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Information about Network Layer

OSI Model
7Application layer
6Presentation layer
5Session layer
4Transport layer
3Network layer
2Data link layer
1Physical layer
The network layer is the third layer out of seven in OSI model and the third layer out of five in TCP/IP model. In the TCP/IP reference model it is called the Internet layer. In all of the models, the network layer responds to service requests from the transport layer and issues service requests to the data link layer.

In essence, the network layer is responsible for end to end (source to destination) packet delivery, whereas the data link layer is responsible for node to node (hop to hop) packet delivery.

The network layer provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks while maintaining the quality of service, and error control functions.

The network layer deals with transmitting information all the way from its source to its destination - transmitting from anywhere, to anywhere. Here are some things that the network layer needs to address:
For example, snail mail is connectionless, because you can send a letter to someone without them doing anything and they will receive the letter. On the other hand, the telephone system is connection-oriented, because the other party is required to pick up the phone before communication can be established. The OSI Network Layer protocol can be either connection-oriented, or connectionless. The TCP/IP Internet Layer (equivalent to OSI's Network Layer) supports only the connectionless Internet Protocol (IP).
  • What are the Global Addresses?
Everybody in the network needs to have a unique address which determines who they are. This address will normally be hierarchical, so you can be "Fred Murphy" to Dubliners, or "Fred Murphy, Dublin" to people in Ireland, or "Fred Murphy, Dublin, Ireland" to people anywhere in the world. On the internet, these addresses are known as IP Addresses.
  • How do you forward a message?
This is of particular interest to mobile applications, where a user may rapidly move from place to place, and it must be arranged that his messages follow him. Version 4 of the Internet Protocol (IPv4) doesn't really allow for this, though it has been hacked somewhat since its inception. Fortunately, the forthcoming IPv6 has a much better designed solution, which should make this type of application much smoother.

List of Network layer services

Examples

See also

Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model for short) is a layered, abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnection (OSI) initiative.
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application layer is the seventh level of the seven-layer OSI model. It interfaces directly to and performs common application services for the application processes; it also issues requests to the presentation layer.
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presentation layer is the sixth level of the seven layer OSI model. It responds to service requests from the application layer and issues service requests to the session layer.
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session layer is level five of the seven level OSI model. It responds to service requests from the presentation layer and issues service requests to the transport layer.

The Session layer provides the mechanism for managing the dialogue between end-user application processes.
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transport layer is the second highest layer in the four and five layer TCP/IP reference models, where it responds to service requests from the application layer and issues service requests to the Internet layer.
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data link layer is layer two of the seven-layer OSI model as well as of the five-layer TCP/IP reference model. It responds to service requests from the network layer and issues service requests to the physical layer.
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Media Access Control (MAC) data communication protocol sub-layer, also known as the Medium Access Control, is a part of the data link layer specified in the seven-layer OSI model (layer 2).
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physical layer is level one in the seven-level OSI model of computer networking as well as in the five-layer TCP/IP reference model. It performs services requested by the data link layer.
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Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model for short) is a layered, abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnection (OSI) initiative.
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The TCP/IP model or Internet reference model, sometimes called the DoD model (DoD, Department of Defense) ARPANET reference model, is a layered abstract description for communications and computer network protocol design.
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transport layer is the second highest layer in the four and five layer TCP/IP reference models, where it responds to service requests from the application layer and issues service requests to the Internet layer.
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data link layer is layer two of the seven-layer OSI model as well as of the five-layer TCP/IP reference model. It responds to service requests from the network layer and issues service requests to the physical layer.
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For other uses, see Data (disambiguation).


Debt, AIDS, Trade in Africa (or DATA) is a multinational non-government organization founded in January 2002 in London by U2's Bono along with Bobby Shriver and activists from the Jubilee 2000 Drop
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Quality of Service, abbreviated QoS, refers to resource reservation control mechanisms. Quality of Service can provide different priority to different users or data flows, or guarantee a certain level of performance to a data flow in accordance with requests from the
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In mathematics, computer science, telecommunication, and information theory, error detection and correction has great practical importance in maintaining data (information) integrity across noisy channels and less-than-reliable storage media.
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In telecommunications, connection-oriented describes a means of transmitting data in which the devices at the end points use a preliminary protocol to establish an end-to-end connection before any data is sent, and in which data is sent over the same path during the communication.
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In a packet-switched network, connectionless mode transmission is a transmission in which each packet is prepended with a header containing a destination address sufficient to permit the independent delivery of the packet without the aid of additional instructions.
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Snail mail is a derogatory retronym — named after the snail with its proverbially slow speed — used to refer to letters and carried by conventional postal delivery services.
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Internet protocol may refer to:
  • The Internet Protocol, a data-oriented protocol used for communicating data across a packet-switched internetwork
  • The Internet protocol suite, a set of communications protocols that implement the protocol stack on which the Internet runs

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Internet Protocol version 4 is the fourth iteration of the Internet Protocol (IP) and it is the first version of the protocol to be widely deployed. IPv4 is the dominant network layer protocol on the Internet and apart from IPv6 it is the only standard internetwork-layer protocol
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Internet Protocol version 6 (IPv6) is a network layer protocol for packet-switched internetworks. It is designated as the successor of IPv4, the current version of the Internet Protocol, for general use on the Internet.
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Forwarding is the relaying of packets from one network segment to another by nodes in a computer network.

The simplest forwarding model - unicasting - involves a packet being relayed from link to link along a chain leading from the packet's source to its destination.
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Routing (or routeing) is the process of selecting paths in a network along which to send data or physical traffic. Routing is performed for many kinds of networks, including the telephone network, the Internet, and transport networks.
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Internet protocol may refer to:
  • The Internet Protocol, a data-oriented protocol used for communicating data across a packet-switched internetwork
  • The Internet protocol suite, a set of communications protocols that implement the protocol stack on which the Internet runs

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The Distance Vector Multicast Routing Protocol (DVMRP) is used to share information between routers to transport IP Multicast packets among networks.

It is based in the RIP protocol to forward packets: the router generates a routing table with the multicast group that
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The Internet Control Message Protocol (ICMP) is one of the core protocols of the Internet protocol suite. It is chiefly used by networked computers' operating systems to send error messages—indicating, for instance, that a requested service is not available or that a
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Protocol-Independent Multicast (PIM) is a family of multicast routing protocols that can provide one-to-many and many-to-many distribution of data over the Internet. The "protocol-independent" part refers to the fact that PIM does not include its own topology discovery mechanism,
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Protocol-Independent Multicast (PIM) is a family of multicast routing protocols that can provide one-to-many and many-to-many distribution of data over the Internet. The "protocol-independent" part refers to the fact that PIM does not include its own topology discovery mechanism,
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IPsec (IP security) is a suite of protocols for securing Internet Protocol (IP) communications by authenticating and/or encrypting each in a data stream. IPsec also includes protocols for cryptographic key establishment.
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