1: Networks Intro Flashcards

1
Q

What is a host?

A

A device connected to a computer network that is connected to other devices/hosts on the network that runs network applications.

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2
Q

What is an end system?

A

A computer connected to a network that are used by end users, i.e. the people intended to use a system (web surfers with the Internet network).

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3
Q

What is forwarding?

A

The process by which a datagram is moved from a source device to an output device: 1 hop along a path.

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4
Q

What is routing?

A

Routing is the process by which a network as a whole determines the paths deciding how packets go from source to destination: forwarding tables are built.

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5
Q

What is a protocol?

A

A communications protocol is a set of rules determining the format and order of data and actions taken when different data are received.

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6
Q

What is an Internet standard?

A

A specification of a networking technology or methodology using the Internet.

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7
Q

What is a network edge? What is an edge device?

A

Network edges are hosts on computer networks: servers or clients on the Internet.

Edge devices connect network edges to a wider network, e.g. consumer home computers in a LAN (access network) to the Internet. Edge devices are usually routers.

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8
Q

What is an access network?

A

A network designed for general and end users that allows them to connect to the core of the network, such as Ethernet-based LANs in homes connecting people to the Internet.

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9
Q

What is the network core?

A

A subset of a network containing connections between routing devices, both of high bandwidth, that act to connect systems towards the network’s edge.

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10
Q

What is an edge router?

A

A router is a networking device that data are forwarded in computer networks.

An edge router is a specialised router that connects two networks, usually an access network to the Internet, or two LANs into a WAN.

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11
Q

What is DSL?

A

Digital Subscriber Line is a group of technologies allowing access to digital data, usually from the Internet, via preexisting telephone lines.

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12
Q

What is multiplexing?

A

Methods of splitting analogue or digital signals into distinguishable channels that allow for multiple signals to be sent as one over a single shared physical medium.

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13
Q

What is FDM?

A

Frequency-division multiplexing is splitting a single signal into multiple channels along the lines of frequency bands which allows you to send multiple signals as one over a single shared physical medium.

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14
Q

What is HFC?

A

A hybrid fibre-coaxial is a physical medium combining optical fibre and coaxial cable that is often used in broadband access networks.

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15
Q

What is a packet?

A

A single formatted unit of data on a network consisting of contents and metadata relating to its control.

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16
Q

How do you find packet transmission delay?

A

Packet transmission delay = packet length, L (bits) ÷ link transmission rate, R (bits / sec)

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17
Q

What is a transmission rate?

A

The amount of information a data link can transmit per unit time; usually measured in Bits/sec.

aka link capacity and link bandwidth

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18
Q

What is a link?

A

Physical infrastructure between the transmitting and receiving node on a network that facilitates the propagation of data between the two.

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19
Q

What is link capacity?

A

Link capacity = the amount of information a data link can transmit per unit time; usually measured in Bits/sec.

aka transmission rate and link bandwidth

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20
Q

What is a physical link?

A

Infrastructure between the transmitting and receiving node on a network that facilitates the propagation of data between the two.

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21
Q

What are guided and unguided media?

A

In guided media, signals move along the physical courses of physical media which are wires and cables, and in unguided media, signals propagate through open space (air), such as Wifi and Bluetooth radio signals.

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22
Q

What is coaxial cable?

A

A bidirectional physical medium compromised of two copper wires, with one wrapped around the other.

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23
Q

What is twisted pair?

A

A physical medium compromised of two insulated copper wires that are commonly used in LAN and Ethernet networks.

24
Q

What is packet-switching?

A

The form of switching (routing and transferring data across a network) in which data to be transmitted are divided into discrete packets which are transferred separately before being recombined at recipient hosts.

25
Q

What is the idea of store and forward?

A

The idea that a packet must arrive at a router in its entirety before it can be transmitted through another link in the next hop.

26
Q

What is packet queueing?

A

The idea that packets are stored in a queue in routers before they are transmitted because packets are transmitted once at a time at full capacity. This happens when packets arrive more rapidly (higher rate in bits/sec) than they can be transmitted (also rate in bits/sec).

27
Q

What is packet loss?

A

Packet loss is when a data packet is not successfully transmitted across a network. It can occur due to congestion: in packet queueing if the buffer queue fills up, so every time further new ones arrive, one is lost. It can also occur due to partial or total failures in transmission across links.

28
Q

What is circuit switching?

