Computer Communications
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Network software ๐
Layered network architecture:
- Most networks are organized into layers to reduce design complexity.
- Each layer provides specific services to the layer above while shielding it from the implementation details of those services.
- A protocol is an agreement between communicating parties about how communication proceeds. A layer provides services to its users while hiding its internal state and algorithms.
Terms ๐
- Peer: An entity that forms a corresponding layer on a different machine.
- Interface: The operations and services that a lower layer provides to the layer above it.
- Network architecture: A set of layers and protocols.
- Protocol stack: The list of protocols used in a particular system.
Service data units (SDUs) vs. protocol data units (PDUs) ๐
- SDU: A unit of data delivered from a service-providing layer to the layer above. For example, the SDU of layer k becomes the PDU of layer k+1.
- PDU: A unit of data used by a protocol.
OSI reference model ๐
OSI stands for Open Systems Interconnection.
- A network model developed by the International Organization for Standardization (ISO).
A network model consisting of seven layers:
- Physical Layer
- Data Link Layer
- Provides reliable information transfer over a physical link.
- Transfers data blocks, or frames, with the necessary synchronization, error control, and flow control.
- MAC (Medium Access Control).
- LLC (Logical Link Control).
- Network Layer
- Transport Layer
- Session Layer
- Presentation Layer
- Application Layer
TCP/IP reference model ๐
The protocol stack for the Internet.
A network model consisting of four layers:
- Host-to-Network Layer
- Internet Layer
- Transport Layer
- Application Layer
Hybrid reference model ๐
A model that combines the OSI and TCP/IP models.
A network model consisting of five layers:
- Physical Layer
- Data Link Layer
- Network Layer
- Transport Layer
- Application Layer
