Information Technology III

Lecture 02 - Reference Model of OSI

Open Systems Interconnection (OSI)

Each layer support the layers above it and offers services to the layers below

Each layer performs unique and specific task

A layer only has knowledge of its neighbour layers only

A layer service is independent of the implementation

Introduction to the OSI layer

Why layered model? It breaks network communication into smaller, simpler parts

It standardizes network components to allow multiple-vendor development and support

It allows different types of network hardware and software to communicate with each other

It prevents changes in one layer from affecting the other layers, so that they can develop more quickly

It breaks network communication into smaller parts to make learning it easier to understand

Protocol Reference Model of OSI

Protocol Reference Model of OSI

Difference between TCP and UDPTCP UDP

Reliability: TCP is connection-oriented protocol. When a file or message send it will get delivered unless connections fails. If connection lost, the server will request the lost part. There is no corruption while transferring a message.

Reliability: UDP is connectionless protocol. When you a send a data or message, you don't know if it'll get there, it could get lost on the way. There may be corruption while transferring a message.

Ordered: data arriving in the sending order. Ordered:  no ordered

Heavyweight: - tracking of connection Lightweight: No ordering of messages, no tracking connections, etc.

Streaming: Data is read as a "stream," There may be multiple packets per read call.

Datagrams: Packets are sent.One packet per one read call.

Examples: World Wide Web e-mail File Transfer Protocol

Examples: Domain Name System streaming media applications such as IPTV or movies, Voice over IP (VoIP)Trivial File Transfer Protocol (TFTP) online multiplayer games

Comparison with TCP/IP• presentation and session layers are not there in TCP/IP model

• The Network Access Layer in TCP/IP model combines the functions of Datalink Layer and Physical Layer

• TCP/IP provides end-to-end connectivity specifying how data should be packetized, addressed, transmitted, routed and received at the destination

What is Internet Protocol (IP)? IP ( Internet Protocol) specifies the

technical format of packets  the addressing scheme for computers

It combined with a higher-level protocol called Transmission Control Protocol (TCP), which establishes a virtual connection between a destination and a source

IPV4 - Internet protocol used to connect devices to the Internet. IPv4 uses a 32-bit address scheme

IPV6 - IPv6 (Internet Protocol Version 6) called IPng (Internet Protocol next generation) IPV6 IS 128-bit IP address

Technologies in IPV6 No more NAT (Network Address Translation) Auto-configuration No more private address collisions Better multicast routing Simpler header format Simplified, more efficient routing True quality of service (QoS), also called "flow labeling" Built-in authentication and privacy support Flexible options and extensions Easier administration