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IEEE has specified the following
standards
The Institute of Electrical and
Electronic Engineers.
LAN standards:
802.1d: Spanning
tree.
802.2: LLC.
802.3: MAC ~
Ethernet.
802.5: MAC ~
Token ring.
802.11: Wireless LAN.
Logical Link Control (LLC):
Transitions up to the network layer.
Media Access Control (MAC):
Transitions down to media.
• LLC serves to communicate
upward to Network layer, independent of the specific LAN technology used and
Upper layer.
• MAC serves to access and
communicate downward to the technology-specific
Physical layer.
LLC: receives a packet from the
network layer and attaches a header it is called the PDU protocol data unit and
sends to the MAC through the interface it is called the SDU service
data unit and through the service
access point SAP. The header will have DSAP d stands for destination and SSAP s
stands for the source.
MAC: does the framing and the
flow control.
Concept of layer 2
1. Layer 2 uses framing to
organize or group the data.
2. Layer 2 uses a flat addressing
convention.
3. Layer 2 communicates with the
upper-level layers through LLC.
4. Layer 2 uses MAC to choose
which computer will transmit binary data, from a group in which all computers
are trying to transmit at the same time.
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