Lec 6 - COMPUTER NETWORKS

A computer network is a group of computer that are connected to each other for the purpose of communication. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and also presents the basic components of a network. (from: resource)

What is network can provide???
Basically, it is logical interface function. For example, sending message, receiving message, executing program, obtaining status information and other network users and their status.

And these are some terminology in networking that I'm sure, you guys that take IT for majoring in university already familiar of these: NODE, HOST, LINK, TOPOLOGY.

Network topologies

Tere are 4 thopology:

1. Bus Topology

To provide a single communication network on which any node can place information and from which any code can retrieve information. One attachment in bus terminology not impacts the other nodes.

2. Star topology

Has switch as a central. The central switch receives all messages, identifies the addresses, selects the link appropriate for that addresses and forwards the messages.

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3. Ring Topology

To connect a sequence of nodes in a loop or ring. Can be implemented with minimum cabling.

4. Mesh Topology

Each node can conceptually be connected directly to each other node and routing logic can be used to select the most efficient route through multiple nodes.

Advantages in network computing

· Resource sharing is used to reduce maintenance and storage costs.

· Increased reliability means if one system fails users can shift to another.

· Distributing the workload means workload can be shifted from a heavily loaded system to an underutilized one.

· Expandability is system is easily expanded by adding new nodes.

Disadvantages in network computing

· Sharing, access controls for a single system may be inadequate.

· Complexity, a network may combine two or more systems with dissimilar operating systems with different mechanisms for interhost connection. Complexity of this nature makes the certification process extremely difficult.

· Unknown perimeter is one host may be a node on two or more different networks.

· Many points of attack, access controls on one machine preserves the secrecy of data on that processor. However, files stored in a remote network host may pass through many host machines to get to the user.

· Unknown path may be many paths from one host to another and users generally do not have control of how their messages are routed.

· Label formats differences is a problem which may occur in multilevel systems is that the access labels may have different formats since there is no standard

· Anonymity is attack can passed through many other hosts in an effort to disguise from where the attack originated