1. -1- Georgia State UniversitySensorweb Research Laboratory CSC4220/6220 Computer Networks Dr. WenZhan Song Professor, Computer Science

2. -2- Georgia State UniversitySensorweb Research Laboratory About Me Homepage: http://sensorweb.cs.gsu.edu/~song/http://sensorweb.cs.gsu.edu/~song/ 2010 – present, Georgia State University Teaching evaluation: 4.8 (CSC 4220) 2005-2010, Washington State University - Vancouver Teaching evaluation: Average: 4.5/5 Research experience: Sensorweb for environment monitoring, smart environments and smart grid 6M+ research funding support from NSF, NASA, USGS, Boeing, including NSF CAREER award http://sensorweb.cs.gsu.edu/news.html a dream: http://www.youtube.com/watch?v=WF-RKzqNtz0 (3:49)http://www.youtube.com/watch?v=WF-RKzqNtz0 Research has been featured in MIT technology review, National Geographic, Network World, etc 2001-2005, Illinois Institute of Technology 2004 Summer, Lucent Technologies 1999-2001, Alcatel Shanghai Bell

3. -3- Georgia State UniversitySensorweb Research Laboratory Several Notes Course website: http://sensorweb.cs.gsu.edu/~song/csc4220/ http://sensorweb.cs.gsu.edu/~song/csc4220/ Announcement through emails Confirm email: have you received an email from me? Is it okay to add your email to it? Announcement and update will be sent through mailing list. You may also ask questions through mailing list. Homework submission needs a printed hard-copy, no hand-written! Programming projects Count Java/C preferences in class – either one is fine

4. -4- Georgia State UniversitySensorweb Research Laboratory What to expect Significant exposure to computer networking concepts and fundamental design principles. Coverage of Internet protocol stacks. running example: TCP/IP Details of network control algorithms. e.g. routing, congestion control, flow control,... Able to design network protocols and systems.

5. -5- Georgia State UniversitySensorweb Research Laboratory What not to expect End-user training. e.g. How to use FTP, NetWare, WWW or HTML, … Trade school stuff. e.g. How to get Novel NetWare certified, how to setup a Cisco router, how to administrate network system Detailed discussion of non-TCP/IP protocols. e.g. OSI, Appletalk,... Massively Parallel Processing e.g. large numbers of interconnected, identical processors programmed to solve problems in parallel Telecommunication networks and standards

6. -6- Georgia State UniversitySensorweb Research Laboratory Course roadmap Introduction Application Layer: WWW, FTP, email, DNS, multimedia Transport Layer: reliable end-end data transfer principles, UDP, TCP Network Layer: routing, congestion control, QoS Data Link Layer: framing, error control, flow control Medium Access Control (MAC) Layer: multiple-access, channel allocation Physical Layer: wired, wireless, satellite Other Topics: network security, social issues, hot topics, research directions

7. -7- Georgia State UniversitySensorweb Research Laboratory Get http://www.google.com/contact.html Human Conversation vs Computer Communication human conversation vs computer communication Hi Got the time? 2:00 TCP connection req TCP connection response time

8. -8- Georgia State UniversitySensorweb Research Laboratory Communication is challenging The two-army problem

9. -9- Georgia State UniversitySensorweb Research Laboratory Introduction Roadmap Physical overview of Internet Physical architecture Network Edge - Internet access technologies Network Core – Switching technologies Software overview of Internet Software architecture The OSI and TCP/IP Reference Models Internet history Network standardization body

10. -10- Georgia State UniversitySensorweb Research Laboratory Physical overview of Internet millions of connected computing devices: hosts = end systems running network apps communication links fiber, copper, radio, satellite transmission rate = bandwidth routers: forward packets (chunks of data)‏ Residential access Company network Network Core router workstation server mobile

