As mentioned in the previous posts we know, what IP addresses are and how an IP network is basically built.
Lets stay with the example from “What is an IP address?” where an IP address is similar to a house address. Therefore we can make the analogy, that a port ist a special entry (door, window or something the like) of a house, which belongs to a special application.
Port numbers can range from 0 to 65535 where some of these are predefined.
System Ports (0 – 1023)
Predefined / standardized ports
User Ports (1024 – 49151)
User can define (if not already occupied by another application) their own ports for their specific application
Dynamic Ports (49152 – 65535)
This area is used primarily by the operating system for dynamically generated port assignments.
In the following screenshot you can see a section of the application “Wireshark”. In this screenshot you can see an HTTPS request which has been sent from a clients (192.168.0.110) automatically generated port 63595 to my server (192.168.0.2) to the default HTTPS port 443.
Since all my websites are secured via HTTPS we can’t see any more human readable data (like z.b. the HTTP Protokoll) since all the data is being encrypted via TLSv1.2.
To standardize the usage of commonly used applications specific ports have been predefined.
Lets image we only have 1 IPv6 address for our client which for example has been automatically generated by SLAAC (which contains the MAC-Address of the network card).
If this IPv6 address is being used to connect to the internet it would be very easy for tracking tools to identify you as an individual and create a profile.
Thats why random temporary IPv6 addresses are being generated to establish connections to the internet. Since these temporary IPv6 addresses are being deleted and regenerated periodically (depends on the system how often) its pretty hard for tracking tools to create a profile just on an IP address basis.
Secured IPv6 address
ATTENTION: I haven’t verified this information, therefore its just my speculation!
Secured IPv6 addresses keep unique for one interface inside a specific network.
For example you will get the same secured IPv6 address in your home network or you company network to access e.g. a special network share.
Currently this “secured” IPv6 feature is only visible by default on MacOS (June 2019)
The basis for the communication in a network is a way to uniquely identify different devices. For exactly that purpose the “Internet Protocol” (short IP) has been developed.
An IP-Address is a unique number, which identifies a device inside the currently used network. This number can be something like:
IPv4: 192.168.0.10 IPv6: fe80::884:34ae:8eaf:a586
The detailed difference between IPv4 and IPv6 can be looked up in the linked posts.
But let’s keep it simple. An IP-Adresse can be seen as a “postal address” of your house to differentiate your house from your neighbours house. The only difference is that its not “Mainstreet 3, 8430 Leibnitz”, instead its “192.168.0.2” and that its not about houses, its about IT devices.
Why did we have to develop IPv6?
Basically IPv4 allows a maximum of 4.294.967.296 (232) devices, which in the grand scheme of the planet earth and its currently 7.7 billion people is not quite sufficient.
Therefore IPv6 was developed and allows a maximum of 340.282.366.920.938.463.463.374.607.431.768.211.456 (2128) devices which should suffice for quite some time.
Why was the internet protocol developed anyway?
Before the internet protocol it was not possible to connect 2 different network systems or let 2 computers from 2 difference network systems communicate with each other.
With the internet protocol it should be as easy as possible to connect multiple computers and networks with each outer without having to adjust thing like baud rates or the need to “hardcode” specific address codes.
Main tasks of the internet protocol
Commands to build and breakdown connections
Control of data flow via start und stopp commands
Error detection via checksums, time-outs etc.
Automatic error correction when an error has been detected
Main traits of the internet protocol
Its independent on the architecture
Connection to and from all network clients possible
The main tasks of the internet protocol have been split up into single “layers” – which build the Open Systems Interconnection model, in short OSI.
The typical subnet sizes are present between /32 and /64.
Basically you can create more subnets after /64 but you will lose a pretty important feature – the “Stateless Address Autoconfiguration” (SLAAC). See bellow for further information.
Link Local and Global address
After connecting an interface to a network it is now default In IPv6 to automatically create a “link local” and (if a IPv6 prefix is present) a “global” address.
