Network Services (DHCP, DNS, NTP)
Learn about the plumbing of the internet DHCP, DNS, NTP
DHCP
DHCP, or Dynamic Host Configuration Protocol, ensures that every device, such as a phone, tablet, or computer, has its unique spot on the network.
DHCP has 10 attributes to it.
Scope: This is the range of IP addresses that DHCP can assign to devices, similar to seat assignments in an auditorium.
Exclusion Ranges: Similar to reserved seats in an auditorium, these IP addresses are set aside and not given out by DHCP because they are specifically assigned to certain devices and don't change.
Reservation: DHCP reserves specific IP addresses for particular devices, building on the concept of exclusion ranges.
Dynamic Assignment: Devices in the network receive IP addresses immediately (dynamically) upon connecting - IP address is reassigned once they disconnect. When they reconnect they get a different IP address.
Static Assignment: Certain devices in the network, such as web servers or printers, always receive the same IP address - they are statically assigned.
Lease Time: It's the duration during which devices can use an IP address before they might need a new one because the lease expires.
Scope Options: These are extra settings and information that DHCP provides to devices, similar to special features offered with certain cinema seats.
Available Leases: In the network, this represents the number of IP addresses still available for devices to use.
DHCP Relay: Much like a messenger communicating between an auditorium owner and the audience, DHCP Relay carries messages from the DHCP Server to the host computer and back, even if they are on different networks.
IP Helper/UDP Forwarding: These mechanisms assist in routing DHCP-related messages between different parts of the network.
DNS
DNS, or Domain Name System, serves as the internet phonebook, containing website names and their corresponding IP address locations.
DNS has 8 attributes to it.
Record Types: These represent distinct categories or sections in the phonebook.
Address (A vs. AAAA): A records correspond to hostnames using IPv4 addresses, while AAAA records correspond to domain names using IPv6 addresses. A records are analoguous to landlines, while AAAA records are analoguous to smartphones.
Canonical Name (CNAME): This acts as an alias for the domain name, finding different names for the same domain.
Mail Exchange (MX): Similar to directing emails to a mailbox, it specifies where to send emails for a website.
Start of Authority (SOA): It's the official owner of a house, but for a website, containing vital website information.
Pointer (PTR): This aids in reverse address lookup, finding a website's name when you know its IP address.
Text (TXT): This is a little note attached to a website's name. In a network, it's for adding extra information to a website.
Service (SRV): Comparable to guiding someone to specific locations in a shopping mall, in a network SRV helps find particular services on a website.
Name Server (NS): Think of this as the phonebook manager, knowing where to find information about different websites on the internet.
Global Hierarchy/Root DNS Servers: These are the top-level authorities, akin to bosses who know where everything is in the phonebook. In a network, these servers help find all the websites in the world.
Internal vs. External: Similar to distinguishing between local and international numbers in a phonebook, it determines whether to find information within your network or on the broader Internet.
Zone Transfers: Imagine copying pages from one phonebook to another. In a network, it's how different DNS servers share information.
Authoritative Name Servers: These are section managers in the phonebook. In network, ANS hold comprehensive details about specific websites.
Time to Live (TTL): Think of it as how long a phone number stays in your memory after looking it up. In a network, it determines how long your device remembers a website's address.
DNS Caching: Similar to your phone remembers the phone numbers you've searched before. In a network, DNS cache stores website addresses they've found to speed up searching it later.
Reverse DNS/Reverse Lookup/Forward Lookup: This is like finding a name from a phone number or vice versa, matching website names with their addresses or the other way around.
NTP
NTP, or Network Time Protocol, serves as the network's official timekeeper, ensuring all devices have synchronized clocks.
Stratum: Stratum represents different tiers of timekeepers, with the highest tier possessing the most precise time. In a network, devices connect to various strata to obtain accurate time.
Clients: Akin to individuals needing the correct time, refer to devices in a network seeking accurate time information
Servers: Servers function as the experts maintaining precise time. Within a network, NTP servers supply accurate time to clients.