11. -11- Georgia State UniversitySensorweb Research Laboratory Physical overview of Internet protocols control sending, receiving of msgs e.g., TCP, IP, HTTP, FTP, PPP Internet: “network of networks” loosely hierarchical public Internet versus private intranet Internet standards Called RFC (Request for comments), developed by IETF (Internet Engineering Task Force)‏ Residential access Company network Network Core router workstation server mobile

12. -12- Georgia State UniversitySensorweb Research Laboratory Metric Units metric prefixes for data rate Note: data rates – kbps (10 3 ), Mbps(10 6 ), Gbps(10 9 ) … bits per second data sizes – KB (2 10 ), MB(2 20 ), GB(2 30 ), … bytes ms(msec): millisecond µs: microsecond ns: nanosecond

13. -13- Georgia State UniversitySensorweb Research Laboratory Introduction Roadmap Physical overview of Internet Physical architecture Network Edge - Internet access technologies Residential access Company access Network Core – Switching technologies Software overview of Internet Software architecture The OSI and TCP/IP Reference Models Internet history Network standardization body

14. -14- Georgia State UniversitySensorweb Research Laboratory Residential Internet Access Phone Company Dialup ADSL Cable TV Company HFC Wireless Company WiMax

15. -15- Georgia State UniversitySensorweb Research Laboratory Residential access Phone Company Dialup via modem up to 56Kbps direct access to router (often less)‏ Can’t surf and phone at same time: can’t be “always on” ADSL: asymmetric digital subscriber line up to 1 Mbps upstream (today typically < 256 kbps)‏ up to 8 Mbps downstream (today typically < 1 Mbps)‏

16. -16- Georgia State UniversitySensorweb Research Laboratory Dialup  Local loops  Analog twisted pairs going to houses and businesses  Trunks  Digital fiber optics connecting the switching offices  Toll Office (Switching offices)‏  Where calls are moved from one trunk to another

17. -17- Georgia State UniversitySensorweb Research Laboratory ADSL: asymmetric digital subscriber line Design goal: (1) Work over exist 3 UTP twisted pair local loops. (2) Not affect customers’ existing telephone and fax machine (3) Much faster than 56kbps (4) Always on – monthly charge

18. -18- Georgia State UniversitySensorweb Research Laboratory ADSL A typical ADSL equipment configuration.

19. -19- Georgia State UniversitySensorweb Research Laboratory ADSL 256 Channel over 1.1MHz: 0 (POTS), 1-5(unused), 6-255(data channels)‏ ANSI T1.413 and ITU G.992.1: up to 8 Mbps downstream and 1 Mbps upstream. Standard service: 512 kbps downstream and 64 kbps upstream Premium service: 1 Mbps downstream and 256 kbps upstream

20. -20- Georgia State UniversitySensorweb Research Laboratory Residential access Cable TV Company HFC: hybrid fiber coax asymmetric: up to 27Mbps downstream, 9 Mbps upstream network of cable and fiber attaches homes to ISP router homes in same community share bandwidth deployment: available via cable TV companies

21. -21- Georgia State UniversitySensorweb Research Laboratory Community Antenna Television An early cable television system.

22. -22- Georgia State UniversitySensorweb Research Laboratory HFC Internet over TV Cable

23. -23- Georgia State UniversitySensorweb Research Laboratory Compare to ADSL Internet over ADSL

24. -24- Georgia State UniversitySensorweb Research Laboratory Cable vs ADSL FlexibleUsually not ISP choices 1Mbps down 256kbps up Depends on # of shared users, Up to 27Mbps/9Mbps Data rate Security Medium access Physical BetterOkay IndependentShared Twisted pairCoax ADSLCable

25. -25- Georgia State UniversitySensorweb Research Laboratory Spectrum Allocation Frequency allocation in a typical cable TV system used for Internet access

26. -26- Georgia State UniversitySensorweb Research Laboratory Signal Splitter

27. -27- Georgia State UniversitySensorweb Research Laboratory Cable Modems Typical details of the upstream and downstream channels in North America. Upstream: QPSK, slotted Aloha with binary exponential backoff Downstream: QAM–64/QAM-256, time division multiplexing

