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Chapter 1: roadmap

Chapter 1: roadmap. 1.1 What is the Internet? 1.2 Network edge end systems, access networks, links 1.3 Network core circuit switching, packet switching, network structure 1.4 Delay, loss and throughput in packet-switched networks 1.5 Protocol layers, service models

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Chapter 1: roadmap

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  1. Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge • end systems, access networks, links 1.3 Network core • circuit switching, packet switching, network structure 1.4 Delay, loss and throughput in packet-switched networks 1.5 Protocol layers, service models 1.6 Networks under attack: security 1.7 History

  2. network edge: applications and hosts A closer look at network structure: • access networks, physical media: wired, wireless communication links • network core: • interconnected routers • network of networks

  3. end systems (hosts): run application programs e.g. Web, email at “edge of network” peer-peer client/server The network edge: • client/server model • client host requests, receives service from always-on server • e.g. Web browser/server; email client/server • peer-peer model: • minimal (or no) use of dedicated servers • e.g. Skype, BitTorrent

  4. Q: How to connect end systems to edge router? residential access nets institutional access networks (school, company) mobile access networks Keep in mind: bandwidth (bits per second) of access network? shared or dedicated? Access networks and physical media

  5. 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” Residential access: point to point access • DSL: digital subscriber line • deployment: telephone company (typically) • up to 1 Mbps upstream (today typically < 256 kbps) • up to 8 Mbps downstream (today typically < 1 Mbps) • dedicated physical line to telephone central office

  6. Access networks • There are • three ways to provide access to the internet to home • Over the telephone • ADSL-based modems • Over the television plant • Cable-based modems • Over an optical fiber • Passive Optical Networks (APON or EPON)

  7. The ADSL-based access network • ADSL • is one of the access technologies that • Can be used to convert the telephone line • into a high-speed digital link • is a part of a family of technologies called • The x-type digital subscriber line (x-DSL) • Where x takes on different values

  8. X-DSL data rates • ADSL modem • is the most commonly used • Rates • Downstream: 8 Mbps • Upstream: 800 Kbps – 1 Mbps

  9. Bandwidth vs. distance • VDSL • 52 Mbps/6.4 Mbps up to 1000 feet (300 m) • 13 Mbps/1.6 Mbps up to 5000 feet (1.5 km) • ADSL • Downstream • 2 Mbps up to 5.4 Km • 8 Mbps up to 2.7 Km • Upstream • 64 Kbps to 800 Kbps

  10. Bandwidth vs distance

  11. Digital subscriber line • Some of the key features • DSL allows analog voice signals and digital data • To be sent over the same local loop wiring • The local loop must be connected to sthg besides • A traditional voice switch at the end office • A device called DSL access multiplexer (DSLAM) is used • Provides high speed access to end users

  12. ADSL: equipment configuration

  13. ADSL equipment

  14. ADSL deployment: at the customer’s permise • ADSL + POTS signals • Travel together down the twisted pair • Using filter you will be isolating each signal ADSL Transmission Unit at the customer premises end

  15. ADSL access multiplexer • Transmission between the end office and customer • is done using the ADSL layer • Speeds are limited to 1.5 Mbps

  16. Discrete multi-tone technique • The twisted pair bandwidth • extends to 1.1 Mbps • is divided into 256 sub-channels • Each occupying 4.3125 KHz • Sub-channel 0 is reserved • For the voice band region • Sub-channels 1-5 separate data and POTS signal • The remaining sub-channels are used by ADSL

  17. Upstream and upstream data • In ADSL • Both the upstream and downstream data • Are sent over the same twisted pair • This can be implemented using • Frequency division multiplexing (FDM) • Up to 32 sub-channels for the upstream direction • Up to 218 downstream sub-channels

  18. Discrete multi-tone technique • ADSL • 8 Mbps in the downstream • 1 Mbps in the upstream

  19. The ADSL reference model architecture • DSLAM can support • Up to 64 homes

  20. HFC: hybrid fiber coax asymmetric: up to 30Mbps downstream, 2 Mbps upstream network of cable and fiber attaches homes to ISP router homes share access to router deployment: available via cable TV companies Residential access: cable modems

  21. Residential access: cable modems Diagram: http://www.cabledatacomnews.com/cmic/diagram.html

  22. Cable Network Architecture: Overview Typically 500 to 5,000 homes cable headend home cable distribution network (simplified)

  23. server(s) Cable Network Architecture: Overview cable headend home cable distribution network

  24. Cable Network Architecture: Overview cable headend home cable distribution network (simplified)

  25. C O N T R O L D A T A D A T A V I D E O V I D E O V I D E O V I D E O V I D E O V I D E O 5 6 7 8 9 1 2 3 4 Channels Cable Network Architecture: Overview FDM (more shortly): cable headend home cable distribution network

  26. company/univ local area network (LAN) connects end system to edge router Ethernet: 10 Mbs, 100Mbps, 1Gbps, 10Gbps Ethernet modern configuration: end systems connect into Ethernetswitch LANs: chapter 4 Company access: local area networks

  27. Bit: propagates betweentransmitter/rcvr pairs physical link: what lies between transmitter & receiver guided media: signals propagate in solid media: copper, fiber, coax unguided media: signals propagate freely, e.g., radio Twisted Pair (TP) two insulated copper wires Category 3: traditional phone wires, 10 Mbps Ethernet Category 5: 100Mbps Ethernet Physical Media

  28. Coaxial cable: two concentric copper conductors bidirectional baseband: single channel on cable legacy Ethernet broadband: multiple channels on cable HFC Physical Media: coax, fiber Fiber optic cable: • glass fiber carrying light pulses, each pulse a bit • high-speed operation: • high-speed point-to-point transmission (e.g., 10’s-100’s Gps) • low error rate: repeaters spaced far apart ; immune to electromagnetic noise

  29. 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” The Network Core

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