CS610 Final Term Notes by Saeed

CS610 FINAL TERM NOTES BY SAEED

NETWORK:

A network is defined as a system for connecting computers using a single transmission technology.

INTERNET:

The Internet is defined as the set of networks connected by routers that are configured to pass traffic among any computers attached to any network in the set.

CLASSIFICATION OF NETWORKS

Computer networks are classified by four factors which are as follow:

1. BY SIZE: LAN,WAN
2. BY CONNECTIVITY: Point-to-Point, Broadcast
3. BY MEDIUM: Copper wire, Co-axial cable, Optical fiber, Radio Waves
4. BY MOBILITY: Mobile Networks, Fixed Networks

BY SIZE: LAN & WAN are compared by the speed of transmission, bandwidth and )latency, management, security, reliability, billing and their standards.

BY CONNECTIVITY:

Networks are also classified by connectivity in which two topologies are discussed. a) Point-to-Point Star, Tree b) Broadcast SATELLITE\RADIO, Ring Topology

BY MEDIUM:

The classification of networks is also based on the Medium of transmission.

• Copper wire
• Co-axial cable
• Optical fiber
• Radio waves

All these mediums differ from each other with respect different parameters. These parameters are speed of transmission, range of the receiver and transmitter computer, sharing of information, topology, installation & maintenance costs and reliability. For example the range of radio waves will be much more than an optical fiber.

There are some issues which are attached with the mobility of networks which are as follows:

• Location and tracking
• Semi persistent connections
• Complex administration and billing as devices and users move around the network.

A computer network is a complex subject due to the following reasons:

1. MANY DIFFERENT TECHNOLOGIES EXIST
2. NO SINGLE UNDERLYING THEORY OR MODEL
3. MODELS ARE EITHER SO SIMPLISTIC OR SO COMPLEX
4. NO SIMPLE OR UNIFORM TERMINOLOGY

MASTERING THE COMPLEXITY

1. CONCENTRATE IN UNDERSTANDING THE CONCEPTS
2. LEARNING THE NETWORKING TERMINOLOGY

Motivation/Benefits/Pros/Advantages of networking

Resource sharing It enhances communication and availability of information It increases cost efficiency It boosts storage capacity

Goal of resource sharing: The goal of resource sharing is to make all programs, equipment and data available to anyone in the network without regard to physical location of the resource and the user.

Main reason for early resource sharing:

The main reason for early resource sharing was not to share the peripheral devices rather to share the large-scale computational power because computer were extremely expensive in those days and the government budgets were not sufficient to provide computers for all scientist and engineers. By resource sharing a researcher could use whichever computer was best suited to perform a given task.

PING:

Ping is a computer network administration software utility used to test the reachability of a host on an Internet Protocol (IP) network. Ping operates by sending Internet Control Message Protocol (ICMP) echo request packets to the target host and waiting for an ICMP echo reply. The program reports errors, packet loss, and a statistical summary of the results, typically including the minimum, maximum, the mean round-trip times, and standard deviation of the mean.

PROBLEM WITH ‘PING’:

If ping does not review any responses from host computer it can not tell the reason of problem. Because one of the following reasons occurs, but ping will not specify the reason.

• Remote computer might have a problem.
• Local computer might have a problem.
• Ping sometimes fails because of congestion.

Tracing a Route:

In computing, traceroute and tracert are computer network diagnostic commands for displaying possible routes (paths) and measuring transit delays of packets across an Internet Protocol (IP) network.

Advantages of tracert over ping:

Tracing a route is more interesting tool than Ping as it tells about each computer that falls in the way of source and destination computers. Ping, on the other hand, only computes the final round-trip times from the destination point.

Packet:

In telecommunications and computer networking, a network packet is a formatted unit of data carried by a packet-switched network. A packet consists of control information and user data;[1] the latter is also known as the payload. Control information provides data for delivering the payload (e.g., source and destination network addresses, error detection codes, or sequencing information). Typically, control information is found in packet headers and trailers.

Why do networks use packets?

Packets are intended to transfer data reliably and efficiently. Instead of transferring a large file as a single block of data, sending smaller packets helps ensure each section is transmitted successfully. If a packet is not received or is "dropped," only the dropped packet needs to be resent. Also the individual connection between each pair of computers is not possible. That’s why to solve these problems shard network connections are made among many workstations.

Problem with sharing:

The demand of sharing is very high because many computers need to use the shared networks. In addition to this some applications have large data transfer. In this way they hold the network for long time. To the fairness, the solution is to divide the data into small block or chunks called ‘PACKETS’. Computers take turns to send one packet at a time over the shared connection. Because each packet is small so no computer experiences a long delay.

Time-division multiplexing (TDM)

It is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time in an alternating pattern. Dividing data into small packets allow time division multiplexing. In TDM each packet leaves the source and is switched on the shared communication channel through a multiplexer. At the destination the packet is switched through a demultiplexer to the destination.

Frame:

A frame is a digital data transmission unit in computer networking and telecommunication. In packet switched systems, a frame is a simple container for a single network packet. In other telecommunications systems, a frame is a repeating structure supporting time-division multiplexing.

A frame typically includes frame synchronization features consisting of a sequence of bits or symbols that indicate to the receiver the beginning and end of the payload data within the stream