Networking: Encapsulation & Modulation Techniques

Study Notes

User input data is converted for transmission on a network
Data is converted to segments, with reliable connections established between sending and receiving hosts
Segments are converted to packets or datagrams with logical addresses in headers, enabling routing
Packets/datagrams are converted to frames using transmission protocols (e.g., Ethernet) where host addresses are included in headers
Frames are converted to bits, employing digital encoding and clocking schemes

Modulation modifies properties of a carrier signal to hold information
Modulation varies properties like wave form to carry transmitted information
Passband refers to a range of frequencies or wavelengths that can travel through a filter without signal loss
Modulators translate digital bit streams into analog signals suitable for bandpass channels (e.g. using Frequency Division Multiplexing)
Analog and digital modulation move digital signals across bandpass channels
Digital baseband modulation methods (e.g., line coding) are used on baseband channels.
Time-division multiplexing (TDM) is a method for handling multiple independent signals over a shared channel, in time slots.

Encapsulation involves adding protocol information to each layer of the OSI model
Each layer adds its own Protocol Data Unit (PDU) as a header or trailer to preceding data/units
Individual layers in the OSI stack attach their specific control information, like addressing data, to layers below them in headers, trailers, or both.

Decapsulation removes headers and protocols added during encapsulation, at each layer up the OSI stack
Data is released as it moves from lower layers to upper layers in the OSI Model
Headers, protocols are stripped away as the data progresses through the layers