Service Primitives Six service primitives that provide a simple connection-oriented service 4/23/2017 www.noteshit.com
A simple client-server interaction using acknowledged datagrams. Service Primitives A simple client-server interaction using acknowledged datagrams. 4/23/2017 www.noteshit.com
OSI Model 4/23/2017 www.noteshit.com
2-1 LAYERED TASKS A network model is a layered architecture Task broken into subtasks Implemented separately in layers in stack Functions need in both systems Peer layers communicate Protocol: A set of rules that governs data communication It represents an agreement between the communicating devices 4/23/2017 www.noteshit.com
Layered Architecture A layered model Each layer performs a subset of the required communication functions Each layer relies on the next lower layer to perform more primitive functions Each layer provides services to the next higher layer. Each layer provides services to the next higher layer Changes in one layer should not require changes in other layers The processes on each machine at a given layer are called peer-to-peer process 4/23/2017 www.noteshit.com
Tasks involved in sending a letter 4/23/2017 www.noteshit.com
2-2 THE OSI MODEL Established in 1947, the International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards. An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. It was first introduced in the late 1970s. 4/23/2017 www.noteshit.com
ISO is the organization. OSI is the model. Note ISO is the organization. OSI is the model. 4/23/2017 www.noteshit.com
Seven layers of the OSI model 4/23/2017 www.noteshit.com
The interaction between layers in the OSI model 4/23/2017 www.noteshit.com
An exchange using the OSI model 4/23/2017 www.noteshit.com
Note The physical layer is responsible for movements of individual bits from one hop (node) to the next. 4/23/2017 www.noteshit.com
Function of Physical layer Physical characteristics of interfaces and media Representation of bits Data rate Synchronization of bits Line configuration (point-to-point or multipoint) Physical topology (mesh, star, ring or bus) Transmission mode ( simplex, half-duplex or duplex 4/23/2017 www.noteshit.com
Physical layer 4/23/2017 www.noteshit.com
Note The data link layer is responsible for moving frames from one hop (node) to the next. 4/23/2017 www.noteshit.com
Data link layer 4/23/2017 www.noteshit.com
Hop-to-hop delivery 4/23/2017 www.noteshit.com
Function of data link layer Framing Physical addressing Flow control Error control Access control 4/23/2017 www.noteshit.com
the source host to the destination host. Note The network layer is responsible for the delivery of individual packets from the source host to the destination host. 4/23/2017 www.noteshit.com
Network layer 4/23/2017 www.noteshit.com
Source-to-destination delivery 4/23/2017 www.noteshit.com
Function of network layer Source-to-destination delivery Responsible from the delivery of packets from the original source to the final destination Functions Logical addressing routing 4/23/2017 www.noteshit.com
Transport layer 4/23/2017 www.noteshit.com
Note The transport layer is responsible for the delivery of a message from one process to another. 4/23/2017 www.noteshit.com
Function of transport layer Port addressing Segmentation and reassembly Connection control ( Connection-oriented or connection-less) Flow control Error control 4/23/2017 www.noteshit.com
Reliable process-to-process delivery of a message 4/23/2017 www.noteshit.com
Session layer 4/23/2017 www.noteshit.com
Note The session layer is responsible for dialog control and synchronization. 4/23/2017 www.noteshit.com
Function of session layer It establishes, maintains and synchronize the interaction between communicating system Dialog control Synchronization (checkpoints) 4/23/2017 www.noteshit.com
Presentation layer 4/23/2017 www.noteshit.com
Note The presentation layer is responsible for translation, compression, and encryption. 4/23/2017 www.noteshit.com
Function of presentation layer Concerned with the syntax and semantics of the information exchanged between two system Translation ( EBCDIC-coded text file ASCII-coded file) Encryption and Decryption Compression 4/23/2017 www.noteshit.com
Application layer 4/23/2017 www.noteshit.com
Note The application layer is responsible for providing services to the user. 4/23/2017 www.noteshit.com
Function of application layer Network virtual terminal (Remote log-in) File transfer and access Mail services Directory services (Distributed Database) Accessing the World Wide Web 4/23/2017 www.noteshit.com
Summary of layers 4/23/2017 www.noteshit.com
OSI layer-Summary 4/23/2017 www.noteshit.com