Lecture 2

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  • This is a very basic view of how DSL works. The customer’s phone line is connected to a splitter. Coming in, the splitter separates your line between voice and data. Going out, it combines the two out to your local loop and into your central office. The circuit is split again, and the voice channel goes to a voice switch and out to the public telephone network. The data channel is connected to a device called a DSLAM, which is a DSL access multiplexer. DSLAMs take traffic from multiple DSL lines and combines them and sends it to a fast packet network, typically an ATM network. The data streams are switched to a gateway router and on to your internet service provider, who provides you with internet access.
  • Lecture 2

    1. 1. Agenda 1. QUIZ 2. HOMEWORK LAST CLASS 3. HOMEWORK NEXT CLASS 4. dBs, NYQUIST & SHANNON 5. NOISE 6. TRANSISSION LINES 7. FIBER 8. ISDN 9. DSL 10. Cable Modems 11. LANS & MANS
    2. 2. Homework Last Week Engineering Group Network Planning and Design Operations Group NOC Network Operations I & M Group Network Installation and Maintenance Network Fault TT Installation Performance & Traffic Data New Technology Management Decision Users TT Restoration Configuration Data
    3. 3. Internet Central Manager Centralized Architecture Central Database
    4. 4. Homework Centralized Arch Engineering Group Network Planning and Design Operations Group NOC Network Operations I & M Group Network Installation and Maintenance Network Fault TT Installation Performance & Traffic Data Latency, Capacity & Avail- ability summaries New Technology Management Decision Users TT Restoration Configuration Data Accounting Management Data Security Management Data
    5. 5. Internet Network Management Server Hierarchial Architecture DBMS Network Management Client Network Management Client Network Management Client
    6. 6. Internet Replication Comm Distributed Architecture DBMS DBMS DBMS DBMS
    7. 7. Physical/Data Link/Network/ Layers?
    8. 8. Homework-P 1 of 3 A company has a corporate network which consists of five Ethernet LANs connected to a mainframe through 56 KBps lines. Each LAN has about 20 workstations which generate one message per second. Each message is 1000 bytes (8 bits per byte). Most workstations interact with each other on their LANs with only 20% of the messages being sent to the mainframe. The messages sent to the mainframe access a corporate database which services 50 I/O per second. How much of a congestion problem exists on the LAN, the WAN and the mainframe database.
    9. 9. Homework P 2 of 3 An Advise To The Lovelorn database operates on a T-1 line. The average input is 1000 bytes of questions. The average output has 1Million bytes of answers. Database processing time averages 3 seconds. What is the total response time if you assume 8 bits per byte.
    10. 10. Homework P 3 of 3 Ping ns1.bangla.net. How many packets were lost? What was the response time? Now do a trace rout and see how many hops it takes to get to get to ns1.bangla.net.
    11. 11. Decibells & Logarithms Converting watts to dB (or milliwatts to dBm): 10 log 10 1000 watts = 30 dBw Converting dB to watts (or dBm to milliwatts): 30 dBw = log -1 , or log -1 (3) or 10 raised to the 3rd power = 10 3 = 1000 watts 35 dBw = 10 3.5 = 3162.3 watts Note: There’s a point between the 3 & 5.
    12. 12. Decibells & Logarithms dBW Watts -3 .5 0 1 3 2 6 4 9 8 10 10 20 100 30 1000 40 10000
    13. 13. Physical Layer Wire & Fiber
    14. 14. Nyquist 1. Nyquist: The maximum practical data rate (samples) per channel. Max R = 2 H log 2 V Logarithmic function to the base 2: For each # V, log V = the exponent to which 2 must be raised to produce V. Then if V = 16, the log 2 of V = 4. If V = 2, the log 2 of V = 1. Then what is the maximum practical data rate for BPSK signal on a line with a bandwidth of 3000 Hz? What is the maximum practical data rate for a QPSK signal on a line with a bandwidth of 3000 Hz?
    15. 15. Shannon Shannon: The maximum theoretical data rate per channel. Max R = CBW x log 2 (1 + S/N) [CBW = H in Nyquist Theorem] Then what is the maximum practical data rate for signal with a 30 dB S/N on a line with a bandwidth of 3000 Hz?
    16. 16. Noise T = SNT = System Noise Temperature N o = Noise Density = k T, where k is Boltzmann’s Constant (-228.6 dBw) N = Noise Power = k TB, where B is bandwidth.
