Link Layer

In computer networking, the link layer is the lowest layer in the Internet Protocol Suite (commonly known as "TCP/IP"), the networking architecture of the Internet (RFC 1122, RFC 1123). It is the group of methods or protocols that only operate on a host's link. The link is the physical and logical network component used to interconnect hosts or nodes in the network and a link protocol is a suite of methods and standards that operate only between adjacent network nodes of a Local area network segment or a wide area network connection.

Despite the different semantics of layering in TCP/IP and OSI, the link layer is often described as a combination of the data link layer (layer 2) and the physical layer (layer 1) in the Open Systems Interconnection OSI model. However, TCP/IP's layers are descriptions of operating scopes (application, host-to-host, network, link) and not detailed prescriptions of operating procedures, data semantics, or networking technologies.

RFC 1122 exemplifies that local area network protocols such as Ethernet and IEEE 802, and framing protocols such as Point-to-Point Protocol (PPP) belong to the link layer.

Internet protocol suite
Application layer
  • DHCP
  • DHCPv6
  • DNS
  • FTP
  • HTTP
  • IMAP
  • IRC
  • LDAP
  • MGCP
  • NNTP
  • BGP
  • NTP
  • POP
  • RPC
  • RTP
  • RTSP
  • RIP
  • SIP
  • SMTP
  • SNMP
  • SSH
  • Telnet
  • XMPP
  • (more)
Transport layer
  • TCP
  • UDP
  • DCCP
  • SCTP
  • RSVP
  • (more)
Internet layer
  • IP
    • IPv4
    • IPv6
  • ICMP
  • ICMPv6
  • ECN
  • IGMP
  • IPsec
  • (more)
Link layer
  • NDP
  • OSPF
  • Tunnels
    • L2TP
  • PPP
  • Media access control
    • Ethernet
    • DSL
    • ISDN
    • FDDI
  • (more)

Read more about Link Layer:  Definition in Standards and Text Books, Link Layer Protocols, Relation To OSI Model, RFC References

Other articles related to "layers, layer, link layer, link":

Layers in The Internet Protocol Suite - OSI and TCP/IP Layering Differences
... The three top layers in the OSI model—the application layer, the presentation layer and the session layer—are not distinguished separately in the TCP/IP model where it is just the application layer ... that a TCP/IP protocol stack must impose monolithic architecture above the transport layer ... Different authors have interpreted the RFCs differently, about whether the link layer (and the TCP/IP model) covers OSI model layer 1 (physical layer) issues, or if a hardware layer is assumed below the link layer ...
Link Layer - RFC References
... RFC 1122, "Requirements for Internet Hosts -- Communication layers," IETF, R ... Braden (Editor), October 1989 RFC 1123, "Requirements for Internet Hosts -- Application and Support," IETF, R ...
Link Layer Discovery Protocol
... The Link Layer Discovery Protocol (LLDP) is a vendor-neutral Link Layer protocol in the Internet Protocol Suite used by network devices for advertising their identity, capabilities, and neighbors on a IEEE ... Protocol, Nortel Discovery Protocol (also known as SONMP), and Microsoft's Link Layer Topology Discovery (LLTD) ...
List Of Network Protocols (OSI Model) - Layer 2 Protocols (Data Link Layer)
... Resource Computer NETwork CDP Cisco Discovery Protocol DCAP Data Link Switching Client Access Protocol Distributed Multi-Link Trunking Distributed Split Multi-Link Trunking Dynamic Trunking ...

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