Section 10: The Internet Flashcards
Chapter 56:
What is an example of where the Internet is used without the World Wide Web?
Online Games,
Messaging platforms,
Smartphone apps.
Chapter 56:
What is the Physical Structure of the Internet?
Continents all have a Backbone that is joined by trans-continental leased lines across the sea bed.
National Internet Service Providers (ISPs) connect directly to the backbone and distribute the connection to smaller ISPs.
These smaller ISPs provide access to individuals’ homes and businesses.
Chapter 56:
What does URL stand for?
Uniform Resource Locator.
Chapter 56:
What does a URL do?
It is a full address for an Internet Resource.
It specifies the location of a resource, including the name and usually the file type, so that a browser can request it from the website server.
Chapter 56:
The URL has 4 main components.
What are they?
Method / Protocol.
Host.
Location.
Resource.
Chapter 56:
What are the different levels to the internet called?
[Who owns IP addresses, who distributes, who uses?]
Internet Registry,
Internet Registrar,
Internet Registrant.
Chapter 56:
What is an Internet Registry?
They control the allocations of IP addresses and domain names.
They allocate to ISPs.
Chapter 56:
What is an Internet Registrar?
Internet Service Providers (ISPs).
Businesses that sell IP addresses and domain names to customers.
Chapter 56:
What is an Internet Registrant?
A person, or company that registers a domain name.
Chapter 56:
What are the 5 Internet Registries?
Who are they all governed by?
All governed by [ICANN]
The Internet Corporation for Assigned Names and Numbers.
ARIN, LACNIC, RIPE NCC, AFRINIC, APNIC.
[ARIN]
American Registry for Internet Numbers (North America).
[LACNIC]
Latin America and Caribbean Network Information Centre (South America).
[RIPE NCC]
Réseaux IP Européens Network Coordination Centre (Europe, Greenland, and all of Russia).
{Réseaux = “Network”} {Européens = “Europeans”}.
[AFRINIC]
African Network Information Centre (Africa).
[APNIC]
Asia Pacific Network Information Centre (Asia and Oceania).
Chapter 56:
What does DNS stand for?
Domain Name System.
Chapter 56:
What does a Domain Name do?
A Domain Name is the area (or domain) that an Internet resource resides in.
Domain Names are structured in a hierarchy that is known as a Domain Name System (DNS).
Each Domain Name has one or more equivalent IP addresses.
Chapter 56:
Why are IP Addresses not used instead of alphanumeric characters?
Because alphanumeric characters are easier to remember, and often more intuitive to humans.
Chapter 56:
What does TLD stand for?
Top Level Domain.
Chapter 56:
What does FQDN stand for?
What is it?
Fully Qualified Domain Name.
A Domain Name that includes the host server name.
For example www, mail, or ftp.
Chapter 56:
What does IP in IP Address stand for?
Internet Protocol.
Chapter 56:
What does an IP Address do?
Unique address that is assigned to one network device at a time.
The IP Address indicates where a packet of data is to be sent to, or has been sent from.
Routers use the IP Address to direct the data packet accordingly.
Chapter 57:
What is Packet Switching?
A method of communicating packets of data across a network.
Different packets are sent down different wires to reduce congestion, and so that they all reach the target in a smaller amount of time.
Chapter 57:
What is a Data Packet?
A manageable chunk of data that has been broken down for transmission across a network.
Chapter 57:
Data Packets are split into 2, or sometimes 3 parts.
What are these parts called?
Header.
Payload.
Trailer. (not always used)
Chapter 57:
What does the Header of a Data Packet do?
Contains the sender’s and the recipient’s IP Addresses,
the protocol used for the packet,
and the index of the transmission that the packet represents. (e.g. package 3 of 8).
They also include a Time To Live (TTL) or hop limit, after which point the data packet expires and is discarded.
Chapter 57:
Why is the sender’s IP Address sent with packets?
To Identify the sender.
This is used to send a reply to the same IP Address.
This allows the Network to send an error message back to the sender.
This is also used in firewalls, and IP Address filtering.
Chapter 57:
What does the Payload of a Data Packet do?
The Payload is the actual data being sent.
The Header and Trailer are more like metadata.
Chapter 57:
What does the Trailer of a Data Packet do?
Contains a checksum or Cyclical Redundancy Check (CRC).
This is used for Error Checking.
Chapter 57:
What route is taken by Data Packets through a network?
A path of lowest transmission time is calculated for every packet.
That path is used.
Chapter 57:
How are Data Packets reassembled by the recipient?
Each packet stores an ordinal number that represents its position in the full transmission.
Each packet also stores the total number of packets, so the receiver can work out if it has all of the packets or not. (If not, it can send a request for the packets that didn’t arrive).
Chapter 57:
What do Routers do?
Connect 2 or more networks together.
Typically LANs and WANs, or LANs to their ISP’s network.
They take packets, read their destination, find the shortest path to the destination, and send it in that direction.
Chapter 57:
What is a common shortest path algorithm?
Dijkstra’s Algorithm.
Chapter 57:
Why does the IP Address of a router need to be registered with the Internet Registry?
Because the IP Address must be unique across the whole Internet.
Chapter 57:
What is a Gateway?
Also known as a Protocol Converter.
Used to connect devices that use different protocols to operate (converts the protocol).
Chapter 57:
What is the difference between a Router and a Gateway?
Router connects two devices to Route Traffic of the same protocol.
Using Dynamic Routing, Routers are usually faster.
