Internet archetecture Flashcards
What is the internet?
Billions of interconnected devices spread throughout the world
What is a source?
A device that wants to send data
What is a device that receives data called?
A destination
What do we call a link from source to destination?
Uplink / Upstream
What doe we call a link from destination to source?
Downlink / Downstream
What is the purpose of intermediate devices?
Direct packets of data to different destinations
What is network media?
Connections
The medium of communication
What is transmission latency?
Delay between transmission and reception on a communication link
What is link throughput?
The number of bits per second
What is an ISP?
Internetwork service provider
What is the structure of communication conversations called?
Protocols
What does OSI stand for and what is it?
The open session interconnection model.
This is the layered architecture of packets
What is Level 7?
Application layer
> This is where the data is being created on a computer
> The data is being formatted and saved into a file
What is Level 6?
Presentation layer > Preparing the data for being transported by: - formatting the data - Compressing - Encoding - Encrypt/decrypting data
What is Level 5?
Session layer
> This is establishing and terminating connections between devices
What is Level 4?
Transport layer
> Sending data
> Deciding the type of data transfer TCP/UDP
> Deciding the protocol for the communication between computers
What is Level 3?
Network layer
> Adding addresses for data transfer (IP address)
> Structure of the network with logical addressing
> Managing packet priority and scheduling
What is Level 2?
Link layer
> Addressing the source and destination (MAC address). This is addressing for the unique connection between two single devices not address for the whole network.
> The overall movement of data around the network
> Wire/cable or wireless
What is Level 1?
Physical layer
> Its role is to carry data from location to location
> The actual physical transfer of data through a medium (e.g. wires, optical-fibres)
> How is the data sent (voltage levels, waveforms)
How does OSI work for hosts?
A device that is sending data passes the data through each layer from Level 7 - Level 1.
A device that is receiving data passes the data through each layer from Level 1 - Level 7.
Each layer only interacts with its layer.
How does OSI work for routers?
When receiving data it passes it through Level 1 - Level 3.
When sending data it passes data through Level 3 - Level 1.
It needs to access Level 3 to see the IP address and determine where to send data
What is the difference between TCPIP and OSI?
TCPIP has just 4 layers and those layers together contain all the OSI layers.
Another form of Network layering achetecture
What are the 4 layers in TCPIP?
L1 - Network Access layer
L2 - Internet layer
L3 - Transport layer
L4 - Application layer
What is TCPIP L1?
Network access layer
Contains the:
> Physical layer
> Link layer
What is TCPIP L2?
Internet layer
Contains the:
> Network layer
What is TCPIP L3?
Transport layer
Contains the:
> Transport layer
What is TCPIP L4?
TCPIP Application layer Contains the: > Application layer > Presentation layer > Session layer
What is the difference between CPS and an embedded system?
A CPS is designed to have multiple connected embedded systems and is used to control physical things.
Embedded systems are used to monitor physical things.
What is a LAN?
Local area network
> Network covering a small area
> Ethernet
> WIFI
What is a WAN?
Wide area network
> Network covering a large area
> Cellular
> Fibre optical
What is a PAN?
Personal area network
> Very small network
> Bluetooth
> USB
What is a MAN?
Metropolitan area network
> Network spanning a large area but usually owned by a single company for company use/data transfer only
What is a Hub?
> Physical layer device > Amplifies signals > Retimes signals > Copies incoming signals to outgoing ports (Relay) > 1 collision domain > 1 broadcast domain
What is a Switch?
> Link layer device
No collision domain
1 broadcast domain
What is a Router?
> Network layer device
No collision domain
No broadcast domain
What is the collision domain?
This is when messages sent from devices can collide with each other and overlap.
What is the broadcast domain?
This is when messages sent over a network can be received by all devices on the network
What is a network hop count?
This is the number of intermediate network devices (e.g. routers) through which data must pass between source and destination
How is Hop count used?
As a packet passes through an intermediate network device, a counter is decremented. When it reaches zero and hasn’t reached its destination, the packet is discarded
Does link throughput depend on the medium the data is passing through?
Yes, the medium will drastically change the throughput
How can the transmission time across a single link be calculated?
T = L / R
T = Time L = Packet length R = Rate of transmission
How can transmission time across multiple links be calculated?
T = NL / R
T = Time N = Number of links L = Packet length R = Rate of transmission across links
What is the equation to calculate the number of routers based off the number of links?
Routers = N - 1
N = Number of links
What is the equation to calculate transmission time for multiple links and multiple packets that are queued up?
τ = ∑ L/Ri + (M - 1)L/R1
[from i = 1 to N]
τ = Transmission time L = Packet length Ri = Rate of transmissions of link i M = Number of packets R1 = Transmission rate of link 1
What is packet switching?
This is when there is no prior reservation of link resources so messages have to wait in queues to access communication link
What is a buffer?
This is the memory where messages are stored before they are are transmitted. They are in a buffer queue
What happens there is a lot of data wanting to be passed through a link?
The buffer can fill up and because the space is finite, the incoming packet will be dropped if the buffer is full
What are the benefits of packet switching?
Data transmission can happen on multiple paths at the same time
What are the disadvantages of packet switiching?
> Wasted bandwith when the source rate (of data) is lower than the link rate.
Congestion is unavoidable when there is heavy traffic
What is circuit switching?
The link is reserved from source to destination for the duration of the communication session. It is reserved ahead of time.
What are the benefits of circuit switching?
Guaranteed quality-of-service.
No queues
What are the disadvantages of circuit switching?
> Wasted bandwith when the source rate (of data) is low.
> Single path reservation
What is multiplexing?
This is sending multiple bits of data along a single wire.
What are the 2 types of multiplexing for links?
> Dividing frequency
> Dividing time
What is dividing frequency multiplexing?
Different channel frequencies can be used to send multiple channels of data
What is dividing time multiplexing?
Sending different sources of data in slots of time one after the other
How can the transmission rate for dividing time multiplexing be calculated from frames?
R = FL
R = Transmission rate F = Frame rate L = Number of bits in each frame
Which is better, packet switching or circuit switching when it comes to number of users?
Packet switching can support 3x the number of users without breaking a sweat.
