Network Criteria - Lecture notes 1 PDF

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Network Criteria: To be considered effective and efficient, a network must meet a number of criteria. The most important of these are performance, reliability, and security. Performance: Performance can be measured in many ways, including transit time and response time. Transit time is the amount of time required for a message to travel from one device to another. Response time is the elapsed time between an enquiry and a response. The performance of a network depends on a number of factors, including the number of users, the type of transmission medium, the capabilities of the connected hardware, and the efficiency of the software. Number of users: Having a large number of concurrent users can slow response time in a network not designed to coordinate heavy traffic loads. The design of a given network is based on an assessment of the average number of users that will be communicating at any one time. In peak load periods, however, the actual number of users can exceed the average and thereby decrease performance. How a network responds to loading is measure of its performance. Type of transmission medium: The medium defines the speed at which data can travel through a connection. Today’s networks are moving to faster and faster transmission media, such as fiber-optic cabling, a medium that can carry data at only 10 megabits per second. However, the speed of light imposes an upper bound on the data rate. Hardware: The types of hardware included in a network affect both the speed and capacity of transmission. A higher-speed computer with greater storage capacity provides better performance. Software: The software used to process data at the sender, receiver, and intermediate nodes also affects network performance. Moving a message from node to node through a network requires processing to transform the raw data into transmittable signals, to route these signals to the proper destination, to ensure error-free delivery, and to recast the signals into a form the receiver can use. The software that provides these services affects both the speed and the reliability of a network link. Welldesigned software can speed the process and make transmission more effective and efficient. Reliability: In addition to accuracy of delivery, network reliability is measured frequency of failure, the time it takes a link to recover from a failure, and the network’s robustness in a catastrophe.

Frequency of failure: All networks fail occasionally. A network that fails often, however, is of little value to a user. Recovery time of a network after a failure: How long does it take to restore service? A network that recovers quickly is more useful than one that does not. Catastrophe: Networks must be protected from catastrophic events such as fire, earthquake, or theft. One protection against unforeseen damage is a reliable system to back up network software. Security: Network security issues include protecting data from unauthorized access and viruses. Unauthorized access: For a network to be useful, sensitive data must be protected from unauthorized access. Protection can be accomplished at a number of levels. At the lowest level are user identification codes and passwords. At a higher level are encryption techniques. In these mechanisms, data are systematically altered in such a way that if an unauthorized user intercepts them, they will be unintelligible.

2. What are the advantages of a multipoint connection over a point-to-point connection? The advantages of a multipoint connection over a point-to-point connection are ease of installation, low cost, reliability. A point to point connection is used for connecting 2 devices, whereas in a multipoint connection more than 2 devices share the communication link. Therefore, multipoint connection provides more reliability.It is easier to add more users in a multipoint connection, than creating individual connections between all users separately. This also leads to low cabling cost and installation cost.

3. Half-duplex data transmission means that data can be transmitted in both directions on a signal carrier, but not at the same time.

MESH TOPOLOGY

4.

PROS

The main advantage of the network is it transmits data from one mode to multiple nodes. CONS Redundancy of the network connection happens in this topology because when one node is connected to multiple nodes the purpose of many connections in the network between nodes is of no purpose.

Star Topology: The general advantage of the Star Topology describes ease of installation and wiring without any disruptions caused to the network while connecting or disconnecting of any devices. They are easy to connect, remove or detect faults in and among the devices or the network. The general Disadvantages of the Star Topology state’s some such as the increase in the necessary of the cable length. The Hub or the device used as hub fails to concentrate then the nodes attached shows to be inactive or disabled automatically. These topologies are considered to be more expensive than the existing linear topologies increasing the cost value of the concentrators.

Bus Topology: Liner Bus Topology – Advantages: The computer of the peripheral shall be attached easily with the linear bus. The requirement of the length of cable is less when compared with the Star Topologies. Linear Bus Topology – Disadvantages: A small break in the cable shuts the entire network. The backbone cable requires terminator at the both ends. A difficulty arises in the understanding of the problem in the shutting down of the system as a whole. This type of solution is never recommended for a stand-alone solution for a large building using large number of networking area. 5. A local area network is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network not only covers a larger geographic distance, but also generally involves leased telecommunication circuits. A wide area network is a telecommunications network that extends over a large geographical area for the primary purpose of computer networking. Wide area networks are often established with leased telecommunication circuits

Figure 1.0

• Transmission System Utilization – Efficient use of tx facilities, eg multiplexing, congestion contro l • Interfacing – Electromagnetic signals propagated over the tx medium

• Signal Generation – Signal must be capable of being propagated through the tx system – Signal must be interpretable as data at the rx • Synchronization – Between tx and rx – Rx should determine when a signal begins to arrive, when it ends, and its duration • Exchange Management — eg if data are exchanged in both directions — Must be decided whether both devices may tx simultaneously or in turns, the amount and format of data, etc...