1. Access and Interconnection Technologies

2. Overview Two important Internet facilities – Access technologies used to connect individual residences and businesses to the ISP (last mile) ADSL, Cable Modem, Hybrid Fiber Coax, Wireless – High-Capacity Connections at the Internet Core Telecommunication-based networking technologies – Know the jargons

3. Upstream and Downstream Internet access through an Internet Service Provider (ISP) – An asymmetric pattern Downstream: data traveling from an ISP – E.g., a streamed movie Upstream: data traveling to an ISP – E.g., upload personal photo

4. 4 Narrowband and Broadband Two broad categories on data services based on data rate – Narrowband: up to 128 kbps – Broadband: about > 1 Mbps

5. 5 Local Loop Local loop – Physical connection between a telephone company Central Office (CO) and a subscriber – Twisted pair connections – Dialup call: 4 kHz of bandwidth – Potential bandwidth: about 1MHz

6. 6 Digital Subscriber Line (DSL) DSL – High-speed data communication services over a local loop AT&T U-Verse, Verizon FiOS, CenturyLink

7. 7 ADSL ADSL is the most widely deployed variant. – May not be so soon. ADSL uses FDM to divide the bandwidth of the local loop into three regions – POTS: Plain Old Telephone Service – Two regions provide data communication

8. 8 Local Loop Characteristics and Adaptation ADSL technology is complex – No two local loops have identical electrical characteristics FDM is implemented by dividing the bandwidth into 286 separate frequencies – 255 sub-channels allocated for downstream data transmission – 31 allocated for upstream data transmission – Not using the bandwidth below 26 kHz. ADSL is adaptive – Negotiation between two ends regarding data rate.

9. 9 Data Rate of ADSL ADSL does not guarantee a data rate – do as well as line conditions allow Downstream rate: up to 8.448 Mbps – Depends on how far away from the central office or local offices. Upstream rate: up to 640 kbps – Network control channel: 64 kbps – Effective upstream rate for user data: 576 kbps ADSL2 is better. – Downstream: close to 20 Mbps

10. 10 ADSL Splitters An FDM device to divide bandwidth – Low frequencies to phone – High frequencies to modem – Passive: require no power. – Installed locally.

11. Compare ADSL with Other DSLs SDSL – Equal downstream and upstream HDSL – Addressing the distance problem of ADSL. VDSL/VDSL2 – FiOS and U-Verse – No longer limited to copper wires. – DSL: only means that the service still relies on the phone infrastructures.

12. 12 Cable Modem High bandwidth & less susceptible to electromagnetic interference than twisted pair. Use FDM to deliver TV signals over coaxial cable – 6 MHz per channel – Shared by all users. From 55MHz (Channel 2) to 1GHz (Channel 158) – Internet services consume the bandwidth of one channel

13. Digital TV Still use the channel frequencies of analog channels. Why are there more than 150 channels? – Compression: more efficient use of frequency resources. 13

14. 14 Data Rate of Cable Modems In theory – Downstream: 52 Mbps – Upstream: 512 kbps upstream In practice, the rate can be much less – Shared among a set of N subscribers via statistical multiplexing About 44 Mbps at my home at 1am Saturday morning

15. 15 Cable Modem Installation Attach to the cable wiring directly – FDM hardware guarantees that data and entertainment channels will not interfere with one another

16. Hybrid Fiber Coax 16 A combination of optical fibers and coaxial cables – Optical fibers: higher speed connection to central facilities – Cables: lower speed connection to subscribes

17. 17 Access Technologies With Optical Fiber From Wikipedia {

18. FiOS: FTTP Service by Verizon FiOS: Fiber Optic Service – 3-in-1: Internet, TV and phone service TV: 200 channels, including high-definition FiOS Internet: up to 50 Mbps downstream and up to 5 Mbps upstream Three wavelength bands – One for TV – Two for data: one upstream and one downstream Phone service is just like regular phone service, but uses fiber. 18

19. Installation of FiOS Requires new equipment outside and inside a premise. – http://www.bricklin.com/fiosinstall.htm http://www.bricklin.com/fiosinstall.htm 19

20. Cable Modem VS. DSL Speed – Usually cable modem is better than DSL. – FiOS and U-Verse have changed the game. Availability – In US, cable is more popular. – Outside US, DSLs dominate. Installation – Cable model and regular DSL are simple – VDSL, HDSL are more complicated

21. High-Capacity Connections What if a company needs more bandwidth, say 10 Gbps? – A point-to-point digital circuit leased from carriers.

22. Telephone Standards for Digital Circuits

23. Highest Capacity Circuits (STS Standards) STS: Synchronous Transport Signal OC: Optical Carrier

24. Wired networking still faces problems Remote farms and villages – No cable services Outdated wires and equipment – impossible to use high frequencies on telephone lines that contain loading coils, bridge taps, or repeaters

25. Wireless Access Technologies Wireless from cellular service providers – 3G or 4G Wifi – Different versions a/b/g/n/ac 2.4G, 3.7G, 5G – Municipal wifi Challenges in finance and policy – Google Loon Project http://www.google.com/loon/ Satellite – Long-delay is problematic