The document summarizes four internet protocols: SMTP, IMAP, POP3, and DNS. SMTP is used for email transmission and uses port 25. IMAP allows clients to access email on remote servers and uses port 143. POP3 is also used for email retrieval but supports a download-and-delete model, using port 110. DNS translates domain names to IP addresses, allowing users to locate internet services by name.

1. Tutorial-2
1. Study of below given protocol:
(i)SMTP: Simple Mail Transfer Protocol (SMTP) is an internet standard
for electronic mail (e-mail) transmission across Internet
Protocol (IP) networks.
 SMTP uses TCP Port 25.
 It uses Layer no. 3 (Network Layer).
 SMTP connections secured by SSL are known by the
shorthand SMTPS.
 SMTP defined by RFC 821 and updated by standard RFC
5321.
 While electronic mail servers and other mail transfer agents
use SMTP to send and receive mail messages, user-level
client mail applications typically use SMTP only for sending
messages to a mail server for relaying.
(ii) IMAP: Internet Message Access Protocol (IMAP) is a protocol for
e-mail retrieval.
 IMAP is an Application Layer Internet protocol that allows
an e-mail client to access e-mail on a remote mail server.
 An IMAP server typically listens on well-known Port 143.
 IMAP over SSL (IMAPS) is assigned well-known port
number 993.
 IMAP supports both on-line and off-line modes of
operation.

2. (iii) POP3: Post Office Protocol (POP) is an application-layer Internet
standard protocol used by local e-mail clients to retrieve
e-mail from a remote server over a TCP/IP connection.
 POP and IMAP are the two most prevalent Internet
standard protocols for e-mail retrieval, Virtually all
modern e-mail clients and servers support both.
 Most webmail service providers such as Gmail and Yahoo!
Mail provide both an IMAP and POP3 service.
 POP supports simple download-and-delete requirements
for access to remote mailboxes.
 A POP3 server listens on well-known port110.
(iv) DNS: The Domain Name System (DNS) is a hierarchical
distributed naming system for computers, services, or any
resource connected to the Internet or a private network.
 It associates various information with domain names
assigned to each of the participating entities.
 Most prominently, it translates easily memorized domain
names to the numerical IP addresses needed for the
purpose of locating computer services and devices
worldwide.
 Domain Name System is an essential component of the
functionality of the Internet.
 For example, the domain name www.example.com
translates to the addresses 192.0.43.10 (IPv4) and
2001:500:88:200::10 (IPv6).