Basics of Networking and TCP/IP

1. Basics of Networking and TCP/IP

2. Old Computing Model predominant in 1960-1985 utilizes a large mainframe computer connected to a set of terminals (host-terminal setup). low speed link TC:Terminal Controller Mainframe (IBM 360) shared high speed link Terminals (IBM 3270)

3. Characteristics of the Old model • All processing is done at the host • A terminal is simply an I/O device (Input: via keyboard; output: via screen) • The host computer is a bottleneck and a central point of failure

4. New Computing Model 1985-present; utilizes desktop computers connected by a Local Area Network (LAN). Network A desktop computers Router Network B

5. Definition of a Computer Network • A computer network is a collection of autonomous (independent of each other) computers that are connected in such a way that data can be exchanged between any two computers. • an internetwork (or simply internet) is a collection of networks that are connected by routers. A router encompasses only the lowest three layers (physical layer, data link layer and network layer). • The Internet (with capital I) is a specific world wide internetwork that is managed by Internic and uses TCP/IP protocols.

6. Benefits of Computer Networks • Resource Sharing. Resources include hardware devices such disk storage and printers and software (data + programs). • Higher Reliability. This is obtained by duplicating devices and replicating data. • Incremental and cheaper growth. • Distributed processing. This comes about in the form of client/server applications (e.g. web browser/web server) and clustering. • Promote communication among network users through resource sharing and e-mail.

7. Design Goals of Networking have two computers exchange data but account for the following. • The two computers may be located in the same room or separated by thousands of miles. • The two computers may have different manufacturers and different operating systems. • The two computers may use different byte ordering for multi-byte data and may have different character encoding for text. • Design must allow for continuing use of existing technology while embracing new technology

8. ISO Protocol Layering • International Standards Organization (ISO) model was developed, based on its recommendation, in the form of seven layers. • The principles of layering: • Each layer should represent a different abstraction level, wherever needed • Each layer should define well defined functions • Information flow between layers should be minimum • Number of layers should be optimum, not too many not too few

9. ISO 7-Layer OSI Model Computer A Computer B Application Layer Application Layer Presentation Layer Presentation Layer Session Layer Session Layer Transport Layer Transport Layer Packet Network Layer Network Layer Data Link Layer Frame Data Link Layer Physical Layer Physical Layer Signal (Bits) Protocol Interface Data flow from A (Sender) to B (Receiver)

10. Standards and Protocols • A standard is an agreed-upon specification for some type of product or service. • Examples: A4 paper size, 2-feet florescent light, PC serial (RS232C) and parallel port interfaces • A protocol is an agreement (contract) between two (or more) parties to conduct a joint task. • Examples: two persons handshaking, passing through traffic light.

11. Network Communication Protocol A network communication protocol(at the application or lower layers) specifies the format and meaning of messages that are exchanged between two peer (at the same layer) entities. Roughly a network protocol specifies the control header and its interpretation. Examples: App. Layer Protocol: HTTP used between web browser and server Network Layer Protocol: Internet Protocol (IP) Data Link Layer Protocol: Point-to-Point Protocol (PPP) - used between two routers connected by phone lines

12. Layering Principle • Layered Protocols are designed so that layer n at the destination receives exactly the same object sent by the layer n at the source. • Protocols are standards that specify how data is represented when being transferred from one machine to another. • Protocols specify how the transfer occurs, how errors are detected, and how acknowledgements are passed.

13. Layers use Control Headers Computer A Computer B Application Layer Application Layer Presentation Layer Presentation Layer Session Layer Session Layer Transport Layer Transport Layer Network Layer Network Layer Data Link Layer Data Link Layer Physical Layer Physical Layer Signal (Bits) Data flow from A (Sender) to B (Receiver)

14. Physical Layer • Interfaces with the physical medium. • Specifies bit to signal encoding such as voltage levels and duration for 0/1. • Transmits a stream of bits without boundaries.

15. Data Link Layer • Transmits frames - a frame is a delimited (has a start and end markers) block of bits. • The frame has a checksum to allow error detection. • Control access to the channel (medium), especially over a broadcast (shared) channel. • Implements flow control.

