Networking: Encapsulation & Modulation Techniques

Encapsulation & Modulation

• 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 Techniques

• 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

• 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

• 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