Networks and Telecommunication

This week we explore networks and telecommunication. The outline presented here is intended to help point out important topics and terms covered in the chapter. It is not intended to replace reading the lecture.

• Describe business and home applications of digital telecommunications
• Identify the major media and devices used in telecommunications
• Explain the concept of protocols
• Compare and contrast various networking and Internet services
• Discuss the pros and cons of telecommuting

• better business communication
• greater efficiency
• better distribution of data
• instant transactions
• flexible and mobile workforce
• alternative channels (e.g. telephone via Internet)
• makes it easy to move jobs overseas

• telecommunication: communication over a distance
• telecommuting: working at a distance; often applied to being able to work from home
• bandwidth: how fast data is communicated; usually measured in bps
• transmission rate: how fast data is communicated; usually measured in bps
• bps: how many bits per second are communicated
  • bps = bits per second
  • Kbps = 1,000 bits per second
  • Mbps = 1,000,000 bits per second
  • Gbps = 1,000,000,000 bits per second
  • Tbps = 1,000,000,000,000 bits per second
• broadband: service that allows multiple communications at one time, usually high speed
• media: what the signals are transmitted through (coaxial cable, twisted pair, fiber optic, microwave, etc.); see table on page 190 (7th edition)
• RFID: Radio Frequency Identification (see the notes for chapter 3 for more information about how RFID works
• NFC: Near-field Communication
• EMI: electromagnetic interference
• RFI: radio frequency interference
• BPL: broadband over power lines
• PLC: power line communication (same as BPL) - but more commonly used in the IT field to mean programmable logic controller (the same abbreviation has a different meaning in many different fields)
• VOIP: Voice Over IP (Internet telephony, such as Vonage, Comcast); computer-to-computer phone calls can be made using Skype or iCall; Google Voice integrates all types of different phones, even allowing one incoming call to ring on all your different types of phones
• FTTH: Fiber to the Home; term for having a fiber optic connection all the way to a house
• OC: Optical Carrier; very high capacity fiber optic connections denoted as OC-n, where n is an integer that specifies the bandwidth (n * 51.84 Mbps); range of speeds goes from OC-1 through OC-3072 (159 Gbps)

How long should it take to transfer a file? An old rule-of-thumb states that it takes about ten bits for every byte of data being transferred. One byte contains eight bits, and two more bits on average are considered part of the communication overhead for each byte.

Let's assume we have a 1.5Mbps (1,500,000 bits per second) transfer speed and we want to transfer a file that is roughly 10MB (10,000,000 bytes). Let's also assume the file is compressed (such as an mp3, jpg, or docx file is). Since it is compressed, we can't save much by trying to compress it further. We have to transfer 10MB. Since the rule of thumb states we should expect to be using 10 bits per byte for the transfer, we should expect to be transferring 10MB * 10 bits/MB = 100,000,000 bits. If we divide 100,000,000 by the transfer speed of 1,500,000 bits/second, we end up with approximately 66.7 seconds, which is a little over a minute.

• cellular phones: now include IM, email, web, PDA, GPS, etc.
• videoconferencing
• fax (facsimile machine)
• wireless - RFID: for instant payments and warehousing uses. RFID requires a product with an RFID tag to come close to an RFID scanner. The scanner causes the RFID tag to send its identification number, which the scanner can then read and look up in a database to decide what to do with it. More sophisticated (and expensive) RFID devices may have their own power suply and be able to perform additional functions. Page 209 (7th edition) of the text provides a list of common RFID applications.
• wireless - NFC: Near-field communication requires close proximity between two devices. A communication is automatically set up between the two devices and information can be exchanged. One common use for NFC is for instant payments from electronic wallets.
• P2P: P2P is used to directly share files between two computers without using a server to transfer the files through.
• web-empowered commerce: Web-empowered commerce includes research, marketing, education, training, shopping, purchasing, and online bill payment.

• twisted pair: high availability (land line phones), low to medium bandwidth, vulnerable to EMI, generally high reliability
• radio waves: high availability, medium to high bandwidth, vulnerable to RFI
• satellite: high availability, medium to high bandwidth (but often low bandwidth due to artificial limits created by provider), vulnerable to weather conditions such as clouds and wind, reliability can be a problem
• microwave: low availability, high bandwidth, not very vulnerable to EMI or RFI, requires line-of-sight, used with ground towers and also satellites
• coaxial/cable: high availability (cable TV), not very vulnerable to EMI or RFI, reliability often poor, high bandwidth theoretically (but companies like Comcast purposely slow down and interfere with transmissions so users can't actually achieve high bandwidth for long)
• optical fiber: moderate availability (purposely limited by cable and phone companies), very high bandwidth (20+Tbps), not vulnerable to EMI or RFI
• electric power lines (BPL): theoretically high availability (but have fun trying to find any provider locally), high bandwidth, very vulnerable to EMI

• network: a combination of connected devices which can communicate
• nodes: devices connected to a network
• LAN: local area network; contained within a small area such as a building
• WAN: wide area network; spread over a large geographic area (e.g. the Internet)
• MAN: metropolitan area network; usually a connected collection of numerous LANs spread out over part of (or all) of a city
• PAN: personal area network; wireless; often a bluetooth connection of two or three devices within a very small area (e.g. camera/computer, phone/car stereo, etc.)
• VAN: value added network; provides the networking needs for an organization so that the organization doesn't have to maintain a network itself
• ISP: Internet service provider; the company you pay to get internet access
• EDI: electronic data interchange; one way of transmitting data between companies; now being replaced by XML over standard Internet services
• VPN: virtual private network; used to connect a remote machine through the Internet to make it seem like it is part of a LAN