28. -28- Georgia State UniversitySensorweb Research Laboratory Residential access Wireless Company Wireless Local Loop Example: IEEE 802.16 WiMax – Verizon Wireless 400~700kbps Up to 2Mbps - according to Verizon

29. -29- Georgia State UniversitySensorweb Research Laboratory Other ways for residential access? How about other utility companies: Gas, Water, …… Electricity company  PLC (Power Line Communication)‏  BPL (Broadband over Power Line)‏ http://en.wikipedia.org/wiki/Power_line_communication

30. -30- Georgia State UniversitySensorweb Research Laboratory Introduction Roadmap Physical overview of Internet Physical architecture Network Edge - Internet access technologies Residential access Company access Network Core – Switching technologies Software overview of Internet Software architecture The OSI and TCP/IP Reference Models Internet history Network standardization body

31. -31- Georgia State UniversitySensorweb Research Laboratory Company access: local area networks company/univ local area network (LAN) connects end system to edge router Ethernet: shared or dedicated link connects end system and router 10 Mbs, 100Mbps, Gigabit Ethernet

32. -32- Georgia State UniversitySensorweb Research Laboratory Wireless access networks Shared wireless access network connects end system to router via base station aka “access point” wireless LANs: 802.11b (WiFi): 11 Mbps 802.11a, 802.11g … wider-area wireless access WiMax – talked before 3G ~ 384 kbps 4G ~ 100Mbps – 1Gbps WAP/GPRS in Europe wireless ad hoc networking Talk with each other directly inside Through a gateway to visit outside base station mobile hosts router Ad hoc networking

33. -33- Georgia State UniversitySensorweb Research Laboratory Introduction Roadmap Physical overview of Internet Physical architecture Network Edge - Internet access technologies Network Core – Switching technologies circuit switching packet switching Software overview of Internet Software architecture The OSI and TCP/IP Reference Models Internet history Network standardization body

34. -34- Georgia State UniversitySensorweb Research Laboratory The Network Core mesh of interconnected routers the fundamental question: how is data transferred through net? circuit switching: dedicated circuit per call: telephone net packet-switching: data sent thru net in discrete “chunks”

35. -35- Georgia State UniversitySensorweb Research Laboratory Network Core: Circuit Switching End-end resources reserved for “call” link bandwidth, switch capacity dedicated resources: no sharing circuit-like (guaranteed) performance call setup required

36. -36- Georgia State UniversitySensorweb Research Laboratory Network Core: Circuit Switching network resources (e.g., bandwidth) divided into “pieces” pieces allocated to calls resource piece idle if not used by owning call (no sharing)‏ dividing link bandwidth into “pieces” frequency division time division

37. -37- Georgia State UniversitySensorweb Research Laboratory Circuit Switching: FDM and TDM FDM frequency time TDM frequency time 4 users Example:

38. -38- Georgia State UniversitySensorweb Research Laboratory Numerical example How long does it take to send a file of 640,000 bits from host A to host B over a circuit- switched network? All links are 1.536 Mbps = 1536 kbps Each link uses TDM with 24 slots 500 msec to establish end-to-end circuit Solution: Each circuit transmission rate: 1.536Mbps/24 = 64kbps Time to transmit file: 640,000bits/64kbps = 10 sec Total: 10.5 sec

39. -39- Georgia State UniversitySensorweb Research Laboratory Network Core: Packet Switching Sequence of A & B packets does not have fixed pattern  statistical multiplexing. In TDM each host gets same slot in revolving TDM frame. A B C 10 Mb/s Ethernet 1.5 Mb/s D E statistical multiplexing queue of packets waiting for output link

