Local Area Network Connections Computer Science Essay


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Local Area Network is the connection of two or more computers together in a college or school using software and hardware. Then the computers can share information each other by using communication link. It is contrast to the WAN such as internet and it covers the large geographical area. It is a small network and it covers the network within the small area such as office, campus and small organizations. In LAN the main computer can be called as the server and the other computers can be called as the clients. By using LAN the computers can share files, resources and documents, printers and other applications. The information can be stored in the server and it can share that information to the clients, by using single cable to connect two computers. If you want to connect large number of computers by using one device that device can be called as hub. Suppose if you connect the internet by LAN then we have router by instead of hub and it is the easiest way to connect the LAN.


The LAN can be divided into two types:

Wired LAN

Wireless LAN

In a Wired LAN to require the Ethernet cable and it connects the all the computers to the network through a main device is called switch.

In a wireless LAN by using radio waves the communication can be done.

In a LAN the hardware can be either wired or wireless type.

The major parts of the network technologies of the LAN are:


Token Ring


The commonly used technology in LAN is Ethernet. The token ring technology can be used in many corporations. The LAN interconnecting Ethernet can be referred as the backbone of the FDDI. The common used technology in industrial automation is ARCNET and it uses the LAN technology. The application can be kept on the LAN server. Suppose if the users want the application and it can be downloading from the LAN server. The files can be shared to one another by the user and it can be done by the LAN server and LAN administrator can access the file by reading and writing. The web server can also be used as the web server.

Design principles of LAN:

To consider the following factors when designing the LAN:

The important thing is broadcast storms in designing the LAN. To consume the broadcast and multicast packets by the host of CPU cycles on a device and that it can be used by the user's computer then the network become cripple and unusable. To detect the multiple access technology by the Ethernet so the traffic can be impacted on the operation of the switch. In the LAN the effect broadcast radiation can be reduced by the VLAN and there is an issue of how many hosts can reside the VLAN. The network designs can be provided by the router and depending on the traffic patterns the VLAN can be segmented within the VLAN. In the VLAN the most of the traffic is local and read the mail of the second VLAN by the user of the first VLAN and these mails can be read and write by the third VLAN of the file servers and these jobs can be printed by the fourth VLAN. To design the network and it can be possible by the 100-mbps and 1-Gbps network links.

To support the routing functions by the Available bandwidth:

To route the VLAN traffic and the network can be design by the traffic and bandwidth from the source through the router and to the destination. To monitor the switches there is an adequate bandwidth between the switches. The incremental trunk speed can be provided by the Etherchannnel between the Fast Ethernet and 10Gigabit Ethernet and combine these multiple Ethernets up to 8 Gbps and 10 Gigabit Ethernet up to 80 Gbps.

The placement of administrative boundaries:

The network can be impacted by the administrative boundary for the deployment of the switches outside the administrative boundary.

To design the switched campus network three topologies can be emerged.

Distributed routing

Large switching

Scalable switching

The network can be deployed by the switched network in all the hierarchical layers without the use of the routers. In this design each layer consists of switches without the speed of the end users.

2.2 What is meant by routing strategy?


In network, Routing is minimizing the hardware. And it is selecting paths in networks to send network traffic. It performs many places like circuit switching, internet, transportation networks.

Static routing:

In computer networks, data communication is described by the static routing. It characterized by the communication between routers regarding the current topology of the network. Opposite of this routing is dynamic routing is called adaptive routing.


Alternative routing:

One routing less preferable than another routing. But preferable routing offering the same terms of the less preferable routing is called alternative routing.



Adaptive routing:

In this, it describes the capability of the system to routes are distinguished by the destination, system is response, when takes the alter paths to change conditions. It controls to allow many routes in response to change.

Examples of the adaptive routing:

Every 10 sec, it collects data from each switch in the network.

In this, routing table derives for each switch

Characteristics of routing protocol:

It prevents routing loops from forming.

Using hop cost information to select preferred routes.

They take time to coverage.

Routing strategies:

Fixed routing:

Fixed route is permanent to source to destination and using least cost algorithm to determine routes. This route is fixed, until we change the topology of network.



Adaptive routing:

This routing is used by packet switching networks. Change the routing decisions, when change the conditions on the network like failures, congestion. In this, decision is more complex and quickly reacting to cause oscillation and slowly to be irrelevant.



