Network layer
 | This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations. (October 2009) |
| OSI model by layer |
|---|
This is what it's all about v
- Host addressing
- Every host in the network needs to have a unique address which determines where it is. This address will normally be assigned from a hierarchical system, so you can be "Fred Murphy" to people in your house, "Fred Murphy, Main Street 1" to Dubliners, or "Fred Murphy, Main Street 1, Dublin" to people in Ireland, or "Fred Murphy, Main Street 1, Dublin, Ireland" to people anywhere in the world. On the Internet, addresses are known as Internet Protocol (IP) addresses.
- Message forwarding
- Since many networks are partitioned into subnetworks and connect to other networks for wide-area communications, networks use specialized hosts, called gateways or routers to forward packets between networks. This is also of interest to mobile applications, where a user may move from one location to another, and it must be arranged that his messages follow him. Version 4 of the Internet Protocol (IPv4) was not designed with this feature in mind, although mobility extensions exist. IPv6 has a better designed solution.
Within the service layering semantics of the OSI network architecture the Network Layer responds to service requests from the Transport Layer and issues service requests to the Data Link Layer.
Protocols
- IPv4/IPv6, Internet Protocol
- DVMRP, Distance Vector Multicast Routing Protocol
- ICMP, Internet Control Message Protocol
- IGMP, Internet Group Multicast Protocol
- PIM-SM, Protocol Independent Multicast Sparse Mode
- PIM-DM, Protocol Independent Multicast Dense Mode
- IPsec, Internet Protocol Security
- IPX, Internetwork Packet Exchange
- RIP, Routing Information Protocol
- DDP, Datagram Delivery Protocol
Relation to TCP/IP model
The TCP/IP model describes the protocol suite of the Internet (RFC 1122). This model has a layer called the Internet Layer, located above the Link Layer. In many text books and other secondary references the Internet Layer is often equated with OSI's Network Layer. However, this is misleading as the allowed characteristics of protocols (e.g., whether they are connection-oriented or connection-less) placed into these layer are different in the two models. The Internet Layer of TCP/IP is in fact only a subset of functionality of the Network Layer. It only describes one type of network architecture, the Internet.
In general, direct or strict comparisons between these models should be avoided, since the layering in TCP/IP is not a principal design criterion and the Internet Engineering Task Force (IETF) considers it to be "harmful" (RFC 3439).
See also
References
- RFC 1122
- RFC 3439
- Tanenbaum, Andrew S. (2003). Computer networks. Upper Saddle River, New Jersey: Prentice Hall. ISBN 0-13-066102-3.
External links
- Template:PDFlink, Hubert Zimmermann, IEEE Transactions on Communications, vol. 28, no. 4, April 1980, pp. 425-432.
- ^ "X.225 : Information technology – Open Systems Interconnection – Connection-oriented Session protocol: Protocol specification". Archived from the original on 1 February 2021. Retrieved 10 March 2023.