Computer network Layers – Data link layer – what is a function of the data link layer and protocols
Computer network Layers – Data link layer – what is a function of the data link layer and protocols
Contents [hide]
- 1 Computer Network Layers – Data Link Layer
- 2 Functions of the Data Link Layer
- 3 1. Framing
- 4 2. Error Detection and Correction
- 5 3. Flow Control
- 6 4. Access Control (MAC – Media Access Control)
- 7 5. Physical Addressing (MAC Addressing)
- 8 6. Reliable Transmission (In Some Cases)
- 9 Protocols of the Data Link Layer
- 10 Common Data Link Layer Protocols
- 11 Summary
- 12 Computer network Layers – Data link layer – what is a function of the data link layer and protocols
- 13 UNIT 1 DATA LINK LAYER FUNDAMENTALS – eGyanKosh
Computer Network Layers – Data Link Layer
The Data Link Layer (DLL) is the 2nd layer in the OSI (Open Systems Interconnection) model. It is responsible for reliable data transfer over a physical link between directly connected devices.
Functions of the Data Link Layer
The Data Link Layer performs the following key functions:
1. Framing
- Converts the raw bit stream from the Physical Layer into frames (structured data units).
- Adds headers and trailers to define frame boundaries.
2. Error Detection and Correction
- Detects errors during data transmission using techniques like Cyclic Redundancy Check (CRC) and Parity Check.
- Some protocols also provide error correction by requesting retransmission (ARQ – Automatic Repeat reQuest).
3. Flow Control
- Manages the rate of data transmission between sender and receiver to prevent congestion.
- Uses techniques like Stop-and-Wait ARQ and Sliding Window Protocol.
4. Access Control (MAC – Media Access Control)
- Regulates how multiple devices share the same communication medium.
- Uses MAC addressing to uniquely identify devices.
- Implements protocols like CSMA/CD (Ethernet) and CSMA/CA (Wi-Fi).
5. Physical Addressing (MAC Addressing)
- Assigns a MAC (Media Access Control) address to each device in a network.
- MAC addresses are unique identifiers for devices in a local network.
6. Reliable Transmission (In Some Cases)
- Some Data Link Layer protocols (like PPP – Point-to-Point Protocol) ensure reliable data transfer by acknowledging received frames.
Protocols of the Data Link Layer
The Data Link Layer consists of two sublayers:
Logical Link Control (LLC) Sublayer – Handles error checking and flow control.
Media Access Control (MAC) Sublayer – Manages device addressing and access control.
Common Data Link Layer Protocols
| Protocol | Description |
|---|---|
| Ethernet (IEEE 802.3) | Wired LAN protocol, uses CSMA/CD for collision detection. |
| Wi-Fi (IEEE 802.11) | Wireless LAN protocol, uses CSMA/CA for avoiding collisions. |
| PPP (Point-to-Point Protocol) | Used in dial-up and DSL connections for point-to-point communication. |
| HDLC (High-Level Data Link Control) | Used in WAN networks for synchronous communication. |
| Frame Relay | Used in high-speed WANs, replaced by MPLS. |
| ATM (Asynchronous Transfer Mode) | Used in telecommunication networks for voice, video, and data. |
Summary
The Data Link Layer provides error-free and efficient data transfer between directly connected devices.
It manages framing, addressing (MAC), error detection, and access control.
Common protocols include Ethernet, Wi-Fi, PPP, and HDLC.
Would you like detailed examples or comparisons between protocols?