• NIC: network interface card
• hub: allows several devices to connect together
• switch: a more intelligent version of a hub
• bridge: connects different networks
• router: can connect dissimilar networks, forwards incoming packets toward destination node
• repeater: used to regenerate signals on long distance runs
• modem: short for modulator/demodulator; converts analog to digital and vice-versa (modulation = digital to analog, demodulation = analog to digital)
• WAP: wireless access point; used to connect wireless devices to the Internet
• wireless hotspot: an area where wireless devices can reach a WAP and connect to the Internet
• packet: a group of bits which are transmitted together
• dial-up: traditional phone line hookup to Internet (slow)
• circuit switching: direct connection is made between sender and receiver so data can be transmitted
• packet switching: messages are broken into packets and sent into network hoping that receiver will get them; packets may arrive out of order and are reassembled on receiving end; lost or corrupted packets are resent; packets are routed around problems in the network; packets travel intermixed with a multitude of other unassociated packets through network
• protocol: rules used to establish and maintain communication
• TCP/IP: Transmission Control Protocol/Internet Protocol; standard rules used to create, address, send, and receive packets on the Internet
• IP address: unique address within a network of a specific device (actually, there are broadcast addresses where every device on a network can be reached at once, and an address for the network itself)
  • IPv4: old standard still widely used, but not enough addresses (a little over 4 billion) available for all the devices in the world; uses 32 bits; IPv4 addresses look like "187.132.27.8" (each octet can range from 0 to 255)
  • IPv6: new standard currently being implemented, enough addresses (~340,000,000,000,000,000,000,000,000,000,000,000,000) available for all the devices in the world; uses 128 bits; IPv6 addresses look like "0A87:4562:9908:1234:BCFF:0CE3:10D1:F0B5" (each digit is a hexadecimal value that can range from 0-F)
• static IP address: an IP address which stays the same over a long period of time; servers on the web have to have static IP addresses so the DNS servers can easily keep track of them; the problem is that there aren't enough static IP addresses to assign one to every device on the Internet (using current IPV4; IPV6 standard greatly increases number of IP addresses)
• dynamic IP address: an IP address which may change relatively frequently; ISPs usually have a limited number of IP addresses and assign an available one to a computer as it logs in to the network; also, certain ranges of IP addresses are used for internal networks (LANS); these addresses must be unique within that LAN, but other LANs can reuse the same IP addresses without a problem
• DNS: domain name system; translates URLs such as www.yahoo.com into its associated IP address
• URL: uniform resource locater; a unique name on the Internet which is used to identify a specific resource such as a company's home page
• Ethernet: the protocol used by most LANs
• WiFi: a standard protocol used for wireless computer communication in LANs
• encryption: converting a message into a format that makes if difficult to read
• decryption: converting an encrypted message back into a readable format
• upstream: refers to sending data
• downstream: refers to receiving data
• client: a machine or software that is requesting a resource or service
• server: a machine or software that is fulfilling requests for a resource or service
• P2P: peer-to-peer is when two machines connect directly to each other without using a server as an intermediary (although the connection can still travel through other devices on the Internet)
• DSL: digital subscriber line; works over phone line; you can still use phones while computer has high-speed Internet connection
• T1: a dedicated telephone company digital circuit consisting of 24 channels of 64Kbps communication capacity
• T3: a dedicated telephone company digital circuit consisting of 672 channels of 64Kbps communication capacity
• 802.11: IEEE 802.11 is a collection of wireless protocols called WiFi. They are intended for short range (300 to 500 feet) wireless access to networks through wireless access points (WAPs) often referred to as hotspots. Variations of the 802.11 standard use different wavelengths and techniques to achieve different speeds and capabilities. Common variants include 802.11a, 802.11b, 802.11g, 802.11n, and 802.11ac. See page 200 in the text (7th edition) for a comparison chart of 802.11 family protocols.
• 802.15: This is the Bluetooth wireless protocol which was designed to connect devices over a very short range (up to about 30 feet). It is used for wireless keyboards and mice, headsets, hands-free phone devices, and music players. This protocol is ideal for PANs (personal area networks).
• 802.16: This is the WiMax standard. It can provide high-speed access at a distance of 8 miles or more, and provide access to moving vehicles.
• 4G LTE: a standard for high speed data transmission for mobile phones which is currently being implemented; 4G stands for Fourth Generation; LTE stands for Long-term Evolution
• fixed wireless: Fixed wireless uses microwaves to connect a building to the Internet. It is a reasonable replacement for traditional land-line phone service. The connection must be line-of-sight. Speed varies depending on distance. The range can be up to about 35 miles, although the bandwidth at that range will not be very good.

• saves time (no commute)
• saves money (no commute, company doesn't have to provide as much infrastructure such as office space)
• employees with special needs can more easily be integrated into the workforce
• can be considered a benefit which may attract more and better employees
• employee schedules can be more flexible and help reduce employee stress
• employees are expected to be more available (and often do work longer and more unusual hours)
• other parts of the economy may suffer (less gas used, fewer business lunches, less office space needed, etc.)
• social interaction within the company can be greatly reduced
• companies must invest in sufficient IT infrastructure to make telecommuting work properly
• employees must either invest in or be given sufficient technology to make telecommuting work well
• employees must be disciplined enough to work well when not physically around other people or they will quickly fail
• traditional management techniques may not work for telecommuting (but those management techniques often don't work well anyway)
• easier to move jobs out of country