RickPlaysWarr
New member
I noticed that there is no really basic primer on pc TCP/IP networking on OC3D, so decided to write a quick primer on what all the terms and funky numbers mean. There are a lot of terms that can be thrown around in networking, so I will try and give a simple explanation of the most common terms / parameters.
The quick definition of what TCP/IP stands for it Transmission Control Protocol / Internet Protocol. There is a whole lot of meaning in those words, but we don't need to go into that. So lets dive in
Whats an IP address: An IP address is a series of four numbers in its most common form IPv4 (octets) in the form of XXX.XXX.XXX.XXX where XXX can be any number from 0 to 255. For example 192.168.100.41. It is basically my computers address on this network. This network is the key as it may or may not be the entire internet as we will discuss later. The four numbers are called octets as if written in binary each number would be composed of 8 zeros and ones (11000000.10101000.01100100.00101001) An IP address can be obtained in one of two ways it can be hardcoded into the network setup or obtained via DHCP as we will discuss below. By far DHCP is the more common mode these days.
Whats a Subnet Mask: Along with the IP address the Subnet mask defines my local network. The more detailed explanation is that the subnet mask defines the computer IP addresses on the network that I can communicate with without routing. The most common subnet mask is 255.255.255.0 and this translates to I can communicate with IP addresses 192.168.100.1 to 192.168.100.255 directly. However there are two addresses that are reserved out of that block. The last one is know as the broadcast address and it is used to communicate with all machines on this subnet. It is the last address of the subnet by default or 192.168.100.255. There is another special address in each subnet called the default gateway or default route.
Whats a Default Gateway: As my computer knows how to communicate directly with only the machines in my network subnet, it needs a place to go if the address I am trying to reach is outside my subnet. This is the Default Gateway. It is usually a router or another device that performs the functionality of a router. In my network it is 192.168.100.1 Using the lowest IP address of the Subnet is a convention that seems to have taken hold, but it is not a hard rule. If my computer wants to communicate with a device outside my subnet, it sends the communication to the Default Gateway as that machine knows where to go next.
That leads to the next question, we are talking about a bunch of numbers here, but we move around the internet by using a series of words called an URL (Uniform Resource Locator) For example www.overclock3d.net. This leads to a concept called DNS.
What is DNS: DNS is a service of the Internet known as Domain Name System. The short answer is that it translates the words that you give it in an URL to the actual IP address numbers that your device hardware uses to make the communication work. DNS in itself is a bit more complex, however the short answer will suffice for now.
What are DNS Servers: In each devices network configuration there are usually two entries for DNS Servers. These can be hardcoded or supplied by DHCP. I promise we will get to DHCP soon. These are the IP addresses that your device will use when it wants to get an URL to IP address translation. When we enter an URL in a program it is automatically sent of to the DNS servers and they reply with the actual destination IP address that you are trying to communicate with.
What is DHCP: As outlined above there are two ways to setup a device on a TCP/IP network. One, hardcode all the settings (IP Address, Subnet, DNS Servers, Default Gateway, and more) or through DHCP. By far DHCP is the most common. It was not the case when I first started in networking. Now that there are Billions of IP devices out there, it would be impossible to correctly setup all the settings needed for TCP/IP to work. DHCP stands for Dynamic Host Configuration Protocol. I know thats a lot of big words, but it is breaks down to this. Your machine if it is configured to get an IP address through DHCP starts out with no networking parameters at all. It broadcasts a DHCP message out and waits for a DHCP server to send it its networking setup information. So somewhere in your local Subnet or reachable via the default gateway there must be a DHCP Server that can manage these requests and hand out the IP addresses and other parameters.
Whats a DHCP Server: Its a computer or other device that responds to DHCP requests and manages and hands out the IP addresses allocated to it. It is a topic for another discussion, but the short answer is that a DHCP Server has a pool of addresses/settings that it sends out to a device requesting an IP address via DHCP. These addresses can be hardcoded to one particular machine (DHCP Reservation) or assigned at random. Each Address comes with all the required information above on how to properly communicate on this IP Subnet. Each IP address also come with a parameter called a DHCP Lease. It is the time that your DHCP request was fulfilled and how long its good for. The device that the DHCP lease was issued to is granted that IP address for the term of the Lease. Also, if the device remains on the subnet, and is on, it will request a release of the same IP address when it reaches the half way point of the lease. This means that for machines that are constantly on, or close, their IP addresses probably wont change. A reserved IP address is always granted to the machine that it is allocated to regardless if it is on constantly or intermittent on the Subnet.
A quick bit of back history. There are a range of subnets that are fictitious addresses on the whole Internet. These were setup so that a company could have an IP network but not actually have purchased an IP network of any size. If your IP address is in one of these subnets you communicate to the whole internet through NAT. The fictitious Subnets are:
24-bit block __ 10.0.0.0-10.255.255.255 _______ 1 single class A network
20-bit block __ 172.16.0.0-172.31.255.255 _____ 16 contiguous class B networks
16-bit block __ 192.168.0.0-192.168.255.255 ___ 256 contiguous class C networks
The short answer to being in one of these networks is that your address is not really on the Internet, its a private network that may access the internet via NAT. Even if you don't have one of these addresses, you might still be accessing the Internet via NAT. It usually costs extra to get a valid IP address that is good throughout the entire Internet. They are usually called Static IP addresses.
What is NAT: NAT stands for Network Address Translation. A quick explanation of NAT is that there is a machine on the edge of the Internet and the network you are on that performs Name Address Translation. It translates all the IP addresses of the messages that you send from inside the network which are not valid ip addresses on the whole internet to a valid IP address that the network owns on the internet. This allows the devices outside of your network/provider respond to your messages and reply back. The translation is both ways and the NAT machine is a gateway all your messages pass through and returning messages pass through.
