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Framework for communication protocols used in IP networking
This article is about the protocols that make up the Internet architecture. For
the IP network protocol only, see Internet Protocol.



Internet protocol suite Application layer
 * BGP
 * DHCP (v6)
 * DNS
 * FTP
 * HTTP (HTTP/3)
 * HTTPS
 * IMAP
 * IRC
 * LDAP
 * MGCP
 * MQTT
 * NNTP
 * NTP
 * OSPF
 * POP
 * PTP
 * ONC/RPC
 * RTP
 * RTSP
 * RIP
 * SIP
 * SMTP
 * SNMP
 * SSH
 * Telnet
 * TLS/SSL
 * XMPP
 * more...

Transport layer
 * TCP
 * UDP
 * DCCP
 * SCTP
 * RSVP
 * QUIC
 * more...

Internet layer
 * IP
   * v4
   * v6
 * ICMP (v6)
 * NDP
 * ECN
 * IGMP
 * IPsec
 * more...

Link layer
 * ARP
 * Tunnels
 * PPP
 * MAC
 * more...

 * v
 * t
 * e

The Internet protocol suite, commonly known as TCP/IP, is a framework for
organizing the set of communication protocols used in the Internet and similar
computer networks according to functional criteria. The foundational protocols
in the suite are the Transmission Control Protocol (TCP), the User Datagram
Protocol (UDP), and the Internet Protocol (IP). Early versions of this
networking model were known as the Department of Defense (DoD) model because the
research and development were funded by the United States Department of Defense
through DARPA.

The Internet protocol suite provides end-to-end data communication specifying
how data should be packetized, addressed, transmitted, routed, and received.
This functionality is organized into four abstraction layers, which classify all
related protocols according to each protocol's scope of networking.[1][2] An
implementation of the layers for a particular application forms a protocol
stack. From lowest to highest, the layers are the link layer, containing
communication methods for data that remains within a single network segment
(link); the internet layer, providing internetworking between independent
networks; the transport layer, handling host-to-host communication; and the
application layer, providing process-to-process data exchange for applications.

The technical standards underlying the Internet protocol suite and its
constituent protocols are maintained by the Internet Engineering Task Force
(IETF). The Internet protocol suite predates the OSI model, a more comprehensive
reference framework for general networking systems.


CONTENTS

 * 1 History
   * 1.1 Early research
   * 1.2 Early implementation
   * 1.3 Adoption
   * 1.4 Formal specification and standards
 * 2 Key architectural principles
 * 3 Link layer
 * 4 Internet layer
 * 5 Transport layer
 * 6 Application layer
 * 7 Layering evolution and representations in the literature
 * 8 Comparison of TCP/IP and OSI layering
 * 9 Implementations
 * 10 See also
 * 11 Notes
 * 12 References
 * 13 Bibliography
 * 14 External links


HISTORY[EDIT]

Further information: History of the Internet


EARLY RESEARCH[EDIT]

Diagram of the first internetworked connection An SRI International Packet Radio
Van, used for the first three-way internetworked transmission

Initially referred to as the DOD Internet Architecture Model, the Internet
protocol suite has its roots in research and development sponsored by the
Defense Advanced Research Projects Agency (DARPA) in the late 1960s.[3] After
DARPA initiated the pioneering ARPANET in 1969, Steve Crocker established a
"Networking Working Group" which developed a host-host protocol, the Network
Control Program (NCP).[4] In the early 1970s, DARPA started work on several
other data transmission technologies, including mobile packet radio, packet
satellite service, local area networks, and other data networks in the public
and private domains. In 1972, Bob Kahn joined the DARPA Information Processing
Technology Office, where he worked on both satellite packet networks and
ground-based radio packet networks, and recognized the value of being able to
communicate across both. In the spring of 1973, Vinton Cerf joined Kahn with the
goal of designing the next protocol generation for the ARPANET to enable
internetworking.[5][6] They drew on the experience from the ARPANET research
community, the International Network Working Group, which Cerf chaired, and
researchers at Xerox PARC.[7][8][9]

