1. Part E: Standards Layered Standards Architectures TCP, IP, and TCP/IP Other Architectures

2. 2 Standards n Standards are rules of operation that most or all vendors follow n Open standards are created and owned by public standards organizations – No single vendor controls these standards

3. 3 Standards Are Layered n For Internet Access to a Webserver, standards are set at five layers – Application – Transport – Internet – Data Link – Physical n Together, these standards provide all that is needed for application programs on different hosts on different networks to work together

4. 4 Internet Standards n Application Layer Standards – Standards at the application layer specify how two application programs communicate – For example, browser on user PC and webserver application program on webserver Browser Webserver Application Program

5. 5 Internet Standards n HTTP (HyperText Transfer Protocol) – World Wide Web standard for browser-webserver application program exchanges – Other applications (E-mail, etc.) have different application standards Browser Webserver Application Program HTTP

6. 6 Internet Standards n Transport Layer Protocols – Standards at the transport layer specify how two host computers will work together, even if they are of different platform types (PCs, workstations, mainframes, and so forth) – For instance, PC and non-PC webserver PC PC or Other Computer

7. 7 Internet Standards n The Transport Layer Gives Platform Independence – Two computers do not have to be of the same platform type n A PC user does not even know what kind of computer the webserver is PC ?

8. 8 Internet Standards n HTTP Requires the Use of the TCP Transport Standard – Transmission Control Protocol – TCP messages are called TCP segments TCP

9. 9 Internet Standards n Internet Layer Protocols – Standards at the internet layer specify how hosts and routers will act to route packets end to end, from the source host to the destination host, across many single networks (subnets) connected by routers Route Single Network (Subnet) Host

10. 10 Internet Standards n The Internet Protocol (IP) is the Main Protocol for Routing Packets Across the Internet – The IP in “TCP/IP” – IP messages are called packets – All internet layer messages are called packets IP Packet

11. 11 Internet Standards n Subnets – Single networks (LANs, WANs, point-to-point link) on the Internet – A packet will pass through several subnets along its route across the Internet Subnet

12. 12 Internet Standards n Different Subnets Can Have Different Subnet Protocols – IP at the internet layer routes across different protocols at the subnet layer Point-to-Point Subnet Protocol 1 WAN Subnet Protocol 2 LAN Subnet Protocol 3

13. 13 Subnets Standards n Subnets are Single Networks on the Internet n Subnet Standards Divided into Two Layers – Physical layer standards govern the transmission of individual bits within a subnet – Data Link layer standards govern the transmission of messages within a subnet n Organize individual bits into structured messages

14. 14 Internet Standards n Data Link Layer Standards – Standards at the data link layer specify how to transmit messages within a single network – Messages at the data link layer are called frames 10010001001 Data Link Frame

15. 15 Internet Standards n Data Link Layer Standards – For accessing the Internet from home... – Point-to-Point Protocol (PPP) dominates – Only used between home and ISP! – Other subnets connecting routers are likely to use different subnet protocols! ISP PPP ?

16. 16 Internet Standards n Physical Layer Standards – While the data link layer is concerned with the organization and transmission of organized messages, standards at the physical layer specify how to transmit single bits one at a time – Work bit by bit; no frame organization

17. 17 Internet Standards n Physical Layer Standards in Internet Access from Home – Telephone jack (RJ11) – Telephone wire – Serial port connection to external modem – Modem Serial Port External Modem Telephone Wire Wall Jack

18. 18 Internet Standards n Subnet Versus Internet Layer Standards – Internet layer provides routing across multiple subnets – Subnet layer standards (data link and physical) provide for transmission within a single network Internet Layer Subnet Layer

19. 19 Internet Standards n Analogy for Subnet versus Internet – Take a vacation – Route from beginning to end (like internet layer) – For different parts, may travel by car, airplane, or boat (like subnet layer) Internet Layer Subnet Layer

20. 20 Standards Organizations and Architectures n Architecture is a Design for Standards Creation – Specifies what types of standards are needed (application, transport, etc.) – After architecture is designed, individual standards of each type are created – Analogy: architecture of house specifies what rooms will be needed and their relationships. – After architecture is settled, individual rooms are designed

21. 21 Standards Organizations and Architectures n TCP/IP Standards – Created by the Internet Engineering Task Force (IETF) – Named after its two most widely known standards, TCP and IP n TCP/IP is the architecture, while TCP and IP are individual standards n However, these are not its only standards, even at the transport and internet layers – IETF standards dominate in corporations at the application, transport, and internet layers n However, application, transport, and internet standards from other architectures are still used

22. 22 Standards Organizations and Architectures n OSI Standards – Reference Model of Open Systems Interconnection – Created by the International Telecommunications Union-Telecommunications Standards Sector (ITU-T) – And the International Organization for Standardization (ISO) – OSI standards dominate the data link and physical layers n Other architectures specify the use of OSI standards at these layers

23. 23 Internet Standards n 5-Layer Hybrid TCP/IP-OSI Architecture – Most widely used architecture in organizations today – Used on the Internet ApplicationTCP/IP TransportTCP/IP InternetTCP/IP Data LinkOSI PhysicalOSI

24. 24 Internet Standards n Recap: Accessing the WWW from Home App Trans Int DL Phy User PC Int DL Phy Router App Trans Int DL Phy Webserver HTTP TCP IP PPP Modem IP ? ?

25. 25 TCP/IP versus OSI n Lowest Four Layers are Comparable in Functionality TCP/IPOSI Application Presentation Session Transport InternetNetwork Data Link (use OSI)Data Link Physical (use OSI)Physical Box

26. 26 OSI Divides the Application Layer n OSI Session Layer – Sets up a connection between two application programs on different machines – Manage streams of transactions (session); if there is a break, can resume at the last roll-back point Transactions Box

27. 27 OSI Divides the Application Layer n OSI Presentation Layer – Handles presentation differences between the two machines (how data are stored and represented) – Two presentation layer processes select and use a common format for exchanging data Application Data Exchange in Common Format Box

28. 28 OSI Divides the Application Layer n OSI Application Layer – Governs application-to-application communication freed from concerns about presentation format and transaction management Box