Framing in data link layer
- 1. Framing in Data Link Layer SUBMITTED BY: Ahtesham Ullah khan 1604610013 CSE - 3RD
- 2. What is framing in networking? Framing is a point-to-point connection between two computers or devices consists of a wire in which data is transmitted as a stream of bits. The data link layer, needs to pack bits into frames, so that each frame is distinguishable from another. The Data Link layer prepares a packet for transport across the local media by encapsulating it with a header and a trailer to create a frame. How it works?
- 4. Parts of a Frame - A frame has the following parts • Frame Header − It contains the source and the destination addresses of the frame • Payload field − It contains the message to be delivered. • Trailer − It contains the error detection and error correction bits.
- 5. Types of Framing - Framing can be of two types Fixed sized framing and Variable sized framing. Fixed-sized Framing - Here the size of the frame is fixed and so the frame length acts as delimiter of the frame. Consequently, it does not require additional boundary bits to identify the start and end of the frame.
- 6. Variable – Sized Framing - Here, the size of each frame to be transmitted may be different. So additional mechanisms are kept to mark the end of one frame and the beginning of the next frame. Two ways to define frame delimiters in variable sized framing are − Length Field − Here, a length field is used that determines the size of the frame.
- 7. End Delimiter - Here, a pattern is used as a delimiter to determine the size of frame. If the pattern occurs in the message, then two approaches are used to avoid the situation − Byte – Stuffing − A byte is stuffed in the message to differentiate from the delimiter. This is also called character-oriented framing. Bit – Stuffing − A pattern of bits of arbitrary length is stuffed in the message to differentiate from the delimiter. This is also called bit – oriented framing.
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