Drawbacks of adaptive routing:

To process the decision, when burden on nodes.

To deliver status information, when extra burden on network.

Slowly react to be irrelevant.

Quickly react to cause congestion producing oscillations.


Improve the performance.


Packet stores the destination distance in submitted packet.

The counter reduced by one at each node and then resubmitted into adjacent nodes.

In this, counter 0 packets are discarded.

Destination node doesn't resubmit the packets.




Highly robust.

It is suitable for virtual circuit.

It useful for broadcasting.


High traffic load.

Random routing:

It is like a flooding, simple and robust. But, with less load on network.

For retransmission of incoming packet, selects an outgoing path by intermediate node.

It can be random or round robin selection.

Based on probability calculation to select outgoing path.

In this, no need information of network.

It is typical not least cost.

In this, not more than net work traffic, to reach final destination to take.



Types of routing protocols:

There are three type of routing protocols, they are:

Interior gateway routing via link state routing protocols, like as OSPF and IS-IS.

Interior gateway routing via distance vector protocols, like as RIP, IGRP and EIGRP.

Exterior gateway routing. BGP v4 is the routing protocol used by the public internet.


Adaptive routing protocol is OSPF (open shortest path first) for IP networks. It uses the link state routing algorithm, operating within a single autonomous system and falls into interior routing protocol group.

Most widely used interior gateway protocol is OSPF in large enterprise networks. In this, having another protocol is IS-IS, it is a large service provider networks.

OSPF router types:

ABR (area border router).

ASBR (autonomous system router).

IR (internal router).

BR (backbone router).

OSPF process attributes are router types. A router connected to more than one area to receive routes from a BGP process connected to another autonomous system.




Routing protocol is IS-IS (intermediate system to intermediate system). It is designed in the computer network like group of devices, to move efficient information; it is an open system interconnection (OSI) reference design. This protocol is called the de facto standard for large service provider network backbones.




Local and wide area networks using dynamic routing protocol is RIP (routing information protocol). It is classified as interior gateway protocol. It uses the distance vector routing algorithm. [11]

RIP is distance vector routing protocol to do the hop count as a routing metric. By implementing a limit on the number of hops allowed in a path from source to destination, routing loops are prevented by RIP.

To prevent incorrect routing information by implements the RIP to split horizon, hold-down and poisoning of route from propagated. It is capable to detect every possible loop with its help.




Distance vector interior routing protocol is IGRP (interior gateway routing protocol). Routers used this protocol to exchange routing data.

In large networks, to overcome the RIP limitations, IGRP was created. For each route, it supports multiple metrics, like as bandwidth, load, MTU, delay, reliability; in this, compare two routers these metrics are integrated into a single metric.[12][10]

It is considered as a classful routing protocol, where these protocols have no field for a subnet mask. Variable length subnet masks are used by the classes routing protocols with this contrast. They wasteful of IP address space. So, they become less popular.




EIGRP (enhanced interior gateway routing protocol) is a distance vector routing protocol. It based on loosely with IGRP. It optimizes the routing, topology changes, bandwidth uses and router processing power. Router support EIRGP and automatically redistribute the information to its neighbors. This optimization based on the DUAL (diffusing update algorithm) to loop free operation and offers fast convergence mechanism.

Collection of three tables stored by EIGRP:

Neighbor table:

Store the neighbor routers data, these data directly accessible through connected interface.

Topology table:

It contains only routing table aggregations from all directly connected neighbors and the destination networks list. It identifies the destination network successor and feasible successor. Then it stored in the table, where they exit. If topology table destination can be marked as a passive, when the routing has stabilized and route to destination or passive, when the topology has changed and updating its route to destination.[12][10]

Routing table:

All destination routes are stored, routing table is occupied from topology table with every destination network. It identifies the successor and feasible successor that serve as the next hop router for this destination.[12][10]


BGP (border gateway protocol) is the path vectored protocol. It makes the decision of routing is based on path and network policies. It maintains the IP networks tables to designate reach ability of the network.

EGP (exterior gateway protocol) was replaced by BGP (border gateway protocol) to allow decentralized routing and then become a truly decentralized system. BGP v4 has been use on the network and it support routing of classless inter domain to routing table size decreases.

