by Dinesh Thakur Category: Multiple Access

In the 1970s, the Department of Defense, or DOD (Department Of Defense), decided before the proliferation of machines using different, incompatible communication protocols, to define its own architecture. This architecture, called TCP / IP, is the source of the Internet. It is also adopted by many private networks, called intranets.

The two main protocols defined in this architecture are:

• IP (Internet Protocol) network level, which provides connectionless service.

• TCP (Transmission Control Protocol) transport level, which provides a service with reliable connection.

TCP / IP define a layered architecture that also includes, without being explicitly defined, an access interface to the network. Indeed, many separate subnets can be taken into account in the TCP / IP architecture, both local type than extended.

This architecture is illustrated in FIG. Note in this figure the appearance of another level protocol message (layer 4), UDP (User Datagram Protocol). This protocol uses a connectionless mode, which allows you to send messages without the recipient's permission.

 Architecture TCP/IP

This architecture for base IP, which corresponds to the packet level (Layer 3) of the architecture of the reference model. In reality, it corresponds only partially at this level. The IP protocol was designed as interconnection protocol defining a data block of a well defined format and containing an address but no other functionality. Its role was to carry that data block in a package according to any other packet transfer technique. This applies to the first generation of IP, called IPv4, which is still heavily used today. The second version of the IP protocol, IPv6, actually plays a role level package, with new features to transport packets from one end of the network to another with some security.

IP packets are independent of each other and are routed individually within the network through routers. The quality of service offered by IP is very low, without detection of lost packets or possibility of error recovery.

TCP includes message-level features (layer 4) of the reference model. This is a fairly complex protocol, which has many options to solve all the problems of packet loss in the lower levels.

In particular, a lost fragment can be recovered by retransmission on the flow bytes. TCP is connection-oriented mode, unlike UDP. This Last UDP is also positioned at the transport level but in a connectionless and offers virtually any functionality. It can not be considered as applications that require little service from the transport layer.

Protocols located above TCP and UDP application type and are derived largely from the UNIX world.

The power of this architecture is based on the flexibility of its implementation over any existing network. So, for example, X and Y, respectively, a local network and a wide area network to switch cells or packets. The IP protocol is implemented on all machines connected to both networks. To make it possible to move from one network to another, router, whose role is to uncap the packet came from the X network and retrieve the IP packet is set up. After treatment, mainly routing, the IP packet is encapsulated in the packet network Y. The role of the router is, as its name suggests, routing the packet to the correct destination.

The Internet network interconnect architecture is illustrated in Figure.

  Interconnection architecture of the Internet

The flexibility of this architecture can sometimes be a default, in the sense that the overall network optimization is performed subnet by subnet, that is to say, it is obtained by a succession of local optimizations .

An important feature of the TCP/IP architecture is that intelligence and network control are almost entirely in the terminal machine and not in the network, at least for IPv4. It is the TCP protocol which is responsible for sending more or fewer packets in the network according to the occupation thereof. The control intelligence is in the PC end, specifically in the TCP software. The TCP window control increases or decreases the traffic according to the speed required to make a return. The cost of infrastructure is extremely low because many software and therefore most of the intelligence, are in terminal machines. The service rendered by this network of networks of best-effort type, which means that the network does its best to carry the traffic.

IPv6 brings a new dimension, since it introduces new features that make the nodes of the network smarter. The new generations of routers have QoS management algorithms to ensure a transport capable of meeting timing constraints or packet loss. However, IPv4 has responded well to novel aspects of IPv6, modifying some fields to offer the same improvements.

In the classic version of IPv4, each new customer is not treated differently from those who are already connected, and resources are distributed fairly among all users. Resource allocation policies of the telecom operators are totally different, a customer already has a certain quality of service that should not be penalized by the arrival of a new customer. As we shall see, the now advocated solution in the Internet environment is to ensure, to the extent possible, customers with real-time requirements, and by appropriate protocols.

The applications available over the TCP/IP environment are many and varied. They include email (SMTP), file transfer it (FTP) and especially the databases distributed with the World-Wide Web (WWW).

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About Dinesh Thakur

Dinesh ThakurDinesh Thakur holds an B.SC (Computer Science), MCSE, MCDBA, CCNA, CCNP, A+, SCJP certifications. Dinesh authors the hugely popular blog. Where he writes how-to guides around Computer fundamental , computer software, Computer programming, and web apps. For any type of query or something that you think is missing, please feel free to Contact us.