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Definition: Internet Protocol

The communications technology of the public Internet, local area networks (LANs) and most wide area networks (WANs). The Internet Protocol (IP) is part of the TCP/IP protocol suite, and the terms "IP network" and "TCP/IP network" are synonymous.

Packet Switching
The Internet uses a packet-switched architecture, in which data are broken up into smaller "packets," with each packet containing a source address and destination address. Internet protocol (IP) packets are handed over to a data link layer protocol, for the physical transmission to the next node in the network path.

IP is the Network Layer
While "IP" refers to the entire TCP/IP protocol suite, "IP layer" refers to just the network-to-network part, occupying layer 3 in the "protocol stack" (see below). To learn about IP networking, see TCP/IP and TCP/IP abc's. See OSI model, IP address and IP on Everything.

The TCP/IP "Stack"
IP layer 3 resides in the middle of the TCP/IP stack. It accepts packets from the upper layer TCP or UDP protocols and hands them to a lower layer data link protocol. Within a local network, the data link protocol is typically Ethernet. Within the public Internet, the data link protocols are SONET, ATM, frame relay and Carrier Ethernet.

The Protocols
Following are the primary standards that keep the Internet running:

  Protocol      Purpose

  TCP/IP   Network packet transmission

     TCP   Reliable delivery
     UDP   Unreliable delivery
     IP    Network to network

  HTTP     Web transmission
  HTTPS    Secure Web transmission

  HTML     Web page formatting

  SMTP     Email

  FTP      File transfer

  DNS      Domain name management

  SNMP     Network management

  Telnet   Remote execution

  OSPF     Routing protocol
  RIP      Routing protocol

  ICMP     Control messages

  DHCP     Assign IP addresses
  ARP      Find MAC addresses

  RTP      Real-time transmission
  RTSP     Real-time transmission + QoS