Networking Flashcards

Question

What happens if your computer to makes an IP request to one on the same LAN?

Answer 1

- Finds MAC address associated with destination IP and send directly over LAN

Answer 2

- logical bitwise AND with sending host’s subnet mask and other host’s IP address - this returns subnet ID, if not same, send packet to local router

Answer 3

- Sending computer makes ARP request to find MAC address of destination computer’s local router - IP packet can be passed to router to send out onto network

Answer 4

- emails are sent as structured text files - email client applications renders the files as a graphical page

Answer 5

1) Manually assigned - tell the OS what IP address you want to use 2) Dynamically assigned - using DHCP (Dynamic Host Configuration Protocol) an IP address is **leased** to hosts for a fixed durations

Answer 6

- Static IP address - Required to be **reliably reachable** on the network at a **known IP address** - Other examples are printers, file and authentication servers, DNS servers, router, default gateway

Answer 7

- **Easier** as no need to enter IP address, subnet mask etc. - **Less error-prone** as it can cause **IP conflicts** - **More efficient** as IP addresses can be reallocated

Answer 8

1) Host that is requesting an IP address broadcasts a **DHCP DISCOVER** packet to all hosts on the entire subnet. 2) DHCP server recognises discover packet and responds with a **DHCP OFFER** packet. This is also broadcase since no IP yet for host. Packet contains an IP address to offer. 3) Host recieves offer and sends a **DHCP REQUEST** packet to confirm it want IP to be allocated. Request packet also includes request for other information to facilitate communication such as subnet mask, default gateway / router IP, and DNS server IP. 4) DHCP server receives request and sends a **DHCP ACK** to acknowledge and confirm allocation of IP address. This packet also includes all the other information requested. 5) Host C will configure itself to use all the given information.

Answer 9

Private IP addresses are **non-routable** as they cannot be used to communicate with hosts across **different networks**. Public IP addresses are routable and hence must be **globally unique**.

Answer 10

The assignment of a single public IP address to the router of a local area network. This means that the devices on the network do not require a public, routable IP address.

Answer 11

1) Since each device is non-routable on the LAN, it will send its IP packets to the LAN. 2) Routers record which device on the network sent the packet by their private IP address. It will also record where the packet is sent by that IP. 3) Router will then replace the private IP as the sending address in the packet as its own public IP address. 4) Once the response is received, it will check the record (for sending IP address) and forward the response to the correct private IP address.

Answer 12

Port forwarding is used when a client needs to communicate with a a server that is connected to a private network. The client sends packets to the public IP of the router. The packets sent by the client contain the **port number** of the application running on the server that the client wants to access. Router can then forward the packets to this server by using NAT.

Answer 13

The Internet is defined as a **network of interconnected computer networks** which uses an **end-to-end** communication protocol.

Answer 14

Mostly a wired network (with wireless parts). Cables pass under oceans to connect different continents.

Answer 15

- Provide human-friendly, easy-to-remember address for a host or service - Given exact location of a particular host within the DNS heirarchy

Answer 16

- Comprised of host name, names of all domains that it belongs to (including top-level domain) - Separated by full stops

Answer 17

- responsible for translating FQDN to IP address - doesn’t translate **whole URL** only the FQDN - required to make requests to the host

Answer 18

1) Check the **local cache** of the sending device for the IP address if it was **recently queried** 2) If not found, send a request for the IP address to the **DNS resolver** (usually run by the **ISP**) 3) If it isn’t there in the **cache of the DNS resolver**, it will send a request to the **root nameserver** for the **IP address of the TLD (top-level domain) nameserver, e.g. .com** 4) Once the response with the IP address of the TLD nameserver is returned, a query is made to the TLD nameserver for the **IP address of the authoritative nameserver** e.g. google 5) Once response with IP of authoritative nameserver is sent, a request is made to the authoritative nameserver for the **IP address for the FQDN** 6) This response is then forwarded to the original device which requested the IP address. 7) This IP address is then stored in the cache of the DNS resolver and local cache of the device to prevent unnecessary repetition of this process.

Answer 19

- when local computer has matching record in local hosts file - when local computer has matching DNS record in local cache - when URL contains IP instead of FQDN - when URL is for local resource - when URL refers to localhost instead of external domain

Answer 20

A reference to a unique **resource file** on a **specific host on the Internet**.

Answer 21

- protocol, FQDN domain name, path - protocol e.g. https:// - FQDN domain name e.g. en.wikipedia.org - path e.g. /wiki/url

Answer 22

Internet registries are organisations that are responsible for administering and organising the allocation of IP addresses and domain names across the internet.

Answer 23

IANA, they provide public IP address and **autonomous system numbers** to other organisations

Answer 24

There are 5 regional internet registries (RIR’s) that IANA delegates the allocation of IP addresses for certain regional areas.