By the summer of 1973, Kahn and Cerf had worked out a fundamental reformulation,
in which the differences between local network protocols were hidden by using a
common internetwork protocol, and, instead of the network being responsible for
reliability, as in the existing ARPANET protocols, this function was delegated
to the hosts. Cerf credits Louis Pouzin and Hubert Zimmermann, designers of the
CYCLADES network, with important influences on this design.[10][11] The new
protocol was implemented as the Transmission Control Program in 1974 by Cerf,
Yogen Dalal and Carl Sunshine.[12]

Initially, the Transmission Control Program (the Internet Protocol did not then
exist as a separate protocol) provided only a reliable byte stream service to
its users, not datagram.[13] As experience with the protocol grew, collaborators
recommended division of functionality into layers of distinct protocols,
allowing users direct access to datagram service. Advocates included Danny
Cohen, who needed it for his packet voice work; Jonathan Postel of the
University of Southern California's Information Sciences Institute, who edited
the Request for Comments (RFCs), the technical and strategic document series
that has both documented and catalyzed Internet development;[14] and Bob
Metcalfe and Yogen Dalal at Xerox PARC.[15][16] Postel stated, "We are screwing
up in our design of Internet protocols by violating the principle of
layering."[17] Encapsulation of different mechanisms was intended to create an
environment where the upper layers could access only what was needed from the
lower layers. A monolithic design would be inflexible and lead to scalability
issues. In version 3 of TCP, written in 1978, Cerf, Cohen and Postel split the
Transmission Control Program into two distinct protocols, the Internet Protocol
as connectionless layer and the Transmission Control Protocol as a reliable
connection-oriented service.[nb 1][18]

The design of the network included the recognition that it should provide only
the functions of efficiently transmitting and routing traffic between end nodes
and that all other intelligence should be located at the edge of the network, in
the end nodes. This design is known as the end-to-end principle. Using this
design, it became possible to connect other networks to the ARPANET that used
the same principle, irrespective of other local characteristics, thereby solving
Kahn's initial internetworking problem. A popular expression is that TCP/IP, the
eventual product of Cerf and Kahn's work, can run over "two tin cans and a
string."[citation needed] Years later, as a joke, the IP over Avian Carriers
formal protocol specification was created and successfully tested.

DARPA contracted with BBN Technologies, Stanford University, and the University
College London to develop operational versions of the protocol on several
hardware platforms.[19] During development of the protocol the version number of
the packet routing layer progressed from version 1 to version 4, the latter of
which was installed in the ARPANET in 1983. It became known as Internet Protocol
version 4 (IPv4) as the protocol that is still in use in the Internet, alongside
its current successor, Internet Protocol version 6 (IPv6).


EARLY IMPLEMENTATION[EDIT]

In 1975, a two-network IP communications test was performed between Stanford and
University College London. In November 1977, a three-network IP test was
conducted between sites in the US, the UK, and Norway. Several other IP
prototypes were developed at multiple research centers between 1978 and 1983.

A computer called a router is provided with an interface to each network. It
forwards network packets back and forth between them.[20] Originally a router
was called gateway, but the term was changed to avoid confusion with other types
of gateways.[21]


ADOPTION[EDIT]

In March 1982, the US Department of Defense declared TCP/IP as the standard for
all military computer networking.[22][23] In the same year, NORSAR/NDRE and
Peter Kirstein's research group at University College London adopted the
protocol.[24] The migration of the ARPANET from NCP to TCP/IP was officially
completed on flag day January 1, 1983, when the new protocols were permanently
activated.[22][25]

In 1985, the Internet Advisory Board (later Internet Architecture Board) held a
three-day TCP/IP workshop for the computer industry, attended by 250 vendor
representatives, promoting the protocol and leading to its increasing commercial
use. In 1985, the first Interop conference focused on network interoperability
by broader adoption of TCP/IP. The conference was founded by Dan Lynch, an early
Internet activist. From the beginning, large corporations, such as IBM and DEC,
attended the meeting.[26]

