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ECEN4533 Data Communications Lecture #4 14 January 2013 Dr. George Scheets

ECEN4533 Data Communications Lecture #4 14 January 2013 Dr. George Scheets. Read 2.3, 2.5 Problems 1.6, 2.6, 2.8 Quiz #1, Lecture 12, 4 February Open book & notes Calculators are allowed No Smart Phones.

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ECEN4533 Data Communications Lecture #4 14 January 2013 Dr. George Scheets

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  1. ECEN4533 Data CommunicationsLecture #4 14 January 2013Dr. George Scheets • Read 2.3, 2.5 • Problems 1.6, 2.6, 2.8 • Quiz #1, Lecture 12, 4 February • Open book & notes • Calculators are allowed • No Smart Phones

  2. ECEN4533 Data CommunicationsLecture #5 16 January 2013Dr. George Scheets • Read 3.1 • Ignore Probability Equations until Review • Scan Design Problem #1 • Problems 2.7, 3.1, 3.2 • Quiz #1 • Lecture 12, 4 February (Live) • < 11 February (Async Distance Learning) • Extra Credit (up to 20 points) • Find errors in text or solutions.

  3. ECEN4533 Data CommunicationsLecture #6 18 January 2013Dr. George Scheets • Read 3.2 • Problems 3.9, 3.10 • Quiz #1 • Lecture 12, 4 February (Live) • < 11 February (Async Distance Learning) • Design #1 due 1 February (Live) • 8 February (Async DL) • Late = -1 per working day • No Class next Monday

  4. PSTN Call Sequencing • User Dials Number • Routing Protocol Determines path thru network • Affected Core Switches notified • Time Slots reserved to support callTime Slot = 1 byte every 1/8000 th second for 64 Kbps • Switches continuously move bytes arriving on input time slot(s) to appropriate output line and time slot(s) • User “sees” dedicated nailed up bandwidth • Source TCP opens logical connection with Sink • Packets transferred, logical connection closed • Switch resources released when user hangs up

  5. ISDN connection using PSTN node c PC Nailed up Circuit PST Network node a PC Long Distance & Local Carriers dedicate 64 Kbps to our use (Circuit Switching).

  6. Carrier PSTN Network PC 1 Trunks Access Line PC 3 PSTN Switch Switches move bytes from input to output. Bytes get moved at line speeds. Trunk capacity is dedicated.

  7. Moving Traffic with Packets • Layer 7 Application Word Perfect • 2,920B file to move • Layer 6 Presentation Windows API • Layer 5 Session TCP • Layer 4 Transport TCP • Maximum TCP Segment Size assumed to be 1460B(Parameter in Windows Registry) • Chops file into 2 x 1460B packets, adds 20B TCP Header to each • Layer 3 Network IP • Adds 20B IP Header to each packet • Layer 2 Data Link Undefined • Adds 10B Layer 2 Header to each frame • Layer 1 Physical Undefined

  8. Wired Phone • Generally analog from phone to CO • One twisted Pair • At Central Office • Filtered (BW about 3.5 KHz) • Analog Voltage is Sampled 8,000 times/second • Rounded off to 1 of 256 possible voltages • Converted to a fixed length 8 bit code word CO CO Digital Bit Stream (1's & 0's) @ 64 Kbps Analog Voice Analog Voice

  9. Ex) Internet PC Location b ISP Network Location a PC Local connection dedicates 64 Kbps to our use. ISP provides connectivity on a random, as needed, basis.

  10. Internet Service Provider Backbone PC 64 Kbps 1 Trunks 45 Mbps Access Line PC 3 Router Routers move packets from input to output. Packets get full trunk line speed. Trunk capacity shared randomly, as needed.

  11. Internet Call Sequencing • Assuming an "Always On" 64 Kbps connection... • Similar to DSL or Cable Modem (but slower) • ... Logical connections opened between end devices • TCP (Layer 5). Routers do not monitor!! • Router I/O decisions based on Layer 3 IP address • Best match found in Look-Up Table • Router Tables updated independently of traffic • ‘Hello’ packets exchanged every 10 seconds with adjacent routers • More detailed routing information (who is connected to whom) exchanged intermittently • Router determines best output port, generally for blocks of hierarchical IP addresses

  12. Moving Traffic with Packets • Layer 7 Application Word Perfect • 2,920B file to move • Layer 6 Presentation Windows API • Layer 5 Session TCP • Layer 4 Transport TCP • Maximum TCP Segment Size assumed to be 1460B(Parameter in Windows Registry) • Chops file into 2 x 1460B packets, adds 20B TCP Header to each • Layer 3 Network IP • Adds 20B IP Header to each packet • Layer 2 Data Link Undefined • Adds 10B Layer 2 Header to each frame • Layer 1 Physical Undefined

  13. Ex) ATM PC locationc VC, a to/from c Location a Carrier ATM Network PC Local Carriers dedicate 64 Kbps to our use. IXC provides random connectivity on an as-needed basis.

