bus networks, ring networks, hub networks, wireless networks and half-duplex point-to-point links. The multiple access protocol may detect or avoid data packet collisions if a packet mode contention based channel access method is used, or reserve resources to establish a logical channel if a circuit switched or channelization based channel access method is used. The channel access control mechanism relies on a physical layer multiplex scheme.

The most widespread multiple access protocol is the contention based CSMA/CD protocol used in Ethernet networks. This mechanism is only utilized within a network collision domain, for example an Ethernet bus network or a hub network. An Ethernet network may be divided into several collision domains, interconnected by bridges and switches.

A multiple access protocol is not required in a switched full-duplex network, such as today's switched Ethernet networks, but is often available in the equipment for compatibility reasons.

Common multiple access protocols

Examples of common packet mode multiple access protocols for wired multi-drop networks are:

Examples of common multiple access protocols that may be used in packet radio wireless networks are:

For a more extensive list, see List of channel access methods.

See also

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.



Mac or MAC may refer to:



Computing and telecommunications

Fictional characters


  • Archaeology Museum of Catalonia (Museu d'Arqueologia de Catalunya), an archaeology museum in Catalonia
  • Museum of Anatolian Civilizations (Anadolu Medeniyetleri Müzesi), a museum in Ankara, Turkey
  • Niterói Contemporary Art Museum (Museu de Arte Contemporânea de Niterói), a museum in Niterói, Brazil
  • Le Musée d'art contemporain de Montréal, Montreal Museum of Contemporary Art




Non-profit organizations


See also


Up to date as of January 15, 2010
(Redirected to MAC article)

Definition from Wiktionary, a free dictionary

See also Mac, and mac





  1. (chemistry) Maximum Allowable Concentration, the maximum concentration of a pollutant which is considered harmless to healthy adults during their working hours, assuming they breathe uncontaminated air at all other times.
  2. (US military) Military Airlift Command, one of three former divisions of the airforce, the others being SAC and TAC.
  3. (computing) Media Access Control, that portion of Ethernet, 802.11 wireless, Bluetooth, FDDI, ATM, and Fiber Channel networks that controls which hardware devices have access to the media over which signals are sent.
  4. (computing) Multiply And Accumulate, a hardware module found in Digital Signal Processors which performs a multiplication and adds the result of that operation to an accumulator, in a single cycle. Used extensively in implementations of digital filters, transforms and codecs.
  5. (mechanics) Mean Aerodynamic Chord.
  6. (cryptography) Message Authentication Code.
  7. (science fiction) magnetic accelerator cannon

Derived terms



Got something to say? Make a comment.
Your name
Your email address