IBM, AT&T and DEC were the first major corporations to adopt TCP/IP, this
despite having competing proprietary protocols. In IBM, from 1984, Barry
Appelman's group did TCP/IP development. They navigated the corporate politics
to get a stream of TCP/IP products for various IBM systems, including MVS, VM,
and OS/2. At the same time, several smaller companies, such as FTP Software and
the Wollongong Group, began offering TCP/IP stacks for DOS and Microsoft
Windows.[27] The first VM/CMS TCP/IP stack came from the University of
Wisconsin.[28]

Some of the early TCP/IP stacks were written single-handedly by a few
programmers. Jay Elinsky and Oleg Vishnepolsky of IBM Research wrote TCP/IP
stacks for VM/CMS and OS/2, respectively.[citation needed] In 1984 Donald
Gillies at MIT wrote a ntcp multi-connection TCP which runs atop the
IP/PacketDriver layer maintained by John Romkey at MIT in 1983–84. Romkey
leveraged this TCP in 1986 when FTP Software was founded.[29][30] Starting in
1985, Phil Karn created a multi-connection TCP application for ham radio systems
(KA9Q TCP).[31]

The spread of TCP/IP was fueled further in June 1989, when the University of
California, Berkeley agreed to place the TCP/IP code developed for BSD UNIX into
the public domain. Various corporate vendors, including IBM, included this code
in commercial TCP/IP software releases. Microsoft released a native TCP/IP stack
in Windows 95. This event helped cement TCP/IP's dominance over other protocols
on Microsoft-based networks, which included IBM's Systems Network Architecture
(SNA), and on other platforms such as Digital Equipment Corporation's DECnet,
Open Systems Interconnection (OSI), and Xerox Network Systems (XNS).

Nonetheless, for a period in the late 1980s and early 1990s, engineers,
organizations and nations were polarized over the issue of which standard, the
OSI model or the Internet protocol suite, would result in the best and most
robust computer networks.[32][33][34]


FORMAL SPECIFICATION AND STANDARDS[EDIT]

The technical standards underlying the Internet protocol suite and its
constituent protocols have been delegated to the Internet Engineering Task Force
(IETF).[35][36]

The characteristic architecture of the Internet protocol suite is its broad
division into operating scopes for the protocols that constitute its core
functionality. The defining specification of the suite is RFC 1122, which
broadly outlines four abstraction layers.[1] These have stood the test of time,
as the IETF has never modified this structure. As such a model of networking,
the Internet protocol suite predates the OSI model, a more comprehensive
reference framework for general networking systems.[34]


KEY ARCHITECTURAL PRINCIPLES[EDIT]

See also: Communication protocol § Software layering
Conceptual data flow in a simple network topology of two hosts (A and B)
connected by a link between their respective routers. The application on each
host executes read and write operations as if the processes were directly
connected to each other by some kind of data pipe. After establishment of this
pipe, most details of the communication are hidden from each process, as the
underlying principles of communication are implemented in the lower protocol
layers. In analogy, at the transport layer the communication appears as
host-to-host, without knowledge of the application data structures and the
connecting routers, while at the internetworking layer, individual network
boundaries are traversed at each router. Encapsulation of application data
descending through the layers described in RFC 1122

The end-to-end principle has evolved over time. Its original expression put the
maintenance of state and overall intelligence at the edges, and assumed the
Internet that connected the edges retained no state and concentrated on speed
and simplicity. Real-world needs for firewalls, network address translators, web
content caches and the like have forced changes in this principle.[37]

The robustness principle states: "In general, an implementation must be
conservative in its sending behavior, and liberal in its receiving behavior.
That is, it must be careful to send well-formed datagrams, but must accept any
datagram that it can interpret (e.g., not object to technical errors where the
meaning is still clear)."[38] "The second part of the principle is almost as
important: software on other hosts may contain deficiencies that make it unwise
to exploit legal but obscure protocol features."[39]

Encapsulation is used to provide abstraction of protocols and services.
Encapsulation is usually aligned with the division of the protocol suite into
layers of general functionality. In general, an application (the highest level
of the model) uses a set of protocols to send its data down the layers. The data
is further encapsulated at each level.

