Question

I have been doing Windows programming in .Net since last two years.
Now I am shifting to web programming so I just stuck in understanding the
fundamentals of web programming, after googling I came to StackOverflow to learn
from all of you great guys.

My confusion is about how messages flow between systems in distributed enviornment ?
I mean suppose I want to send a message "Hello" to a system connected to LAN or Internet,
then what will be the steps taken to send the message.

Second thing is suppose my system is "A" and I wana send message to system "B" which is connected via a wire, so how the message flows on wire and how system "B" reads it from the wire ?

Please someone explain me in a layman terms.

Thank you all in advance.

Answer 1

Here’s the short layman explanation of what is happening. you can search for any highlighted term to read more about the particular layer in the whole stack.

• Your browser creates an HTTP packet containing the GET request details for the page it needs.
• It then asks the OS networking stack to deliver that packet over the TCP/IP protocol to the target machine.
• If the browser gave the network stack the domain name (ie, http://google.com), the network stack makes a request to its DNS server to resolve that domain name to an IP address (ie, 74.125.155.99).
  The DNS server might need to contact other DNS servers, if it doesn’t have that info cached locally.
• Once the DNS server has determined the IP address and returned it to the OS networking stack, or if the HTTP request is addressed to an IP address directly, the networking stack will create a TCP/IP packet for that IP address and give it to the network card driver.
• The network card driver will wrap the TCP/IP packet in an Ethernet frame packet.
• If the IP address is on the local network, the network card driver will try to determine what’s the target machine MAC address in the ARP table. If it succeeds, then it will send the Ethernet frame packet over the network wire directly addressed to the MAC address of that machine.
• If the IP address is not on the local network, the network card will send the Ethernet frame packet to MAC address of the local network gateway machine.
• The network card driver on the gateway machine will unwrap the TCP/IP packet and hand it off to that machine TCP/IP stack.
• The gateway machine TCP/IP stack will look at the destination IP address and repeat the proper steps above to deliver the packet to the target machine or the next machine in the route.