very basic concepts are:
From the very bottom of the data flow (ie from your computer outward)
Your system needs an IP address (analogous to your home has a street address).
That IP address is most frequently acquired by a
Dynamic Host Configuration Protocol (
DHCP) request on your Network Adaptor with an active driver.
That results in settings on your system like
Code:
Physical Address. . . . . . . . . : aa-bb-cc-dd-ee-ff
Dhcp Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.0.4
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.0.1
DHCP Server . . . . . . . . . . . : 192.168.0.1
DNS Servers . . . . . . . . . . . : 209.18.47.61
209.18.47.62
The DHCP request is
broadcast and the first DHCP server that can respond will provide the above.
Here's what's important:
Gateway: the IP address to which all data flows to exit this system.
IP address: is my systems location on this subnet (meaning everything attached to the gateway)
Mask: is a technical detail in the hardware operation of reading address.
All Internet traffic is from
one IPaddress to another.
If systemA wants to
talk to systemB, the sequence (technical details omitted for simplicity) is like
- systemA opens a connection to systemB
- systemB accepts or rejects the connection
- if accepted, systemB acknowledges that with a short message which is defined by something known as a protocol
(a well defined and agreed sequence of events and data flows). For example, talking to a webserver, the acknowledgment is
"HTTP/1.0 200 OK"
Notice:
one IPaddress to another - - good golly Batman, I don't know IP addresses for any website - - how do I find the right one?
That's the job if the Domain Name System (
DNS).
If a browser wants to access google.com, it needs google's IPaddress, so it asks DNS where is
www.google.com.
Where does it sent that question - - to the DNS Server address give to the DHCP request above. So it asks
where is www,google.com
and the reply is one of google's ip addresses
Having that IPaddress, the browser can then access the site using the
open shown above
and use the HTTP or HTTPS protocols to
talk to the server.