An early architectural document, RFC 1122, titled Host Requirements, emphasizes
architectural principles over layering.[40] RFC 1122 is structured in sections
referring to layers, but the document refers to many other architectural
principles, and does not emphasize layering. It loosely defines a four-layer
model, with the layers having names, not numbers, as follows:

 * The application layer is the scope within which applications, or processes,
   create user data and communicate this data to other applications on another
   or the same host. The applications make use of the services provided by the
   underlying lower layers, especially the transport layer which provides
   reliable or unreliable pipes to other processes. The communications partners
   are characterized by the application architecture, such as the client–server
   model and peer-to-peer networking. This is the layer in which all application
   protocols, such as SMTP, FTP, SSH, HTTP, operate. Processes are addressed via
   ports which essentially represent services.
 * The transport layer performs host-to-host communications on either the local
   network or remote networks separated by routers.[41] It provides a channel
   for the communication needs of applications. UDP is the basic transport layer
   protocol, providing an unreliable connectionless datagram service. The
   Transmission Control Protocol provides flow-control, connection
   establishment, and reliable transmission of data.
 * The internet layer exchanges datagrams across network boundaries. It provides
   a uniform networking interface that hides the actual topology (layout) of the
   underlying network connections. It is therefore also the layer that
   establishes internetworking. Indeed, it defines and establishes the Internet.
   This layer defines the addressing and routing structures used for the TCP/IP
   protocol suite. The primary protocol in this scope is the Internet Protocol,
   which defines IP addresses.[42][failed verification][43] Its function in
   routing is to transport datagrams to the next host, functioning as an IP
   router, that has the connectivity to a network closer to the final data
   destination.[43][failed verification]
 * The link layer defines the networking methods within the scope of the local
   network link on which hosts communicate without intervening routers. This
   layer includes the protocols used to describe the local network topology and
   the interfaces needed to effect the transmission of internet layer datagrams
   to next-neighbor hosts.[44]


LINK LAYER[EDIT]

The protocols of the link layer operate within the scope of the local network
connection to which a host is attached. This regime is called the link in TCP/IP
parlance and is the lowest component layer of the suite. The link includes all
hosts accessible without traversing a router. The size of the link is therefore
determined by the networking hardware design. In principle, TCP/IP is designed
to be hardware independent and may be implemented on top of virtually any
link-layer technology. This includes not only hardware implementations but also
virtual link layers such as virtual private networks and networking tunnels.

The link layer is used to move packets between the internet layer interfaces of
two different hosts on the same link. The processes of transmitting and
receiving packets on the link can be controlled in the device driver for the
network card, as well as in firmware or by specialized chipsets. These perform
functions, such as framing, to prepare the internet layer packets for
transmission, and finally transmit the frames to the physical layer and over a
transmission medium. The TCP/IP model includes specifications for translating
the network addressing methods used in the Internet Protocol to link-layer
addresses, such as media access control (MAC) addresses. All other aspects below
that level, however, are implicitly assumed to exist and are not explicitly
defined in the TCP/IP model.

The link layer in the TCP/IP model has corresponding functions in Layer 2 of the
OSI model.


INTERNET LAYER[EDIT]

See also: IP header

Internetworking requires sending data from the source network to the destination
network. This process is called routing and is supported by host addressing and
identification using the hierarchical IP addressing system. The internet layer
provides an unreliable datagram transmission facility between hosts located on
potentially different IP networks by forwarding datagrams to an appropriate
next-hop router for further relaying to its destination. The internet layer has
the responsibility of sending packets across potentially multiple networks. With
this functionality, the internet layer makes possible internetworking, the
interworking of different IP networks, and it essentially establishes the
Internet.

The internet layer does not distinguish between the various transport layer
protocols. IP carries data for a variety of different upper layer protocols.
These protocols are each identified by a unique protocol number: for example,
Internet Control Message Protocol (ICMP) and Internet Group Management Protocol
(IGMP) are protocols 1 and 2, respectively.

