Internet protocol family

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The Internet protocol family is a family of around 500 network protocols that form the basis for network communication on the Internet . The term TCP / IP protocol family is also often used.

TCP / IP reference model

Development began in the late 1960s with a study by the DARPA (Defense Advanced Research Projects Agency), under the United States Department of Defense (DoD), on the development of protocols for data communication. This resulted in the DoD layer model , in which the tasks were divided into four layers. This model is the basis of the Internet protocol family.

Communication in computer networks by network protocols implemented and in practice in functional layers ( layer divided). For the Internet and the Internet protocol family , the structure according to the so-called TCP / IP reference model , which describes 4 layers that build on one another, is decisive. This is tailored to the Internet protocols that enable data exchange beyond the boundaries of local networks (these are mainly TCP and IP ). Neither the access to a transmission medium nor the data transmission technology are defined here. Rather, the Internet protocols are responsible for forwarding data packets over several point-to-point connections ( hops ) and, on this basis, to establish connections between network participants over several hops.

The more detailed ISO / OSI reference model is used to look at network communication problems in general . It should be noted, however, that the naming of the individual layers differs in the models, and subsequent assignments between OSI layers and TCP-IP layers do not always match completely.

OSI layer TCP / IP layer example
Applications (7) Applications HTTP , UDS , FTP , SMTP , POP , Telnet , DHCP , OPC UA


Representation (6)
Session (5)
Transport (4) transport TCP , UDP , SCTP
Mediation (3) Internet IP ( IPv4 , IPv6 ), ICMP (over IP)
Fuse (2) Network access Ethernet , Token Bus , Token Ring , FDDI
Bit transmission (1)

The individual layers fulfill the following functions:

Application layer
The application layer comprises all protocols that work together with application programs and use the network infrastructure for the exchange of application-specific data.
Transport layer
The transport layer enables end-to-end communication. The most important protocol of this layer is the Transmission Control Protocol (TCP), which establishes connections between two network participants for the reliable transmission of data streams. However, unreliable protocols  - for example the User Datagram Protocol (UDP) - also belong in this layer.
Internet layer
The Internet layer is responsible for the forwarding of packets and the route selection ( routing ). Direct connections are considered on this layer and the layers below it. The task of this layer is to determine the next intermediate destination for a received packet and to forward the packet there. The core of this layer is the Internet Protocol (IP) version 4 or 6, which provides a package delivery service. So-called dual stacks can automatically recognize whether they can reach a communication partner via IPv6 or IPv4 and preferably use IPv6. This is transparent for appropriately programmed applications. The Internet layer corresponds to the network layer of the ISO / OSI reference model.
Network access layer
The network access layer ( link layer ) is specified in the TCP / IP reference model, but does not contain any protocols from the TCP / IP family. Rather, it should be understood as a placeholder for various techniques for transferring data from point to point. The Internet protocols were developed with the aim of connecting different subnets. Therefore, the host-to-network layer can be filled by protocols such as Ethernet , FDDI , PPP (point-to-point connection) or 802.11 ( WLAN ). The network access layer corresponds to the security and bit transmission layer of the ISO / OSI reference model.


Construction of Ethernet - frames with maximum IPv4 / TCP data
TCP / IP layer structure
4th transport TCP headers Payload (1460 bytes)
3 Internet IP header Payload (1480 bytes)
2 Network access MAC receiver MAC sender 802.1Q tag (opt.) EtherType Payload (1500 bytes) Frame check sequence
1 preamble Start of frame Payload (1518/1522 bytes) Interframe gap
Octets 7th 1 6th 6th (4) 2 20th 20th ≤1460 4th 12

Protocol stack

Application layer (corresponds to OSI layers 5–7)

