CCNA/CCNP preparation notes

by Andreas Ryf
OSI reference model
1: Physical Layer
2: Data Link Layer
3: Network Layer
4: Transport Layer
5: Session Layer
6: Presentation L.
7: Application Layer
IP Network Classes
Subnetting
Cables & fibres
Terms
Links
BCMSN
ONT

Layer 1: Physical layer

 

Bits to send and receive, electrical/optical signals, cables (UTP/STP/coax) fibres & radio waves.
Connectors, voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, ...

 

Ethernet, token ring, CSMA/CD, ...

 

Repeater, hubs, MAU, ...

 

The physical layer has no corresponding representation in the DoD model, it is according to Cisco represented in the Network Access layer of the DoD model, together with the Data Link layer.

 

The physical layer only knows bits, if they represent frames or packets or segments is of no concern to the physical layer.

 


 

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