There is more, and I would be happy to answer any questions or expand the guide if it is not clear
Thanks
--Rick--
The quick definition of what TCP/IP stands for it Transmission Control Protocol / Internet Protocol. There is a whole lot of meaning in those words, but we don't need to go into that. So lets dive in
Whats an IP address: An IP address is a series of four numbers in its most common form IPv4 (octets) in the form of XXX.XXX.XXX.XXX where XXX can be any number from 0 to 255. For example 192.168.100.41. It is basically my computers address on this network. This network is the key as it may or may not be the entire internet as we will discuss later. The four numbers are called octets as if written in binary each number would be composed of 8 zeros and ones (11000000.10101000.01100100.00101001) An IP address can be obtained in one of two ways it can be hardcoded into the network setup or obtained via DHCP as we will discuss below. By far DHCP is the more common mode these days.
Whats a Subnet Mask: Along with the IP address the Subnet mask defines my local network. The more detailed explanation is that the subnet mask defines the computer IP addresses on the network that I can communicate with without routing. The most common subnet mask is 255.255.255.0 and this translates to I can communicate with IP addresses 192.168.100.1 to 192.168.100.255 directly. However there are two addresses that are reserved out of that block. The last one is know as the broadcast address and it is used to communicate with all machines on this subnet. It is the last address of the subnet by default or 192.168.100.255. There is another special address in each subnet called the default gateway or default route.
Whats a Default Gateway: As my computer knows how to communicate directly with only the machines in my network subnet, it needs a place to go if the address I am trying to reach is outside my subnet. This is the Default Gateway. It is usually a router or another device that performs the functionality of a router. In my network it is 192.168.100.1 Using the lowest IP address of the Subnet is a convention that seems to have taken hold, but it is not a hard rule. If my computer wants to communicate with a device outside my subnet, it sends the communication to the Default Gateway as that machine knows where to go next.
That leads to the next question, we are talking about a bunch of numbers here, but we move around the internet by using a series of words called an URL (Uniform Resource Locator) For example www.overclock3d.net. This leads to a concept called DNS.
What is DNS: DNS is a service of the Internet known as Domain Name System. The short answer is that it translates the words that you give it in an URL to the actual IP address numbers that your device hardware uses to make the communication work. DNS in itself is a bit more complex, however the short answer will suffice for now.
What are DNS Servers: In each devices network configuration there are usually two entries for DNS Servers. These can be hardcoded or supplied by DHCP. I promise we will get to DHCP soon. These are the IP addresses that your device will use when it wants to get an URL to IP address translation. When we enter an URL in a program it is automatically sent of to the DNS servers and they reply with the actual destination IP address that you are trying to communicate with.
What is DHCP: As outlined above there are two ways to setup a device on a TCP/IP network. One, hardcode all the settings (IP Address, Subnet, DNS Servers, Default Gateway, and more) or through DHCP. By far DHCP is the most common. It was not the case when I first started in networking. Now that there are Billions of IP devices out there, it would be impossible to correctly setup all the settings needed for TCP/IP to work. DHCP stands for Dynamic Host Configuration Protocol. I know thats a lot of big words, but it is breaks down to this. Your machine if it is configured to get an IP address through DHCP starts out with no networking parameters at all. It broadcasts a DHCP message out and waits for a DHCP server to send it its networking setup information. So somewhere in your local Subnet or reachable via the default gateway there must be a DHCP Server that can manage these requests and hand out the IP addresses and other parameters.
Whats a DHCP Server: Its a computer or other device that responds to DHCP requests and manages and hands out the IP addresses allocated to it. It is a topic for another discussion, but the short answer is that a DHCP Server has a pool of addresses/settings that it sends out to a device requesting an IP address via DHCP. These addresses can be hardcoded to one particular machine (DHCP Reservation) or assigned at random. Each Address comes with all the required information above on how to properly communicate on this IP Subnet. Each IP address also come with a parameter called a DHCP Lease. It is the time that your DHCP request was fulfilled and how long its good for. The device that the DHCP lease was issued to is granted that IP address for the term of the Lease. Also, if the device remains on the subnet, and is on, it will request a release of the same IP address when it reaches the half way point of the lease. This means that for machines that are constantly on, or close, their IP addresses probably wont change. A reserved IP address is always granted to the machine that it is allocated to regardless if it is on constantly or intermittent on the Subnet.
A quick bit of back history. There are a range of subnets that are fictitious addresses on the whole Internet. These were setup so that a company could have an IP network but not actually have purchased an IP network of any size. If your IP address is in one of these subnets you communicate to the whole internet through NAT. The fictitious Subnets are:
24-bit block __ 10.0.0.0-10.255.255.255 _______ 1 single class A network
20-bit block __ 172.16.0.0-172.31.255.255 _____ 16 contiguous class B networks
16-bit block __ 192.168.0.0-192.168.255.255 ___ 256 contiguous class C networks
The short answer to being in one of these networks is that your address is not really on the Internet, its a private network that may access the internet via NAT. Even if you don't have one of these addresses, you might still be accessing the Internet via NAT. It usually costs extra to get a valid IP address that is good throughout the entire Internet. They are usually called Static IP addresses.
What is NAT: NAT stands for Network Address Translation. A quick explanation of NAT is that there is a machine on the edge of the Internet and the network you are on that performs Name Address Translation. It translates all the IP addresses of the messages that you send from inside the network which are not valid ip addresses on the whole internet to a valid IP address that the network owns on the internet. This allows the devices outside of your network/provider respond to your messages and reply back. The translation is both ways and the NAT machine is a gateway all your messages pass through and returning messages pass through.
There is more, and I would be happy to answer any questions or expand the guide if it is not clear
Thanks
--Rick--
Last edited:
and NAT is Evil 
