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Kirk Flashcards

1
Q

What are the layers in the TCP/IP model?

A

Application
Transport
Internet
Link

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2
Q

What are the layers in the OSI Model?

A

Application
Presentation
Session
Transport
Network
Data Link
Physical

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3
Q

What is the Domain Name System?

A

It gives user friendly names to IP addresses and more

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4
Q

What is ICANN?

A

The internet corporation for assigned names and numbers maintains the domain name system

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5
Q

What is IANA?

A

Internet assigned numbers authority oversees addresses and autonomous system allocation

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6
Q

What does the World Wide Web do?

A

It integrates resources across the interent

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7
Q

What is cloud computing?

A
  • Cluster computers provide integrated storage and compute
  • Removes reliance on localised resource management
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8
Q

What does the DNS do?

A

It maps host/domain names to IP addresses and vice versa

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9
Q

Why do we need DNS?

A

The amount of domain names got too large for the original way they were held (on file on the computer)

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10
Q

What is DNS?

A

DNS is a distributed, hierarchical system that operates on port 53 (mostly UDP). Domain names are delegated from ICANN through Top Level Domain registrars

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11
Q

What is AAAA (DNS Record Types)?

A

IPv6 record that is a 128-bit address

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12
Q

What is A (DNS Record Types)?

A

IPv4 record that is a 32-bit address

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13
Q

What is the most common DNS lookup?

A

Host name to IP which requires clients to know about a DNS server they can send queries to

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14
Q

What is a resolver?

A

A program that extracts information from name servers, they “resolve” the query and return the answer

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15
Q

What is an Iterative mode on a DNS server?

A

It responds with a referral to another server

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16
Q

What is a Recursive mode on a DNS server?

A

It responds from local cache or resolves the query before replying to the client

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17
Q

What is a forwarder?

A

It sends queries to a different DNS server, even if the RD bit is set

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18
Q

How are Network clients configured?

A

They are configured to use one or more local DNS servers which are usually sent by SLAAC, DHCPv6 or DHCP that can be specified manually

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19
Q

How does DNS hierarchy work?

A

Each node stores names that end with the same suffix

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20
Q

What is a DNS Zone?

A

A continuous chunk of name space (A complete tree, subtree or single node) where each zone has an associated set of name servers

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21
Q

What is Zone Delegation?

A
  • Zones require the owner to delegate a subzone
  • Records within a zone should be stored redundantly
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22
Q

What are Root Nameservers?

A
  • Responsible for the “root” zone
  • Currently only 13
  • Operated by 12 independent organisations
  • Queried when local name servers can’t resolve a name
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23
Q

What is Anycast?

A
  • Allows a client to reach the nearest instance of a service
  • Can advertise the same IP or small IP block, at multiple points on the Internet
  • Routers then learn of the new instance
  • Which means you will access a difference instance, depending on where you are
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24
Q

What does mDNS do?

