2. © MMII JW Ryder CS 428 Computer Networks 1 Motivation for Internetworking Most networks are independent entities Networking is old idea Internetworking is more than 25 years old –Heterogeneous interconnect networks –Network hardware details hidden

3. © MMII JW Ryder CS 428 Computer Networks 2 Open Systems Interconnection Open System = Publicly available specifications Proprietary Communication systems = One vendor, self- serving Our network benefits from OSI standards

4. © MMII JW Ryder CS 428 Computer Networks 3 OSI Why? “More importantly, the entire technology has been designed to foster communication between machines with diverse hardware architectures, to use almost any packet switched network hardware, and to accommodate multiple computer operating systems.” Doug Comer, page 1 Would that the world were so were so facile.

5. © MMII JW Ryder CS 428 Computer Networks 4 TCP/IP Internet Advanced Research Projects Agency (ARPA) –Defense Advanced Research Projects Agency (DARPA) in mid-80’s ARPA technology defines a set of network standards that specify how computers communicate Set of conventions for interconnecting and routing At one point, all addresses were kept in a single file

6. © MMII JW Ryder CS 428 Computer Networks 5 TCP/IP Standards & conventions called Protocols TCP/IP is a blend of Transmission Control Protocol and Internet Protocol TCP/IP Internet Protocol Suite Across any set of interconnected networks

7. © MMII JW Ryder CS 428 Computer Networks 6 TCP/IP Forms base for a global internet An internet = private internets that use TCP/IP The Internet = The Global Internet Many U.S. gov’t agencies have funded the Internet development The ARPA/NSF Internet –The TCP/IP Internet –The global Internet –The Internet

8. © MMII JW Ryder CS 428 Computer Networks 7 To user, TCP/IP appears to be a set of application programs Interoperability - the ability of diverse computing systems to cooperate in solving computational problems Internet application programs demonstrate a high degree of interoperability Application Level Internet Services

9. © MMII JW Ryder CS 428 Computer Networks 8 Electronic mail File transfer Remote login Applications

10. © MMII JW Ryder CS 428 Computer Networks 9 Programmer’s view provides 2 broad services Connectionless Packet Delivery System Reliable Stream Transport Service Network Level Internet Services

11. © MMII JW Ryder CS 428 Computer Networks 10 What Distinguishes TCP/IP? Network Technology Independence –Datagram Universal Interconnection –Addresses universally recognized throughout the Internet End to End Acknowledgements –Others are just between stations (intermediate routing nodes) Application protocol standards

12. © MMII JW Ryder CS 428 Computer Networks 11 History & Scope of the Internet ARPA began internet technology in mid-70’s –Architecture & protocols taking current form ‘77-’79 (ARPANET) Point to Point leased line interconnection, radio networks, satellites Funding $$$ prevalent in ‘79, many researchers

13. © MMII JW Ryder CS 428 Computer Networks 12 ICCB Internet Control and Configuration Board ARPA formed informal committee to coordinate –Design of protocols –Architecture Met through about 1983

14. © MMII JW Ryder CS 428 Computer Networks 13 Global Internet Began around 1980 ARPA started converting machines attached to its research computers with TCP/IP ARPANET became the backbone of new Internet January 1983 Office of Secretary of Defense mandated that all computers connected to the long haul network use TCP/IP

15. © MMII JW Ryder CS 428 Computer Networks 14 ARPANET/BSD/BBN Split, 1 for research, 1 for military research Made ARPANET available to universities at low cost At time, most CS departments were using Unix –University of California’s Berkeley Software Distribution, Berkeley Unix, BSD Unix ARPA funded Bolt Beranek and Newman (BBN) to implement its TCP/IP protocols for use with Unix ARPA funded Berkeley to integrate the protocols with its software distribution Ergo, ARPA able to reach very high percentage (90%) of all university CS departments

16. © MMII JW Ryder CS 428 Computer Networks 15 BSD Unix Offered a set of networking functions that resembled Unix services used on single machines Experienced Unix users have no problems learning TCP/IP networking interfaces because they are so similar New operating system abstraction called the socket –Allows application programs to access communications protocols

17. © MMII JW Ryder CS 428 Computer Networks 16 Internet Youth 1985 - Six supercomputer centers 1986 - Expanded to funding wide area backbone called NSFNET Tied above to ARPANET NSF in 1986 provided seed money for regional networks All NSF funded networks use TCP/IP 1987 (7 years later) the Internet spanned hundreds of individual networks in the U.S. and Europe Connected nearly 20.000 computers, by late 1987 estimate was that the Internet was growing at 15% per month

18. © MMII JW Ryder CS 428 Computer Networks 17 Internet Teenager 1994 - the Internet reached over 3,000,000 computers in 61 countries Rapid expansion problems of an unanticipated scale Motivated researchers to find techniques to manage large, distributed resources Original design –Names and addresses of all computers attached to the Internet were kept in 1 file –Mid-80’s apparent central data base not right solution

19. © MMII JW Ryder CS 428 Computer Networks 18 Domain Name System Name servers answer queries about name/address pairs No single machine contains entire name base

20. © MMII JW Ryder CS 428 Computer Networks 19 Internet Architecture Board (IAB) TCP/IP internet protocol did not arise from a specific vendor or from a recognized professional society Who sets the technical standard? The IAB provides focus and coordination for –Research –Development –Guides Evolution –IAB is almost exclusively volunteers

21. © MMII JW Ryder CS 428 Computer Networks 20 IAB Activities Formed in 1983 from reorganized ICCB First 6 years, it changed from ARPA specific to autonomous organization Each member of IAB chaired a specific Internet Task Force –Approx. 10 task forces –Charters from how traffic load from an application affects the Internet to short term Internet Engineering problems

22. © MMII JW Ryder CS 428 Computer Networks 21 IAB Activities Did not manage a large budget Volunteers Members responsible for recruiting volunteers to serve on task forces –usually from research organizations of industry where TCP/IP was used Active researcher participated because –Serving on task force allowed learning about new research problems –Could have direct influence on standards

23. © MMII JW Ryder CS 428 Computer Networks 22 IAB ReOrg Summer 1989 Political and Commercial realities Researchers moved from IAB Board to subsidiary group New IAB Board with representatives from wider community

24. © MMII JW Ryder CS 428 Computer Networks 23 IAB Organization area 1area n IESGIRSG The Board IETFIRTF Research Groups Working Groups