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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,

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Presentation on theme: "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,"— Presentation transcript:

1 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 2 A closer look at network structure: network edge: applications and hosts access networks, physical media: wired, wireless communication links network core: interconnected routers network of networks

3 3 The network edge: end systems (hosts): run application programs e.g. Web, email at edge of network client/server peer-peer 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 4 Access networks and physical media 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?

5 5 Residential access: point to point access Dialup via modem up to 56Kbps direct access to router (often less) Cant surf and phone at same time: cant be always on 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 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 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 8 X-DSL data rates ADSL modem is the most commonly used Rates Downstream: 8 Mbps Upstream: 800 Kbps – 1 Mbps

9 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 10 Bandwidth vs distance

11 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 12 ADSL: equipment configuration

13 13 ADSL equipment

14 14 ADSL deployment: at the customers 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 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 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 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 18 Discrete multi-tone technique ADSL 8 Mbps in the downstream 1 Mbps in the upstream

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

20 20 Residential access: cable modems 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

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

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

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

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

25 25 Cable Network Architecture: Overview home cable headend cable distribution network Channels VIDEOVIDEO VIDEOVIDEO VIDEOVIDEO VIDEOVIDEO VIDEOVIDEO VIDEOVIDEO DATADATA DATADATA CONTROLCONTROL 1234 56789 FDM (more shortly):

26 26 Company access: local area networks 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 Ethernet switch LANs: chapter 4

27 27 Physical Media Bit: propagates between transmitter/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

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

29 29 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


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