L2 protocols

Layer 2 (L2) protocols operate at the Data Link Layer of the OSI model. They are primarily responsible for node-to-node data transfer, error detection, flow control, and managing physical addressing (e.g., MAC addresses). Here's a categorized list of the most common Layer 2 protocols:

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1. Ethernet-Based Protocols

These are protocols used in Ethernet networks for framing, addressing, and media access control.

• Ethernet (IEEE 802.3):

  • The most widely used L2 protocol for wired LANs.

  • Defines MAC addressing, frame format, and CSMA/CD for shared media.

• VLAN Tagging (IEEE 802.1Q):

  • Adds VLAN information to Ethernet frames for network segmentation.

2. Wireless-Based Protocols

These protocols provide data link layer functionality for wireless communication.

• Wi-Fi (IEEE 802.11):

  • Handles wireless LAN communication, framing, error control, and addressing.

• WiMAX (IEEE 802.16):

  • Provides L2 connectivity for broadband wireless networks.

3. Address Resolution Protocols

These protocols resolve network layer addresses (IP) to data link layer addresses (MAC).

• ARP (Address Resolution Protocol):

  • Maps IPv4 addresses to MAC addresses in local networks.

• NDP (Neighbor Discovery Protocol):

  • IPv6 equivalent of ARP, plus additional features like router discovery.

4. Switching and Bridging Protocols

These protocols manage data forwarding and loop prevention in L2 switches and bridges.

• STP (Spanning Tree Protocol, IEEE 802.1D):

  • Prevents loops in a switched network.

  • Learn: https://www.youtube.com/watch?v=GSKoQ8ZR8rw&ab_channel=NesoAcademy

• RSTP (Rapid Spanning Tree Protocol, IEEE 802.1w):

  • Faster convergence version of STP.

• MSTP (Multiple Spanning Tree Protocol, IEEE 802.1s):

  • Extends RSTP for multiple VLANs.

• LACP (Link Aggregation Control Protocol, IEEE 802.3ad):

  • Combines multiple physical links into a single logical link.

5. Point-to-Point Protocols

These are used for direct communication between two devices.

• PPP (Point-to-Point Protocol):

  • Used for direct connections, often in WAN links.

• HDLC (High-Level Data Link Control):

  • Common in WANs for encapsulating Layer 3 protocols.

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6. Metro Ethernet and Carrier Ethernet Protocols

Used in provider networks for Ethernet-based connectivity.

• Q-in-Q (IEEE 802.1ad):

  • Extends VLAN tagging for provider networks.

• Provider Backbone Bridges (IEEE 802.1ah):

  • Adds hierarchical MAC addressing for scalability.

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7. Flow Control and Error Detection Protocols

Protocols that ensure reliable data transmission and manage congestion.

• PAUSE Frames (IEEE 802.3x):

  • Provides flow control in Ethernet networks.

• FEC (Forward Error Correction):

  • Corrects errors in frames without retransmission.

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8. Virtualization and Overlay Protocols

Used in virtualized environments and overlay networks.

• VXLAN (Virtual Extensible LAN):

  • Encapsulates Layer 2 frames for communication over Layer 3 networks.

• NVGRE (Network Virtualization using GRE):

  • Similar to VXLAN, but uses GRE encapsulation.

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9. Miscellaneous Layer 2 Protocols

• LLDP (Link Layer Discovery Protocol, IEEE 802.1AB):

  • Device discovery protocol for network topology mapping.

• CDP (Cisco Discovery Protocol):

  • Cisco-specific protocol for device discovery.

• MACsec (IEEE 802.1AE):

  • Provides encryption at Layer 2.

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L2 Protocol Examples in Use