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Data Communications

Data Communications. Topics. What is data communications Data communications media Fundamental data communications considerations Data network topologies Building cabling LAN / MAN / WAN Communications equipment Systems architectures. Data Communications Defined.

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Data Communications

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  1. Data Communications

  2. Topics • What is data communications • Data communications media • Fundamental data communications considerations • Data network topologies • Building cabling • LAN / MAN / WAN • Communications equipment • Systems architectures

  3. Data Communications Defined • Electronic transport of “data” between two endpoints • End point types: • Communications equipment • Computer • Phone • Terminal • Sensor (e.g. temperature, smoke detector) • Equipment (e.g. robotic arm) A B

  4. Data Communications Packetization • Sending of a file, email, etc. requires that the data be broken into packets • To avoid monopolizing the network • To recover in the event of an error while sending • Each packet addressed to and sent to the receiver(s) in a transmission • The receiver(s) acknowledge successful receipt to the sender Sender Receiver …

  5. Data Communications Media • Channels for the data communications signal • Types

  6. Data Communications Media, cont’d • Distance/cable length dependent • Fiber less sensitive to distance w/o the need to refresh, greater bandwidth, not effected by electromagnetic interference

  7. Wireless variations • WiFi vs. Wireless • WiFi = Wireless Fidelity • Generally refers to short distance wireless access, e.g. within a building, your home wireless network • Wireless telecommunications carrier options Notes: *1st gen iPhone, **2nd gen iPhone ***No longer sensitive to smartphone movement

  8. Transmission Considerations • Bandwidth • Amount of data that can be transmitted between endpoints within a period of time (common usage) • Expressed in bits per second (bps) • Attenuation • Signal loss during travel between endpoints • Latency • The time it takes to for a signal to travel between endpoints • Something less than the speed of light (66% good estimate) • Factors include distance and media type, equipment processing time, and number of stops along the way

  9. Transmission considerations, cont’d • Narrowband • Communications speed 56 Kbps or less (common usage) • Transport capable of supporting a single channel • Broadband • Communications speed greater than 56 Kbps (common usage) • Transport capable of supporting multiple channels

  10. Network Topologies Bus • Easy to extend • Simple / reliable • Fault diagnosis Difficult Ring • Simple fault diagnosis • Dual ring implementation very reliable Star • Easy to maintain/diagnose • Potential for more cable than bus or ring • Most common LAN topology Mesh Highly reliable Efficient Point-to-point communications Largest number/amount of cables

  11. LAN / MAN / WAN • Local Area Network • Network within building or campus • Network segments owned/maintained by company/institution • Speeds up to 10 Gbps • Metropolitan Area Network • Network extended between buildings/campuses generally within a few miles of one another (generally less than 30 miles) • Carrier supplied network segments at very high speed links (up to 1 Gbps) • Wide Area Network • Network spanning longer distances • Carrier supplied network segments • Speeds up to x00s Mbps

  12. Network Signals Signals on a network are either: • Analog (old phone system, radio, TV (until recently)) • Digital Amplitude Modulated Frequency Modulated 0’s and 1’s

  13. Network Equipment Network Interface Card (NIC) • Computer network interface • Multiple types e.g.: • Connect to LAN or WAN • Wired versus wireless network PC NIC Network Server NIC NIC Network NIC

  14. Network Equipment “Traditional” Modem (Modulator/Demodulator) • Used to convert digital to analog signal • Required for a computer to communicate over plain old telephone lines • Modems can be internal or external to the computer Digit 1 = + wave form Digit 0 = - waveform

  15. Network Equipment, cont’d Cable Modem • Required for a computer to communicate over cable system • Used to convert digital to analog signaling used by cable systems • Can also provide: • “Channel” for phone • Network hub/switch • Wireless hub

  16. Network Equipment, cont’d Network Hub/Switch • Connects multiple computers, printers, LANs to form a network • “Network in a box” • A Hub is a “dumb” device that simply passes network traffic • A Switch can filter out traffic it forwards

  17. Network Equipment, cont’d Wireless Access Point (wireless network hub) • Provides wireless connections to wired network • Many also provides ports for wired connections • Not the same as a wireless router

  18. Network Equipment, cont’d Router • Join multiple networks (e.g. home network to internet service provider network) by providing • Address translation • Routing process and routing decisions • Versions for home may include wireless access point and switch functionality

  19. Network Protocol • Rules observed by equipment on a shared network • Different protocols for: • LANs/MANs • Very High speed LANs • WAN • Most common for LANs and MANs is called: • Ethernet, a.k.a. • CSMA/CD (Carrier Sense Multiple Access/Collision Detect) , a.k.a. • IEEE 802.3 (Institute of Electrical & Electronic Engineers 802.3) • The bulk of the LANs in businesses and homes uses this protocol

  20. Ethernet Carrier Sense – Is anyone currently transmitting? Multiple Access – Looks clear.Let’s try sending data? A A C C B B D D

  21. Ethernet, cont’d Collision Detect – Were multiple devices transmitting? Back-off/Retry – There were multiple concurrently transmitting! Reset and try again later. A A C C B B D D

  22. Data and Voice Network Convergence • What is it? • Using the same network resources for handling both Data and Voice traffic • Why now? • Increased processing power allows for the effective digitizing of voice and video • Why at all? • Digitizing voice and video allows for the transport of that traffic by the same equipment and communications media as the data traffic. • Support staff formerly support just data networks can also support the voice and video elements • Network Example

  23. Data and Voice Network Convergence, cont’d Application examples • Phone systems, using standard computer systems • Price and support advantages • Video conferencing systems • Unified Messaging • One inbox for email, voice mail • Calendar scheduled and initiative conference calls • Services like Skype that offer a rich user experience: • Voice and video over the internet • Shared applications • Shared whiteboard • Video sharing services such as YouTube

  24. TCP/IP • Design guidelines and implementations for networking protocols enabling computers to communicate over a network. • The protocol used on the Internet. • TCP/IP provides end-to-end connectivity: • Specifying how data should be formatted, addressed, transmitted, routed and received at the destination. First developed for the Internet. • Vehicle for web, email and other such traffic to flow. • TCP = Transmission Control Protocol • Guaranteed communication between end points • IP = Internet Protocol • Addressing and routing methods

  25. TCP/IP Application Layer TCP Transport Layer Internet Layer IP Physical Layer

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