LAYER 2 DATA LINK
OSI MODEL DEFINITION
Provides reliable transit of data across a physical link by using the MAC address
Specifies different netwrork and protocol characteristics including physical addressing, network topology error notification, sequencing of frames and flow control.
Composed of two sub-layers - LLC & MAC (see below)

DATA LINK SUBLAYER
Logical Link Control Sublayer handles error control, flow control, framing and MAC-sublayer addressing
Media Access Control Sublayer deals with the protocols that a host follows in order to access the physical media. IEEE 802.2 LLC standard

MEDIA & TECHNOLOGIES
Ethernet 802.3 and 802.2

 

Etherent and 802.3 LANs are broadcast networks, IEEE 802.3 specifies the physical layer, and the channel-access portion of the data link layer, Layer 2. 

This International Standard describes the functions, features, protocol, and services of the Logical Link Control sublayer in the ISO/IEC 8802 LAN Protocol.

Bridges Connects and passes packets between two or more network segments, uses MAC addresses
LAN Switches Connect LAN segments, use table of MAC addresses, faster than bridges
MAC Address Physical address burned into NIC and used by Switches and Bridges to to determine specific nodes on a LAN, using in Swithing and Bridging tables.
   

WAN Encapsulations
Frame Relay - More Switched L2 protocal that handles multiple virtual circuits using HDLC encapsulation between connected devices.
PPP - More  
ISDN - More  
LAPB  
Cisco IETF  
HDLC  
SMDS  
   
   

 

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