Internetworking Technology

Archive for the ‘Computer Networking’ Category

ROUTERS:
A router is a three layer devices, it operates in physical layer, data link layer, and network layer. As a physical layer device, it regenerates the signal it receives. As a data link layer devices, the router checks the physical addresses contained in the packet. As a network layer device, a router checks the network layer addresses. A router connects independent LANs or WANs to create as internet.

SWITCHES:
When we use the team switch, we should be careful because a switch can mean two different things. We must clarify the term by adding the level at which the devices operates. We have two types of switch based on number of layer present. They are two layer switch and three layer switch.

An enduring occasion of incidents pertaining to network security caused a immense concern to the people using computers as their intermediate to exchange data across the country. This requirement was felt for a method of scheming the traffic, which allows admittance of information to computers. Organization required an application that could defend and segregate their internal systems from the internet and it is called firewall. Firewall prevents certain courtside connection from inflowing into the network. It analyses them, and permits them or access them or rejects them.

Firewall system comprises software, entrenched in a router, computer host, or a collection of host set up exclusively to shield a site or subnet from protocols and services that can be a hazard from hosts outside the subnet. It acts as the gatekeeper between an entrusted network and the lots of trusted internal networks. If a remote user tries to access the internal networks without referring the firewall, its efficiency is thinned. In most cases, traveling managers has an office computer that they can dial into while traveling, and their computer is on the protected internal network, then an aggressor who can dial into the data computer has circum vented the firewall. In case of individual user, he or she has dial up internet account and it may connects to internet from his or her office computer sometimes, he or she opens an unsecured connection to the circum vents the firewall.

UDP does not do any of the above. It can only receive a data unit from the processes and deliver it, unreliably, to the receiver. The data unit must be small enough to fit in a UDP packet. UDP is called a connectionless, unreliable transport protocol. It does not add anything to the services of IP except for providing process to process communication instead of host to host communication. Also, it performs very limited error checking. If UDP is so powerless, why would a process want to use it? With the disadvantages come some advantages. UDP is a very simple protocol using a minimum of over head. This are some important about UDP.

Dear all! The most popular packet-switched LAN technology invented at the Xerox PARC is known as the Ethernet. After it was standardized by the Xerox, Intel and digital equipment corporations, it has become the most familiar LAN technology and hence it exists in different forms.

Now it has replaced all the other technologies and used in many of the corporate and personal networks. A coaxial cable had been used to connect all the computers in the original wiring system. But the twisted pair Ethernet is the advanced technology in which Ethernet can be accessed by unshielded copper wires as in telephones.

With the twisted pair wiring, installation becomes easy and hence it requires very low capital cost. Usually every computer and the Ethernet hub are connected by a set of eight wires. But out of eight wires, only four are effective. These four wires are divided into two pairs.

One pair is used to carry data from the computer to the hub and the other to carry data from the hub to the computer. All the signals carried by the Ethernet cable are simulated by the hub. For reliable operation, the distance between a hub and a computer should not exceed 100 meters.

Dear all! In some applications it’s very important to send and receive messages via the internet that should only be understood by the sender and receiver and no one else. This needs various techniques to perform network security. Cryptography is the technique which needs a huge expertise to work with it in the areas such as mathematics, electronics and programming and hence very complex.

Cryptography is Greek word which means “security writing”. It actually refers to the art and science of sending and receiving messages in a secure way by resisting the attacks. Here the original message from the source is transformed to some other form and this transformed message travels in the network and while reaching the destination it is once again transformed to form the original message.

The original message called plaintext is transformed in some other form to form cipher text with the help of an encryption algorithm. To extract the original message from the cipher text, a decryption algorithm is used at the destination side. This encryption and decryption algorithms are referred to as ciphers. To establish a secure communication, one cipher can have many communicating pairs with the presence of keys.

A key is a value that can be number on which the cipher works. Actually the encryption and decryption algorithms are public and hence anyone can access them in the network. But the keys are private. The sender should have an encryption key to encrypt the message and the receiver should have a decryption key to extract the original message from the cipher text.

One of the most important services provided by the TCP/IP for copying a file from one host to another is the File Transfer Protocol (FTP). It seems to be very simple for transferring files between the systems. But there are a lot of complexities involved in the process. For instance the two systems may use different file name conventions and they may also express text and data in different formats. But FTP handles these conditions elegantly differing from other client-server applications. It creates two connections between the hosts, one for data transfer and the other for information control. It is famous for its efficiency and effectiveness as it handles commands and data transfer separately. The protocols used by the control connection are very simple for establishing communication whereas for the data connection more complex protocols have been employed only due to the presence of various data formats.

It transfers commands and responses line by line with one line at a time. The FTP client and server may use different operating systems, different software, different file formats. But it should be capable of dealing with this heterogeneity. It has two approaches over the control and data connections. For control connection, commands and responses are responsible for achieving communication. Therefore one short line of commands or responses at a time relieves from worrying about different file structure. For data connection, transfer of files is the ultimate task. Here, the client defines all the information about the data prior to transmission. This makes the control connection to be prepared for transmission thereby solving the heterogeneity problem.