The Internet Protocol is the principal component of the internet layer, and it
defines two addressing systems to identify network hosts and to locate them on
the network. The original address system of the ARPANET and its successor, the
Internet, is Internet Protocol version 4 (IPv4). It uses a 32-bit IP address and
is therefore capable of identifying approximately four billion hosts. This
limitation was eliminated in 1998 by the standardization of Internet Protocol
version 6 (IPv6) which uses 128-bit addresses. IPv6 production implementations
emerged in approximately 2006.


TRANSPORT LAYER[EDIT]

See also: Transport layer

The transport layer establishes basic data channels that applications use for
task-specific data exchange. The layer establishes host-to-host connectivity in
the form of end-to-end message transfer services that are independent of the
underlying network and independent of the structure of user data and the
logistics of exchanging information. Connectivity at the transport layer can be
categorized as either connection-oriented, implemented in TCP, or
connectionless, implemented in UDP. The protocols in this layer may provide
error control, segmentation, flow control, congestion control, and application
addressing (port numbers).

For the purpose of providing process-specific transmission channels for
applications, the layer establishes the concept of the network port. This is a
numbered logical construct allocated specifically for each of the communication
channels an application needs. For many types of services, these port numbers
have been standardized so that client computers may address specific services of
a server computer without the involvement of service discovery or directory
services.

Because IP provides only a best-effort delivery, some transport-layer protocols
offer reliability.

TCP is a connection-oriented protocol that addresses numerous reliability issues
in providing a reliable byte stream:

 * data arrives in-order
 * data has minimal error (i.e., correctness)
 * duplicate data is discarded
 * lost or discarded packets are resent
 * includes traffic congestion control

The newer Stream Control Transmission Protocol (SCTP) is also a reliable,
connection-oriented transport mechanism. It is message-stream-oriented, not
byte-stream-oriented like TCP, and provides multiple streams multiplexed over a
single connection. It also provides multihoming support, in which a connection
end can be represented by multiple IP addresses (representing multiple physical
interfaces), such that if one fails, the connection is not interrupted. It was
developed initially for telephony applications (to transport SS7 over IP).

Reliability can also be achieved by running IP over a reliable data-link
protocol such as the High-Level Data Link Control (HDLC).

The User Datagram Protocol (UDP) is a connectionless datagram protocol. Like IP,
it is a best-effort, unreliable protocol. Reliability is addressed through error
detection using a checksum algorithm. UDP is typically used for applications
such as streaming media (audio, video, Voice over IP, etc.) where on-time
arrival is more important than reliability, or for simple query/response
applications like DNS lookups, where the overhead of setting up a reliable
connection is disproportionately large. Real-time Transport Protocol (RTP) is a
datagram protocol that is used over UDP and is designed for real-time data such
as streaming media.

The applications at any given network address are distinguished by their TCP or
UDP port. By convention, certain well-known ports are associated with specific
applications.

The TCP/IP model's transport or host-to-host layer corresponds roughly to the
fourth layer in the OSI model, also called the transport layer.

QUIC is rapidly emerging as an alternative transport protocol. Whilst it is
technically carried via UDP packets it seeks to offer enhanced transport
connectivity relative to TCP. HTTP/3 works exclusively via QUIC.


APPLICATION LAYER[EDIT]

The application layer includes the protocols used by most applications for
providing user services or exchanging application data over the network
connections established by the lower-level protocols. This may include some
basic network support services such as routing protocols and host configuration.
Examples of application layer protocols include the Hypertext Transfer Protocol
(HTTP), the File Transfer Protocol (FTP), the Simple Mail Transfer Protocol
(SMTP), and the Dynamic Host Configuration Protocol (DHCP).[45] Data coded
according to application layer protocols are encapsulated into transport layer
protocol units (such as TCP streams or UDP datagrams), which in turn use lower
layer protocols to effect actual data transfer.