    17. 17. Transmission Lines We understand transmission lines by oversimplifying them: a. Lump all resistances into a single large resistance. b. Lump all inductances into a single large inductance. c. Lump all capacitances into a single large capacitance. d. Lump all conductance (leakage) into a single large conductance. e. Assume perfectly uniform construction and perfect symmetry so it looks exactly the same from both ends. f. Lump all of the above into a simple impedance network and assume stability.
    18. 18. Transmission Lines
    19. 19. Transmission Lines Impedance mismatches (impedance of load does not equal impedance of the line) result in a standing wave ratio (how much energy is reflected back to the transmitter).
    20. 20. Transmission Line Connector Distortion Normal Power Level: - 120 dBm Problem Power Level +/- 10 dB Linear Non-Linear
    21. 21. Fiber Optics Attenuation: Light loss due to both scattering and absorption. Absorption: The amount of light loss due to its conversion to heat. Scattering: The disappearance of light due to its leaving the core of of a fiber. Chromatic dispersion: The tendency of a fiber to cause slightly differing wavelengths of emitted light to travel through the fiber at different speeds. (See Handout)
    22. 22. Integrated Services Digital Network (ISDN) Standard 1. A major TELCO attempt to integrate voice and non-voice services. 2. Integrated multiple channels interleaved with time division multiplexing. A - 4 KHz analog telephone channel B - 64 Kbps digital PCM channel for voice or data C - 8 or 16 Kbps digital channel D - 16 Kbps digital channel for out of band signalling E - 64 Kbps channel for internal ISDN signalling H - 384, 1536, or 1920 Kbps digital channel Basic Rate = 2B + 1D (the nominal 128 frequently used in homes) Primary Rate = 23 B + 1D
    23. 23. Integrated Services Digital Network (ISDN) Standard TE 1 ISDN Terminal TE 1 ISDN Telephone Non-ISDN Terminal TA S S S R ISDN PBX NT1 ISDN Exchange T U R, S, T & U are CCITT defined reference Points TA is terminal adapter
    24. 24. Digital Subscriber Line (DSL) Standard <ul><li>Drivers: </li></ul><ul><li>ISDN didn’t capture significant market share for TELCOs </li></ul><ul><li>Higher speed applications require new technologies </li></ul><ul><li>Users want to stay connected longer </li></ul><ul><li>High cost of converting infrastructure </li></ul><ul><li>Telephone lines weren’t designed to provide simultaneous </li></ul><ul><li>digital and analog services </li></ul><ul><li>Competition from satellite (e.g., DirectTV/Direct PC) & cable </li></ul><ul><li>industry </li></ul>
    25. 25. Digital Subscriber Line (DSL) Standard Services Type DSL Speed Asymmetric DSL 1.5 to 8 Mbps to user 16 to 640 Kbps to network High-data-rate DSL 1.544 Mbps to and from user Single-line DSL 768 Kbps full duplex on a pair Rate-adaptive DSL 1.5 to 8 Mbps to user 16 to 640 Kbps to network (can adjust speeds) Consumer DSL 1 Mbps to user 16 to 128 Kbps to network (does not include splitter) ISDN DSL Basic ISDN rate Very-high-data-rate DSL 13 to 52 Mbps to user 1.5 to 6 Mbps to network
    26. 26. DSL Rates (using 24 gauge wire) Connection Max Data Rate Distance Limit ADSL 1.5-8 Mbps downstream 12-18 K feet Up to 1.544 Mbps upstream HDSL T1 - 1.544 Mbps (4 wire) 12,000 feet IDSL 144 Kbps (symmetric) 18,000 feet (36 w rptr) SDSL T1 - 1.544 Mbps (2 wire) 11,000 feet VDSL 13-52 Mbps downstream 1-4.5 K feet 1.5-2.3 Mbps upstream Up to 34 Mbps Symmetric R-ADSL 1.5-8 Mbps downstream 12-18 K feet Up to 1.544 Mbps upstream
    27. 27. DSL Network Configuration
    28. 28. Asymmetric DSL <ul><li>Characteristics </li></ul><ul><li>Uses frequency division multiplex occupying spectrum above voice </li></ul><ul><li>Principal modulation scheme is Discrete multitone (DMT), a </li></ul><ul><li>quadrature amplitude modulation coding technique developed by </li></ul><ul><li>Bell Labs (ANSI T1.413 standard) </li></ul><ul><li>Can be mapped into higher layer protocol mechanisms that can </li></ul><ul><li>include IP frames or ATM cells </li></ul><ul><li>Can interface to Simple Network Management Protocol (SNMP) </li></ul><ul><li>for operations, administration and management </li></ul>0-4 KHz 25KHz 200KHz 1.1MHz To Network To User
    29. 29. Cable Modem DSL Access
