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CS 335 - Computer Networks > Ch. 1 - Intro to Computer Networks > Flashcards

Ch. 1 - Intro to Computer Networks Flashcards

Internet overview, protocols, networks, performance, layering

1
Q

What is the Internet?

A

Millions of connected computing devices.

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2
Q

Network Protocols

A

Define the format and order of messages sent/received among network entities, and actions taken on message transmission and receipt.

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3
Q

Network structure

A

Network edge, access networks, physical media, and network core

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4
Q

Network Edge

A
  • hosts, access network, physical media
  • Devices connected to the network, such as computers, smartphones, and IoT devices.
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5
Q

Network core

A

mesh of interconnected routers; network of networks

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6
Q

Performance

A

loss, delay, throughput

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7
Q

Key Network Core functions (2)

A
  • forwarding (a.k.a. “switching”)
  • routing
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8
Q

Store-and-Forward

A

entire packet must arrive at router before it can be transmitted on the next link

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9
Q

Packet queueing and loss

A

if arrival rate (in bps) to link exceeds transmission rate (bps) of link for some period of time:
* packets will queue, waiting to be transmitted on output link
* packets can be dropped (lost) if memory (buffer) in router fills up

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10
Q

How are end systems connected to edge routers?

A

Via access networks/nets

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11
Q

DSL

A

Digital Subscriber Line. A method of connecting to the Internet via a phone line. Voice goes over the DSL to the telephone net, and Data goes over to the internet.

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12
Q

Frequency Division Multiplexing

A

different channels transmitted in different frequency bands

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13
Q

Time Division Multiplexing

A

each call allocated periodic slot(s), can transmit at maximum rate of (wider) frequency band (only) during its time slot(s)

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14
Q

What is The difference between DSL and HFC

A

For HFC homes share access network to cable headend, where as DSL (digital subscriber line) has dedicated access

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15
Q

Hybrid Fiber Coax (HFC)

A

A network architecture that typically uses fiberoptic cables to bring signals to selected areas of the system called nodes, which are usually based on number of subscribers to be served.

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16
Q

Wireless access networks

A

Connects end system to router via base station (“access point”)

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17
Q

Packet switching

A

Where the host breaks application-layer messages into packets

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18
Q

Circuit switching

A

end-end resources allocated to and reserved for “call” between source and destination

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19
Q

What methods are used for resource allocation?

A

Packet switching and Circuit switching

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20
Q

What can a ‘bad guy’ do in network security?

A

Eavesdrop, impersonate, hijack, and DoS.

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21
Q

DoS

A

Denial of service. Attackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resources.

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22
Q

What is packet sniffing?

A

An application/device monitors and reads network packets as they transverse the network. Plaintext/Cleartext can be read.

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23
Q

What is IP spoofing?

A

Sending information into the network with false “Sender IP” information.

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24
Q

Communication links

A

fiber, copper, radio, satellite
transmission rate = bandwidth

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25
Q

What are Networks?

A

Collection of devices, routers, links: managed by an organization

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26
Q

Internet standards (2)

A

RFC: Request for comments
IETF: Internet Engineering Task Force

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27
Q

ISP

A

Internet Service Provider

28
Q

Packet switches

A

forward packets (chunks of data)
e.g. routers and switches

29
Q

IXP

A

Internet Exchange Point

30
Q

Packet delay formula

A

d[nodal] = d[proc] + d[queue] + d[trans] + d[prop]

31
Q

d[proc]

A

Nodal processing
- check bit errors, determine output link

32
Q

d[queue]

A

Queueing delay
- time waiting at output link for transmission
- depends on congestion level of router

33
Q

d[trans]

A

Transmission delay

34
Q

d[prop]

A

Propagation delay

35
Q

Transmission delay formula

A

d[trans] = L / R
L = Length (bits)
R = Link Transmission Rate (bits/sec)

36
Q

Propagation delay formula

A

d[prop] = d / s
D = Distance (m)
S = Speed (m/s)

37
Q

Traffic intensity formula

A

(L * a) / R
L = packet length (bits)
a = average packet arrival rate
R = link bandwidth

38
Q

Traceroute program

A

Provides delay measurement from source to router along end-end internet path towards destination

39
Q

Throughput

A

Rate at which bits are sent from sender to receiver (in bits/[time unit])

40
Q

Bottleneck link

A

The link on an end-end path that constrains the end-end throughput

41
Q

Packet “sniffing”

A

An attack on wireless networks to capture data and register data flows in order to analyze what data is contained in a packet.

