Mod 2 - Network Organization Flashcards
What is a network?
it is all the “stuff” & devices that connect and allow computers to communicate with each other (infrastructure)
ex. the internet is the largest network
What is synchronous communication?
It is real time communication.
ex. talking on the phone, radio broadcast
What is asynchronous communication?
It uses a time stamp to keep track (like a postcard) and is not done on a particular schedule, meaning there is a time lag.
ex. internet, text messages
(if there is a time stamp on it, it is likely asynchronous)
What are communication layers?
When a message comes in, it goes from low layers to high layers. When a message is sent out, it goes from high layers to low layers.
Ex. postcard coming in:
mail delivery system>letters on postcard>words>semantic meaning of words
(vice versa for sent out)
What are protocols?
They are found in every layer of communication. Some protocols will be strict or basic, etc. Think about computer protocols like a form - it must be filled out to work.
Ex. postcard: needs a stamp, address, postal code, etc.
What are examples that fall under the physical layer (lowest)?
It provides physical interactions & components
- ethernet
- phone, ADSL & cable modems (all used to communicate from one computer to another)
- wifi
- 3G/LTE
- IMEI
What is required to use ethernet?
It needs a device that can transmit info over a wire & each connection requires a unique identifier known as a Media Access Control (MAC) address (every device with an ethernet port has one).
How does communication through ethernet work?
It uses sophisticated protocols to allow conversation. So, if one device is “talking”, others back off until there is a gap for them to “talk” - like a dinner party. There are different speed ratings for cables & devices, so a slower device/cable may slow down the entire communication chain.
How do phone modems (dial-up) work?
It connects a computer to a modem and is also connected to the phone line. There are many different protocols that occur because two devices must communicate to work.
How does ADSL work?
Asymmetric Digital Subscriber Line (ADSL) evolved from a modem and uses the same idea, but is slightly more sophisticated. The asymmetric means the download speed is faster than the upload speed.
How do cable modems work?
It uses the the same idea as other modems but communicates over frequencies designed to transmit TV signals & has a higher bandwidth.
How does wifi work?
It is just a radio wave on the electromagnetic radiation spectrum (can go through walls). Wifi ranges are typically 20-100m & use less power than radio signals. To work, an access point that broadcasts & receives from devices is required. Broadcasting name & security is part of protocol.
How does cellular 3G/LTE work?
It uses electromagnetic radiation similar to wifi, but has different protocols, frequencies & energies. Cellular range is much farther than wifi (several km) & often communicates with cell towers which is a much noisier environment. This means better error correction & signal change detection is required, so more power is needed (uses lots of battery).
What does 3G stand for? What does LTE stand for?
3G: 3rd generation (marketing scheme)
LTE: Long-Term Evolution (basically a 3 1/2 G)
What is IMEI?
an International Mobile Equipment Identity (IMEI) is required by all devices that communicate with cell towers. It is a unique identifier and explains why phones are locked to carriers.
