Group of internetworking methods in the TCP/IP suite
The
internet layer
is a group of
internetworking
methods, protocols, and specifications in the
Internet protocol suite
that are used to transport
network packets
from the originating
host
across
network boundaries
; if necessary, to the destination host specified by an
IP address
. The internet layer derives its name from its function facilitating
internetworking
, which is the concept of connecting multiple networks with each other through
gateways
.
The internet layer does not include the protocols that fulfill the purpose of maintaining link states between the local nodes and that usually use protocols that are based on the framing of packets specific to the link types. Such protocols belong to the
link layer
. Internet-layer protocols use IP-based packets.
A common design aspect in the internet layer is the
robustness principle
: "Be liberal in what you accept, and conservative in what you send"
[1]
as a misbehaving host can deny Internet service to many other users.
Purpose
[
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]
The internet layer has three basic functions:
- For outgoing packets, select the next-hop host (
gateway
) and transmit the packet to this host by passing it to the appropriate
link layer
implementation;
- For incoming packets, capture packets and pass the packet payload up to the appropriate
transport layer
protocol, if appropriate.
- Provide error detection and diagnostic capability.
In Version 4 of the Internet Protocol (
IPv4
), during both transmit and receive operations, IP is capable of automatic or intentional
fragmentation or defragmentation
of packets, based, for example, on the
maximum transmission unit
(MTU) of link elements. However, this feature has been dropped in
IPv6
, as the communications end points, the hosts, now have to perform
path MTU discovery
and assure that end-to-end transmissions don't exceed the maximum discovered.
In its operation, the internet layer is not responsible for
reliable transmission
. It provides only an
unreliable
service, and
best effort
delivery. This means that the network makes no guarantees about the proper arrival of packets. This in accordance with the
end-to-end principle
and a change from the previous protocols used on the early
ARPANET
. Since packet delivery across diverse networks is an inherently unreliable and failure-prone operation, the burden of providing reliability was placed with the end points of a communication path, i.e., the hosts, rather than on the network. This is one of the reasons of the resiliency of the Internet against individual link failures and its proven
scalability
. The function of providing reliability of service is the duty of higher level protocols, such as the
Transmission Control Protocol
(TCP) in the
transport layer
.
In IPv4, a
checksum
is used to protect the header of each datagram. The checksum ensures that the information in a received header is accurate, however, IPv4 does not attempt to detect errors that may have occurred to the data in each packet. IPv6 does not include this header checksum, instead relying on the link layer to assure data integrity for the entire packet including the checksum.
Core protocols
[
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]
The primary protocols in the internet layer are the
Internet Protocol
(IP). It is implemented in two versions,
IPv4
and
IPv6
. The
Internet Control Message Protocol
(ICMP) is primarily used for error and diagnostic functions. Different implementations exist for IPv4 and IPv6. The
Internet Group Management Protocol
(IGMP) is used by IPv4 hosts and adjacent
IP multicast
routers to establish multicast group memberships.
Security
[
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]
Internet Protocol Security
(IPsec) is a suite of protocols for securing IP communications by authenticating and encrypting each IP packet in a data stream. IPsec also includes protocols for
key exchange
. IPsec was originally designed as a base specification in IPv6 in 1995,
[2]
[3]
and later adapted to IPv4, with which it has found widespread use in securing
virtual private networks
.
Relation to OSI model
[
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]
Because the internet layer of the TCP/IP model is easily compared directly with the
network layer
(layer 3) in the
Open Systems Interconnection
(OSI) protocol
stack,
[4]
[5]
[6]
the internet layer is often improperly called
network layer
.
[1]
[7]
IETF standards
[
edit
]
- J. Postel
, ed. (September 1981).
INTERNET PROTOCOL - DARPA INTERNET PROGRAM PROTOCOL SPECIFICATION
.
IETF
.
doi
:
10.17487/RFC0791
. STD 5.
RFC
791
. IEN 128, 123, 111, 80, 54, 44, 41, 28, 26.
Internet Standard 5.
- J. Postel
(September 1981).
INTERNET CONTROL MESSAGE PROTOCOL - DARPA INTERNET PROGRAM PROTOCOL SPECIFICATION
. Network Working Group.
doi
:
10.17487/RFC0792
. STD 5.
RFC
792
.
Internet Standard 5.
- David D. Clark (July 1982).
IP DATAGRAM REASSEMBLY ALGORITHMS
.
IETF
.
doi
:
10.17487/RFC0815
.
RFC
815
.
Unknown.
- David D. Clark (July 1982).
FAULT ISOLATION AND RECOVERY
.
IETF
.
doi
:
10.17487/RFC0816
.
RFC
816
.
Historic.
- J. Postel
(November 1983).
The TCP Maximum Segment Size and Related Topics
. Network Working Group.
doi
:
10.17487/RFC0879
.
RFC
879
.
Obsolete.
- J. Mogul;
J. Postel
(August 1985).
Internet Standard Subnetting Procedure
. Network Working Group.
doi
:
10.17487/RFC0950
. STD 5.
RFC
950
.
Internet Standard 5.
- S. Kent (November 1991).
U.S. Department of Defense - Security Options for the Internet Protocol
. Network Working Group.
doi
:
10.17487/RFC1108
.
RFC
1108
.
Historic.
- S. Deering
(August 1989).
Host Extensions for IP Multicasting
. Network Working Group.
doi
:
10.17487/RFC1112
. STD 5.
RFC
1112
.
Internet Standard 5.
- R. Braden
, ed. (October 1989).
Requirements for Internet Hosts -- Communication Layers
. Network Working Group.
doi
:
10.17487/RFC1122
. STD 3.
RFC
1122
.
Internet Standard 3.
- R. Braden
, ed. (October 1989).
Requirements for Internet Hosts -- Application and Support
. Network Working Group.
doi
:
10.17487/RFC1123
. STD 3.
RFC
1123
.
Internet Standard 3.
- R. Bush; D. Meyer (December 2002).
Some Internet Architectural Guidelines and Philosophy
. Network Working Group.
doi
:
10.17487/RFC3439
.
RFC
3439
.
Informational.
See also
[
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]
References
[
edit
]
- ^
a
b
R. Braden
, ed. (October 1989).
Requirements for Internet Hosts -- Communication Layers
. Network Working Group.
doi
:
10.17487/RFC1122
. STD 3.
RFC
1122
.
Internet Standard 3.
Updated by
RFC
1349
,
4379
,
5884
,
6093
,
6298
,
6633
,
6864
,
8029
and
9293
.
- ^
R. Atkinson (August 1995).
Security Architecture for the Internet Protocol
. Network Working Group.
doi
:
10.17487/RFC1825
.
RFC
1825
.
Obsolete.
Obsoleted by
RFC
2401
.
- ^
P. Karn; P. Metzger; W. Simpson (August 1995).
The ESP DES-CBC Transform
. Network Working Group.
doi
:
10.17487/RFC1829
.
RFC
1829
.
Proposed Standard.
- ^
"What's The Difference Between The OSI Seven-Layer Network Model And TCP/IP?"
.
Electronic Design
. 2 October 2013.
- ^
"Four Layers of TCP/IP model, Comparison and Difference between TCP/IP and OSI models"
.
www.omnisecu.com
.
- ^
"Network Basics: TCP/IP and OSI Network Model Comparisons"
.
- ^
R. Braden
, ed. (October 1989).
Requirements for Internet Hosts -- Application and Support
. Network Working Group.
doi
:
10.17487/RFC1123
. STD 3.
RFC
1123
.
Internet Standard 3.
Updated by
RFC
1349
,
2181
,
5321
,
5966
and
7766
.
External links
[
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]