OSI - Ref: OSI by Uyless Black, Prentice-Hall, 1991
Physical Layer
- Transmit raw bits in noise free manner
- Most of the issues have to do with the physical connection (e.g. activating, maintaining and deactivating circuit between Data Terminal Equipment (DTE) and Data Circuit Terminating Equipment (DCE) )
- No interpretation of the bit pattern is performed
Data link layer
- Responsible for transfer of data across link.
- Provides for the identity of the bits in relation to their place in the data unit (breaks data into data frames & puts bit patterns at beginning & end)
- Transmits frames sequentially & processes responses
- Provides flow control so DCE does not overwhelm DTE
- Error recovery performed here
- Worries about full-duplex channels
Reference Models/OSI layers