Communication Network Protocols ----Krishna Priyanka Chebrolu

~ Given a Network Architecture, some rules and standards must be set up to govern the communication i.e.; communication protocols. ~ Ensures secure, fast and error-free data delivery.

Division of protocols: ~ Connection-oriented and connectionless ~ Circuit-switching and Packet-Switching ~ Virtual circuit and datagram

Circuit and Packet Switching

Protocol Hierarchies: ~ Most networks are organized as stack of layers, each one built upon the one below it. ~ Number of layers, Name, Content and Function of each layer varies from network to network.

Reference Models: Reference Models: 1. OSI Reference Model 2. TCP/IP Reference Model

OSI Reference Model The OSI model has seven layers. The principles that were applied to arrive at the seven layers can be briefly summarized as follows: 1. A layer should be created where a different abstraction is needed. 2. Each layer should perform a well-defined function. 3. The function of each layer should be chosen with an eye toward defining internationally standardized protocols. 4. The layer boundaries should be chosen to minimize the information flow across the interfaces. 5. The number of layers should be large enough that distinct functions need not be thrown together in the same layer out of necessity and small enough that the architecture does not become unwieldy.

The Physical Layer ~ The physical layer is concerned with transmitting of raw bits over a communication channel.

Definition of Hardware Specifications Encoding and Signaling Data Transmission and Reception Topology and Physical Network Design

The data link layer ~ Link Layer ~ DLL = Logical Link Layer + Media Access Control

Data Framing Addressing Error Detection and handling

The network layer is the lowest one in the OSI model that is concerned with actually getting data from one computer to another even if it is on a remote network; in contrast, the data link layer only deals with devices that are local to each other. The Network Layer The network layer is the lowest one in the OSI model that is concerned with actually getting data from one computer to another even if it is on a remote network; in contrast, the data link layer only deals with devices that are local to each other.

Logical Addressing Routing Datagram Encapsulation Fragmentation and Reassembly Error handling and Diagnostics

The Transport Layer ~Accepts data from above and splits into smaller units ~ Determines what type of service to provide to the session layer.

~ Primary goal is create reliable end to end communication. ~ The OSI protocol suite implements two types of services at the transport layer: connection-oriented transport service and connectionless transport service.

The Session Layer Session service provides four basic services to SS-users. Establishes and terminates connections between SS- users and synchronizes the data exchange between them. Performs various negotiations for the use of session layer tokens, which the SS-user must possess to begin communicating. Inserts synchronization points in transmitted data that allow the session to be recovered in the event of errors or interruptions. Enables SS-users to interrupt a session and resume it later at a specific point.

The Presentation Layer the presentation layer is charged with taking care of any issues that might arise where data sent from one system needs to be viewed in a different way by the other system. It also takes care of any special processing that must be done to data from the time an application tries to send it until the time it is sent over the network.

Translation Compression Encryption

The Application Layer The application layer contains a variety of protocols that are commonly needed by users. One widely-used application protocol is HTTP (HyperText Transfer Protocol), which is the basis for the World Wide Web. When a browser wants a Web page, it sends the name of the page it wants to the server using HTTP. The server then sends the page back. Other application protocols are used for file transfer, electronic mail, and network news.

TCP/IP Reference Model

The host-network layer The Internet Layer The Transport Layer The Application Layer

Comparison OSI vs TCP/IP

References Andrew S. Tenenbaum,Computer Networks,4 th edition. Pearson Education, ectureandProtocolSuite.htm Jim Kurose, Keith Ross, Computer Networking: A Top Down Approach Featuring the Internet, 3rd edition. Addison-Wesley, July ectureandProtocolSuite.htm