1. TCOM 509 – Internet Protocols (TCP/IP) Lecture 01 Instructor: Dr. Li-Chuan Chen lichen@mitre.orglichen@mitre.org TA: Waqar Ishaq wishaq@gmu.edu Date: 08/25/2003 Based in part upon slides of Prof. J. Kurose (U Mass), Prof. B. Yener (Rensselaer Polytechnic Institute)

2. Topics - Tentative Concepts Overview (1 lecture) IP Protocol (2 lectures) TCP/UDP (1 lecture) Routing Protocols (1 lecture) Internet Multicasting (1/2 lecture) Application Protocols (1/2 lecture)

3. Grading Homeworks 30% Midterm 30% Final Exam 40% Grades will be curved. No late homeworks will be accepted.

4. Outline Introduction and Overview Internetworking Concept and Architectural Model

5. Internet: History U.S. Department of Defense had multiple networks. Advanced Research Projects Agency (ARPA) funded research on packet-switched networking. Late 60’s - ARPANET went on-line with point-to-point leased line interconnection. The goal was to interconnect all machines at different sites so that researchers could share data and their findings across the ARPANET. ARPA researchers designed networking software called TCP/IP Internet Protocol Suite or TCP/IP in the mid 70’s.

6. Internet: History 1983 - Defense Communications Agency (DCA) mandates all computers connected to backbone Internet use TCP/IP. 1983 - commercial implementation of TCP/IP begins. ARPA reached over 90% of university computer science department by funding UC Berkeley to integrate TCP/IP into UNIX. 1983-1993: Internet changed from a small experimental research project into the world’s largest computer network. By late 1987, estimated the growth rate had reached 15% per month. By 2000, the global Internet reached over 50 million computers in 209 countries. Both the size and the use of the Internet continued to grow much faster than anticipated.

7. Internet Host Count

8. Exponential Web Growth Source: http://wcp.oclc.org/ Number of Web Sites: 1997: 1,570,000 1998: 2,851,000 1999: 4,882,000 2000: 7,399,000 2001: 8,745,000 Source: Network Wizards

9. What are Internet Standards and RFC? All activities on the Internet are governed by the Internet standards. Who makes up these standards? How they are organized? Where to find these standards? What is RFC?

10. The Internet Architecture Board (IAB) IAB decides which protocols are a required standard of the TCP/IP suite, sets official policies, and guides the evolution of the Internet. –Internet Research Task Force (IRTF) – coordinates research activities –Internet Engineering Task Force (IETF) – short-term and medium-term engineering problems The Board IESGIRSG research groups working groups … area n … area 1 … … The IAB Organization IRTFIETF

11. What is RFC? RFCs – Request For Comments –Most protocols of the TCP/IP are specified by RFCs –Internet Engineering Steering Group (IESG) edits and approves the RFCs. RFCs publications are for the Internet community. RFCs are published by the IAB and are freely available online. Internet drafts are preliminary versions of RFC documents.

12. Internet Services Internet is a set of applications that use the underlying network to carry out communication tasks. Popular Internet application services are: –World Wide Web or Web allows users to view multimedia documents and to follow hyper links from one computer to another. –Electronic Mail or E-mail allows a user to compose and send messages to other individuals or groups on the Internet. –File Transfer application allows users to send or receive a coy of a data file. Will discuss these applications in greater detail later.

13. Internet Services Internet provides a connectionless or connection- oriented packet delivery service for transporting data across network. Data is divided (fragmented) into smaller pieces called packets. Packets may take different routes from a given source to a given destination. Connectionless –No guaranteed delivery of packets. Packets may arrive out- of-order. Connection-oriented –Reliable transmission of packets delivery. Will retransmit packet if errors (transmission error, lost packets, hardware failure).

14. The Problem Before Internet: different packet-switching networks –Proprietary communication systems: only nodes on the same network could communicate.

15. The Internetworking Problem Two nodes, A and B, communicating across a cloud of networks –How to transport packets through this heterogeneous networks? BA

16. The Internetworking Problem Problems: heterogeneous networks and systems, interoperability, and scalability Heterogeneous networks and systems –How to interconnect a large number of disparate networks ? –How to support a wide variety of applications ? Interoperability –How to interoperate between various vendors’ products? Scalability –How to support a large number of end-nodes and applications in this interconnected network (Internet)?

17. Internetworking Solution IP Gateways

18. Definitions A network is a collection of hosts and nodes (routers, switches, or gateways) interconnected by communication links. Protocols are standards which specify the procedures for passing messages, the details of message formats and describe how to handle error conditions. A gateway interconnects two disparate networks, translates protocols, and forwards packets from one to the other.

19. Outline Introduction and Overview Internetworking Concept and Architectural Model

20. Network-Level Interconnection FTP – File Transfer Protocol SMTP – Simple Mail Transfer Protocol HTTP – World Wide Web protocol Application Transmission Media Telnet Coaxial cable Optical fiber FTPSMTP Packet Radio HTTP Not scalable – Each new application has to be re-implemented for every transmission media.

21. Network-Level Interconnection Transmission Media Application Coaxial cable Optical fiber TelnetFTPSMTPHTTP Advantages –Efficient: mapping packets directly onto network media –Flexible: adding or modifying network software without the need for changing the application software. –Hides low-level details from the user. Internet Layer (IP) IP Packet Radio

22. Properties of the Internet Interconnects all computers by assigning a universal unique IP address. Universal interconnection - allows any two nodes to communicate irrespective of their network architectures, network topologies, and distance.

23. Internet Architecture Net 2 Net 1 Net 3 R1R1 R2R2 A collection of cooperative, interconnected networks by IP gateways or routers (R i ). IP routers provide interconnections among physical networks. Routers use the destination network, not the destination computer, when forwarding a packet. All networks are equal. A network can be a local area network (LAN), a wide area network (WAN), or a point-to-point link between two computers.

24. Internet Architecture – User’s View internet hosts

25. Internet Architecture hosts

26. Internetworking Protocols