A

Allows local DNS resolution without a DNS server

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25
What is a socket?
- Represents a way to send and receive data - Allows IPv4 and IPv6 addressing - UDP, TCP etc
26
What is a Remote Procedure Call?
- Allows you to call a function on another machine - Each machine has to run an RPC server - Client calls functions
27
What are Web sockets?
Makes a special HTTP link which can process multiple requests later
28
What does the Link layer do?
It shields upper layers from specific connection type
29
What are the different types of media transmission in the link layer?
- Coaxial cable - Twisted pair - Power line - Fibre optic - Wireless
30
What are the functions of the link layer?
- Transmission of frames over physical media - Receiving frames, passing IP datagrams up the stack - Detection & handling of transmission errors
31
What is in the link layer frame?
The packet and has extra fields added to aid in transmission
32
How many bytes is the header of an Ethernet Frame?
14 bytes
33
What is Flow Control in the link layer?
- May regulate flow of data - Can use messages to sender saying more data can be sent - Can be rate-based so the speed is agreed
34
What are the three general link layer models?
- Connectionless, no acknowledgements - Acknowledged, connectionless service - Acknowledged, connection-oriented services
35
What is Connectionless, no acknowledgements for the link layer?
- For low error rate networks e.g. wired ethernet - No signalling path is established in advance - the frames are sent, and may or may not be received by the destination
36
What is Acknowledged, connectionless service for the link layer?
- E.g. wireless 802.11, WIFI - 802.11n supports block acknowledgements
37
What is Acknowledged, connection-orientated services for the link layer?
For long delay, unreliable links, e.g. satellite
38
How are ACKs and errors handled?
ARQ (Stop-and-wait Automatic Repeat reQuest) - Send a frame, wait for ACK, send next frame - Will not get an ACK if frame is lost or damaged
39
How does the Link Layer detect errors?
- Parity bit - Cyclic Redundancy Check Result held in "checksum" field of the frame and calculated by sender and receiver, then results are compared
40
How does framing work?
Uses some bandwidth to indicate the start/end of frames e.g. Use a FLAG byte value to mark the start and end
41
What is a FLAG byte value?
- If FLAG occurs in the actual data, use an escape byte - When receiving, strip (ignore) first escape byte - If an Escape byte occurs in the data, Escape that
42
What is Media Access Protocol?
MAC manages access to/from the Phys medium. It has a mechanism for sending frames to from the Phys and typically manages channels frequencies collisions
43
How is media contention handled?
Uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD) used to ensure only one sender is transmitting at a time
44
How does CSMA/CD work?
- Sender listens to see if the media is busy - When channel is free, the sender starts to talk - Back off before retransmitting if collisions detected
45
What doe the Ethernet Frame include?
- 48-bit source and destination MAC addresses - 802.1Q tag for optional VLAN ID and frame priority - Maximum Transmission unit is 1500 bytes
46
How do Link Layer addresses work?
- Usually refer to MAC addresses - Currently define to be 48 bits, extensible to 64 bits - Needs to be unique, 24 bits for vendor allocations
47
How do Ethernet Networks work?
- Each host typically connects to a port on a switch - Desktops now typically 1 GBit/s or (2.55) Ethernet - Servers and backbone on 10 Gbit/s Ethernet
48
How do Ethernet Switches work?
- Receive Ethernet frames and make a decision whether to forward the frame, and if so, on which port - Can store and forward Ethernet frames - Some switches support more advanced functions
49
How are IP datagrams sent on the Link Layer?
- Encapsulates these as the payload - IP datagram has a source and destination IP address - Forwarded to the destination IP address using the Ethernet layer
50
What does Address Resolution Protocol (ARP) do?
- Used to determine the destination's MAC address
51
How does ARP work?
- Uses a link layer broadcast message - To the special Ethernet broadcast address - Seen by all hosts in the same Ethernet LAN - Sender can then use result to send Ethernet frame
52
What are the different message types?
- Unicast - Broadcast - Multicast - Anycast
53
How does Unicast work?
From one sender to one receiver
54
How does Broadcast work?
- From one sender to all potential receivers - Some protocols rely on one device being able to send a message seen by all other devices at that network layer - Can have link layer and network layer broadcasts
55
What are the nuances of ARP?
- Not as secure as open to spoofing - Change of IP or MAC address requires a gratuitous ARP (send to check-up on it) - ARP probe
56
How do Ethernet broadcasts handle large amounts of hosts?
The Ethernet LANs are limited to reasonable size
57
How are Ethernet LANs conencted?
An IP router is used to forward IP packets between the LANs
58
How does IPv4 access a destination in a different LAN?
It is sent on the default router on the link layer
59
How does IPv6 access a destination in a different LAN?
It find the router with a Router Solicitation
60
What do IP routers do for the network layer?
Acts as a gateway between individual link layer Ethernet LANs
61
How are address spaces assigned to LANs?
The allocations come from the campus prefix, 152.78.0.0 through 152.78.255.255
62
What are the ways Intra-building Ethernet?
- Data riser - Flood wiring per floor - Ethernet switch stacks - Are a fibre link
63
What are the benefits of virtual switched networks?
- Avoids need to physical re-cable - Can control broadcasts
64
What is tcpdump?
- Old Unix tool - Allows you to capture Ethernet or WiFi frames - Can save captured frames to a file
65
How does Wireshark or tcpdump affect the network?
It does not, it merely observes it
66

Network and Security (5 decks)

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