Standards and Implementation:
The first LAN ever was Ethernet.
Robert Metcalfe and coworkers at Xerox in mid 70s.
The first Ethernet standard published 1980 by DigitalEquipCorp, Intel, Xerox (DIX).
Metcalfe wanted it to be a shared open standard.
1985 IEEE published standards for LANs.
For compatibility with OSI, small mods made to Ethernet standards with 802.3.
Ethernet –L1 and L2:
Ethernet implemented in MAC sublayer and L1 only.
LLC:
The use of these sublayers contributes significantly to compatibility between diverse end devices.
802.2 describes LLC sublayer functions.
802.3 describes the Media Access Control (MAC) sublayer and L1 functions.
LLC – software (drivers) – independent physical equipment.
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Tags: study, wan, ip, cisco, interface, guides
Physical Layer Protocols and Services:
L1 controls how data is placed on the media.
It has to encode bits into signals and Tx/Rx these signals across the physical media.
The delivery of frames across media requires.
Physical media and connectors.
A representation of bits – code.
Encoding of data and control information.
Tx and Rx circuitry on devices.
The purpose of L1 is to create the electrical, optical, or radio signal that reqresents the bits in each frame.
It also must retrieve signals from media, restore them to bit representations, and pass them to L2 as a complete frame.
The type of signal – depends on the type of media.
Copper = electrical pulses.
Fiber = patterns of light.
Wireless = patterns of radio transmissions.
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Tags: wan, 802.1q, guides, cisco, vlan, router
