Networks (Week 10) Flashcards
What do Communication Systems do?
Transmit information from a source to a destination, typically over a network.
Networks can use either analog signals (e.g. old fashioned telephone) or digital signals (e.g. Wi-Fi).
At the source: convert information into a representation that can be transmitted over the chosen network
At the destination: convert signal back into the original representation
What is an example of an conversion for Communication Systems??
Well known example for such a conversion is Morse code.
Developed in the 1830s for telegraph communication
Every letter is encoded by a sequence of short and long signals (e.g. light or sound)
What is Bandwidth?
Bandwidth is about how fast a network can transmit data. If the bandwidth is large enough, data flows smoothly. If the bandwidth is constricted, data flow can halt or stutter.
How is Bandwidth measured?
The speed at which data can be transmitted (per direction) Bandwidth is measured in bits per second: kbps, Mbps, Gbps, Tbps
Kbps – kilobits per second
Mbps – Megabits per second (a megabit is over 1000x faster than a kilobit)
Gbps – Gigabits per second
Tbps – Terabits per second (fiber optic network that carry internet traffic across major expanses such as oceans or continents)
What is Latency or Delay?
How long does it take one particular chunk of information to get from the source to the destination?
What is Ping Time?
A term related to Latency or Delay.
Ping time is the time it takes for a packet of data to go from a device, to a server, and back to the device. This time is measured in milliseconds. A high ping means longer lag time.
In terms of online gaming, lower ping means smoother gameplay.
What is Jitter?
The variability of the delay in a system (high jitter degrades quality in transmissions involving live speech or live video).
Jitter is caused by the disruption of the normal sequence sending data sets or packets. Measured in milliseconds (ms)
What is Range?
Geographical size a network can cover depending on a given technology.
Local Area Networks can span several metres (LAN)
Metropolitan Area Network (MAN) can span over 50kms.
What are some Network Types?
Network types may be based on geographical size:
- WAN – wide area network, e.g. landline telephone system
- MAN – metropolitan area network, e.g. city fibre network
- LAN – Local area network, e.g. Camosun Campus Wi-Fi Network
- PAN – personal area network, e.g. smartphone connected to headphones via Bluetooth
What is the difference between Wired and Wireless Networks?
Wired networks require physical connections with different types of cables, typically containing electrical conductors
Wireless networks use radio frequency signals (electromagnetic waves) to transmit information
What is Broadcast?
Broadcast (one-to-many)
- Radio, TV, CB radio => one sender and multiple receivers are a desired
feature of the network type - Ethernet (both Wi-Fi and wired) => multiple receivers are an unwanted side effect (in most cases)
- In many usage scenarios, there is a need to consider security measures (e.g. to avoid eavesdropping)
What are some Network Types? (regarding how many receivers)
Unicast (one-to-one)
Multicast (one-to-many)
Broadcast (one-to-all)
What is the Point to Point network type?
Point to point (one-to-one)
* Telephone network (typically connects 1 sender and 1 receiver)
* Dedicated channel or line (e.g. for company networks)
What is Ethernet? (part 1)
Ethernet (both Wi-Fi and wired) => multiple receivers are an unwanted side effect (in most cases)
In many usage scenarios, there is a need to consider security measures to avoid eavesdropping
What is Ethernet? (part 2)
Ethernet is the predominant technology for local area networks
Uses a broadcast system (invented back in the 1960s)
* Messages are broadcasted to all connected workstations…
* …but are ignored by all except the destination workstation
Every workstation (WS) has it ́s unique ID – the Media Access Control Address (MAC address) => 12 digit hexadecimal number (48 bit)
What are TV Cable Networks?
Cable networks built for analog television are currently one of the options to get a high speed Internet connection:
Designed to carry multiple TV channels simultaneously => have enough excess capacity for upload and download of data in addition to TV channels
Originally a “broadcast” (one way) system, it had to be upgraded to allow two way communication
* e.g. to enable data uploads, allow pay per view options, etc.
Upload speeds tend to be slower as most traffic is downloading.
Internet cable users may experience slower speeds at peak times (due to shared access, e.g. in an apartment building)
Typically use coaxial cables
What is a Coaxial Cable?
Coaxial cable is reliable, accurate transmission.
Shielded design – transmit data quickly due to copper core, without succumbing to interference or damage from environmental factors.
There are limitations and fibre optic cable can replace the use of coaxial.
Typically Fibre Optic cable is more expensive to start. Is becoming more and more popular as residential neighbourhoods are being wired for Fibre Optic.
What are Fiber-Optic Cables?
Fiber-optic communication transmits data as light signals through an optical fibre (instead of copper wires). Advantages:
- Higher bandwidth (up to Tbps and more)
- Longer distances (between signal repeaters)
- Immunity to electromagnetic interference, e.g. from large electrical machinery, lightning strokes
Fibre is the technology of the future for wired high speed internet access (“fibre to the home”)
Fibre Optic vs Coaxial
Fibre Optic carries signals for several miles before needing a repeater.
Coaxial Cable signal loss is greater than Fibre Optic so it is better for shorter distances.
Fibre Optic is more expensive though carries more info.
Coaxial are easy to install and are durable
Coaxial is most common in residential.
TV Cable Networks
Use a “cable modem” to convert digital data to analog signals that are sent over the network
Upload and Download have different speeds (asymmetric), download speed is significantly higher. Bandwidth is typically higher to the home than out of the home.
What is a Digital Subscriber Loop (DSL)?
DSL modem is a device that connects a computer to a telephone line. This provides the DSL a connection to the Internet.
The DSL analog signals do not interfere with telephone voice traffic (you can talk and surf at the same time)
Allows high bandwidth connections over twisted pair cables of the telephone network, requires a DSL modem.
What is an Asymmetric Digital Subscriber Loop (ADSL)?
Often, ADSL (asymmetric DSL) is used because of higher bandwidth coming to the home than out of the home thus download speeds are faster than upload speeds.
You must live within approx. 5 km of a telephone switching location to get a decent performance
Does not use shared lines with neighbours as it uses a dedicated wire from your home to the phone company.
Basic Internet Service in Canada
Many rural communities in Canada have troubles getting basic Internet services at affordable prices => a major cause of the digital divide
Minimum service levels are essential to participate in the digital economy
Basic Internet service is defined by the Canadian Radio-television and Telecommunications Commission (CRTC) as 50 Mbps for downloads and 10 Mbps for uploads.
By the end of 2022, estimated 96% of Canadian homes and businesses are expected to have or exceed basic service.
Broadband Internet access through satellite
Various providers offer Internet access through a network of satellites.
Features lower bandwidth and higher latency than wired technologies, but can achieve basic Internet service levels as defined by CRTC
Improvements in coverage and speed are expected soon
* Satellite Internet operator Starlink (SpaceX) over 3,000 small satellites in orbit. 12,000 are planned.