The TCP/IP model does not consider the specifics of formatting and presenting
data and does not define additional layers between the application and transport
layers as in the OSI model (presentation and session layers). According to the
TCP/IP model, such functions are the realm of libraries and application
programming interfaces. The application layer in the TCP/IP model is often
compared to a combination of the fifth (session), sixth (presentation), and
seventh (application) layers of the OSI model.

Application layer protocols are often associated with particular client–server
applications, and common services have well-known port numbers reserved by the
Internet Assigned Numbers Authority (IANA). For example, the HyperText Transfer
Protocol uses server port 80 and Telnet uses server port 23. Clients connecting
to a service usually use ephemeral ports, i.e., port numbers assigned only for
the duration of the transaction at random or from a specific range configured in
the application.

At the application layer, the TCP/IP model distinguishes between user protocols
and support protocols.[46] Support protocols provide services to a system of
network infrastructure. User protocols are used for actual user applications.
For example, FTP is a user protocol and DNS is a support protocol.

Although the applications are usually aware of key qualities of the transport
layer connection such as the endpoint IP addresses and port numbers, application
layer protocols generally treat the transport layer (and lower) protocols as
black boxes which provide a stable network connection across which to
communicate. The transport layer and lower-level layers are unconcerned with the
specifics of application layer protocols. Routers and switches do not typically
examine the encapsulated traffic, rather they just provide a conduit for it.
However, some firewall and bandwidth throttling applications use deep packet
inspection to interpret application data. An example is the Resource Reservation
Protocol (RSVP).[citation needed] It is also sometimes necessary for
Applications affected by NAT to consider the application payload.


LAYERING EVOLUTION AND REPRESENTATIONS IN THE LITERATURE[EDIT]

The Internet protocol suite evolved through research and development funded over
a period of time. In this process, the specifics of protocol components and
their layering changed. In addition, parallel research and commercial interests
from industry associations competed with design features. In particular, efforts
in the International Organization for Standardization led to a similar goal, but
with a wider scope of networking in general. Efforts to consolidate the two
principal schools of layering, which were superficially similar, but diverged
sharply in detail, led independent textbook authors to formulate abridging
teaching tools.

The following table shows various such networking models. The number of layers
varies between three and seven.

Arpanet Reference Model
(RFC 871) Internet Standard
(RFC 1122) Internet model
(Cisco Academy[47]) TCP/IP 5-layer reference model
(Kozierok,[48] Comer[49]) TCP/IP 5-layer reference model
(Tanenbaum[50]) TCP/IP protocol suite or Five-layer Internet model
(Forouzan,[51] Kurose[52]) TCP/IP model
(Stallings[53]) OSI model
(ISO/IEC 7498-1:1994[54]) Three layers Four layers Four layers Four+one layers
Five layers Five layers Five layers Seven layers Application/ Process
Application Application Application Application Application Application
Application Presentation Session Host-to-host Transport Transport Transport
Transport Transport Host-to-host or transport Transport Internet Internetwork
Internet Internet Network Internet Network Network interface Link Network
interface Data link (Network interface) Data link Data link Network access Data
link — — — (Hardware) Physical Physical Physical Physical

Some of the networking models are from textbooks, which are secondary sources
that may conflict with the intent of RFC 1122 and other IETF primary
sources.[55]


COMPARISON OF TCP/IP AND OSI LAYERING[EDIT]

See also: OSI model § Comparison with TCP/IP model

The three top layers in the OSI model, i.e. the application layer, the
presentation layer and the session layer, are not distinguished separately in
the TCP/IP model which only has an application layer above the transport layer.
While some pure OSI protocol applications, such as X.400, also combined them,
there is no requirement that a TCP/IP protocol stack must impose monolithic
architecture above the transport layer. For example, the NFS application
protocol runs over the External Data Representation (XDR) presentation protocol,
which, in turn, runs over a protocol called Remote Procedure Call (RPC). RPC
provides reliable record transmission, so it can safely use the best-effort UDP
transport.