16. Network Layer • Routing of packet over an internetwork. The network layer examines the network destination address of an incoming packet and re-encapsulates the packet in a new frame that it sends down again through the data link layer of an (outgoing) link. • Provides software abstraction independent of communication hardware (for example, while data link layer addresses are permanently fixed in hardware, network layer address are dynamically configured through software).

17. TCP/IP 5-Layer Model Application Transport Network Data Link Physical Application Transport Network Data Link Physical TCP IP Network Data Link Physical Computer A Computer B IP Router The transport layer is an end-to-end layer. This means that the corresponding stations (hosts) are the actual source and actual destination of the application data.

18. What is TCP/IP? • TCP/IP: Transmission Control Protocol / Internet Protocol • TCP/IP is the name of a protocol suite (protocol stack). • Applications interface with TCP layer to communicate with other peer applications

19. History of TCP/IP • TCP/IP is the brain child of ARPAnet which was developed by the USA DoD (Department of Defense) supported project (Advanced Research Project Agency). • TCP/IP was first defined in 1974, meant to be used for geographically distant communication. It has evolved with many improvements since then. • The University of Berkeley has incorporated TCP/IP in their BSD Unix. Since than it has been a very good marriage between the two.

20. The Internet • The Internet is a network of networks. • Today, the Internet connects tens of thousands of networks and millions of computer • 1990: 3000 networks ( 200,000 users.) • 1992: 992,000 hosts. • Present: millions of networks, computers, and users.

21. Why TCP/IP is Popular? • Popularity of TCP/IP • simpler than ISO-OSI model • provides an elegant solution to world wide data communication. • Open Protocol Standards, freely available, and independent from any hardware platform.

22. TCP/IP Features • Independence from specific network hardware • Allows TCP/IP to integrate many types of networks (Ethernet, Token Ring, X.25, dial-up) • TCP/IP is used in both LANs and WANs • Common addressing scheme • every host on the Internet has a unique address • Standardized high-level protocols for world wide available network services

23. IP Protocol • The primary network layer protocol of TCP/IP stack • Provides basic packet delivery service on which TCP/IP networks are built • Main functions • Defines datagram (packet) format, basic unit of transmission in the Internet • Provides Internet addressing • Routing of datagrams

24. TCP Protocol • TCP facilitates process-to-process (i.e. application to application) communication. Any application that needs to send and receive via TCP is assigned an address (i.e. a TCP-port number). • Whereas IP is limited to providing a connectionless service (packets may be dropped at will), TCP provides a connection-oriented service (virtual circuit).

25. IP-Layer Operation B Y X C A X Y Application TCP IP Data Link Physical Application TCP IP Data Link Physical TCP is an end-to-end layer IP Data Link Physical IP Data Link Physical IP Data Link Physical A B C

26. Application Layer • Includes all software programs that use the Transport Layer protocols to deliver data messages • Examples of protocols: • Telnet: Network Terminal Protocol • FTP: File Transfer Protocol • SMTP: Simple Mail Transfer Protocol • DNS: Domain Name Service • WWW: World Wide Web

27. Layer Decapsulation T e l n e t F T P S M T P H T T P Port Number, Destination (Source) Port identifies receiving (sending) application Type, SAP, or other control info MAC or WAN addressing Applications Transport Network Data Link Physical 23 21 25 80 TCP Segments IP Packets Frames Bits

28. LAN Hardware: Ethernet • The most widely used LAN hardware. • Developed originally in 1980 as 10 Mbps (10 million bits per second) by Digital, Intel and Xerox • Today, the mainstream Ethernet is known as Fast Ethernet (100 Mbps) which uses HUB and Category 5 UTP wiring • Also Gigabit Ethernet (1000 Mbps) is available but limited in distance.

29. Ethernet (Cont.) • Ethernet encompasses Data-Link and Physical Layers only • The Ethernet card is responsible for frame generation and reception • An Ethernet frame encapsulates a network layer packet

30. Fast Ethernet Layout and Components Fast Ethernet HUB Category 5 UTP PC1 PC2 PCn • An ordinary HUB is an active physical-layer device acting as signal repeater • Hubs can be cascaded • Each PC is equipped with Fast Ethernet Card (50 SR) • Hub Cost is proportional to the # of ports (25 SR per port)

31. Break