Networking - The OSI Seven-Layer Model - The Data Link Layer

The Data Link layer is generally thought of as being made up of two equal sublayers, each with specific functions. The two sublayers are:

• Media Access Control, and
• Logical Link Control

The purpose of the Data Link layer is to:

• Create frames from the bits of the Physical layer,
• Control data flow,
• detect errors, and
• Identify network devices

Various network devices are normally associated with the Data Link layer:

• Bridges,
• Switches, and
• Network Interface Cards

The Data Link Media Access Control sublayer is responsible for three processes, each of which is responsible for a series of methods:

1. Logical Topology
   • Bus
   • Ring
2. Media Access
   • Contention
     • carrier sense
     • collision detection & notification
   • Token-passing
   • Polling
3. Addressing
   • Physical device

The Data Link Logical Link Control sublayer is responsible for two processes, each of which is responsible for a series of methods:

1. Transmission Synchronization
   • Asynchronous
   • Synchronous
   • Isochronous
2. Connection Services
   • Logical Link Control-level flow control
   • Error control

Let's move on to layer 3, the Network Layer.

Nah, I want to skip around:

• Introduction
• Physical (Layer 1)
• Data Link (Layer 2)
• Network (Layer 3)
• Transport (Layer 4)
• Session (Layer 5)
• Presentation (Layer 6)
• Application (Layer 7)
• Conclusion

Copyright 1999, Marc Elliot Hall, DBA Sensation! Services