Chapter 2 Lecture

 The Elements of Communication ➢ Data is divided into smaller parts during transmission – segmentation ➢ Benefits:  Many different conversations can be interleaved on the network. The process used to interleave the pieces of separate conversations together on the network is called multiplexing  Increase the reliability of network communications. The separate pieces of each message need not travel the same pathway across the network from source to destination ➢ Downside:  Level of complexity is added  Each segment of the message must go through a similar process to ensure that it gets to the correct destination and can be reassembled into the content of the original message ➢ End Devices and their roles  End devices are referred to as hosts  A host device is either the sender or receiver  A sender uses the address of the dest. Host to specify where the message should be sent  Software determines the role of a host. (client, server, both)  OSI Model ♦ All People Seem To Need Data Processing (7-1) ♦ Please Do Not Throw Sausage Pizza Away (1-7) ➢ Application - 7  Provides the means for end-to-end connectivity between individuals in the human network using data networks ➢ Presentation - 6  Provides for common representation of the data transferred between application layer services • Makes sure data is in right format, before other machine can read it ➢ Session - 5  Provides services to the Presentation layer to organize its dialogue and to manage data exchange • Establishes a session between sender & receiver and terminates when complete ➢ Transport - 4  Defines services to segment, transfer, and reassemble the data for individual communications between the end devices • Layer handles details of reliable transfer (ensures that the data arrives completely) ➢ Network - 3  Provides services to exchange the individual pieces of data over the network between identified end devices • Many paths to same destination – which path to follow? • Segmented data needs address to reach the destination ➢ Data Link - 2  Protocols describe methods for exchanging data frames between devices over a common media

• • •

Provides means for exchanging data frames over a common media Detect and possibly correct errors that may occur in the Physical layer Physical addressing, topologies and flow control

➢ Physical - 1  Protocols describe the mechanical, electrical, functional, and procedural means to activate, maintain and de-activate physical-connections for bit transmission to and from a network device • Voltage control  TCP/IP Model ➢ Application – 4 ➢ Transport – 3 ➢ Internet – 2 ➢ Network Access – 1