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Published on November 28, 2007

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CS455 Introduction to Computer Networks:  CS455 Introduction to Computer Networks Dr. Wenzhan Song Assistant Professor, Computer Science WSU Vancouver About Me:  About Me Working Experiences 1997-1999, Jiangsu Intrasoft Network 1999-2001, Alcatel Shanghai Bell 2004 Summer, Lucent Technologies 2001-2005, Ph.D. research, Illinois Institute of Technology 2005-present, Assistant Professor, Washington State University - Vancouver Teaching evaluation: Fall 2005 - CS455 (4.42/5) Spring 2006 - CS580 (4.74/5) Research experiences: 20+ articles in top journal and conferences 1.5M+ research funding support from NASA and WSU Course information:  Course information Instructor: WenZhan Song Office: VELS 130A Tel: (360)546-9144 Email: song@vancouver.wsu.edu Homepage: http://www.vancouver.wsu.edu/fac/song Textbooks: [Required] Computer Networking - a top-down approach featuring the Internet, 3rd Edition, by James F. Kurose, Keith W. Ross [Optional] Computer Networks, 4th Edition, by Andrew S. Tanenbaum [Optional] Unix Network Programming - Vol. 1, 3rd Edition, by W. Richard Stevens, Bill Fenner, Andrew M. Rudoff Prerequisite courses CS360 – System Programming Grading:  Grading Homework Assignments (30%) About five Written Network Programming (40%) Client/Server, UDP, TCP sockets Protocol simulation, system design TinyOS Midterm (15%) Final (15%) * Highly encourage innovation and think out of box!!! What to expect:  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 do UNIX network programming. Berkeley Sockets What not to expect:  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 Course roadmap:  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 Human Talk vs Computer Communication:  Human Talk vs Computer Communication human conversation vs computer network protocol Hi Hi TCP connection req Communication is challenging:  Communication is challenging The two-army problem Introduction Roadmap:  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 Physical overview of Internet:  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) 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) Physical overview of Internet Metric Units:  Metric Units metric prefixes for data rate Note: data rates – kbps (103), Mbps(106), Gbps(109) … bits per second data sizes – KB (210), MB(220), GB(230), … bytes ms(msec): millisecond µs: microsecond ns: nanosecond Introduction Roadmap:  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 Residential Internet Access:  Residential Internet Access Phone Company Dialup ADSL Cable TV Company HFC Wireless Company WiMax Residential access Phone Company:  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) Dialup:  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 ADSL: asymmetric digital subscriber line:  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 ADSL:  ADSL A typical ADSL equipment configuration. ADSL:  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 Residential access Cable TV Company:  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 Community Antenna Television:  Community Antenna Television An early cable television system. HFC:  HFC Internet over TV Cable Compare to ADSL:  Compare to ADSL Internet over ADSL Cable vs ADSL:  Cable vs ADSL Spectrum Allocation:  Spectrum Allocation Frequency allocation in a typical cable TV system used for Internet access Signal Splitter:  Signal Splitter Cable Modems:  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 Residential access Wireless Company:  Residential access Wireless Company Wireless Local Loop Example: IEEE 802.16 WiMax – Verizon Wireless 400~700kbps Up to 2Mbps - according to Verizon Other ways for residential access?:  Other ways for residential access? How about other utility companies: Gas, Water, Sewer ……? Electricity company PLC (Power Line Communication) BPL (Broadband over Power Line) http://en.wikipedia.org/wiki/Power_line_communication Introduction Roadmap:  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 Company access: local area networks:  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 Wireless access networks:  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 Will it happen?? WAP/GPRS in Europe wireless ad hoc networking Talk with each other directly inside Though a gateway to visit outside base station mobile hosts router Ad hoc networking Introduction Roadmap:  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 The Network Core:  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” Network Core: Circuit Switching:  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 Network Core: Circuit Switching:  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 Circuit Switching: FDM and TDM:  Circuit Switching: FDM and TDM Numerical example:  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 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 Network Core: Packet Switching:  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 statistical multiplexing queue of packets waiting for output link Network Core: Packet Switching:  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 Packet-switching: store-and-forward:  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 Packet switching versus circuit switching:  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 > 10 active less than .0004 Packet switching allows more users to use network! N users 1 Mbps link Packet switching versus circuit switching:  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?” Packet-switched networks: forwarding:  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 Network Taxonomy:  Network Taxonomy 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 networks e.g., ATM networks e.g., Internet Connection-oriented vs Connectionless:  Connection-oriented vs Connectionless Key differences: Connection-oriented: packets arrives in the order of sending out (e.g., FIFO), and need call setup phase Connectionless: packets may (or may not) arrive in different order of sending out, and need call 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 Introduction Roadmap:  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 Protocol “Layers”:  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? Internet protocol stack:  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” Analogy scenario:  Analogy scenario The philosopher-translator-secretary architecture. Services to Protocols Relationship:  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 Why layering?:  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? Typical network flow:  message segment datagram frame source application transport network link physical destination application transport network link physical router switch Typical network flow General situation of end-end flow:  General situation of end-end flow Example information flow supporting virtual communication in layer 5. Introduction Roadmap:  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 The design principles of OSI Reference Models:  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 OSI Reference Models:  OSI Reference Models The OSI reference model. Concern the syntax and semantics of information transmitted Allow users on different machines to establish sessions TCP/IP Reference Models:  TCP/IP Reference Models The TCP/IP reference model. TCP/IP Reference Models:  TCP/IP Reference Models Major protocol and application components common to most commercial TCP/IP software packages and their relationship 123 A Critique of the OSI Model and Protocols:  A Critique of the OSI Model and Protocols Bad timing Bad technology Bad implementations Bad politics A Critique of the TCP/IP Reference Model:  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 Hybrid flow in the lecture:  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” Introduction Roadmap:  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 Internet History:  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. Internet History:  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. Internet History:  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 Internet History:  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 Internet Usage:  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 … … Introduction Roadmap:  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 Network Standardization:  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 IEEE 802 Standards:  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. Summary:  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! Suggestion:  Suggestion Read Chapter 1 Preview Chapter 2 (Application Layer)

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