please, answer the all questions. Module 2 Hardware and System Architecture Ques
ID: 3594169 • Letter: P
Question
please, answer the all questions.
Explanation / Answer
Question:1
Adaptive Routing Algorithm: These algorithms change their routing decisions to reflect changes in the topology and in traffic as well. These get their routing information from adjacent routers or from all routers. The optimization parameters are the distance, number of hops and estimated transit time. This can be further classified as follows:
Centralized: In this type some central node in the network gets entire information about the network topology, about the traffic and about other nodes. This then transmits this information to the respective routers. The advantage of this is that only one node is required to keep the information. The disadvantage is that if the central node goes down the entire network is down, i.e. single point of failure.
Isolated: In this method the node decides the routing without seeking information from other nodes. The sending node does not know about the status of a particular link. The disadvantage is that the packet may be send through a congested route resulting in a delay. Some examples of this type of algorithm for routing are:
Hot Potato: When a packet comes to a node, it tries to get rid of it as fast as it can, by putting it on the shortest output queue without regard to where that link leads. A variation of this algorithm is to combine static routing with the hot potato algorithm. When a packet arrives, the routing algorithm takes into account both the static weights of the links and the queue lengths.
Backward Learning: In this method the routing tables at each node gets modified by information from the incoming packets. One way to implement backward learning is to include the identity of the source node in each packet, together with a hop counter that is incremented on each hop. When a node receives a packet in a particular line, it notes down the number of hops it has taken to reach it from the source node. If the previous value of hop count stored in the node is better than the current one then nothing is done but if the current value is better then the value is updated for future use. The problem with this is that when the best route goes down then it cannot recall the second best route to a particular node. Hence all the nodes have to forget the stored informations periodically and start all over again.
Distributed: In this the node receives information from its neighbouring nodes and then takes the decision about which way to send the packet. The disadvantage is that if in between the the interval it receives information and sends the paket something changes then the packet may be delayed.
Question:2
highway effect:
The tendency of users to quickly adopt new technology as soon as it proves its usefulness;bcoz of the Highway effect, the demands placed on the system often exceed projections. This term was initially coined in the 1950’s when the traffic load on the Pennsylvania Turnpike exceeded the designers long term, worst case projections soon after the road opened.
Question:3
Introduction: Network Documentation
Network documentation is a form of technical documentation. It is the practice of maintaining records about networks of computers.[1] The documentation is used to give administrators information about how the network should look, perform and where to troubleshoot problems as they occur.
Essential Parts of Network Documentation
As the purpose of network documentation is to keep networks running as smoothly as possible while minimizing downtime when repairs are necessary, essential parts of network documentation include:
Notation that helps administrators remember key details are the basics of network documentation while visual representations assist in helping administrators understand how equipment and the notation relates to one another.
Network Documentation Software
Though network documentation can be done by hand, for larger organizations network documentation software is utilized. Software applications can include diagrams, inventory management and circuit and cable traces. Examples include XIA Configuration
Question:4
Star Topology
A star network consists of a central hub to which all other components are connected. This type of network is more appropriate for larger networks because of its increased fault tolerance, especially compared to ring and bus topologies.
In a star topology, each device is connected to a wiring centre of some kind that is responsible for relaying data to other devices on the network segment. Most modern networks use some variation of the star topology, even if electronically they behave like a bus or a ring. One big advantage of star networks is that the ease with which additional devices can be added to the network, facilitating network expansion. Because each device has its own dedicated connection to the wiring centre, problems are easier to isolate, and a break in a cable affects only one node. If the central device develops a fault, of course, all nodes may be affected.
Advantages and disadvantages:
Advantages
If one node or its connection breaks it doesn’t affect the other computers and their connections.
Devices can be added or removed without disturbing the network
Disadvantages
An expensive network layout to install because of the amount of cables needed
The central hub is a single point of failure for the network
Question:5
The purpose of requirements identification is to ensure that the network designers have clear definitions and a detailed understanding of the essential network requirements and related network design attributes.
Geographical requirements analysis begins with a careful study of the system’s geographical location and focus on such issues as topology and transmission media.
Traffic flow pattern analysis is also used to help define the network’s topology and connections as well as message volumes associated with the various data flows.
Traffic load analysis includes such elements as peak load analysis, message duration analysis, and busy hour analysis. Together, they are used to determine the required number of communication lines, the maximum required capacity for each line, the time slots during which the communication lines are likely to be busy, and several related network performance parameters. The purpose of availability requirements analysis is to determine and document the effect of time differences between the different geographical areas covered by the network.
Response time analysis is concerned with determining the system’s response time requirements.
Reliability requirement analysis provides information that helps the designer develop a back up plan or create necessary redundancies.
Hardware analysis is used to define the requirements for the personal computers, workstations, terminals, peripherals, communication interfaces, modems, and other hardware that will be attached to the network.
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