2. Bridges To Computing General Information: This document was created for use in the "Bridges to Computing" project of Brooklyn College. You are invited and encouraged to use this presentation to promote computer science education in the U.S. and around the world. For more information about the Bridges Program, please visit our website at: http://bridges.brooklyn.cuny.edu/http://bridges.brooklyn.cuny.edu/ Disclaimers: All images in this presentation were created by our Bridges to Computing staff or were found online through open access media sites and are used under the Creative Commons Attribution-Share Alike 3.0 License. If you believe an image in this presentation is in fact copyrighted material, never intended for creative commons use, please contact us at http://bridges.brooklyn.cuny.edu/ so that we can remove it from this presentation.http://bridges.brooklyn.cuny.edu/ This document may include links to sites and documents outside of the "Bridges to Computing" domain. The Bridges Program cannot be held responsible for the content of 3 rd party sources and sites.

3. Internet Hardware Dial-up –POTS (Plain Old Telephone System) –Modems. –UART chips - universal asynchronous receiver/transmitter. –Point-to-Point Protocol (PPP)- streaming protocol developed especially for dial-up Internet access. –28.8 Kbps (56 K modems, which were big surprise, didn’t appear until 1995)

4. Modem Stand for MOdulate DEModulate. Converts analogue signals to digital signals.

5. UART Universal Asynchronous Receiver Transmitter. Converts serial data to parallel data. Neccesary so that information can "get on the BUS".

6. Internet Hardware... cont ISDN (integrated services digital network) –POTS –ISDN Devices (look a lot like modems) –Full digital communication over multiple "channels". B channels carry data and voice information at 64 Kbps. D channels carry setup and configuration information and carry data at 16 Kbps. –BRI - one physical line, 2 B's 1 D, throughput total to 128 Kbps. –PRI (aka T1) - 23 64-Kbps B's, 1 64-Kbps D, total throughput of 1.5 Mbps.

7. Internet Hardware... cont DSL (digital subscriber line) –POTS –DSL Devices (look a lot like modems) –Replacing ISDN –Requires special tested lines, and equipment. –Typical upload speed is ~768 Kbps, download ~3+ Mbps. –Requires short distance from a main phone service switching, center (18,000 feet). –Many, many channels on one line. –Much much faster communication over each channel.

8. Internet Hardware... cont Cable –Uses regular insulated cable TV cables. –Cable Devices (look a lot like modems) –Offers faster service than most DSL connections: 1–10 Mbps upload and 6–50+ Mbps download. Variable bandwidth becoming more common. –Cable Internet connections are theoretically available anywhere you can get cable TV. –Many, many channels on one line. –Much much faster communication over each channel.

9. Internet Hardware... cont Wireless (WiFi, 102.11B, Bluetooth, IR, Cellphones) –Variety of device protocols. –Variety of ranges. –Unique problems (hidden sender, manets, security) –Emerging technology. –Don't leave your wireless device unsecured (anyone can listen). –Long distance WiFi now available in bandwidth that used to be used for TV signals.

10. DHCP & NAT DHCP (Dynamic Host Configuration Protocol) –Protocol that allows IP address information to be automatically handed out to machines. –Eliminates need to hand enter lots of tedius network information. –Allow network addresses to be retrieved and reused. NAT (Network Address Translation) –Allows multiple machines to share one Internet IP address connection (NAT). –Router keeps track of all members of network and acts as proxy on the web.