Link layer
Internet protocol suite |
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Application layer |
Transport layer |
Internet layer |
Link layer |
In
Despite the different semantics of layering between the Internet protocol suite and OSI model, the link layer is sometimes described as a combination of the OSI's data link layer (layer 2) and physical layer (layer 1).
The link layer is described in
Definition in standards and textbooks
Local area networking standards such as
Link layer protocols
The link layer in the TCP/IP model is a descriptive realm of networking protocols that operate only on the local network segment (link) that a host is connected to. Such protocol packets are not routed to other networks. The link layer includes the protocols that define communication between local (on-link) network nodes which fulfill the purpose of maintaining link states between the local nodes, such as the local network topology, and that usually use protocols that are based on the framing of packets specific to the link types.
The core protocols specified by the Internet Engineering Task Force (IETF) in this layer are the Address Resolution Protocol (ARP), the Reverse Address Resolution Protocol (RARP), and the Neighbor Discovery Protocol (NDP), which is a facility delivering similar functionality as ARP for IPv6.
Relation to OSI model
The link layer of the TCP/IP model is often compared directly with the combination of the data link layer and the
Another term sometimes encountered, network access layer, tries to suggest the closeness of this layer to the physical network. However, this use is misleading and non-standard, since the link layer implies functions that are wider in scope than just network access. Important link layer protocols are used to probe the topology of the local network, discover routers and neighboring hosts, i.e. functions that go well beyond network access.
IETF standards
- R. Coltun; D. Ferguson; J. Moy (July 2008). A. Lindem (ed.). OSPF for IPv6. Network Working Group.
- .
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- C. Hornig (April 1984). A Standard for the Transmission of IP Datagrams over Ethernet Networks. Network Working Group. . Internet Standard 41.
- S. J. Leffler; M. J. Karels (April 1984). Trailer Encapsulations. Network Working Group. . Unknown.
- David C. Plummer (November 1982). An Ethernet Address Resolution Protocol. Network Working Group. .
See also
- Carrier-sense multiple access
- Carrier-sense multiple access with collision detection
- Network interface layer security