Dear all! Networks like LANs or WANs can’t operate separately. They should be connected to each other or to the internet. So for connecting them, connecting devices are used. Connecting devices can operate in physical, data link and network layers of the internet model. Repeaters, bridges and routers are the three types of connecting devices generally used. First is the repeater which is generally operated in physical layer. It is a device that carries signals on which the information resides within a network for a limited distance before attenuation affects the coherence of data. Therefore after receiving the signal, it regenerates the signal bit pattern wherever the data is likely to get attenuated or corrupted.

A repeater can stretch the physical length of a LAN and thereby the portions separated by it are called segments. Second is the bridge which can be operated in both the physical and the data link layers. In the first layer, it reconstructs the signal it receives and in the second layer, it checks the physical addresses in the frame. For long distance communication, bridges can do a lot to overcome the collision domain restriction. With their filtering capability, after checking for the destination address in the frame, they can decide whether to forward or to drop the frame. Third is the router which can operate in all the first three layers. It is capable of doing the jobs of a bridge in the physical and data link layers. In the network layer, it checks for network layer address. A router limits the broadcast domains whereas a bridge will alter the collision domains.

Dear all! Every day the demand for network addresses from organizations that want to be connected to the internet. Therefore the availability of network addresses for assigning to such organizations keeps on decreasing. There are two solutions available at present namely subnetting and supernetting. In subnetting, one big network is split into a large number of smaller networks. Every subnet is given its own subnet address. IP addresses are designed containing two levels of hierarchy with network and host being its levels. There will be default mask which masks the hosted and the rest of the bits define the address of the network. Due to the addition of more subnets, a hierarchy with three levels is needed. The three levels are site, subnet and host.

Subnet is the intermediate level between site and host. A subnet mask is needed whenever a network is to be subnetted. Therefore the subnet mask will take care of the subnet address and the default mask will take care of network address. In some cases, the maximum number of addresses assigned to an organization will not be sufficient to satisfy their needs. Supernetting will be an ideal solution for that problem. Here, the organization is allowed to combine a number of class C blocks after their class A and B addresses had depleted to produce a large range of addresses. It is certainly needed to know the first address in the superblock which is created by combining several blocks and the supernet mask. The supernet mask defines the number of blocks combined to make a superblock.

TCP is the abbreviation of Transmission Control Protocol. Nowadays, the popular of application protocols make use of the Internet’s consistent TCP. The functionality of TCP is intended to be sufficient not only for Internet applications but also for the collection of fundamental networks. The protocol seeks at provided that dependable services with the features like Fairness to other surges that potentially split a channel’s bandwidth and Dynamic detection of current ease of use of bandwidth. The central component of trustworthy protocol is error control mechanism. They influence a protocol’s presentation with reverence to good put, energy outflow, and transparency. Error control is generally a two-step procedure one is error detection and the other one is followed by error recovery.

TCP imagine a comparatively consistent fundamental network wherever most packet losses are due to blocking. TCP error control is centered on blocking losses and disregards the opportunity of transient random errors owing to handoffs and comprehensive burst errors that are archetypal in wireless networks. TCP observe errors by scrutinizing the sequence of data segments recognized. As soon as the timeouts are properly configured, an omitted segment is considered to locate an error, namely that the segment is misplaced owed to congestion. Reliable protocols frequently implement an error renewal strategy found on dual techniques like diffusion of vanished segments; and downward alteration of the dispatcher’s window size and readjustment of the timeout perio. When it comes to wireless network, though packet looses will happen more frequently owed to undependable wireless links than owed to congestion i.e. blocking.

Local area network is defined as a network that covers only a little geographical area such as home, office, any other establishment or building. In a local area network, computers are connected with network operating system. One computer is nominated as the file server, which act as a leader and stores work operating system installed onto them. The power of the workstation is less than the file server, and it may require additional software on their hard drives.

WAN:

Wide area network is known as a system of interconnecting loads of computers over a huge geographical area such as countries, states, cities or even the whole world. These kinds of networks normally use telephone lines, satellite links and other communications technologies to connect. Such type of networks is intended to serve an area of thousands or millions of miles like public and private packet switching networks and national telephone networks.

MAN:

Metropolitan area network is known as networks of computers extend over a metropolitan area such as a city and its suburban areas. This type of network is generally apprehended in reserve for metropolitan areas where the city bridges its local area networks with a sequence of backbones, making one huge network for the complete city. It may be a particular network such as a cable television network or it may be a means of connecting a numeral way of LANs.

Bus topology:

Bus topology uses a universal bus or backbone to connect both the devices and terminators. The back bone acts as a mutual communication medium and each node is involved to it with an interface connector. Whenever a message is transmitted on the network, it is accepted back and along the cable, past the stations and connecting the two terminators, from one end of the networks to the other if message passes every station. The station checks the messages and destination address. Once if the address in the message matches the stations then it receives the message. If the address does not match with each other, the bus carries the message to the subsequent station, so on.