Internet layer

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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.

Contents

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

The internet layer has three basic functions:

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 communication endpoints, the hosts, now have to perform path MTU discovery and ensure 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 endpoints 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

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

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

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

See also

Related Research Articles

An Internet Protocol address is a numerical label such as 192.0.2.1 that is assigned to a device connected to a computer network that uses the Internet Protocol for communication. IP addresses serve two main functions: network interface identification, and location addressing.

The Internet Control Message Protocol (ICMP) is a supporting protocol in the Internet protocol suite. It is used by network devices, including routers, to send error messages and operational information indicating success or failure when communicating with another IP address. For example, an error is indicated when a requested service is not available or that a host or router could not be reached. ICMP differs from transport protocols such as TCP and UDP in that it is not typically used to exchange data between systems, nor is it regularly employed by end-user network applications.

<span class="mw-page-title-main">IPv4</span> Fourth version of the Internet Protocol

Internet Protocol version 4 (IPv4) is the first version of the Internet Protocol (IP) as a standalone specification. It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. IPv4 was the first version deployed for production on SATNET in 1982 and on the ARPANET in January 1983. It is still used to route most Internet traffic today, even with the ongoing deployment of Internet Protocol version 6 (IPv6), its successor.

<span class="mw-page-title-main">IPv6</span> Version 6 of the Internet Protocol

Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. IPv6 was developed by the Internet Engineering Task Force (IETF) to deal with the long-anticipated problem of IPv4 address exhaustion, and was intended to replace IPv4. In December 1998, IPv6 became a Draft Standard for the IETF, which subsequently ratified it as an Internet Standard on 14 July 2017.

The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet.

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.

In computer networking, the maximum transmission unit (MTU) is the size of the largest protocol data unit (PDU) that can be communicated in a single network layer transaction. The MTU relates to, but is not identical to the maximum frame size that can be transported on the data link layer, e.g., Ethernet frame.

In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages to other hosts on an Internet Protocol (IP) network. Within an IP network, UDP does not require prior communication to set up communication channels or data paths.

A multicast address is a logical identifier for a group of hosts in a computer network that are available to process datagrams or frames intended to be multicast for a designated network service. Multicast addressing can be used in the link layer, such as Ethernet multicast, and at the internet layer for Internet Protocol Version 4 (IPv4) or Version 6 (IPv6) multicast.

In computing, Internet Protocol Security (IPsec) is a secure network protocol suite that authenticates and encrypts packets of data to provide secure encrypted communication between two computers over an Internet Protocol network. It is used in virtual private networks (VPNs).

The Address Resolution Protocol (ARP) is a communication protocol used for discovering the link layer address, such as a MAC address, associated with a given internet layer address, typically an IPv4 address. This mapping is a critical function in the Internet protocol suite. ARP was defined in 1982 by RFC 826, which is Internet Standard STD 37.

In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers.

Generic routing encapsulation (GRE) is a tunneling protocol developed by Cisco Systems that can encapsulate a wide variety of network layer protocols inside virtual point-to-point links or point-to-multipoint links over an Internet Protocol network.

The Neighbor Discovery Protocol (NDP), or simply Neighbor Discovery (ND), is a protocol of the Internet protocol suite used with Internet Protocol Version 6 (IPv6). It operates at the internet layer of the Internet model, and is responsible for gathering various information required for network communication, including the configuration of local connections and the domain name servers and gateways.

Internet Control Message Protocol version 6 (ICMPv6) is the implementation of the Internet Control Message Protocol (ICMP) for Internet Protocol version 6 (IPv6). ICMPv6 is an integral part of IPv6 and performs error reporting and diagnostic functions.

An IPv6 transition mechanism is a technology that facilitates the transitioning of the Internet from the Internet Protocol version 4 (IPv4) infrastructure in use since 1983 to the successor addressing and routing system of Internet Protocol Version 6 (IPv6). As IPv4 and IPv6 networks are not directly interoperable, transition technologies are designed to permit hosts on either network type to communicate with any other host.

The Internet checksum, also called the IPv4 header checksum is a checksum used in version 4 of the Internet Protocol (IPv4) to detect corruption in the header of IPv4 packets. It is carried in the IP packet header, and represents the 16-bit result of summation of the header words.

An IPv6 packet is the smallest message entity exchanged using Internet Protocol version 6 (IPv6). Packets consist of control information for addressing and routing and a payload of user data. The control information in IPv6 packets is subdivided into a mandatory fixed header and optional extension headers. The payload of an IPv6 packet is typically a datagram or segment of the higher-level transport layer protocol, but may be data for an internet layer or link layer instead.

In computer networking, the link layer is the lowest layer in the Internet protocol suite, the networking architecture of the Internet. The link layer is the group of methods and communications protocols confined to the link that a host is physically connected to. 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 network segment.

References

  1. 1 2 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.
  2. ↑ R. Atkinson (August 1995). Security Architecture for the Internet Protocol. Network Working Group. doi: 10.17487/RFC1825 . RFC 1825.Obsolete. Obsoleted by RFC  2401.
  3. ↑ P. Karn; P. Metzger; W. Simpson (August 1995). The ESP DES-CBC Transform. Network Working Group. doi: 10.17487/RFC1829 . RFC 1829.Proposed Standard.
  4. ↑ "What's The Difference Between The OSI Seven-Layer Network Model And TCP/IP?". Electronic Design. 2 October 2013.
  5. ↑ "Four Layers of TCP/IP model, Comparison and Difference between TCP/IP and OSI models". www.omnisecu.com.
  6. ↑ "Network Basics: TCP/IP and OSI Network Model Comparisons".
  7. ↑ 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.
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