A

The form of switching (routing and transferring data across a network) in which dedicated end-to-end links (circuits) are made between source and destination hosts to guarantee performance throughout the process of data transmission.

29
Q

What is TDM?

A

Time-division multiplexing is splitting a single signal into multiple channels along the lines of timed turns which allows you to send multiple signals as one over a single shared physical medium.

30
Q

What is an IXP?

A

An Internet exchange point is a set of physical infrastructure that joins ISPs on the Internet.

31
Q

What are peering links, in terms of global Internet infrastructure?

A

Data links directly between different ISPs that aren’t routed through the remainder of the Internet.

32
Q

What are tier-1 ISPs?

A

Relatively large ISPS that have span whole or multiple nations or even continents.

33
Q

What are content provider networks?

A

Geographically distributed private networks run by an organisation that connects its data centres to the Internet.

34
Q

What is a point-of-presence?

A

An interface between the backbone/core of the Internet (ISPs) and end user’s access networks.

35
Q

How does packet loss occurr?

A

Packet loss occurs when data transmission fails or while packet arrival rate to a link exceeds its output link capacity.

36
Q

How does packet delay occur?

A

Packet delay arises from the delay in processing the packet when it arrives at a network node, the time it queues in the node before retransmission, the delay before the whole packet can be delayed from the limit of the bandwidth of the output link, and the delay of the transmission of the packet across the output link.

37
Q

What are the four sources of packet delay?

A

Nodal processing, queueing, transmission, and propagation.

38
Q

How do you find transmission delay?

A

Transmission delay, dtrans (s) = packet length, L (bits) ÷ link bandwidth, R (bits/sec)

39
Q

How do you find propagation delay?

A

Propagation delay, dprop (s) = link length, s (metres) ÷ transmission speed, s (metres/sec)

40
Q

How do you find the average packet arrival rate?

A

Divide the number of packets that arrived over some time by the time taken.

41
Q

What does the traceroute program do?

A

Provides delay measurements along each hop in the path of the transmission of a data packet on the Internet, from source to destination.

42
Q

What is throughput?

A

The rate at which data are transferred between sender and receiver nodes on a network.

43
Q

What is a bottleneck link?

A

A link on a path from source to receiver nodes on a network that constrains the throughput over the whole path. it will be the link with the smallest throughput on the path.

44
Q

What are protocol layers?

A

Separated parts of larger functionality a protocol implements that implement different subsets of the larger process implementing the functionality. It allows you to break down complex functionality into smaller abstractable modules.

45
Q

What is a reference model?

A

A theoretical framework that acts as an approximation to ease the understanding of a large, complex system.

46
Q

What are the elements of the Internet protocol stack?

A

The application, transport, network, link, and physical layers.

application = supporting network apps: FTP, HTTP
transport = interprocess data transfer: TCP, UDP
network = datagram routing: IP
link = how to transfer if data between adjacent hosts: Ethernet, wifi
physical = transferring bits along a medium
47
Q

What are the elements of the ISO/OSI reference model?

A

The application, presentation, session, transport, network, link, and physical layers.

application = supporting network apps: FTP, HTTP
presentation = methods for applications to interpret data, such as encryption and compression
session = synchronisation and checkpointing data exchange and allowing recovery
transport = interprocess data transfer: TCP, UDP
network = datagram routing: IP
link = how to transfer if data between adjacent hosts: Ethernet, wifi
physical = transferring bits along a medium
48
Q

What is a botnet?

A

A number of Internet-connected devices that act in coordinated security attacks.

49
Q

What is a worm?

A

A self-replicating malicious program that spreads between computers without human action.

50
Q

What is a DoS attack? What is a DDoS attack?

A

An attack that seeks to make a network server resource unavailable to users by flooding the target with bogus traffic.

51
Q

What is packet sniffing?

A

When a device seeks to gain information about network traffic by reading/recording and interpreting all packets that pass it on a network.

52
Q

What is IP spoofing?

A

Attacks based on sending packets with false source addresses, effectively pretending to be someone you’re not. Could be used to affect protocol progression.

53
Q

What is ARPAnet?

A

An early predecessor of the Internet that was a computer implemented with TCP/IP packet switching.

54
Q

What is a cable network?

A

A physical medium implementing end-user access networks for the Internet that uses FDM to split channels between multiple Internet and TV devices.

55
Q

What is an Ethernet-based network?

A

A type of Internet end-user access network using the Ethernet family of protocols for connecting edge devices in LANs.