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- 1. Computer Networking Yehuda Afek( afekatcs.tau.ac.il ) Adopted the slides from Yishay Mansour Teaching Assistant:Yahav Nussbaum
2. Course Information
- Lectures:Sunday4 7 Schreiber 006
- Exercises:Wednesday 11 12,12 1Orenstein 103
- An Engineering Approach to Computer Networking / Keshav
- Computer Networks / Tanenbaum
- Data Networks / Bertsekas and Gallager
- A Top-down Approach to Computer Networking / Kurouse-Ross
Books: 3. Practical Information Homework assignment: MandatoryBoth theoretical and programmingGrades: Final Exam:60%theory exercises:20% Programming exercises:20% 4. Motivation
- Todays economy
- manufacturing, distributing, and retailinggoods
- but also creating and disseminatinginformation
- film making.
- part of the information economy
- Future economy is likely to be dominated by information!
- Arepresentationof knowledge
- CDs & DVDs
- Can be represented in two ways
- analog (atoms)
- digital (bits)
- the Digital Revolution
- convert information as atoms to information as bits
- use networks to move bits around instead of atoms
6. The Challenges
- represent all types of information as bits.
- move the bits
- Inlarge quantities ,
- cheaply ,
- withquality of service,
7. Todays Networks are complex!
- links of various media
- hardware, software
Tomorrows will be even more! 8. Internet Physical Infrastructure
- Residentiala ccess
- Campus access, e.g.,
- The Internet is a network of networks
- Each individually administrated network is called an Autonomous System (AS)
BackboneISP ISP ISP 9. This courses Challenge
- To discuss this complexity in anorganizedway, that will make todays computer networks (and their limitations) more comprehensive.
- identification, and understanding relationship of complex systems pieces.
- Problems that are beyond a specific technology
10. Early communications systems
- I.e. telephone
- point-to-point links
- directly connect together the users wishing to communicate
- use dedicated communication circuit
- if distance between users increases beyond the length of the cable, the connection is formed by a number of sections connected end-to-end in series.
11. Data Networks
- set of interconnected nodes exchange information
- sharing of the transmission circuits= "switching".
- many links allow more than one path between every 2 nodes.
- network must select an appropriate path for each required connection.
12. 13. Qwest backbonehttp://www.qwest.com/largebusiness/enterprisesolutions/networkMaps/preloader.swf 14. Networking Issues - Telephone
- Addressing- identify the end user
- phone number 1-201-222-2673 = country code + city code + exchange + number
- Routing- How to get from source to destination.
- Telephone circuit switching: Based on the phone number.
- Information Units - How is information sent
- telephone Samples @ Fixed sampling rate. not self descriptive! have to knowwhereandwhena sample came
15. Networking Issues - Internet
- Addressing -identify the end user
- IP addresses 126.96.36.199, Refer to ahost interface= network number + host number
- Routing-How to get from source to destination
- Packet switching: move packets (chunks) of data among routers from source to destination independently.
- Information Units -How is information sent.
- Self-descriptive data: packet = data + metadata (header).
- Telephone networks support a single, end-to-end quality of service but is expensive to boot
Internet supports no quality of service but is flexible and cheap Future networks will have to support a wide range of service qualities at a reasonable cost 17. History 1961-1972: Early packet-switching principles
- 1961:Kleinrock - queuing theory shows effectiveness of packet-switching
- 1964:Baran - packet-switching in military networks
- 1967:ARPAnet conceived by Advanced Research Projects Agency
- 1969:first ARPAnet node operational
- 1972: ARPAnet demonstrated publicly
- NCP (Network Control Protocol) first host-host protocol
- first e-mail program
- ARPAnet has 15 nodes
18. History 1972-1980: Internetworking, new and proprietary nets
- 1970:ALOHAnet satellite network in Hawaii
- 1973:Metcalfes PhD thesis proposes Ethernet
- 1974:Cerf and Kahn - architecture for interconnecting networks
- late70s:proprietary architectures: DECnet, SNA, XNA
- late 70s:switching fixed length packets (ATM precursor)
- 1979:ARPAnet has 200 nodes
19. Cerf and Kahns internetworking principles:
- minimalism, autonomy - no internal changes required to interconnect networks
- best effort service model
- stateless routers
- decentralized control
Defines todays Internet architecture 20. History 1980-1990: new protocols,proliferation of networks
- 1983:deployment of TCP/IP
- 1982:SMTP e-mail protocol defined
- 1983:DNS defined for name-to-IP-address translation
- 1985:FTP protocol defined
- 1988:TCP congestion control
- new national networks: CSnet, BITnet, NSFnet, Minitel
- 100,000 hosts connected to confederation of networks
21. History 1990 - : commercialization and WWW
- early 1990s: ARPAnet decomissioned
- 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995)
- early 1990s:WWW
- hypertext [Bush 1945, Nelson 1960s]
- HTML, http: Berners-Lee
- 1994: Mosaic, later Netscape
- late 1990s: commercializationof WWW
22. Demand and Supply
- Huge growth in users
- The introduction of the web
- Faster home access
- Better user experience.
- Significant portion of telecommunication.
- New evolving industries
- Although, sometimes temporary setbacks
23. Internet: Users 24. Users around the Globe (2002) 25. Users around the Globe (2007) http://www.internetworldstats.com/stats.htm 26. Penetration around the Globe (2008) http://www.internetworldstats.com/stats.htm 27. Users around the Globe (2002/5/8) 28. Technology: Modem speed 29. Todaysoptions
- Modem: 56 K
- ISDN: 64K 128K
- Frame Relay: 56K ++
- Today High Speed Connections
- Cable, ADSL, Satellite.
- All are available at 5Mb (2005)
OBSOLETE 30. Coming soon(1999) 31. Today (2005) 32. Why do we need Standards
- Networks (and other media) support communication between different entities
- Need agreement to ensure correct, efficientand meaningful communication
33. Various Organizations Issue Standards
- IEEE ( Institute for Electrical and Electronic Engineers )
- IETF ( Internet Engineering Task Force )