Layer 1 (physical media) only describes bit streams and cannot communicate with upper layers in OSI model
Layer 2 can and its sub-layers can
Data Link layer has 2 sub-layers LLC closer to Network layer and MAC (media access control) closer to physical layer
IEEE (institute of electrical and electronic engineers) 802.3 & 802.5 are dominant and best known LAN standards
MAC Add 48 bits (12 Hex digits) first six Manufacturer OUI (organizational unique identifier) and last six vendor assigned number
BIAs (burned in MAC addresses/this is what all MAC addresses are) MAC address in ROM and copied to RAM when in use
MAC addresses are flat they have no structure
Layer 1 puts out a meaningless bit stream in layer two it is interpreted and given a meaning
OSI Model
Layer 7-4 hosts
Layer 3 layer that routers operate at
Layer 2 is the layer switches operate at
Layer 1 Repeater, hubs, cables, etc.
PDU (protocol Data Unit)
Layer 1 Bits
Layer 2 Frames
Layer 3 Packets
Layer 4 Segments
Layer 5-7 Data
Ethernet (802.3 Frame)
Preamble
Destination Address
Source Address
Length/
Type
Data
FCS
(Frame Check Sequence)
6.1.5 know three primary ways and process of FCS