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Outlines Received due 9 October (Local) By 16 October (Remote)

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Outlines Received due 9 October (Local) By 16 October (Remote)

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  1. ECEN5553 Telecom SystemsDr. George ScheetsWeek 6Read [11a] "Cybercrime: Dissecting the State of Underground Enterprise"[11b] "The Real Story of Stuxnet"Exam #1 27 September (Local) No later than 3 October (Remote DL)Outline Lecture 22, 9 October (Local) No later than 16 October (Remote)

  2. OutlinesReceiveddue 9 October (Local)By 16 October (Remote) 30 %

  3. Internet (Inside the Cloud) • Infinite Buffers • "OK" so long as Average Offered Input Rate < Output Line Speed Internet Router 100 Mbps Trunk ?? 1.54 Mbps Connections P(Access Line is Active) = 10% How many access lines can this switch support? 100 Mbps/154 Kbps = 649 (theoretically)

  4. Internet (Inside the Cloud) • Negligible Buffers • OK so long as Instantaneous Offered Input Rate < Output Line Speed Internet Router 100 Mbps Trunk ?? 1.54 Mbps Connections P(Access Line is Active) = 10% How many access lines can this switch support? With 404 users, 99.99% sure Input Rate < Line Speed

  5. Bounds on Packet Switch Carrying Capacity 100 Mbps Trunk, 1.54 Mbps Inputs with 154 Kbps average loads Lower Upper90% 553 64999% 485 64999.9% 439 64999.99% 404 649 Instantaneous Input < Line Speed Where switch could operate Where switch probably operates

  6. WAN Connectivity Options • Leased Line • Cross Connects are byte aware • Circuit Switched • Resources dedicated to customer use for duration of connection • Connection Set-Up Procedure • Coordinates byte time slot assignments between switches • Bytes are assigned at 1/8000th second intervals (TDM) • Switch then repetitively moves input bytes to designated output byte time slots • Pricing a function of connection size & distance

  7. LAN LAN Carrier Leased Line Network PC Trunks Byte Aware Leased Line Cross-Connect Corporate customers might attach via Edge Router & Leased Lines. WS

  8. Leased Lines (Inside the Cloud) • OK so long as Sum of Input Line Speeds < Output Line Speeds Leased Line Cross-Connect 100 Mbps Trunk ?? 1.54 Mbps Connections P(Access Line is Active) = 10% How many access lines can this switch support? 64

  9. 3 2 1 3 3 2 2 1 1 3 2 1 Leased Lines (TDM) • TDM time slots are moved from input to output • TDM switch is not "packet aware" • Time slots are allocated whether or not there is any traffic on them Leased Line Cross-Connect

  10. Circuit Switched connections waste bandwidth for bursty traffic. traffic NYC to OKC 1.54 Mbps Line Speed 146 Kbps Average time Idle Time >> Active Time

  11. Given 100 Mbps of Bandwidth... • 64 1.54 Mbps Circuit SwitchedTDM Customers with 154 Kbps average load & 100% availability • 404 - 649 1.54 Mbps Packet SwitchedStatMux Customers with 154 Kbps average load & 99.99% availability 64 x 154 Kbps = 9.856 Mbps 404 x 154 Kbps = 62.22 Mbps More Bursty Data Traffic can be moved with the Packet Switched StatMux network.

  12. Switched Network Carrying Capacities Carrying Capacity Packet Switch StatMux Circuit Switch TDM 0% Bursty 100% Bursty 100% Fixed Rate 0% Fixed Rate Offered Load

  13. Network Cost... • Can be spread over 64 Leased Line customers • Can be spread over 404 Internet customers • The Internet Is a Packet Switched StatMux network Largely hauling bursty data traffic Effectively hauling bursty data traffic Inexpensive (compared to a Leased Line)

  14. Internet Performance This type of plot valid for all real world full duplex statistically multiplexed switches: Ethernet, Internet, Frame Relay Number of dropped packets Average Delay for delivered packets 0% 100% Trunk Offered Load

  15. Internet Performance Effect of priorities Average Delay for low priority packets Average Delay for all delivered packets Average Delay for high priority packets 0% 100% Trunk Offered Load

  16. Internet Performance Effect of priorities Number of low priority drops Number of dropped packets Number of high priority drops 0% 100% Trunk Offered Load

  17. Internet Backbone Engineering • Option A)Deploy ‘best effort’ RoutersRapidly Deploy Trunk BandwidthKeep Trunks Lightly Loaded • Delays will be small • Dropped packets will be few • Quality fine for all traffic

  18. Backbone Engineering: Option A Number of dropped packets Average Delay for delivered packets 0% 100% Keep Trunks Lightly Loaded

  19. Internet Backbone Engineering • Option B)Deploy more complex QoS enabled Routers Deploy fewer, more heavily loaded Trunks Give preferential treatment to interactive Voice/Video • Option A seems to be preferred today

  20. Backbone Engineering: Option BHigh Priority delay at 50% Load = Delay for all traffic at 20% Load Average Delay for low priority packets Average Delay for all delivered packets Average Delay for high priority packets 0% 70% Heavier Trunk Load

  21. Frame Relay • ANSI Standard covering OSI Layer 2 • Accessed by Routers • Derived from X.25 Protocol Dumps almost all error checking Requires fiber on the long haul • Uses Virtual Circuits (VC’s) VC differs from Datagram Long Term Connection Requires Carrier intervention to change

  22. Frame Relay • 1st Commercial Deployment 1990 • WilTel → Worldcom→ bankrupt → Verizon • Cheaper alternative to Leased Lines • Faster alternative to X.25 • Internet a small network in 1990 • Academia • Military • Some commercial traffic • See CUCKOO'S EGG to get a flavor

  23. Frame Relay • 7 Application • 6 Presentation • 5 Session TCP • 4 Transport TCP • 3 NetworkIP • 2 Data Link Frame Relay • 1 Physical

  24. Wide Area Connectivity Options • Frame Relay Network • Switches are frame aware • Virtual Circuit is assigned trunk BW via StatMux • BW required based more so on average input rates • Routing through system determined in advance • Pricing a function of Port Speed, CIR, and maybe distance

  25. Frame Relay • Committed Information Rate (CIR) Is a Quality of Service Guarantee "Guaranteed" minimum Bandwidth Should be set > average traffic during appropriate peak period • Port Connection Speed a.k.a. Port Speed or Burst Speed Bandwidth you can burst to provided network capacity exists. Set = Bit Rate of Access Line

  26. Frame Relay Packet Format 3 20 20 up to 8,146 3 FR Header FR Trailer IP TCP Data + Padding Header includes 10 bit Data Link Connection Identifier (DLCI) - Locally Unique (FR ports)Trailer includes 2 byte CRC Sequence that only checks Header I/O decisions based on FR address & look-up table.

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