Internet service provider must use the BGP to establish a routing between one to another. It is most important internet protocol. Even large private networks also use BGP. For better redundancy, BGP to use multi homing to access multi points of a single ISP or multiple ISP's.

2.3Distance vector routing protocols:

We require this protocols that each router inform its routing table of neighbors. For each network path, advertising the lowest cost at the receiving routers. For re-advertising, add entry into its routing table. Distance vector routing protocols are Hello and RIP. This algorithm contains horizon split, reverse poison, triggered update and hold down.[12]

Distance vector routing protocols include these are:

Routing Information Protocol (RIP) for IP

Xerox Networking System's XNS RIP

Novell's IPX RIP

Internet Gateway Routing Protocol (IGRP)

DEC's DNA Phase IV

AppleTalk's Routing Table Maintenance Protocol (RTMP)

Characteristics of distance vector routing protocol:[10]

Updates of periodic:

At the certain time period ends, updates the periodic that will be transmitted. Frequently send the updates then congestions are may occur and convergence time may be high inappropriately.


In routers, data link is shared by neighbors. This protocol sends its updates to neighbor routers and pass the update information to neighbors, where it depends on them. So, distance vector routing is called hop-by-hop updates.

Updates of broadcast:

In this, several methods are available to find other routers and announce its own presence. There, send updates to broadcast address like And then neighbor routers verbal communication the same routing protocol and take proper action.

Updates of full routing table:

Entire route table, this protocol takes the advance of telling their neighbors to everything by broadcasting, with following sections of exceptions are covered. Updates are received by the neighbors and collect the information, where they need and remove everything.

Distance vector protocol converge hop-by-hop:



At t1 time, updates are received and processed by the routers. At the same time, router B's update to router A and router B can reach the networks and, if router B hops 0, router A hop must be 1. Then it inspected the route table. Already we know the network and hop count 0 less than the hop count B. so, A disregarded that information.[12][11] Network was new information. So, A enters this in the route table. Update packet of the source address was router B's interface ( that information is entered along with calculated hop count.

At t1 time, other routers perform the same operations. For instance, router C removed the information from router B and from router C. information entered and it reachable via interface of router B and via router C's interface We calculated both networks as 1 hop.

At t2 time, again expired the update period and broadcast the updated set. Sent its router B's latest table and advertised hop counts by 1 and compared, where router A again incremented. Discarded information of already knew the information of the hasn't change and discarded. New information of is entered into the route table.

At t3 time, covered the network and every router knows the every network. Address of the next hop router for every network and distance in hops to every network.[12]

In networks, road sign like direction, distance are provided by distance vector algorithm. They are vulnerable to misdirection controls.



2.4 Security in routing strategy:

Securing IP network traffic planes:

It gives the implementation and understanding of IP protection and separation on IP routers. It gives the detail view of the advanced techniques how we will give the security to traffic planes of the IP networks. It includes the management and control and data. The IP infrastructure can be provided by the service plans. [11]

In this fist section the detailed explanation of the IP networking and Internet protocol. The brief explanation of the fundamental principles of defense and breadth security to the IP traffic planes can be at the end of the section. In the Second section the detail security techniques of the IP control plane, IP services plane, IP management plane, IP data plane.[12]

In the final section the case study of the service provider network and enterprise network. The security techniques of the IP traffic plane can be reviewed that can help to create in an integrated and breadth security architecture.

It is critical to understand and to give the security to the IP infrastructure. The brief explanation of the techniques in this book can protect against the attacks. To protect the IP infrastructure is very critical if the vulnerability continues for both network providers and vendors.

The IP core network security architecture and technology can be supported by the Gregg for users of the web services.

The service provider organization was invented by the consulting system engineer in 1995. The edge architectures and IP core were supported by the David and he includes the MPLS technologies and IP routing and infrastructure security.

  The operations of the IP routers and networks can be understood.

The layer2 Ethernet switching and environments, IP networks were faced

Many threat models.

How to protect the IP traffic plane if it is applied in breadth and depth principles?

The rate limiting, IP option filtering, uRPF, Qos, RTBH these security techniques can used to protect the data plane of IP and Ethernet networks.

The techniques such as ICMP, MDS, and GTSM can secure the IP control plane in layer 2 switched networks.

To protect the password management and access management and IP management plane techniques [3].

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