U408 by https://padlet.com/ianslater/syuwwl9a6dny Revision Support en-us 2017-10-19 09:58:33 UTC 2017-10-23 14:57:38 UTC hello@padlet.com Data Communication Links ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/198581814 Revision

http://www.sqa.org.uk/e-learning/NetTechDC01BCD/page_01.htm

Covering the following areas:
  • Serial and Parallel Communication
  • Error Detection
  • Data Communication Equipment (DCE)
  • Data Terminal Equipment (DTE)
  • Transmission Modes (Simplex, Half-duplex and Full-duplex)
  • Baud and Data Rates
  • The OSI Model
  • Digital and Analogue Signaling
  • Asynchronous and Synchronous Communication
  • Transmission Problems (attenuation, crosstalk (NEXT, FEXT, Attenuation to Crosstalk Ratio), interference, noise and skew)
]]> 2017-10-19 10:00:07 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/198581814 Analog Modulation ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/198582314 http://www.sqa.org.uk/e-learning/NetTechDC01DCD/index.htm
 
  • Amplitude Modulation
  • Frequency Modulation
  • Amplitude Shift Keying
  • Frequency Shift Keying
  • Phase Shift Keying Quadrature Amplitude Modulation 
  • Analogue broadcast media
  • Analogue modems
]]> 2017-10-19 10:02:25 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/198582314 Video on ALOHA ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/198718470 https://www.youtube.com/watch?v=0DF6ekaFC8U]]> 2017-10-19 15:19:47 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/198718470 What is packet switching? ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/198720852 https://www.techopedia.com/definition/5603/packet-switching]]> 2017-10-19 15:23:44 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/198720852 Circuit Switching ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/199604748 https://www.webopedia.com/TERM/C/circuit_switching.html]]> 2017-10-23 14:46:09 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/199604748 Digital to analogue conversation ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/199605105 Digital-to-analogue conversion is the process of changing one of the characteristics of an analogue signal based on the information in digital data.

1. Data element vs. signal element
2. Bit rate is the number of bits per second. 
2. Baud rate is the number of signal elements per second.
 3. In the analogue transmission of digital data, the baud rate is less than or equal to the bit rate.

An analogue signal carries 4 bits per signal element. If 1000 signal elements are sent per second, find the bit rate.
]]> 2017-10-23 14:46:50 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/199605105 Amplitude Shift Keying (ASK) ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/199606178
The amplitude (or height) of the sine wave varies to transmit the ones and zeros

Major disadvantage is that telephone lines are very susceptible to variations in transmission quality that can affect amplitude
]]> 2017-10-23 14:48:39 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/199606178 QAM – Quadrature Amplitude Modulation ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/199606968 Modulation technique used in the cable/video networking world

Instead of a single signal change representing only 1 bps“ multiple bits can be represented by a single signal change

Combination of phase shifting and amplitude shifting (8 phases, 2 amplitudes)
]]> 2017-10-23 14:49:50 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/199606968 Sync & Async ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/199607851 http://techdifferences.com/difference-between-synchronous-and-asynchronous-transmission.html]]> 2017-10-23 14:51:20 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/199607851 Virtual Switching ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/199608582 http://searchservervirtualization.techtarget.com/definition/virtual-switch]]> 2017-10-23 14:52:08 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/199608582 Error Control in Data Networks ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/199608951 http://searchnetworking.techtarget.com/definition/cyclic-redundancy-checking

https://en.wikibooks.org/wiki/Communication_Networks/Error_Control,_Flow_Control,_MAC]]> 2017-10-23 14:52:46 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/199608951 Simplex, Duplex, Semi-Duplex ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/199609562 http://techdifferences.com/difference-between-simplex-half-duplex-and-full-duplex.html]]> 2017-10-23 14:53:46 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/199609562 Asynchronous & Synchronous transmission ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/199609935 Asynchronous transmission
Asynchronous transmission is when a signal is sent with the timing signal within it. In a simple form this would be the start bit used in a modem-to-modem communication. The connecting modem first sends a training signal to establish the bit rate, etc. when no data is being transmitted, the connecting modem sends a continuous stream of high signals or 1s. The start bit is then a zero. There would also be a stop bit at the end of each byte. These start and stop bits effectively do the timing in an asynchronous transmission.

Synchronous transmission
Synchronous transmission involves the use of another wire or carrier to carry the clock signal. When the clock pulses, the receiving end knows that the transmission of one byte has finished and the next one starts.
Synchronous transmission signals can be embedded into the signal on the main wire.
This method is used in Manchester encoding.
]]> 2017-10-23 14:54:28 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/199609935 Routing Protocol ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/199610802   
OSPF (Open Shortest Path First) IS-IS (Intermediate System to Intermediate System) and NLSP (Netware Link State Protocol) are link state protocols, meaning that they transmit the change state of any links attached to them to other routers.

All of the above are IGPs (Interior Gateway Protocols) and are referred to as type 1.

RIP (Routing Information Protocol), RIP 2 and IGRP (Interior Gateway Routing Protocol)are distance vector routing algorithms.

Look up distance vector routing protocols on Wikipedia.org

]]> 2017-10-23 14:56:08 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/199610802 Lease Lines ianslater https://padlet.com/ianslater/syuwwl9a6dny/wish/199611362 A lease line would be a T1 – T4 or E1 – E5 line. Each of these lease line types represent an amount of 64Kbps channels linked together. For instance a T1 line has 24 x 64Kbps channels, giving it a throughput or bandwidth of 1.544Mbps. this is also termed a DS1 line, where a DS0 line is 1 x 64Kbps channel. This can be provided for with one T1 unit. An E5 lease line is 7,680 channels linked together, giving 565.148Mbps. This would require 320 T1 units. The other term for this is a DS5 line.

Lease line protocols in use are; SNA (System Network Architecture). This is a proprietary protocol used by IBM; DECnet (Digital Equipment Corporation. This was taken over by Compaq and later by HP) and TCP/IP, which is the de facto standard on the internet and local LANs today.

Lease lines provide a dedicated, always on connection for the customer and are therefore more expensive than the alternative offerings, like; ADSL, SDSL & VDSL, however, the alternative offerings only support half-duplex, whereas lease lines are full duplex.

]]> 2017-10-23 14:57:03 UTC https://padlet.com/ianslater/syuwwl9a6dny/wish/199611362