07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing The OSI Model and TCP/IP Slide 1

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 Format  Networking Standards  Introduction to root concepts  Layered models of processes  Why do we need protocols?  The seven layers Slide 2

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 Standards  Standards are documented agreements containing technical specifications or other precise criteria that stipulate how a particular product or service should be designed or performed Slide 3

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 Networking Standards Organizations  American National Standards Institute (ANSI)  Electronics Industry Alliance (EIA)  Institute of Electrical and Electronic Engineers (IEEE)  International Organization for Standardization (ISO)  International Telecommunication Union (ITU) Slide 4

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IEEE Networking Specifications Slide 5

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 Protocols  The Open Systems Interconnect (OSI) model is not a protocol  It is a conceptual system that most real protocols are based upon  A protocol is an agreed set of rules, an interface between two systems, “a mutually agreed treaty or diplomatic document” –E. g. Traffic lights at a junction control the flow of vehicles on a road system –This is a simple, world-wide protocol Although in France they do not use amber between red and green! Slide 6

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 OSI model – Why bother?  Real-world network protocols don’t implement the OSI seven layer protocol stack model  But nearly all network protocols are based on a simplified layered model  The layered model helps us think about the many processes involved in communicating over networks  A good model provides support for thinking  “First, solve the problem. Then implement a solution.” Slide 7

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 Why a “Layered Model”?  Answer by providing an analogy - The “Big Data Corporation” wants 10,000 mouse mats showing its new corporate logo –The CEO makes the decision, the budget is agreed, the requirements set and the order processed –The order is then transferred to a manufacturer –The order is processed, then sent to the design team –The design is then created and checked  Note that the process of handling the order goes through many layers within two businesses Slide 8

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 A Fine-Grained Breakdown  This is a multilayer model  It shows two different “protocol stacks”  The courier service is analogous to network cabling (in a wired system) President/CEO Directors Quality Control Marketing Clerical Mail Room Courier or Postal Service Clerical Design Manufacture Slide 9

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing Communication Between Two Systems Slide 10

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 Version2 10/07/09Slide 11 ISO OSI Reference Model Slide 11

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing Data Transformation Slide 12

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 The Seven Layer Model  Nmemonics – –Please do not throw sausage pizza away! –All PC’s seem to network data poorly  At the top, the Application layer provides OS services for application software  At the bottom, the Physical layer deals with wiring issues Application Presentation Session Transport Network Data link Physical Slide 13

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 The Application Layer  Provides interface to the software enabling programs to use network devices  Definition of the way that network services use the network  Defines how many services work, including –File sharing, Network Printing, Message Services etc  E.g Application Program Interface (API) –Routine that allows a program to interact with the operating system –Belongs to the Application layer of OSI Model  Microsoft Message Queuing (MSMQ) –Used in API network environment –Stores messages sent between nodes in queues –Forwards them to their destination Slide 14

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 The Presentation Layer  This layer “presents” data, which is to say it does some pre-processing, such as –data compression –encryption –character set conversion  Translates between the application and the network Slide 15

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 The Session Layer  A communications management layer  Defines how two computers synchronise, maintain and close a communication session  This includes such things as –security authentication –acknowledgement of data transfer –establishing and relinquishing a connection identity Slide 16

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 The Transport Layer  Data packet management  Ensures that chunks of data have been transferred without error – does lots of error and flow control  Takes data and packs it into chunks or chops it up into chunks suitable for transmission  Takes chunks and unpacks them or combines them into data streams Slide 17

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 The Network Layer  This is Internet Protocol address layer for path selection around the network  Routing of packets uses IP addresses  Network Layer Address –Resides at Network level of OSI Model –Follows hierarchical addressing scheme –Can be assigned through operating system software Slide 18

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 The Data Link Layer  Decodes packets into what are called frames which contain –Physical source and destination addressing –data validity / error checking  The network technology being used will influence how this layer works e.g. Ethernet, token ring …..  To accommodate shared access for multiple network nodes, the IEEE expanded the OSI Model by separating the Data Link layer into two sublayers –Logical Link Control (LLC) sublayer –Media Access Control (MAC) sublayer Slide 19

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing Subdivided Data Link Layer LLC and MAC sublayers Slide 20

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 Data Link Layer Sublayers  LLC –Upper sublayer –Provides common interface –Supplies reliability and flow control services  MAC – (Media Access Control) –Lower sublayer –Appends the physical address of the destination computer onto the frame –Number uniquely defining a network node –Manufacturer-hard codes the address Block ID Device ID Slide 21

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 The Physical Layer  This is the physical networking media layer which includes the cabling technology  Defines the transmission technique and the hardware definitions (connectors and so on)  Networking may take place over copper cables, optical fibres, infra-red radiation, radio waves… and this variation should be transparent to the user Slide 22

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing OSI Model Summary Slide 23

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 OSI Model TCP/IP Transmission Control Protocol/Internet Protocol (TCP/IP) Suite Slide 24 Application Layer Transport Layer Network Layer Physical and Data Link Layers

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 Addressing and Protocols SMTP, FTP, HTTP, DNS, SNMP, Telnet,… SCTP, TCP, UDP ICMP, IGMP, ARP, RARP Port Address Logical Address Physical Address Application Layer Transport Layer Network Layer Physical and Data Link Layers

07/10/09 M.Chai; E.R.Edwards 07/10/09 Staffordshire University School of Computing IADCN - Week 2 Slide 26 Conclusion We have discussed:-  Organizations that set standards for networking  Standard “root concepts” of networking  Layered models of processes and layers in our conceptual model of networking  Why protocols are required for interoperability  Details of the seven layers of the OSI model