Computer Networks

A History Lesson of Networking 1969 – ARPANET, first packet switched network consist of UCLA, Stanford, UC Santa Barbara and Utah University 1971 – first email program 1974 – TCP/IP 1980’s – Local Area Networks (LANs) 1984 – OSI Layer 1990’s – WWW / Internetworking Introduction Computer Network

Introduction Computer Network Why Networking? Efficiency and Productivity Reliability Distributed Systems Introduction Computer Network

Introduction Computer Network What Applications? Client/Server Business Applications Electronic Messaging Information Retrieval Introduction Computer Network

Network Classification by Area Wide Area Network Metropolitan Area Network Local Area Network Personal Area Network Ad Hoc Network Introduction Computer Network

Introduction Computer Network Protocols Driving Force: need for different proprietary networking system to communicate Protocol: set of rules for acceptable behaviour (how communication should take place in) Specifically: the set of rules used by communicating parties for that communication to be successful Suite of protocols cover all required behaviour Mostly implemented in Software Complexity demands that protocols are ‘layered’ Introduction Computer Network

Advantages of Layering Protocols Dividing complex network operation into more manageable layers Defining the standard interface for the “plug-and-play” multi-vendor integration Facilitate Modular Engineering Simplifies Teaching and Learning Introduction Computer Network

ISO/OSI Reference Model ISO in 1984 Open Systems Interconnect (OSI) A design guideline for network layering Abstract layers provide different services Defines 7 layers of service Each layer provides service to adjacent layers Each layer communicates with same layer in remote machine… Introduction Computer Network

Introduction Computer Network OSI Reference Model Physical Layer Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer Physical Layer Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer Introduction Computer Network

Introduction Computer Network Layer 1 - Physical Physical Layer: Move bits between devices Specifies voltage, wire speed, and pin out cables Passes data up to data link layer (and receives from data link layer) Introduction Computer Network

Introduction Computer Network Layer 2 – Data Link Data Link Layer: Performs framing of bits, flow and error control but not correction Responsible for transmission of frames across the physical link Provide access to media using MAC address Passes data between physical and network layers Introduction Computer Network

Introduction Computer Network The Institute of Electrical and Electronics Engineers (IEEE) has subdivided the data link layer into two sublayers: Logical Link Control (LLC) and Media Access Control (MAC). Introduction Computer Network

Introduction Computer Network The Logical Link Control (LLC) 802.2 sublayer is responsible for identifying Network Layer protocols and then encapsulating them. An LLC header tell the Data Link Layer what to do with the packet if a frame is coming. Also provide flow control and sequencing of control bits The Media Access Control (MAC) sublayer of the data link layer manages protocol access (logical topologies) to the physical network medium. The IEEE MAC specification defines MAC addresses, which enable multiple devices to uniquely identify one another at the data link layer. IEEE 802.3 dan 802.5 Introduction Computer Network

Introduction Computer Network Layer 3 - Network Network Layer: Passes data between data link and transport layers Responsible for routing data across a network, from source to destination using network-wide addressing Pass data between (separate) subnetworks Hides network topology from higher layers Introduction Computer Network

Introduction Computer Network Layer 4 - Transport Transport Layer: Passes data between network and session layers Provides reliable end-to-end delivery of data, including flow and error control of packets Fragmentation of large messages Quality of Service (QoS), usually with layer 3 Last of the pure network layers Introduction Computer Network

Introduction Computer Network Layer 5 - Session Session Layer: Passes data between presentation and transport layers Responsible for managing network sessions (series of related data streams) Provides synchronization and scheduling Introduction Computer Network

Introduction Computer Network Layer 6 - Presentation Presentation Layer: Passes data between application and session layers Provides translation services for data to ensure applications are using compatible formats E.g. converting from ASCII to EBCDIC text representations Introduction Computer Network

Introduction Computer Network Layer 7 - Application Application Layer: Passes data to presentation layer (and receives from presentation layer) … to and from the user! Communicates with remote applications Determines the user capability within the network Introduction Computer Network

Introduction Computer Network Data Encapsulation Introduction Computer Network

Introduction Computer Network Data Encapsulation Introduction Computer Network

OSI Layer vs. TCP/IP Layer Introduction Computer Network

Introduction Computer Network FTP – File Transfer Protocol HTTP – Hypertext Transfer Protocol WAP – Wireless Application Protocol SMTP – Simple Mail Transfer Protocol 5-7 TCP UDP 4 3 IP 1-2 e.g. IEEE 802.x Introduction Computer Network

Some Protocols in TCP/IP Suite Introduction Computer Network

Introduction Computer Network Quiz Protocols What are they? Why do we layer protocols? ISO/OSI – 7 layer reference model How does the OSI abstract services? How does data pass between layers (local/remote)? How does Internet stack relate to OSI? Introduction Computer Network