Framing, Error Detection and Correction

41 vocabulary flashcards reviewing key terms from the lecture on framing, error detection, and error correction.

Framing

The data-link layer process of dividing a bit stream into discrete frames for reliable transmission between two directly connected devices.

Data Link Layer

OSI layer responsible for framing, physical addressing, flow control, and error detection/correction over a single link.

Frame Header

The part of a frame that holds control information such as source and destination addresses.

Payload Field

The data portion of a frame that carries the network-layer packet or message being delivered.

Frame Trailer

The section of a frame containing error-detection or error-correction bits (e.g., CRC).

Frame Flag

A special pattern that marks the beginning and end of a frame (e.g., 01111110).

Fixed Size Framing

Framing technique in which every frame has the same length, so no explicit delimiter is needed.

Variable Size Framing

Framing method where frame lengths vary and boundaries are identified by length fields or delimiters.

Length Field

A field inside a variable-size frame that states the frame’s byte length (used in Ethernet 802.3).

End Delimiter (ED)

A unique pattern signaling the end of a frame in some networks, e.g., Token Ring.

Character-oriented Approach

Variable-size framing that treats each byte as a character and uses special characters as delimiters.

Bit-oriented Approach

Variable-size framing that uses specific bit patterns (not byte values) to mark frame boundaries.

Character Count Method

Obsolete framing technique that stores the number of characters in a header field to locate the frame end.

Byte Stuffing

Technique that inserts an escape byte before any data byte identical to a flag byte to preserve framing.

Flag Byte

The dedicated byte (often 01111110 in binary) used as both start-of-frame and end-of-frame marker.

Bit Stuffing

Process of inserting a 0 after every sequence of five consecutive 1s in the data to avoid flag imitation.

Stuffing

General practice of adding extra bits or bytes to data so that framing patterns are not mimicked inside the payload.

Single-Bit Error

A transmission fault in which exactly one bit of a data unit is altered.

Multiple-Bit Error

An error event that flips two or more, but not necessarily consecutive, bits in a data unit.

Burst Error

An error that affects consecutive bits, typically spanning several bits in one continuous sequence.

Error Detection

Techniques that reveal the presence of transmission errors without fixing them (e.g., parity, CRC).

Error Correction

Methods enabling a receiver to both detect and repair errors without needing retransmission.

Parity Bit

A single redundant bit added to data to make the total number of 1s either even or odd.

Checksum

Error-detection value obtained by summing data words and sending the result with the message.

Cyclic Redundancy Check (CRC)

Robust error-detection scheme that treats data as coefficients of a polynomial and applies polynomial division.

Backward Error Correction

Strategy where the receiver requests retransmission after detecting an error (automatic repeat request).

Forward Error Correction (FEC)

Strategy in which the receiver corrects errors by itself using redundant coding, avoiding retransmission.

Single-bit Error Detection

Minimal redundancy technique that can detect but not correct a one-bit fault within a data unit.

Hamming Code

Error-correcting scheme that introduces multiple parity bits to locate and correct single-bit errors.

Even Parity

Parity scheme where the parity bit is chosen so the total number of 1s in the data plus parity is even.

Odd Parity

Parity scheme where the parity bit makes the total count of 1s (data + parity) odd.

Reed–Solomon Code

Powerful block error-correcting code widely used in CDs, DVDs, and deep-space communication.

Turbo Code

Iterative forward error-correcting code that approaches the Shannon limit and is used in modern wireless links.

Error Detection Advantages

Low overhead, simple implementation, and quick processing because only error presence is checked.

Error Detection Disadvantages

Cannot fix errors; may miss some patterns; relies on potentially costly retransmissions.

Error Correction Advantages

Allows data recovery without retransmission, raising reliability in noisy or high-latency channels.

Error Correction Disadvantages

Introduces extra redundancy, higher computational complexity, and added latency for decoding.

Data Integrity

The assurance that received data is identical to what was sent, free of transmission errors.

Resynchronization

Receiver action of regaining frame boundary alignment after losing track due to bit errors.

Escape Byte

Special byte inserted during byte stuffing to indicate that the following byte is user data, not a delimiter.

Polynomial Division

Mathematical operation underlying CRC generation and checking, using modulo-2 arithmetic.