Gateways also connect two devices to Route Traffic, but can convert to different protocols, so are more versatile.
Using Static Routing, Gateways are usually Slower.
Chapter 58:
What is a firewall?
A security checkpoint designed to prevent unauthorised access between two networks, usually an internal, trusted network with an external, untrusted network (e.g. the Internet).
Chapter 58:
Is a firewall Hardware, or Software?
Can be either.
Hardware: A device that links networks.
Software: Installed on all devices.
Chapter 58:
What is the process of a firewall?
Packets attempt to pass.
Firewall checks the packet against preconfigured rules (packet filters).
Packet is either accepted or rejected.
Firewalls can also act as proxy servers.
Chapter 58:
What is Packet Filtering?
Also known as Static Filtering.
Controls network access according to network administrator rules and policies.
This is done by looking at the source and destination IP Addresses in the header of a packet.
If IP Addresses match those recorded on the administrator’s ‘permitted’ list, they are accepted.
Packet Filtering can also block packets based on the protocols being used, and the port numbers (location) they’re trying to access.
Chapter 58:
What is the difference between a Dropped Packet and a Rejected Packet?
Dropped Packets are quietly removed, whereas Rejected Packets will cause a rejection notice to be sent back to the sender.
Chapter 58:
What is Stateful Inspection?
Also known as Dynamic Filtering.
The payload of a Packet is also checked for better safety.
It can also create temporary contextual rules based on previous packets in the ‘conversation’.
Chapter 58:
What structure does Stateful Inspection use to store temporary rules?
Connection Table.
Chapter 58:
What is an example of Stateful Inspection?
When a Browser requests a web page, the web page packets are returned, and allowed through the Dynamic Filter.
Chapter 58:
What does a Proxy Server do?
Interprets all packets entering and leaving a network, hiding the true network addresses of the source from the recipient.
This allows for privacy and anonymous surfing.
Chapter 58:
Proxy Servers have a Cache Store.
What is this used for?
When a Proxy server receives a request, it will check its cache for web data.
If the data is not present, the server will send a request to the web server.
The web data is then stored to cache before being transmitted to the client, so that other users can access that data quicker, while also reducing web traffic.
This also allows some web data to be accessed without access to the web server.
Chapter 58:
What is an example of a Proxy Server?
School Web-Proxy Server.
Clients send a request to the School Web-Proxy.
The School Web-Proxy can assess if that data is appropriate, and provide or reject the page.
Chapter 58:
What is the idea of Encryption?
Turning valuable data (plaintext) into a form that is not understood without a key (ciphertext).
The process of encryption is carried out using a cryptographic algorithm and a key.
Chapter 58:
What is Symmetric Encryption?
The same key is used to Encrypt and Decrypt data. This means that the key must be transmitted as well (called key exchange), which can cause security issues.
Chapter 58:
What is a disadvantage of Symmetric Encryption?
The Cipher key must be exchanged, usually through transmission like the ciphertext. This means that interceptions of both can be taken, and the security can fail.
Chapter 58:
What is Asymmetric Encryption?
Two separate, but related keys are used in the Encryption.
Chapter 58:
What are the two Asymmetric Encryption Keys called?
Public Key (Available to anyone). Private Key (Available to user only).
Chapter 58:
What is the process of Asymmetric Encryption?
The sender of data acquires the Public Key of the intended receiver to Encrypt data and send it off.
The receiver uses their own Private Key to Decrypt the data, as the two keys are mathematically related.
Chapter 58:
Why is it so hard to derive the Private Key from the Public Key?
Private Keys are very large random numbers.
Public Keys are points on an Elliptic Curve, generated by using the Private Key as a Scalar.
Security is derived from the Discrete Log Problem;
Given a starting value and an ending value, it is difficult to derive the Scalar.
Chapter 58:
Governments sometimes demand copies of Encryption Keys in order to Decrypt messages if necessary.
What are reasons for and against this?
For:
Help track down criminals.
Help prevent crime.
Against:
Personal Privacy.
Potential to leak secret business projects.
Chapter 58:
What is a Digital Signature?
An attachment to a file that confirms that the sender is who they say they are. It also prevents external parties from changing the data, as it will be detected.
Chapter 58:
What is the process of using a Digital Signature?
Mathematical Value is calculated from the data to send. (Hash Value / checksum / digest).
Hash Value is Encrypted by the sender using their private key. (Digital Signature) [only the real user could create it, unless their private key has been breached].
Digital Signature is attached to the message.
Message (with Digital Signature) is Encrypted using the receiver’s public key. (Ciphertext)
Ciphertext is transmitted.
Ciphertext is received.
Ciphertext is Decrypted by the receiver using their private key.
Receiver Decrypts the Digital Signature using the sender’s public key. At the same time, the receiver calculates the Hash Value of the message without the Digital Signature.
If the receiver’s Hash Value is equal to the sender’s Hash Value, the Hash Value has been taken of the same data, thus the data is official.
Chapter 58:
How can Digital Signatures help against viruses?
If the sender is trustworthy, you know you can use Digital Signatures, as the unchanged data is sent from a good source.
If the sender is trustworthy, but doesn’t use a Digital Signature, that can mislead people into downloading data that has been changed by an untrustworthy source.
This can also damage the reputation of the trustworthy source, leaving users with less reputable senders.
If the sender is untrustworthy, and they use a Digital Signature, they can be exposed as untrustworthy, as their data is marked with their name.
