Consider the steps required for a client to get ready to send an HTTP request to
ID: 3596973 • Letter: C
Question
Consider the steps required for a client to get ready to send an HTTP request to www.facebook.com. Assume the client already has an IP address and knows the IP addresses of its default router and local DNS server (i.e., DHCP has already been completed).On the left side are the ordered step numbers, and on the right side are potential steps required. Match the steps to the order in which they are executed (i.e., put the operations in order). Please explain as welll.
-User types www.facebook.com into their web browser.
-The TCP SYN is sent in a link-layer frame with the client's MAC address as its source and its default router's MAC address as its destination.
-The IP address of www.facebook.com is inserted into the network layer header of the TCP SYN packet, and the network layer determines that it needs to send the packet to its default router.
-The client's operating system creates a DNS query message, requesting the IP address of www.facebook.com from its local DNS server.
-A DNS reply is received, containing the IP address of www.facebook.com.
-The DNS query for www.facebook.com is sent to the local DNS server in an Ethernet frame
-Web browser at the application layer creates the HTTP request message.
-The link layer uses ARP to determine the MAC address of the local DNS server.
-At the transport layer, the client starts to create a TCP socket for communication and determines that it needs the IP address of www.facebook.com.
-The TCP 3-way handshake is completed and the TCP socket is connected.
Explanation / Answer
Answer
The steps can be numbered as shown below:
Explanation:
When a user request for an URL in the web browser, it needs to be converted into an IP address. It looks in all the cache to retrieve this information. If this is available in cache, the data is accessed directly. That means according to our steps, the step 10 is executed. If not, the procedure to find the IP address is started. The DNS look up server is used for this purpose. Then the browser creates a TCP connection to the server, and then sends an HTTP request message to server. TCP handshake is done. After connection establishment, IP address is received using DNS query and response. And, finally IP address is used to access Facebook.