Different authors have interpreted the TCP/IP model differently, and disagree
whether the link layer, or any aspect of the TCP/IP model, covers OSI layer 1
(physical layer) issues, or whether TCP/IP assumes a hardware layer exists below
the link layer.

Several authors have attempted to incorporate the OSI model's layers 1 and 2
into the TCP/IP model since these are commonly referred to in modern standards
(for example, by IEEE and ITU). This often results in a model with five layers,
where the link layer or network access layer is split into the OSI model's
layers 1 and 2.

The IETF protocol development effort is not concerned with strict layering. Some
of its protocols may not fit cleanly into the OSI model, although RFCs sometimes
refer to it and often use the old OSI layer numbers. The IETF has repeatedly
stated[35][failed verification] that Internet Protocol and architecture
development is not intended to be OSI-compliant. RFC 3439, referring to the
internet architecture, contains a section entitled: "Layering Considered
Harmful".

For example, the session and presentation layers of the OSI suite are considered
to be included in the application layer of the TCP/IP suite. The functionality
of the session layer can be found in protocols like HTTP and SMTP and is more
evident in protocols like Telnet and the Session Initiation Protocol (SIP).
Session-layer functionality is also realized with the port numbering of the TCP
and UDP protocols, which are included in the transport layer of the TCP/IP
suite. Functions of the presentation layer are realized in the TCP/IP
applications with the MIME standard in data exchange.

Another difference is in the treatment of routing protocols. The OSI routing
protocol IS-IS belongs to the network layer, and does not depend on CLNS for
delivering packets from one router to another, but defines its own layer-3
encapsulation. In contrast, OSPF, RIP, BGP and other routing protocols defined
by the IETF are transported over IP, and, for the purpose of sending and
receiving routing protocol packets, routers act as hosts. As a consequence,
RFC 1812 include routing protocols in the application layer. Some authors, such
as Tanenbaum in Computer Networks, describe routing protocols in the same layer
as IP, reasoning that routing protocols inform decisions made by the forwarding
process of routers.

IETF protocols can be encapsulated recursively, as demonstrated by tunnelling
protocols such as Generic Routing Encapsulation (GRE). GRE uses the same
mechanism that OSI uses for tunnelling at the network layer.


IMPLEMENTATIONS[EDIT]

This section does not cite any sources. Please help improve this section by
adding citations to reliable sources. Unsourced material may be challenged and
removed. (March 2014) (Learn how and when to remove this message)

The Internet protocol suite does not presume any specific hardware or software
environment. It only requires that hardware and a software layer exists that is
capable of sending and receiving packets on a computer network. As a result, the
suite has been implemented on essentially every computing platform. A minimal
implementation of TCP/IP includes the following: Internet Protocol (IP), Address
Resolution Protocol (ARP), Internet Control Message Protocol (ICMP),
Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and Internet
Group Management Protocol (IGMP). In addition to IP, ICMP, TCP, UDP, Internet
Protocol version 6 requires Neighbor Discovery Protocol (NDP), ICMPv6, and
Multicast Listener Discovery (MLD) and is often accompanied by an integrated
IPSec security layer.


SEE ALSO[EDIT]

 * BBN Report 1822, an early layered network model
 * Fast Local Internet Protocol
 * List of automation protocols
 * List of information technology initialisms
 * List of IP protocol numbers
 * Lists of network protocols
 * List of TCP and UDP port numbers


NOTES[EDIT]

 1. ^ See Abbate, Inventing the Internet, 129–30; Vinton G. Cerf (October 1980).
    "Protocols for Interconnected Packet Networks". ACM SIGCOMM Computer
    Communication Review. 10 (4): 10–11.; and RFC 760. doi:10.17487/RFC0760..
    For records of discussions leading up to the TCP/IP split, see the series of
    Internet Experiment Notes at the Internet Experiment Notes Index.


