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1. Communication Protocol Communication protocols define the manner in which peer processes communicate between computer hardware devices. The protocols give the rules for such things as the passing of messages, the exact formats of the messages and how to handle error conditions. If two computers are communicating and they both follow the protocol(s) properly, the exchange is successful, regardless of what types of machines they are and what operating systems are running on the machines. As long as the machines have software that can manage the protocol, communication is possible. Essentially, therefore, a computer protocol is a set of rules that coordinates the exchange of information. 2. Packet The term packet is used often in data communications, sometimes incorrectly. To transfer data effectively, it is usually better to transfer uniform chunks of data than to send characters singly or in widely varying sized groups. Usually these chunks of data have some information ahead of them ( called the header ) and sometimes an indicator at the end (called the trailer). These chunks of data are loosely called packets. In some data communications systems, "packets" refer to the units of data passed between two specific layers in a protocol hierarchy e.g. the Data Link Layer and the Network Layer of the OSI 7 layer model. The amount of data in a packet and the composition of the header or trailer may vary depending on the communications protocol as well as some system parameters, but the concept of a packet always refers to the entire chunk of data (including header and trailer). 3. A Host A network host is a computer or other device connected to a computer network. A network host may offer information resources, services, and applications to users or other nodes on the network. A network host is a network node that is assigned a network layer host address. Computers participating in networks that use the Internet Protocol Suite may also be called IP hosts. Specifically, computers participating in the Internet are called Internet hosts, sometimes Internet nodes. Internet hosts and other IP hosts have one or more IP addresses assigned to their network interfaces. The addresses are configured either manually by an administrator, automatically at start-up by means of the Dynamic Host Configuration Protocol (DHCP), or by stateless address autoconfiguration methods 4. Gateways In a communications network, a network node equipped for interfacing with another network that uses different protocols. A gateway may contain devices such as protocol translators, impedance matching devices, rate converters, fault isolators, or signal translators as necessary to provide system interoperability. It also requires the establishment of mutually acceptable administrative procedures between both networks. A protocol translation/mapping gateway interconnects networks with different network protocol technologies by performing the required protocol conversions. Loosely, a computer or computer program configured to perform the tasks of a gateway. For a specific case, see default gateway. gateways, also called protocol converters, can operate at any network layer. The activities of a gateway are more complex than that of the router or switch as it communicates using more than one protocol.[citation needed] Both the computers of Internet users and the computers that serve pages to users are host nodes, while the nodes that connect the networks in between are gateways. For example, the computers that control traffic between company networks or the computers used by internet service providers (ISPs) to connect users to the internet are gateway nodes. 5. A Router A router is a device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP's network. Routers are located at gateways, the places where two or more networks connect. Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols such as ICMP to communicate with each other and configure the best route between any two hosts. Very little filtering of data is done through routers. 6. Routing Routing is the process of selecting best paths in a network. In the past, the term routing was also used to mean forwarding network traffic among networks. However this latter function is much better described as simply forwarding. Routing is performed for many kinds of networks, including the telephone network (circuit switching), electronic data networks (such as the Internet), and transportation networks. This article is concerned primarily with routing in electronic data networks using packet switching technology. In packet switching networks, routing directs packet forwarding (the transit of logically addressed network packets from their source toward their ultimate destination) through intermediate nodes. Intermediate nodes are typically network hardware devices such as routers, bridges, gateways, firewalls, or switches. General-purpose computers can also forward packets and perform routing, though they are not specialized hardware and may suffer from limited performance. The routing process usually directs forwarding on the basis of routing tables which maintain a record of the routes to various network destinations. Thus, constructing routing tables, which are held in the router's memory, is very important for efficient routing. Most routing algorithms use only one network path at a time. Multipath routing techniques enable the use of multiple alternative paths. 7. Network protocol n networking, a communications protocol or network protocol is the specification of a set of rules for a particular type of communication. Multiple protocols often describe different aspects of a single communication. A group of protocols designed to work together are known as a protocol suite; when implemented in software they are a protocol stack. The terms are often intermingled; people may use the term "protocol" to refer to a software implementation, or use "protocol stack" to refer to the specification. Most recent protocols are assigned by the IETF for Internet communications, and the IEEE, or the ISO organizations for other types. The ITU-T handles telecommunications protocols and formats for the PSTN. As the PSTN and Internet converge, the two sets of standards are also being driven towards convergence 8. Protocol layering In modern protocol design, protocols are "layered". Layering is a design principle which divides the protocol design into a number of smaller parts, each of which accomplishes a particular sub-task, and interacts with the other parts of the protocol only in a small number of well-defined ways. For example, one layer might describe how to encode text (with ASCII, say), while another describes how to inquire for messages (with the Internet's simple mail transfer protocol, for example), while another may detect and retry errors (with the Internet's transmission control protocol), another handles addressing (say with IP, the Internet Protocol), another handles the encapsulation of that data into a stream of bits (for example, with the point- to-point protocol), and another handles the electrical encoding of the bits, (with a V.42 modem, for example). Layering allows the parts of a protocol to be designed and tested without a combinatorial explosion of cases, keeping each design relatively simple. Layering also permits familiar protocols to be adapted to unusual circumstances. For example, the mail protocol above can be adapted to send messages to aircraft. Just change the V.42 modem protocol to the INMARS LAPD data protocol used by the international marine radio satellites. 9. Internet If you wish to expose information to everyone in the world, then you would build an Internet-type application. An Internet-type application uses Internet protocols such as HTTP, FTP, or SMTP and is available to persons anywhere on the Internet. We use the Internet and web applications as ways to extend who the application can reach. For example, I no longer need to go to the bank to transfer funds. Because the bank has built a web site on the Internet, I can do that from the comfort of my own home. 10. Circuit Switching The concept of circuit switching works very much like common telephone networks today. To establish a data connection from point A to point Z, a person must work out a direct path over a number of connection routes to the destination. Once a route has been determined, the person needs to set aside resources on that line to establish his connection, after which he may start transmitting data. While resources have been allocated for that connection, no one else may use that line until the first user has disconnected his host. This raises some questions as to how people can share a circuit switched connection, 2 of methods of which are outlined below. One of the cons of a Circuit Switched network is that it relies on a user reserving and allocating resources for himself in order to use the network. This adds to connection time and can form significant overhead in establishing connections. In the event the user decides to hop off and get a coffee without disconnecting, he will not have released the resources reserved for use by others. 11. Time Division The circuit is divided into time slots, each of which are allocated to users wanting to use the network. In each time slot available to a user, the user has the full amount of bandwidth provided by the circuit. The more people using the circuit, the more time it takes for each frame to be passed from destination to receiver. 12 Frequency Division The circuit is divided into a number of frequencies, each of which are allocated to a user. The user has full control of that connection, only to be limited by the bandwidth his frequency provides. Naturally the more people utilising the circuit, the less bandwidth each person has.

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