Computer Networks · TEE · papers
Q2(c) · Framing
2023-11-22 · AI-only Sem V variant; incomplete recovered scan
Exact historical variant. Current-syllabus questions solved; excluded topics and source limitations stated.
Q2(c). Explain methods of framing. What are the advantages of variable-length frames over fixed-length frames? [5 marks]
Answer
Framing separates a continuous bit stream into data-link units so the receiver knows where each frame begins and ends.
| Method | Operation | Key issue |
|---|---|---|
| Fixed size | Every N bytes forms one frame | No delimiter needed, but padding may waste capacity |
| Length/character count | Header gives frame length | A damaged count can lose synchronization |
| Byte stuffing | Flag bytes delimit frames; escape any flag/escape inside payload | Receiver removes inserted escape bytes |
| Bit stuffing | Flag01111110; insert0 after five consecutive data1s | Receiver removes the stuffed0 |
| Coding violation | Reserve physical symbols unavailable to data | Depends on the line code |
Variable-length frames fit different packet sizes, reducing padding and often using bandwidth efficiently. They need boundary/length handling and variable buffering; fixed-size frames give simple predictable processing. Example: a20-byte payload need not occupy an entire500-byte fixed frame when a suitable short variable frame is allowed.