  14. ATM Backbone Trunks Access Line ATM Switch Switches move cells from input to output. Cells get full trunk line speed. Trunk capacity shared randomly, as needed.

  15. ATM Call Sequencing • End device requests logical connection • Routing Protocol determines path thru network • Affected Core Switches notified • Look-Up table updated to show proper output port where specific input cells should be placed • Switch resources (bandwidth, buffer space) reserved as appropriate • User appears to see dedicated nailed up bandwidth • Path is known as a Virtual Circuit • TCP opens logical connection with far site • Packets transferred, TCP logical connection closed • Switch resources released when user finished

  16. Moving Traffic with ATM Cells • Layer 7 Application Word Perfect • 2,920B file to move • Layer 6 Presentation Windows API • Layer 5 Session TCP • Layer 4 Transport TCP • Maximum Segment Size assumed to be large, say 64 KB • 2,920B file not segmented. Adds 20B TCP Header • Layer 3 Network IP • Adds 20B IP Header • Layer 2 Data Link ATM • Adds 8B padding & 8B SAR Trailer. • Chops into 2976/48 = 62 cells (53 byte cell size). Adds 5B ATM header to each cell. • Layer 1 Physical Undefined

  17. Internet Packet Format ?? 20 20 0-1460 ?? Layer 2 Trailer? Layer 2 Header IP TCP Traffic Probably originated or passed through an Ethernet.

  18. Internet Protocal v4 4 Bytes TOS TTL Source Address Destination Address

  19. LAN LAN LAN OSU Campus Network (> 2001) OneNet Ethernet Switch 802.3 LAN 1 Gbps Ethernet 802.3 LAN 802.3 LAN Routers

  20. OSU 2009 Internet Connectivity

  21. Example Tracert Handy site for figuring out who owns IP addresses: www.arin.net (has links to databases covering other regions)

  22. Traceroute to WWW.CISCO.COM • 4 Internal OSU-Stillwater routers • 3 OneNet routers (all in Tulsa?) • 5 Cogent Communications routers te4-3.ccr01.tul01.atlas.cogentco.com te2-2.mpd01.dfw01.atlas.cogentco.com • 1 Akamai Technologies (Hosting Service) • (3:30 pm, 12Sept11, rtt = 8 msec, 12 routers)

  23. Traceroute to WWW.TULSA.COM • 4 Internal OSU-Stillwater routers • 3 OneNet routers (Tulsa?) • 4 Cogent Communications routers • te4-4.1052.ccr01.tul01.atlas.cogentco.com • te0-2-0-7.ccr22.dfw01.atlas.cogentco.com • 1 Global Crossing router • GigabitEthernet2-3.ar2.HOU1.gblx.net • 4 Routers in Houston • te2-5.dsr01.hstntx2.networklayer.com • The Planet server (hosting service) • (3:55 pm, 12Sept11, rtt = 14 msec, 16 routers)

  24. # Routers not necessarily f(distance) Launched 14 September 2011, 2 miles from OSU campus • 1 Scheets' home router • 5 SBC (now AT&T) & AT&T routers • dist2-vlan50.okcyok.sbcglobal.net • ggr6.dlstx.ip.att.net • 3 Cogent Communications routers • te3-2.ccr01.tul01.atlas.cogentco.com • 3 ONENET routers • Probably in Tulsa, maybe Oklahoma City • 3 Oklahoma State routers • (11:19 am, 14Sept11, rtt = 71 msec, 15 routers)

  25. Fall 2007 Weird Route Seen by StudentTulsa to OSU Stillwater • Tracert launched from Tulsa, hitAtlantaWashington, D.C.IllinoisKansas CityTulsaOklahoma CityOSU Stillwater

  26. Internet Protocal v6 4 Bytes Flow Label Hop Limit Source Address Destination Address

  27. RedNeckNet ISP MegaMoron Salina Joplin Stillwater Little Rock Lubbock Dallas

  28. RedNeckNet VoIP MegaMoron Full Mesh N(N-1)/2 Connections

  29. RedNeckNet VoIP MegaMoron Bus 5 Connections

  30. RedNeckNet VoIP MegaMoron Star 5 Connections

  31. Grading MegaMoron • Real World: • 1 team gets full credit • Everyone else gets a zero • Partial credit • Awarded on Quizzes & Tests • NOT AWARDED ON DESIGN PROJECTS! • Real world designs don't get partial credit • Either Work or They Don't • Double check your work!!! Use a spreadsheet

  32. Different channels use all of the frequency some of the time, at random, as needed. StatMux frequency 1 3 1 time 2

  33. Different channels use all of the bandwidth all of the time. CDM frequency Channels use different codes. Other channels cause noise-like interference. time

  34. CDMA: 3D View frequency code #3 code #2 code #1 time

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