Network Engineer

A device or program that uses predefined algorithms to encode, or compress audio or video data for storage or transmission use. A circuit that is used to convert between digital video and analog video.

☛ Frequency Division Multiplexing (FDM)

☛ Time Division Multiplexing (TDM)

1: Synchronous TDM

2: ASynchronous TDM Or Statistical TDM.

☛ Wave Division Multiplexing (WDM)

Multiplexing is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link.

Defining a useful channel involves both understanding the applications requirements and recognizing the limitations of the underlying technology. The gap between what applications expects and what the underlying technology can provide is called semantic gap.

Error control is both error detection and error correction. It allows the receiver to inform the sender of any frames lost or damaged in transmission and coordinates the re-transmission of those frames by the sender. In the data link layer, the term error control refers primarily to methods of error detection and re-transmission. Error control in the data link layer is often implemented simply: Any time an error is detected in an exchange, specified frames are re-transmitted. This process is called automatic repeat request (ARQ).

The sliding window is an abstract concept that defines the range of sequence numbers that is the concern of the sender and receiver. In other words, he sender and receiver need to deal with only part of the possible sequence numbers.

In byte stuffing (or character stuffing), a special byte is added to the data section of the frame when there is a character with the same pattern as the flag. The data section is stuffed with an extra byte. This byte is usually called the escape character (ESC), which has a predefined bit pattern. Whenever the receiver encounters the ESC character, it removes it from the data section and treats the next character as data, not a delimiting flag.

Bit stuffing is the process of adding one extra 0 whenever five consecutive Is follow a 0 in the data, so that the receiver does not mistake the pattern 0111110 for a flag.

Error correction in Stop-and-Wait ARQ is done by keeping a copy of the sent frame and re-transmitting of the frame when the timer expires.

A technique called piggybacking is used to improve the efficiency of the bidirectional protocols. When a frame is carrying data from A to B, it can also carry control information about arrived (or lost) frames from B; when a frame is carrying data from B to A, it can also carry control information about the arrived (or lost) frames from A.

☛ Broadcast and

☛ point-to-point

In networking and in other areas, a task is often begun before the previous task has ended. This is known as pipe-lining.

The protocol specifies that frames need to be numbered. This is done by using sequence numbers. A field is added to the data frame to hold the sequence number of that frame. Since we want to minimize the frame size, the smallest range that provides unambiguous communication. The sequence numbers can wrap around.

In Stop and wait protocol, sender sends one frame, waits until it receives confirmation from the receiver (okay to go ahead), and then sends the next frame.

In fixed-size framing, there is no need for defining the boundaries of the frames. The size itself can be used as a delimiter.

☛ Simplex

☛ Half-duplex

☛ Full-duplex.

A generic term for section of a large networks usually separated by a bridge or router.

The function of PAD (Packet Assembler Dis-assembler) is described in a document known as X.3. The standard protocol has been defined between the terminal and the PAD, called X.28; another standard protocol exists between hte PAD and the network, called X.29. Together, these three recommendations are often called "triple X".

NETBIOS is a programming interface that allows I/O requests to be sent to and received from a remote computer and it hides the networking hardware from applications.

A method for providing fault tolerance by using multiple hard disk drives.