1.2 Software (Protocols)

• Conventions for governing the exchange of data
• Decomposed into logical layers, to support modularity and reusability.

3-Layer Model

Layers

Protocols

With the exception of the bottom layer, communication between corresponding layers are virtual

Protocol Data Unit (PDU)

The combination of the data from the higher layer and the control information placed by the layer into the header

Transport PDU

Destination SAP The address of the application within the destination host, called service access point (SAP).

Sequence number Allow the destination transport to reorder units that arrive out of order.

Error-detection code

Network PDU

Destination host address

Priority request

TCT/IP Model

A dominant five-layers protocol architecture resulted from the experimental ARPANET packet switching network.

Open Systems Interconnection (OSI) Model

The OSI seven-layers model developed by the International Organization for Standardization (ISO) as a framework for developing protocol standards

[prev] [prev-tail] [front] [up]