Answer 25

Regional internet registries allocate blocks of addresses to local internet registries to assign to customers and organisations.

Answer 26

Organisation responsible for distributing responsibility for maintaining authoritative nameservers within each TLD to different organisations.

Answer 27

Organisations that have permission to register domains on behalf of the organisation that operates a given TLD.

Answer 28

The process of using an algorithm converting plaintext message data into a form that is not understandable (called ciphertext) without a key.

Answer 29

Encryption where the **same key** is used for **both encryption and decryption**. This requires the use of a method of secret key exchange such as Diffie-Hellman.

Answer 30

Encryption where a pair of **different (but mathematically related)** keys are used for encryption and decryption processes.

Answer 31

1) A device will have **a public key and a private key**. 2) A sending device can use the public key to encrypt the message. 3) Only the receiving device knows its own private key, so only it is unable to decrypt the message once it is received.

Answer 32

- It is faster to use symmetric encryption such as AES - But any symmetric method uses a single key - Encryption key must bee passed from sender to receiver securely so that the message cannot then be intercepted and decrypted

Answer 33

RSA is an algorithm used for public-key cryptography. The public key is used for encryption and the private key is used for decryption.

Answer 34

1) Sender A generates a symmetric key to share with recipient B 2) A encrypts shared key with B’s public key 3) A sends encrypted key to B 4) B decrypts the encrypted shared key using their own private key 5) Both parties have the shared symmetric key and can use it for ongoing communication

Answer 35

Digital signatures are used to verify the identity of the sender of an encrypted message and detect whether the message has been tampered with or altered during transmission.

Answer 36

1) An application on computer A generates a message / data to be sent securely to computer B. 2) A hashing algorithm is used to generate a **hash** of the message, which is encrypted using A’s private key. 3) Encrypted message **hash** is the **digital signature** and is **appended** to the original message. 4) A’s original message and digital signature are then encrypted using B’s public key and encrypted message is sent to B.

Answer 37

1) The encrypted message sent by A is received by B. 2) B uses its own private to decrypt the message. 3) The received message is rehashed by B to create a new hash. 4) The received digital signature is decrypted using A’s public key to reveal the original message hash. 5) Original message hash is compared to the recalculated hash to ensure that they match. 6) If there is a match, A’s identity is verified. If not, message is discarded as message could be corrupt.

Answer 38

A certificate authority generates and issues digital signatures from the keys that are submitted to it. Certificate contains the public key and additional information such as who owns the key and how long the certificate is valid for.

Answer 39

A firewall is a security measure designed to provide protection to a network by inspecting IP packet headers and restricting the exchange of data between the protected network and an external network, typically the Internet. - implemented as network **hardware or software** running on a router or computer - purpose is to protect a network from unauthorised access

Answer 40

- Dedicated firewalls are placed between the router and the switch - They are used for more advanced inspection of packets and more complex access rules - Non-dedicated firewalls are built into the router

Answer 41

- Same concepts of packet filtering and inspection to protect local machine - Considered less secire as their ability to manipulate and manage rogue packets are less sophisticated - Data has to be processed by OS before it can be inspected by the firewall

Answer 42

- Blocking traffic in **specific TCP/UDP ports** and traffic from specific IP addresses or domains - Blocking certain **types of packet** which hides the presence of a device on a network - Use **stateful inspection** to maintain information about current connections and only allowing packets which are relevant to those connections - Acting as a proxy server, forces traffic to pass through it, stops computers from being directly accessed - Identify unusual behaviour from an internal host

Answer 43

- As packet passes through firewall, header is inspected and information is compared to rules within firewall's **access control list** - Simple packet filtering doesn't inspect packet payload - Inspects information such as: - source and destination addresses of packet - size of payload - source of destination TCP and UDC ports

Answer 44

- Limited in terms of how effectively it can identify acceptable and unacceptable data

Answer 45

1) Inspects **transport and application-layer protocols** used in the contents of packets to detemine if payload data should be permitted 2) Dynamically generate **filtering rules** to allow packets as a part of an ongoing exchange between two devices that was initiated by an **internal device**

Answer 46

A proxy sits between an internal and external device and handles communications on behalf of the internal device. Prevents direct connection between the internal and external device.

Answer 47

- Anonymity to the internal host - Application / request level filtering - Maintain a log of all incoming and outbound requests - Detect malformed incoming packets anr repair or reject them

Answer 48

Malware is category of software designed to damage or destroy data / systems. - Viruses, worms and trojans are all examples - Designed to exploit a vulnerability within a system

Answer 49

A virus is a form of malware that **attaches itself to, or conceals itself within another program or file**. Requires a host to replicate and execute its damage.

