ApplicationLayerII

Question 1

What is the difference between non-persistent and persistent HTTP?

Answer 1

Non-persistent HTTP opens a new TCP connection for each object request. Persistent HTTP reuses a single TCP connection for multiple requests.

Question 2

What is DNS caching?

Answer 2

DNS caching stores previous DNS query results locally to speed up future lookups and reduce the load on DNS servers.

Question 3

Describe the structure of the DNS hierarchy.

Answer 3

DNS hierarchy: Root servers -> Top-level domain (TLD) servers -> Authoritative name servers -> Local DNS servers.

Question 4

What services are provided by DNS?

Answer 4

DNS provides hostname-to-IP translation, host aliasing, and load distribution across replicated servers.

Question 5

List the four types of DNS servers.

Answer 5

Root DNS servers, Top-level domain (TLD) servers, Authoritative DNS servers, Local DNS servers.

Question 6

What is the function of SMTP?

Answer 6

SMTP (Simple Mail Transfer Protocol) is used to send emails between mail servers over a reliable TCP connection.

Question 7

What does POP3 do?

Answer 7

POP3 (Post Office Protocol 3) downloads emails from the server to the client and usually deletes them from the server.

Question 8

How does IMAP differ from POP3?

Answer 8

IMAP keeps emails on the server and allows management of mailboxes and folders directly on the server.

Question 9

What is the role of a socket in communication?

Answer 9

A socket provides a communication endpoint that combines an IP address and a port number for sending/receiving data.

Question 10

How is a TCP connection established between client and server?

Answer 10

The client creates a socket and connects it to the server’s socket (IP address + port number), initiating a connection request.