A network has to fulfill delivery, reliability, performance, and security


Delivery

The first responsibility of a network is to deliver the message to the receiver. When the sender and receiver are directly connected to each other, this is not difficult. But in most cases there are many intermediate nodes between the sender and receiver, and then routing is important. This means what it does in general usage, following a "route." In this case, routing determines the path a message will take from the sender to the receiver, which involves determining the intermediate nodes the message passes through along the way.

Reliability

For a computer network, reliability means that the message that arrives to the receiver is the same message that left the sender. Unfortunately for computer networks, the world is full of things that can corrupt signals. If you have ever moved a telephone too close to a television or other electrical device and heard static on the line, you've experienced this problem firsthand.

All electrical devices emit electromagnetic radiation, which can interfere with networks. In fact, two network connections can even interfere with each other, a phenomenon known as crosstalk. When you faintly hear someone else's phone conversation during your own, you're experiencing crosstalk. In order to ensure reliability, networks must be designed both to reduce the influence of other devices and to safely handle the situation when a signal is corrupted.

Performance

For networks, performance means that the message arrives at the receiver on time. Note that performance is relative to the application. For example, it's acceptable for an e-mail to take several minutes to arrive at the receiver, but in teleconferencing, a delay of several minutes would make communication between the conference attendees so frustrating as to be unusable. Performance means getting the message there when it needs to be there, whenever that is.

Performance is a function of both the underlying physical media and the network rules for transmission. The amount of data a particular network can transfer in a given time frame is referred to as the network's bandwidth, which is usually measured in bits per second.

Security

Network security encompasses several points. First, a private network must prevent unauthorized access. If people could gain access to a bank's network, for example, they could potentially access the sensitive financial data of the bank's customers. Even on a public network like the Internet, security is a concern

If you do any shopping on the Internet, you know that at some point you are sending your credit card number in a message over the network. While you may trust the message's receiver - the merchant you are buying from - with that data, the message passes through many nodes along the way, nodes that you don't know or trust. Thus, a mechanism must exist for passing sensitive data through unknown hands.

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This article was sent to us by: Adam Moore at 02132011

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