40. -40- Georgia State UniversitySensorweb Research Laboratory Network Core: Packet Switching each end-end data stream divided into packets user A, B packets share network resources each packet uses full link bandwidth resources used as needed resource contention: aggregate resource demand can exceed amount available congestion: packets queue, wait for link use store and forward: packets move one hop at a time Node receives complete packet before forwarding Bandwidth division into “pieces” Dedicated allocation Resource reservation

41. -41- Georgia State UniversitySensorweb Research Laboratory Packet-switching: store-and-forward Takes L/R seconds to transmit (push out) packet of L bits on to link of R bps Entire packet must arrive at router before it can be transmitted on next link: store and forward delay = 3L/R Example: L = 7.5 Mbits R = 1.5 Mbps delay = 15 sec R R R L

42. -42- Georgia State UniversitySensorweb Research Laboratory Packet switching versus circuit switching 1 Mb/s link each user: 100 kb/s when “active” active 10% of time circuit-switching: 10 users packet switching: with 35 users, probability of more than 10 active users is less than.0004 Packet switching allows more users to use network! N users 1 Mbps link probability of exact n of N users active:

43. -43- Georgia State UniversitySensorweb Research Laboratory Packet switching versus circuit switching Great for bursty data resource sharing simpler, no call setup Excessive congestion: packet delay and loss protocols needed for reliable data transfer, congestion control Q: How to provide circuit-like behavior? bandwidth guarantees needed for audio/video apps still an unsolved problem Is packet switching a “slam dunk winner?”

44. -44- Georgia State UniversitySensorweb Research Laboratory Packet-switched networks: forwarding Goal: move packets through routers from source to destination we’ll study several path selection (i.e. routing) algorithms datagram network: destination address in packet determines next hop routes may change during session analogy: driving, asking directions virtual circuit network: each packet carries tag (virtual circuit ID), tag determines next hop fixed path determined at call setup time, remains fixed thru call routers maintain per-call state

45. -45- Georgia State UniversitySensorweb Research Laboratory Network Taxonomy Networks Circuit-switched networks FDM TDM Packet-switched networks Networks with VCs Datagram Networks Datagram network is not either connection-oriented or connectionless. Internet provides both connection-oriented (TCP) and connectionless services (UDP) to apps. e.g., telephone networkse.g., ATM networks e.g., Internet

46. -46- Georgia State UniversitySensorweb Research Laboratory Connection-oriented vs Connectionless Key differences: Connection-oriented: packets arrives in the order of sending out (e.g., FIFO), and need connection setup phase Connectionless: packets may (or may not) arrive in different order of sending out, and does not need connection pre-setup Example: Circuit Switch Network: connection-oriented Packet Switch Network Virtual circuit network: connection-oriented Datagram network depends on layers and protocols: TCP – connection-oriented UDP, IP - connectionless

47. -47- Georgia State UniversitySensorweb Research Laboratory Introduction Roadmap Physical overview of Internet Physical architecture Network Edge - Internet access technologies Residential access: dialup, ADSL, cable, WiMax Company access: LAN, WLAN Network Core – Switching technologies Circuit switching: setup path before communication, have dedicated resource per call Packet switching: store and forward, share resource and need contend for Software overview of Internet Software architecture The OSI and TCP/IP Reference Models Internet history Network standardization body

48. -48- Georgia State UniversitySensorweb Research Laboratory Protocol “Layers” Networks are complex! many “pieces”: hosts routers links of various media applications protocols hardware, software Question: Is there any hope of organizing structure of network? Or at least our discussion of networks?

49. -49- Georgia State UniversitySensorweb Research Laboratory Internet protocol stack application: supporting network applications FTP, SMTP, HTTP, etc transport: host-host data transfer TCP, UDP network: routing of datagrams from source to destination IP, routing protocols link: data transfer between neighboring network elements, including encapsulating bits into frames PPP, Ethernet, etc physical: bits “on the wire” application transport network link physical

50. -50- Georgia State UniversitySensorweb Research Laboratory Analogy scenario The philosopher-translator-secretary architecture.