Answer 50

Worms are **standalone** software that **do not require a host file in order to run**. Worms are almost always self-replicating and can **exploit network vulnerabilities** in order to spread to other devices.

Answer 51

Trojans are malicious software that appear legitimate and trustworthy.

Answer 52

- Ineffective firewall rules - Remote management software being enabled - Default passwords being used - Out-of-date operating systems and implementations of network protocols - Also exploits applicatins where memory is not correctly managed - Users can also be exploited

Answer 53

- Correctly configured firewalls - Back up data - Install anti-virus software - Disable removable media

Answer 54

- Network monitoring systems to check for high network traffic - Slow performance and high fan speeds and disk activity could be signs of malware

Answer 55

- Host machine should be powered off or disconnected from the local nerwork - Antivirus software can quarantine infected files - Backups can be used to restore original files

Answer 56

The server provides resources that are required by the clients. A single can responds to requests from multiple clients at any given time.

Answer 57

Clients utilise resources requested from the server.

Answer 58

Use of commonly agreed protocols e.g. HTTP

Answer 59

- CS model describes flow of **application-layer** data between hosts, where each host has a different role - Star topology shows flow of **link-layer** data between hosts, where a central hub or switch is used to connect hosts

Answer 60

1) Server **hosts the resources** that clients require 2) Data exchange is initiated by client that sends a **request** to the server 3) Once request is sent, client **waits for response** from server 4) The server responds by providing resource in a **response message** 5) The client **processes the response** that it recieved

Answer 61

JSON and XML

Answer 62

- JSON is more compact, which facilitates **faster transmission**, smaller file sizes and uses less memory to store - Easier for **humans to read**, create and understand - Quicker for computers to parse - Understood directly in some programming languages (native support of arrays)

Answer 63

Provides a standardised interface for clients to request resources from servers over HTTP or HTTPS

Answer 64

Each item or collection of data is available at a specific URL, where **query parameters** specify values or filters. Data will be returned in JSON or XML

Answer 65

- Represnt each resource at an **endpoint** - Cause server to carry out an appropriate action - Can be used to express more complex queries i.e. filtering

Answer 66

HTTP and REST cannot **maintain a constant stream of communication** or handle **regular background requests**. Websocket is an **alternate protocol** to HTTP that browsers use to communicate with servers over a **persistent two-way connection over a TCP socket**, allowing both parties to send data to each other at any time.

Answer 67

- Real-time appplications requiring constant data exchange - Situations where low latency and bi-directional communication are essential - Complex applications where performance and real-time updates are prioritised

Answer 68

Thick-client are machines that natively **run much richer applications** since they are capable of significant processing and only use the server for **data storage** and **co-ordination activities**. Thin-client computing is where the client **relies upon the server** to perform most of the **processing** and **storage** requirements, so the client is only used to access the resources that the server provides.

Answer 69

Thin: - Client machines have lower-powered processors, less RAM and storage - Servers require multiple processors, lots of RAM and storage Thick: - Client-machines have faster, more powerful processors, larger memory and storage - Servers can be lower-powered

Answer 70

- Client machines are cheaper to purchase due to lower hardware requirements - Adding / replacing clients is easier as less setup - All data resides on server, more security - All clients use same, latest version of applications and OS - Client machines consume less power and are more energy-efficient 1 mark AO1 (knowledge) and 2 marks AO1 (understanding) What it is (1 mark): Processing is carried out // applications/programs are executed on an application server (A. server); NE. Resources are stored on the server Why selected (Max 2 marks): Clients are cheaper to purchase // clients can have lower hardware specification; NE. cheaper without further explanation Less configuration of clients is necessary // easier to configure/add a new client // easier to replace a client; Simpler installation/updating of software (as only done on server); R. if implication that software is on client Impossible to install unauthorised software on workstations // more secure as fewer settings can be changed; Workstations consume less electricity/power; Licensing can be cheaper (as licence per active user not per client); Longer MTBF for workstations // workstations do not fail/break as often // workstations need less maintenance;

Answer 71

- Not dependent on reliable and highly-available internet connection to access applications and data - Doesn't require higher-bandwidth network or powerful servers - More powerful applications e.g. video editing or 3D modelling

Answer 72

It is the new version of IP addresses. It is needed because there were too few IPv4 addresses.

Answer 73

IPv4 does not use enough **bits** to be able to represent a unique value for every device - IPv4 addresses use 32 bits / 4 bytes and IPv6 addresses use 128 bits / 16 bytes // IPv6 addresses uses 96 more / four times as many bits than IPv4 addresses // IPv4 (theoretically) allows 2³² / 4 294 967 296 (unique) addresses and IPv6 (thoeretically) allows 2¹²⁸ (unique) addresses

Networking Flashcards

(102 cards)