Network Engineer

At the lowest level, a network can consist of two or more computers directly connected by some physical medium such as coaxial cable or optical fiber. Such a physical medium is called as Link.

A network can consist of two or more computers directly connected by some physical medium such as coaxial cable or optical fiber. Such a physical medium is called as Links and the computer it connects is called as Nodes.

A node that is connected to two or more networks is commonly called as router or Gateway. It generally forwards message from one network to another.

A network is a set of devices connected by physical media links. A network is recursively is a connection of two or more nodes by a physical link or two or more networks connected by one or more nodes.

Network performance is measured in Bandwidth (throughput) and Latency (Delay). Bandwidth of a network is given by the number of bits that can be transmitted over the network in a certain period of time. Latency corresponds to how long it takes a message to travel from one end off a network to the other. It is strictly measured in terms of time.

The process of determining systematically hoe to forward messages toward the destination nodes based on its address is called routing.

The processes on each machine that communicate at a given layer are called peer-peer process.

It is possible that a switch receives packets faster than the shared link can accommodate and stores in its memory, for an extended period of time, then the switch will eventually run out of buffer space, and some packets will have to be dropped and in this state is said to congested state.

☛ Frequency of failure

☛ Recovery time of a network after a failure

☛ Unauthorized Access

☛ Viruses

☛ Number of Users

☛ Type of transmission medium

☛ Hardware

☛ Software

☛ Performance:

It can be measured in many ways, including transmit time and response time.

☛ Reliability:

It is measured by frequency of failure, the time it takes a link to recover from a failure, and the network's robustness.

☛ Security:

Security issues includes protecting data from unauthorized access and viruses.

☛ Security/Encapsulation

☛ Distributed database

☛ Faster Problem solving

☛ Security through redundancy

☛ Collaborative Processing

If the physical links are shared by more than two nodes, it is said to be Multiple Access.

If the physical links are limited to a pair of nodes it is said to be point-point link.

A linear block code is a code in which the exclusive OR (addition modulo-2) of two valid code-words creates another valid code-word.

"r" redundant bits are added to each block to make the length n = k + r. The resulting n-bit blocks are called code-words. 2n - 2k code-words that are not used. These code-words are invalid or illegal.

Cyclic codes are special linear block codes with one extra property. In a cyclic code, if a code-word is cyclically shifted (rotated), the result is another code-word.

A technique in which the receiver detects the occurrence of an error and asks the sender to resend the message. Re-sending is repeated until a message arrives that the receiver believes is error-freed.

In block coding, we divide our message into blocks, each of k bits, called data-words. The block coding process is one-to-one. The same data-word is always encoded as the same code-word.