51. -51- Georgia State UniversitySensorweb Research Laboratory Services to Protocols Relationship The relationship between a service and a protocol: each layer implements a service via its own internal-layer actions or protocols relying on services provided by layer below

52. -52- Georgia State UniversitySensorweb Research Laboratory Why layering? Dealing with complex systems: explicit structure allows identification, relationship of complex system’s pieces layered reference model for discussion modularization eases maintenance, updating of system change of implementation of layer’s service transparent to rest of system e.g., changing common language of translators does not affect the communication between the philosopher layering considered harmful?

53. -53- Georgia State UniversitySensorweb Research Laboratory message segment datagram frame source application transport network link physical HtHt HnHn HlHl M HtHt HnHn M HtHt M M destination application transport network link physical HtHt HnHn HlHl M HtHt HnHn M HtHt M M network link physical link physical HtHt HnHn HlHl M HtHt HnHn M HtHt HnHn HlHl M HtHt HnHn M HtHt HnHn HlHl M HtHt HnHn HlHl M router switch Typical network flow

54. -54- Georgia State UniversitySensorweb Research Laboratory General situation of end-end flow Example information flow supporting virtual communication in layer 5.

55. -55- Georgia State UniversitySensorweb Research Laboratory Introduction Roadmap Physical overview of Internet Physical architecture Network Edge - Internet access technologies Network Core – Switching technologies Software overview of Internet Software architecture The OSI and TCP/IP Reference Models Internet history Network standardization body

56. -56- Georgia State UniversitySensorweb Research Laboratory The design principles of OSI Reference Models A layer should be created when a different abstraction is needed Each layer should perform a well-defined function The function of each layer should be chosen with an eye toward defining internationally standardized protocols The layer boundaries should be chosen to minimize the information flow across the interfaces The number of layers should be large enough that functions need not be thrown together in the same layer out of necessity and small enough that the architecture does not become unwieldy

57. -57- Georgia State UniversitySensorweb Research Laboratory OSI Reference Models The OSI reference model. Concern the syntax and semantics of information transmitted Allow users on different machines to establish sessions

58. -58- Georgia State UniversitySensorweb Research Laboratory TCP/IP Reference Models The TCP/IP reference model.

59. -59- Georgia State UniversitySensorweb Research Laboratory TCP/IP Reference Models Major protocol and application components common to most commercial TCP/IP software packages and their relationship 123

60. -60- Georgia State UniversitySensorweb Research Laboratory A Critique of the OSI Model and Protocols Bad timing Bad technology Bad implementations Bad politics

61. -61- Georgia State UniversitySensorweb Research Laboratory A Critique of the TCP/IP Reference Model Service, interface, and protocol not distinguished Not a general model Host-to-network “layer” not really a layer No mention of physical and data link layers Minor protocols deeply entrenched, hard to replace

62. -62- Georgia State UniversitySensorweb Research Laboratory Hybrid flow in the lecture application: supporting network applications FTP, SMTP, HTTP, DNS transport: host-host data transfer TCP, UDP network: routing of datagrams from source to destination IP, routing protocols link: data transfer between neighboring network elements, including encapsulating bits into frames MAC (Multiple Access Control) sublayer physical: bits “on the wire” application transport network link physical

63. -63- Georgia State UniversitySensorweb Research Laboratory Introduction Roadmap Physical overview of Internet Physical architecture Network Edge - Internet access technologies Network Core – Switching technologies Software overview of Internet Software architecture The OSI and TCP/IP Reference Models Internet history Network standardization body

64. -64- Georgia State UniversitySensorweb Research Laboratory Internet History 1961: Kleinrock - queueing theory shows effectiveness of packet- switching 1964: Baran - packet-switching in military nets 1967: ARPAnet conceived by Advanced Research Projects Agency 1969: first ARPAnet node operational 1961-1972: Early packet-switching principles (a) Structure of the telephone system. (b) Baran’s proposed distributed switching system.

