02-01-2013, 10:01 AM
A SEMINAR REPORT ON The Internet Layer Protocols And IP
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Introduction to internet layer
The internet layer or IP layer is a group of internetworking methods in the Internet
Protocol, commonly also called TCP/IP, which is the foundation of the Internet. It is the
group of methods, protocols, and specifications that are used to transport datagrams (packets)
from the originating host across network boundaries, if necessary, to the destination host
specified by a network address (IP address) which is defined for this purpose by the Internet
Protocol(IP). The internet layer derives its name from its function of forming an internet
(uncapitalized), or facilitating internetworking, which is the concept of connecting multiple
networks with each other through gateways.
Internet-layer protocols use IP-based packets. The internet layer does not include the
protocols that define communication between local (on-link) network nodes which fulfill the
purpose of maintaining link states between the local nodes, such as the local network
topology, 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.
Early researches
The Internet protocol suite resulted from research and development conducted by the Defense
Advanced Research Projects Agency (DARPA) in the early 1970s. After initiating the
pioneering ARPANET in 1969, DARPA started work on a number of other data transmission
technologies. In 1972, Robert E. Kahn joined the DARPA Information Technologies 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, the developer of the existing ARPANET Network Control Program (NCP)
protocol, joined Kahn to work on open-architecture interconnection models with the goal of
designing the next protocol generation for the ARPANET.
By the summer of 1973, Kahn and Cerf had worked out a fundamental reformulation, where
the differences between network protocols were hidden by using a common internetwork ,
and, instead of the network being responsible for reliability, as in the ARPANET, the hosts
became responsible. Cerf credits Hubert Zimmerman and Louis Pouzin, designer of the
CYCLADES network, with important influences on this design.
The network's design included the recognition 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. Using a simple design, it
became possible to connect almost any network to the ARPANET, irrespective of their local
characteristics, thereby solving Kahn's initial problem. One popular expression is that
TCP/IP, the eventual product of Cerf and Kahn's work, will run over "two tin cans and a
string."
Purpose
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. In addition it provides 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 packets' proper arrival (see also Internet Protocol#Reliability). This was an
important design principle and change from the previous protocols used on the early
ARPANET. Since packet delivery across diverse networks is inherently an 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.
OSI model
The Open Systems Interconnection model (OSI model) is a product of the effort at the
International Organization for Standardization. It is a prescription of characterizing and
standardizing the functions of a communications system in terms of abstraction layers.
Similar communication functions are grouped into logical layers. A layer serves the layer
above it and is served by the layer below it.
For example, a layer that provides error-free communications across a network provides the
path needed by applications above it, while it calls the next lower layer to send and receive
packets that make up the contents of that path. Two instances at one layer are connected by a
horizontal connection on that layer.
network layer
The network layer provides the functional and procedural means of transferring variable
length data sequences from a source host on one network to a destination host on a different
network, while maintaining the quality of service requested by the transport layer (in contrast
to the data link layer which connects hosts within the same network). The network layer
performs network routing functions, and might also perform fragmentation and reassembly,
and report delivery errors. Routers operate at this layer, sending data throughout the extended
network and making the Internet possible. This is a logical addressing scheme – values are
chosen by the network engineer. The addressing scheme is not hierarchical.
Cross-layer functions
There are some functions or services that are not tied to a given layer, but they can affect
more than one layer. Examples include the following:
security service (telecommunication) as defined by ITU-T X.800 Recommendation.
management functions, i.e. functions that permit to configure, instantiate, monitor, terminate the communications of two or more entities: there is a specific application layer protocol, common management information protocol (CMIP) and its corresponding service, common management information service (CMIS), they need to interact with every layer in order to deal with their instances.
Multiprotocol Label Switching (MPLS) operates at an OSI-model layer that is generally considered to lie between traditional definitions of layer 2 (data link layer) and layer 3 (network layer), and thus is often referred to as a "layer-2.5" protocol. It was designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients which provide a datagram service model. It can be used to carry many different kinds of traffic, including IP packets, as well as native ATM, SONET, and Ethernet frames.
Conclusion
Thus, we have learned about the different protocols of the internet layer like ICMP, ARP, RARP, IP, etc. There are number of protocols in this layer but these are some important protocols. Since internet layer is the third layer of the OSI model, therefore we also learnt about the different layers of the OSI model. The OSI model helped in the interconnection of the computers of the different manufacturers. Initially, interconnection of two different manufacturer’s computer was not possible but OSI model made this possible.
Internet Protocol is the important protocol of the internet layer. It was designed to allow hosts on one network to communicate with the host of the different network irrespective of the type of LAN they are participating in. The designers of the IP addressing had made different Classes for IP addressing. Class A, Class B and Class C are generally used.