The “Link Local” address is used – as you probably already expected – only for the locally connected network. This address is always a part of the subnet fe80::/64
The “Global” address is used – as you probably already expected too – for the “global” network aka the “Internet”. But this address only appears if the connected router has a correctly configured IPv6 prefix.
Additionally there are “temporary” and “secured” IPv6 addresses for security reasons. What these are and why they are needed can be looked up right HERE.
New features of IPv6
Larger amount of available addresses
An IPv6 address has 128 bits – IPv4 only has 32 bits.
In comparison IPv6 has 340.282.366.920.938.463.463.374.607.431.768.211.456 (2128) and IPv4 only 4.294.967.296 (232) total available addresses.
Stateless Address Autoconfiguration (SLAAC)
To automatically get an IPv4 address assigned to your device there needs be a “DHCP” server present in the current network. Most of the time this is built into everyones wireless router.
But in a IPv6 network with at least a subnet size of /64 the MAC address of each client can be used as part of the IPv6 address. This is used for the “link-local” as well as the “global” address.
The following illustration just shows how a 48 bit MAC address and the 64 bit “link-local” prefix is used to automatically create an IPv6 address.
Implementation of security measures (IPsec)
The “Internet Protocol Security” (IPsec) is a protocol residing in the 3rd layer of the OSI-Layer Models which allows the encryption and authentication of IP packets.
Basically everyone know what HTTPS, SSL and TLS are but these protocols work on higher OSI layers (HTTPS in the 7th and TLS in der 4th). Thats why “someone” can still manipulate data in the 3rd layer.
Thats why the IPsec protocol has been integrated into the IPv6 standard.
Conservation of the “Point-to-Point principal“
The “Point-to-Point principal” says, that only the endpoints in a connection are allowed to perform active protocol operations, not the stations between the 2 clients. A global unique IP address per client is a requirement for that.
In the current state of the IPv4 network this is not possible since not every client in the world has a unique IPv4 address.
Reserved IPv6 spaces
As well as in IPv4 there are reserved spaces, which are used for specific “functionalities“.
The “Domain Name System” (short DNS) is kind of a telephone book for the internet.
Basically the communication between 2 computers happens over IP addresses. Due the the fact, that these (and especially IPv6) addresses are not easily memorable for humans so called “domain names” can be connected to these IP addresses.
Therefore a DNS-Server “translates” a request like “google.com” into the IP address 126.96.36.199 (v4) and 2a00:1450:400d:802::200e (v6).
The 8 steps of a DNS lookup:
A user enters the address “example.com” in a web browsers. This creates a request to the next available “DNS recursive resolver”.
This “resolver” creates an additional request to the next available “DNS Root Server” (.)
The “Root Server” redirects this request to next available “Top Level Domain (TLD) DNS Server” (like z.B. “.at” or “.net”). Due to the fact, that our request contains the domain “example.com” the DNS resolver gets the address of the next available “.com” TLD DNS Servers.
The “resolver” now sends the request to the newly available “.com” TLD DNS Server.
The TLD DNS Server returns (if available) the IP address of the Domain Name Server for “example.com”.
Finally the “resolver” sends a request to the specific Domain Name Server.
Finally the IP address for “example.com” will be returned to the “resolver”.
The “resolver” sends this now resolved IP address for the requested domain back to the client.
DNS records are instructions how a DNS server handles specific DNS requests for a specific Domain.
These instructions are basically pure text files written in a specific DNS syntax.
Also every DNS record has a “Time-to-live” (TTL), which defines how often a DNS server refreshes its configuration.
Most important DNS record types
A and AAAA
Contains the IP address (A = v4, AAAA = v6)
“Canonical Name” refers to another domain (not IP address!)
“Mail Exchange” refers to a mail server
Allows an Domain-Admin to enter pure text entries
Mostly these are used for SPF entries or to verify a domain
“Start of authority” show important Admin information about the domain owner an (e.g. an E-Mail address)
“Service” refers to a special host and port for a specific service like VOIP
“Pointer” is the opposite of an “A”-Record and is used for the “Reverse-Lookup” get the connected domain out of an IP address.
There are many more DNS record types, but mostly they aren’t used that often. See more HERE.
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