65. -65- Georgia State UniversitySensorweb Research Laboratory Internet History 1972: ARPAnet demonstrated publicly NCP (Network Control Protocol) first host-host protocol first e-mail program ARPAnet has 15+ nodes 1961-1972: Early packet-switching principles Growth of the ARPANET (a) December 1969. (b) July 1970. (c) March 1971. (d) April 1972. (e) September 1972.

66. -66- Georgia State UniversitySensorweb Research Laboratory Internet History 1970: ALOHAnet satellite network in Hawaii 1973: Metcalfe’s PhD thesis proposes Ethernet 1974: Cerf and Kahn - architecture for interconnecting networks late70’s: proprietary architectures: DECnet, SNA, XNA late 70’s: switching fixed length packets (ATM precursor)‏ 1979: ARPAnet has 200 nodes Cerf and Kahn’s internetworking principles: minimalism, autonomy - no internal changes required to interconnect networks best effort service model stateless routers decentralized control define today’s Internet architecture 1972-1980: Internetworking, new and proprietary nets

67. -67- Georgia State UniversitySensorweb Research Laboratory Internet History Early 1990’s: ARPAnet decommissioned 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995)‏ early 1990s: Web hypertext [Bush 1945, Nelson 1960’s] HTML, HTTP: Berners-Lee 1994: Mosaic, later Netscape late 1990’s: commercialization of the Web Late 1990’s – 2000’s: more killer apps: instant messaging, P2P file sharing network security to forefront est. 50 million host, 100 million+ users backbone links running at Gbps 1990, 2000’s: commercialization, the Web, new apps

68. -68- Georgia State UniversitySensorweb Research Laboratory Internet Usage Traditional applications (1970 – 1990) E-mail News Remote login File transfer Today in addition WWW: news, shopping, gaming, maps, trading, etc Multimedia: Internet video, audio, radio P2P file sharing Blogs Messenger … …

69. -69- Georgia State UniversitySensorweb Research Laboratory Introduction Roadmap Physical overview of Internet Physical architecture Network Edge - Internet access technologies Network Core – Switching technologies Software overview of Internet Software architecture The OSI and TCP/IP Reference Models Internet history Network standardization body

70. -70- Georgia State UniversitySensorweb Research Laboratory Network Standardization Telecommunications World ITU (International Telecommunication Union), called CCITT during 1956-1993 International Standards World ISO (International Standards Organization)‏ U.S: ANSI (American National Standards Institute) Other countries … IEEE (Institute of Electrical and Electronics Engineers)‏ Internet Standards World Internet Society IAB (Internet Activities Board)‏ IRTF (Internet Research Task Force): long-term research IETF (Internet Engineering Task Force): short-term engineering issues – RFC documents

71. -71- Georgia State UniversitySensorweb Research Laboratory IEEE 802 Standards The 802 working groups. The important ones are marked with *. The ones marked with  are hibernating. The one marked with † gave up.

72. -72- Georgia State UniversitySensorweb Research Laboratory Summary Covered a “ton” of material! Physical overview of Internet Physical architecture Network Edge - Internet access technologies Network Core – Switching technologies Software overview of Internet Software architecture The OSI and TCP/IP Reference Models Internet history Names and terms in network society You now have: context, overview, “feel” of networking more depth, detail to follow!

73. -73- Georgia State UniversitySensorweb Research Laboratory Suggestion Read Chapter 1 Preview Chapter 2 (Application Layer)‏ Install WireShark and read its manual: http://www.wireshark.org/download.html http://www.wireshark.org/download.html Wireshark is a free and open-source packet analyzer. It is used for network troubleshooting, analysis, software and communications protocol development, and education. Originally named Ethereal, in May 2006 the project was renamed Wireshark due to trademark issues.