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When You Visit a URL

URL - Uniform Resource Locator

1. DNS Lookup​

  • First thing is to resolve IP address of the domain name.

Check browser cache -> OS cache -> ISP cache -> TLD (Top level domain) Server -> Authorative Name Server -> Root Server

2. Browser Initiates TCP Connection​

  • Client sends SYN
  • Server sends SYN + ACK
  • Client sends ACK
  • See Networking/HTTP for HTTPS initialization
  • Initialized
MessageDescription
SYNUsed to initiate and establish a connection. It also helps you to synchronize sequence numbers between devices.
ACKHelps to confirm to the other side that it has received the SYN.
SYN-ACKSYN message from local device and ACK of the earlier packet.

3. Request Response Process​

  • Client sends request
  • Server sends response

References: