Computer Networks

Introduction Computer Network2 A History Lesson of Networking 1969 – ARPANET, first packet switched network consist of UCLA, Stanford, UC Santa Barbara and Utah University 1971 – first program 1974 – TCP/IP 1980’s – Local Area Networks (LANs) 1984 – OSI Layer 1990’s – WWW / Internetworking

Introduction Computer Network3 Why Networking? Efficiency and Productivity Reliability Distributed Systems

Introduction Computer Network4 What Applications? Client/Server Business Applications Electronic Messaging Information Retrieval

Introduction Computer Network5 Network Classification by Area Wide Area Network Metropolitan Area Network Local Area Network Personal Area Network Ad Hoc Network

Introduction Computer Network6 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 Network7 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 Network8 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 Network9 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 Network10 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 Network11 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 Network12 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 Network13 The Logical Link Control (LLC) 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 dan 802.5

Introduction Computer Network14 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 Network15 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 Network16 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 Network17 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 Network18 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 Network19 Data Encapsulation

Introduction Computer Network20 Data Encapsulation

Introduction Computer Network21 OSI Layer vs. TCP/IP Layer

Introduction Computer Network22 IP TCPUDP FTP – File Transfer Protocol HTTP – Hypertext Transfer Protocol WAP – Wireless Application Protocol SMTP – Simple Mail Transfer Protocol e.g. IEEE 802.x

Introduction Computer Network23 Some Protocols in TCP/IP Suite

Introduction Computer Network24 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?