    30. 30. Cable Modem Access
    31. 31. DSL Roll-Out TeleChoice 1999 2000 2001 2002 2003 2004 2005 50 40 30 20 10 0 Millions of Lines
    32. 32. Simplified xDSL Architecture PSTN Fast Packet Internet Local Loop Splitter Voice Switch DSLAM ISP Router
    33. 33. The transparent network … Ideally, the network is transparent — the end user simply wants to get information to or from a remote location End User Business or Residential Application e-business Content Provider Enterprise Host
    34. 34. …isn’t really so transparent But today’s reality is that the transparent network is a complex value chain of individual networks NSP NSP LEC NAP Transport Transport E-business LEC Backbone Backbone Backbone Backbone Consumer Residential Business Application e-business Content Provider Application e-business Content Provider
    35. 35. The Value Chain PSINet AOL XYZ Consumer Residential Business Application e-business Content Provider SBC Sprint GTEI New Edge UUNet Williams Qwest eBay The players in this value chain have many names and may be linked in different configurations GTE Application e-business Content Provider
    36. 36. The Value Chain PSINet AOL XYZ Consumer Residential Business Application e-business Content Provider Application e-business Content Provider SBC Sprint GTEI New Edge UUNet Williams Qwest eBay These value chains are held together by very thin threads of linkages between legacy operations support systems (OSSs) and a lot of manual processes GTE
    37. 37. Who Fixes The Network? Serving CO Hub office DSLAM ADM DWDM Internet DWDM ATM Network Verizon ILEC Verizon ILEC Worldcom Verizon Advanced Data Verizon Advanced Data Verizon Advanced Data AOL AOL ADM ADM ADM LEC NAP LEC NAP Backbone NAP NSP Application e-business Content Provider
    38. 38. Providers Ask Two Pivotal Questions <ul><li>Is the network service up </li></ul><ul><li>and running properly? </li></ul><ul><li>If it’s not, where’s the problem </li></ul><ul><li>and how do we fix it ? </li></ul>
    39. 39. The Answer... LEC Providers must tightly link their operations with their trading partners through integrated service assurance NAP NSP
    40. 40. Service Assurance Market Test & Measurement Operations Support Systems Service Assurance <ul><li>$3.5B* in 2000 $8.4B* in 2004 </li></ul><ul><li>Growing at 25% </li></ul><ul><li>Includes OSS software, services, and remote probes </li></ul><ul><li>Key players: Spirent Communications, Telcordia, Lucent, Acterna (TTC/WWG), Micromuse </li></ul>* RHK Estimates
    41. 41. Service Assurance Activities Monitor SLAs Report Allocate Resources Determine SLA Violations Test Isolate Root Cause Detect Alarms/Events Detect Performance/Traffic Problems Decide Repair
    42. 42. Network “Communication” is Key Need to provide service information within and between networks LEC NAP NSP
    43. 43. Outsourcing Net Mgt <ul><li>IT Spending averages 3% of revenue & revenue is down </li></ul><ul><li>No outsourcer will meet all the needs of your business or agency </li></ul><ul><li>The annual cost of 9 networking and 6 help desk staffers averages $1.08 million (including benefits) </li></ul><ul><li>Four vendors investigated that cost approximately $350,000 to $500,000 </li></ul><ul><li>Worth while thoughts: </li></ul><ul><ul><li>Double check special requests (what, who, when, where, how) </li></ul></ul><ul><ul><li>Lay-offs hurt you and the outsourcer </li></ul></ul><ul><ul><li>Willingness to accept fines or reimbursement is a big deal </li></ul></ul><ul><ul><li>Block & Level the SLA vs. the network </li></ul></ul>
    44. 44. Outsourcing Net Mgt   PerformanceIT Net Mgt Service iNOC Imonitor HCL Technologies iNOC Services NetProactive Services Remote Infrastructure Management IT B dg t Reduction 30% 4 5 3 1 Svce-level Mgt 30% 5 4.5 3 3 Other Costs 20% 5 4 4 3 Operations 10% 4 4 5 3 Reporting 10% 5 4 5 4 Total Score 100% 4.60 4.45 3.60 2.50 Grade A A - B - C -
    45. 45. Outsourcing Net Mgt   Company Name Service Name Svc Yrs Sales Per Yr Employees HCL Technologies iNOC Services 3 $336M 8748 America iNOC IMonitor 3 $4.8M 30 NetProactive Remote 4 $500K 28 Services Infrastructure Management PerformanceIT PerformanceIT 6 $10M 100 Network Mgt Service

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