IEEE_802.md

IEEE 802 Standards

Data Link Layer divided into two sublayers:

• Logical Link Control (LLC, upper sublayer)
• Media Access Control (MAC, lower sublayer)

Serveral IEEE 802 standards:

• IEEE 802.1: General standard for LANs
• IEEE 802.2: Logical Link Control (LLC)
• MAC standards for specific medium:
  • IEEE 802.3: Ethernet
  • IEEE 802.4: Token Bus
  • IEEE 802.5: Token Ring
  • IEEE 802.11: Wireless LAN
  • IEEE 802.15: Wireless PAN (Bluetooth, ZigBee, etc.)
  • IEEE 802.16: Broadband Wireless

Service Access Points (SAPs)

Each station can have multiple SAPs, which are used to access services provided by the data link layer.

Logical Link Control (LLC)

LLC exposes services to the network layer and has knowledge of SAPs.

Provides three types of services:

• Connectionless
  • Unacknowledged connectionless service (Suitable for wired networks)
  • Acknowledged connectionless service (Suitable for wireless networks)
• Connection-oriented (Suitable for applications communicate directly on top of the data link layer)

LLC Frame Format

Destination SAP	Source SAP	Control	Data

Destination SAP

• First bit 0: Individual address
• First bit 1: Group address
• All 1s: Broadcast address

Source SAP

• First bit 0: Command frame
• First bit 1: Response frame

Control

Like the control field in HDLC.

Three types of frames:

• Information frames
• Supervisory frames
• Unnumbered frames

but differs in some details.

• No SREJ (Selective Reject) frame
• No FCS (Frame Check Sequence), it is handled by the MAC sublayer

Data

Media Access Control (MAC)

MAC is responsible for controlling access to the network medium and has knowledge of the physical addressing (MAC addresses).