  • DNS (Domain Name System) - conversion between domain names and IP addresses
  • DoIP (Diagnostics over IP) - transport protocol for vehicle diagnostics
  • FTP (File Transfer Protocol) - file transfer
  • HTTP (Hypertext Transfer Protocol, WWW )
  • HTTPS (Hypertext Transfer Protocol Secure)
  • IMAP (Internet Message Access Protocol) - access to e-mail
  • IPFIX (Internet Protocol Flow Information Export)
  • LLMNR (Link-local Multicast Name Resolution)
  • NDMP (Network Data Management Protocol,, no IETF RFC)
  • MBS / IP (Multi-purpose Business Security over IP)
  • NNTP (Network News Transfer Protocol) discussion forums ( Usenet )
  • NTP (Network Time Protocol)
  • POP3 (Post Office Protocol, Version 3) - E-mail on demand
  • PTP (Precision Time Protocol) - time synchronization of clocks in a network
  • RDP (Remote Desktop Protocol) - display and control of desktops on remote computers ( Microsoft )
  • RTP (Real-Time Transport Protocol)
  • SIP (Session Initiation Protocol) - establishment, control and termination of communication sessions ( VoIP )
  • SNMP (Simple Network Management Protocol) - management of devices on the network
  • SMTP (Simple Mail Transfer Protocol) - sending emails
  • SOCKS (Internet Sockets Protocol)
  • SSH (Secure Shell) - encrypted remote terminal
    • SCP (Secure Copy) - file transfer (uses SSH session)
    • SFTP - SSH file transfer (uses SSH session)
  • Telnet - unencrypted login on remote computers ( remote terminal )
  • XMPP (Extensible Message and Presence Protocol)
  • Z39.50 - Query of information systems

Transport layer (corresponds to OSI layer 4)

  • TCP (Transmission Control Protocol) - transmission of data streams ( connection-oriented , reliable)
  • UDP (User Datagram Protocol) - transmission of data packets ( connectionless , unreliable, low overhead)
  • SCTP (Stream Control Transmission Protocol) - transport protocol
  • TLS (Transport Layer Security, formerly 'Secure Socket Layer [SSL]) - extension of TCP to include encryption
  • DTLS (Datagram Transport Layer Security) - TLS-based encryption protocol, which can also be transmitted via stateless protocols such as UDP

Internet layer (corresponds to OSI layer 3)

  • IP (Internet Protocol) - data packet transmission (connectionless)
  • IPsec (Internet Protocol Security) - secure data packet transmission (connectionless)
  • ICMP (Internet Control Message Protocol) - control messages (for example error messages), part of every IP implementation
  • IGRP (Interior Gateway Routing Protocol) - information exchange between routers ( distance vector ) (obsolete - will be replaced by EIGRP )
  • EIGRP (Enhanced Interior Gateway Routing Protocol) - information exchange between routers via IP
  • OSPF (Open Shortest Path First) - information exchange between routers (link status) via IP
  • BGP (Border Gateway Protocol) - information exchange between autonomous systems on the Internet ( path vector ) via TCP
  • RIP (Routing Information Protocol) - information exchange between routers ( distance vector ) via UDP
  • IGMP (Internet Group Management) - Organization of multicast groups, part of IP on all hosts that support the reception of IP multicasts

Network access layer (corresponds to OSI layer 1–2)

  • Ethernet with CSMA / CD - network standard IEEE 802.3 - and the first graphic on Ethernet
  • WLAN - network standard IEEE 802.11
  • PPP - Point-to-Point Protocol, RFC 1661
  • Token Bus - IEEE 802.4 network standard
  • Token Ring - network standard IEEE 802.5
  • FDDI - Fiber Distributed Data Interface
  • ARP (Address Resolution Protocol) - address translation between IP and device addresses (MAC)
  • L2TP (Layer 2 Tunneling Protocol)
  • RARP (Reverse Address Resolution Protocol) - address translation between device (MAC) and IP addresses (obsolete - will be replaced by BOOTP )
  • IPoAC (Internet Protocol over Avian Carriers) - Internet protocol using air carriers - RFC 1149

See also


Web links

Individual evidence

  1. ^ Vinton G. Cerf , Edward Cain: The DoD Internet Architecture Model (PDF; 866 kB) Pennsylvania State University . 1983. Retrieved July 6, 2013.
  2. ^ D. Waitzman:  RFC 1149 . - Standard for the transmission of IP datagrams on avian carriers . April 1, 1990. (English).