REFERENCES[EDIT]

 1.  ^ a b Braden, R., ed. (October 1989). Requirements for Internet Hosts –
     Communication Layers. doi:10.17487/RFC1122. RFC 1122.
 2.  ^ Braden, R., ed. (October 1989). Requirements for Internet Hosts –
     Application and Support. doi:10.17487/RFC1123. RFC 1123.
 3.  ^ Cerf, Vinton G. & Cain, Edward (October 1983). "The DoD Internet
     Architecture Model". Computer Networks. 7 (5). North-Holland: 307–318.
     doi:10.1016/0376-5075(83)90042-9.
 4.  ^ Reynolds, J.; Postel, J. (1987). The Request For Comments Reference
     Guide. doi:10.17487/RFC1000. RFC 1000.
 5.  ^ Hafner, Katie; Lyon, Matthew (1996). Where wizards stay up late : the
     origins of the Internet. Internet Archive. New York : Simon & Schuster.
     p. 263. ISBN 978-0-684-81201-4.
 6.  ^ Russell, Andrew L. (2014). Open standards and the digital age: history,
     ideology, and networks. New York: Cambridge Univ Press. p. 196.
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BIBLIOGRAPHY[EDIT]

 * Douglas E. Comer (2001). Internetworking with TCP/IP – Principles, Protocols
   and Architecture. CET [i. e.] Computer Equipment and Trade.
   ISBN 86-7991-142-9.
 * Joseph G. Davies; Thomas F. Lee (2003). Microsoft Windows Server 2003 TCP/IP
   Protocols and Services. Microsoft Press. ISBN 0-7356-1291-9.
 * Forouzan, Behrouz A. (2003). TCP/IP Protocol Suite (2nd ed.). McGraw-Hill.
   ISBN 978-0-07-246060-5.
 * Craig Hunt (1998). TCP/IP Network Administration. O'Reilly.
   ISBN 1-56592-322-7.
 * Maufer, Thomas A. (1999). IP Fundamentals. Prentice Hall.
   ISBN 978-0-13-975483-8.
 * Ian McLean (2000). Windows 2000 TCP/IP Black Book. Coriolis Group Books.
   ISBN 1-57610-687-X.
 * Ajit Mungale (September 29, 2004). Pro .NET 1.1 Network Programming. Apress.
   ISBN 1-59059-345-6.
 * W. Richard Stevens (April 24, 1994). TCP/IP Illustrated, Volume 1: The
   Protocols. Addison-Wesley. ISBN 0-201-63346-9.
 * W. Richard Stevens; Gary R. Wright (1994). TCP/IP Illustrated, Volume 2: The
   Implementation. Addison-Wesley. ISBN 0-201-63354-X.
 * W. Richard Stevens (1996). TCP/IP Illustrated, Volume 3: TCP for
   Transactions, HTTP, NNTP, and the UNIX Domain Protocols. Addison-Wesley.
   ISBN 0-201-63495-3.
 * Andrew S. Tanenbaum (2003). Computer Networks. Prentice Hall PTR.
   ISBN 0-13-066102-3.
 * Clark, D. (1988). "The Design Philosophy of the DARPA Internet Protocols"
   (PDF). Proceedings of the Sigcomm '88 Symposium on Communications
   Architectures and Protocols. ACM. pp. 106–114. doi:10.1145/52324.52336.
   ISBN 978-0897912792. S2CID 6156615. Retrieved October 16, 2011.
 * Cerf, Vinton G.; Kahn, Robert E. (May 1974). "A Protocol for Packet Network
   Intercommunication" (PDF). IEEE Transactions on Communications. 22 (5):
   637–648. doi:10.1109/TCOM.1974.1092259.


EXTERNAL LINKS[EDIT]

Wikiversity has learning resources about Internet protocol suite
 * Internet History – Pages on Robert Kahn, Vinton Cerf, and TCP/IP (reviewed by
   Cerf and Kahn).
 * RFC 1180 A TCP/IP Tutorial – from the Internet Engineering Task Force
   (January 1991)
 * The Ultimate Guide to TCP/IP
 * The TCP/IP Guide – A comprehensive look at the protocols and the procedure
   and processes involved
 * A Study of the ARPANET TCP/IP Digest, archived from the original on December
   4, 2021