B3 – Networking Infrastructure Services and Resources Flashcards
B – Use of Networking Architectures and Principles for Security
Protocol
👉 A set of rules that manage the communication between different computers on a network. The most important of these are the Transmission Control Protocol and the Internet Protocol.
👉 More commonly known as TCP/IP, these are the protocols that are used to connect network devices over the internet.
👉 When transmitting data over a network we use something called the TCP/IP model. This model has four layers that must each be followed through when transmitting data over a network like the internet.
Protocol 4 layers
👉 Application Layer– This is the top layer that directly interfaces with your applications software, such as your web browser, and passes data from the application to the transport layer.
👉 Transport Layer– The next layer is where TCP is used. TCP will split our data up into small chunks of the data called packets. It will also attach a header that contains information on sender/recipient ports, packet order information & a checksum that is used for error detection when received. These packets can then be sent to the internet layer.
👉 Internet Layer– This layer is where IP is used. This protocol will format the packets into something called an IP datagram and attaches the origin and destination IP addresses. This ensures that the data will be sent to the correct destination. This can then be passed to the network interface layer.
👉 Network Interface Layer– This final layer will add mac addresses to each packet to ensure the data arrives at the correct physical device. It will also convert the data into a form that can actually be transported over the physical cables of the network.
network port
👉 the endpoint of a network communication. The network port identifies the application that is being used so that our computer can handle data coming from many applications at once (e.g. web browsing & email).
👉 It’s important to note that these are nothing like the physical ports you have on your computer, such as the HDMI port. These ports are a logical port, they exist in software, not hardware.
Ports examples
Port 80– The HTTP port that is used for transferring web pages.
Port 443– The HTTPS port that is used for transferring web pages with encryption.
Port 25– The SMTP port that is used for sending and routing emails.
Port 143– The IMAP port that is used for retrieving emails.
Port 20/21– The FTP ports that are used for uploading and downloading files.
The practical purpose of these ports is that when we send a data packet we don’t just need the IP address of the destination; we also identify the port being used.
That way when the recipient device receives the data it will know which application to forward the data to. So, if it is port 80, it will pass it to the web browser.
If we didn’t have ports the receiver wouldn’t know which application requires the data, so we would only be able to use one application at once.
Packets
👉 A piece of data or message that we are sending across a network. However, each packet contains more than just a chunk of the data.
👉 Each packet contains a header that contains information that will ensure the packet arrives correctly at the destination, as well as a piece of the original data.
IP address
👉 An IP address is a string of numbers that will uniquely identify a computer that is connected to the internet (or any network that uses the IP protocol). Earlier this lesson we learnt about the Internet Protocol. For a long time, we used a version of the IP called IPv4.
👉 IP addresses when using IPv4 were made up of a 32-bit number, which we usually express in dot-decimal notion, made up of 4 decimal numbers each between 0 & 255. This allowed for a little under 4.3 billion addresses.
Domains
👉 A key part of the role of the network operating system is to centrally administrate our network and control access for security purposes. We can do this through using the NOS to setup domains.
Domain Controller
👉 any user that tries to connect a device with our network will need to authenticate themselves (through a username & password) in order to access the domain, and thus the network.
subdomains
👉 By creating multiple domains, we can decentralise the administration of the network, so rather than having one giant network to administrate, we can have several smaller ones. This will also limit access for better security.
👉 By making these domains a subdomain though, we can still perform administration on the parent network that will apply to the subdomains.
An example of where we would use this is a large organisation with offices in many cities. We can define each cities domain as a subdomain of the head office. This way each city will have some semi-autonomous control over the network, while the company can still make administrative changes to all domains.
network segmentation.
When creating a single large network though, we can split a network into multiple subnetworks.
Advantages of network segmentation
👉 Performance– it reduces the amount of network traffic by dividing that traffic over multiple networks.
👉 Security– it can minimise the impact when a malicious user gains access to a network as they will only have access to devices & data on one segment
Domain Name System (DNS)
👉 The Domain Name System (DNS) is used to translate domain names into IP addresses.
👉 If we want to visit a website, we would write the domain name of the website, e.g. Facebook.com. However, as we’ve learnt in earlier lessons, the address for a device, such as a web server, is actually an IP address.
👉 Thankfully, DNS will take the domain name you have entered and sends it to a domain name server which will lookup the correct IP address associated with the name. This allows us to use easy to remember text-based addresses for web sites, rather than the difficult to remember IP addresses.
👉 We can also use DNS on our private network to assign names to the domains and subdomains we setup.
Directory Services (DS)
👉 Directory services are used to organise information on network objects such as users & computers. This way all information about the network is available from a single repository making it easily accessible to users to allow for centralised administration, authorisation and authentication.
👉 The server that is running directory services is called the Domain Controller. You should remember this from when we learnt about domains. The directory services are what allows us to create & manage our domains.
👉 Some common directory services include:
Active Directory– the directory service included in the Windows Server NOS.
Open Directory– the directory service included in the macOS Server NOS.
OpenLDAP– a free open source directory service included in many Linux NOS.
Authentication Services
👉 Authentication services provide username/password login authentication based on the details in your directory services on your domain controller.
👉 When a user wants to connect a device to a network they will need to first authenticate themselves. This prevents malicious users from connecting unauthorised devices to the network in order to launch an attack.
👉 This can also allow for users to connect to the network domain from outside the organisation to support remote working.
Dynamic Host Configuration Protocol (DHCP)
👉 DHCP is a protocol that is used to automatically assign IP addresses to the different devices connected to a network and allows a network administrator to centrally manage them.
👉 The device that is used to issue the IP addresses is known as the DHCP server. In a small home network, this will likely be the router. However, larger networks run by organisations will have a dedicated computer as the DHCP server.
👉 Dynamically assigning IP address helps to prevent clashes in IP addresses (which can happen when using only static IP addresses) and allows you to use a small number of IP addresses as you can reuse them on different devices as they connect & disconnect from the network.
