Part 4: communication Flashcards
iso osi protocol
Introduction:
The International Standards Organization (ISO) developed the Open Systems Interconnection Reference Model, commonly abbreviated as ISO OSI or simply the OSI model. While the protocols developed as part of the OSI model were not widely adopted and are essentially obsolete, the underlying model itself has been valuable for understanding computer networks. [Pages: 178]
Purpose:
The OSI model was designed to facilitate open systems communication. An open system is one that is prepared to communicate with any other open system. [Pages: 178]
Layered Structure:
The OSI model divides communication into seven levels or layers. Each layer offers specific communication services to the layer above it. This division allows the problem of communication to be broken down into manageable pieces, each solvable independently. [Pages: 179,180]
Seven Layers:
The seven OSI layers are briefly mentioned, with the Physical layer being the one that deals with standardizing how two computers are connected and how 0s and 1s are represented. The Physical layer is concerned with aspects like voltage levels for binary values, bit transmission rates, and the design of network connectors. [Pages: 179,180]
Comparison with Other Protocols:
The OSI model provides a reference, but in practice, other protocols like TCP and IP (from the Internet suite) have been more popular. The OSI protocols were never as popular as these Internet protocols. [Pages: 180,181]
Layers and Protocols:
The OSI model’s layers, interfaces, and protocols are illustrated. The model emphasizes the importance of layered protocols, with each layer providing specific services and interfaces to the layers above and below it. [Pages: 179]
tcp vs udp
✦ TCP (Transmission Control Protocol):
Definition and Context:
TCP is part of the Internet protocol suite and is used as a de facto standard for network communication. It is a connection-oriented protocol that ensures reliable data transfer between two network devices. [Pages: 182,183]
Comparison with Other Protocols:
TCP is often used in conjunction with IP (Internet Protocol) to form the combination TCP/IP. The Internet protocol suite also supports a connectionless transport protocol called UDP. [Pages: 182,183]
Usage in Internet Application Protocols:
Most Internet application protocols are based on reliable TCP/IP connections. When a client requests a service, it sets up a connection to the server before sending the request. The server typically uses the same connection to send the reply message, after which the connection is torn down. However, setting up and tearing down a connection can be relatively costly, especially for small request and reply messages. [Pages: 91]
✦ UDP (Universal Datagram Protocol):
Definition and Context:
UDP is a connectionless transport protocol, essentially just IP with some minor additions. User programs that do not need a connection-oriented protocol normally use UDP. [Pages: 182,183]
Usage in Specific Scenarios:
In scenarios where both communicating parties are on the public Internet, the actual call (e.g., in a voice communication setup) takes place using UDP packets between negotiated ports at the caller and callee. [Pages: 103]