42
Q

IP spoofing

A

When an intruder uses another site’s IP address to masquerade as that other site. : injection of a packet with a false source address.

43
Q

Network security lines of defense

A

Authentication
Confidentiality
Integrity checks
Access restrictions
Firewalls

44
Q

[Network security] Authentication

A

Proving you are who you say you are

45
Q

[Network security] Confidentiality

A
  • Protecting sensitive information from unauthorized access.
  • Ensuring data privacy and secrecy.
46
Q

[Network security] Integrity checks

A

Verify the authenticity and completeness of data transmitted over a network.
* checking for data corruption, unauthorized modification, ensuring data hasn’t been tampered with during transmission.
* Common methods: checksums, message authentication codes (MACs), and digital signatures.

47
Q

[Network security] Access restrictions

A
  • Limiting access to authorized users.
  • authentication, authorization, and encryption.
  • e.g. Password-protected VPNs
48
Q

[Network security] Firewalls

A

specialized “middleboxes” in access and core networks:
- off-by-default: filter incoming packets to restrict senders, receivers, applications
- detecting/reacting to DOS attacks

49
Q

5 Layers of the Internet Protocol Stack

A

Physical, Data Link, Network, Transport, Application

50
Q

Physical Layer

A

Transmits raw bit streams over physical media.

51
Q

Data Link Layer

A

Provides reliable data transfer between nodes on a network.

52
Q

Network Layer

A

Routes packets between networks.

53
Q

Transport Layer

A

Provides end-to-end reliable data delivery.

54
Q

Application Layer

A

Provides services to users, such as email, web browsing, and file transfer.

55
Q

Packet-Switched Networks

A

Data is divided into packets and routed independently through the network.

56
Q

Circuit-Switched Networks

A

Dedicated circuit is established between the sender and receiver.

57
Q

Radio link types (5)

A
  • Wireless LAN (WiFi)
  • Wide-area (e.g. 4G/5G cellular)
  • Bluetooth
  • Terrestrial microwave
  • satellite
58
Q

Peering link

A

a process by which two Internet networks connect and exchange traffic

59
Q

Content provider network

A

(e.g, Google); private network that connects its data centers to internet, often bypassing tier-1, regional ISPs

60
Q

Ethernet (speeds)

A

Wired access at 100Mbps, 1Gbps, 10Gbps

61
Q

WiFi

A

Wireless access points at 11, 54, 450Mbps

62
Q

IP

A

Internet Protocol - An addressing system that finds paths to distant computers. Specifies how a router handles a request for another IP address.

63
Q

Network frame

A

When the network interface card takes the packets and wraps them up and send them out along the cable to the central hub or switch.

64
Q

Data center

A

Physical or virtual infrastructures used by enterprises to house computer, server and networking systems and components for the company’s IT needs

65
Q

OSI Model

A

Layers: Physical, Data Link, Network, Transport, Session, Presentation, Application
Focus: Conceptual framework for network communication.
Approach: Vertically layered, clear separation of concerns
Protocol Examples: Not tied to specific protocols, but examples include HTTP (Application), SSL/TLS (Presentation), TCP (Transport), IP (Network), Ethernet (Data Link)
Usage: Primarily educational and conceptual

66
Q

TCP/IP Model

A

Layers: Application, Transport, Internet, Network Interface
Focus: Practical model based on internet protocols
Approach: Horizontally layered, with some overlap in responsibilities
Protocol Examples: HTTP, FTP, TCP, UDP, IP, Ethernet
Usage: Widely used in real-world network implementations.

CS 335 - Computer Networks (7 decks)

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