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Common Protocols: HTTP, FTP, SMTP, DNS, etc.

Common Network Protocols HTTP FTP SMTP DNS — Notes & MCQs | GyanDesk
Computer Networks · Exam Notes

Common Network Protocols — HTTP, FTP, SMTP, DNS & More

Exam-focused notes on common network protocols for SSC, Banking (IBPS/SBI), Railway, UPSC, NIELIT, JAIIB/CAIIB and IT officer papers. Learn full forms, ports, uses, comparisons, TCP vs UDP links, and practice with interactive MCQs.

20+ key protocols Port table must-memorise 60 practice MCQs Quick revision ready

What is a Network Protocol?

Definition + why exams love this topic

Must Know

A network protocol is a set of rules that devices follow to communicate on a network. It defines how data is formatted, sent, received, and acknowledged.

Simple exam line
Protocol = agreed language/rules between sender and receiver so communication works correctly.
Where they sit
HTTP, FTP, SMTP, DNS are mainly Application layer protocols. TCP/UDP are Transport layer.
Highest weightage in exams: full form + default port + one-line purpose. Memorise the port table first.

Application protocols

HTTP, HTTPS, FTP, SMTP, POP3, IMAP, DNS, DHCP, SSH, Telnet, SNMP, LDAP, RDP

Transport helpers

TCP (reliable) and UDP (fast). Many app protocols run over one of these.

Port number

A number that identifies a service on a host (e.g., web server on 80/443).

1. Web Protocols — HTTP & HTTPS

Most common pair in banking & SSC computer awareness

Very Important

HTTP

Port 80 TCP

HyperText Transfer Protocol — transfers web pages and resources between browser and web server.

Key points

  • Application layer protocol
  • Request–response model
  • Commonly called stateless
  • Methods: GET, POST, PUT, DELETE…

Exam hot points

  • Port 80
  • Used for web browsing
  • Not encrypted by itself
  • Full form must be perfect

HTTPS

Port 443 TCP Secure

HTTP Secure — HTTP over TLS/SSL encryption for safe web communication (logins, payments, banking).

Why HTTPS

  • Encrypts data in transit
  • Protects passwords & cards
  • Uses digital certificates
  • Default modern web standard

Exam hot points

  • Port 443
  • HTTP + SSL/TLS
  • Secure alternative to HTTP
  • Same methods as HTTP
Memory tip: HTTP = highway (80). HTTPS = locked highway (443).

2. File Transfer — FTP & SFTP

Control vs data ports is a favourite trap

FTP

20 data / 21 control TCP

File Transfer Protocol — upload and download files between client and server.

Key points

  • Two channels: control + data
  • Control commands on 21
  • Data transfer on 20 (active mode)
  • Basic FTP is not encrypted

Exam hot points

  • Full form + ports 20/21
  • Used to upload website files
  • Separate control & data connections

SFTP

22 (via SSH) Secure

SSH File Transfer Protocol — secure file transfer, commonly over SSH.

Key points

  • Encrypts file transfer
  • Usually uses port 22
  • Preferred over plain FTP
  • Different from FTPS (FTP + TLS)

Exam hot points

  • Secure alternative to FTP
  • Linked with SSH port 22
  • Do not confuse SFTP with SMTP
Trap: SFTP ≠ SMTP. SFTP = secure files. SMTP = send mail.

3. Email Protocols — SMTP, POP3, IMAP

Send vs receive is the core exam distinction

Very Important

SMTP

25 / 587 / 465

Simple Mail Transfer Protocol — sends email (push).

  • Client → mail server
  • Mail server → mail server
  • 25 common between servers
  • 587 often for submission

POP3

110 / 995

Post Office Protocol v3 — download mail to one device.

  • Often deletes from server after download
  • Less ideal for multi-device sync
  • 110 plain / 995 secure (POP3S)

IMAP

143 / 993

Internet Message Access Protocol — access/sync mail on server.

  • Best for phone + laptop + webmail
  • Folders & read status sync
  • 143 plain / 993 secure (IMAPS)
Protocol Main job Mail stays on server? Multi-device friendly? Common ports
SMTP Send / push mail N/A (sending) N/A 25, 587, 465
POP3 Download mail Often no (default behaviour) Weak 110 / 995
IMAP Access & sync mail Yes Strong 143 / 993
Memory tip: SMTP = Send Mail To People. POP3 = Post Office pickup (take home). IMAP = Internet Multi-device Access.

4. Name & Addressing — DNS & DHCP

Phonebook + automatic IP assignment

DNS

Port 53 UDP/TCP

Domain Name System converts domain names (like gyandesk.com) into IP addresses.

Important records

  • A → IPv4 address
  • AAAA → IPv6 address
  • MX → mail server
  • CNAME → alias name
  • NS → name server

Exam hot points

  • Port 53
  • “Phonebook of the Internet”
  • Queries often UDP; large/zone = TCP
  • MX for email routing

DHCP

67 server / 68 client UDP

Dynamic Host Configuration Protocol automatically assigns IP address, subnet mask, gateway, and DNS settings to devices.

Key points

  • No need to set static IP manually
  • Lease-based temporary assignment
  • Used in homes, offices, campuses
  • Replaced older RARP/BOOTP roles largely

Exam hot points

  • Full form + auto IP assignment
  • Ports 67/68
  • Server = 67, Client = 68
Do not mix: DNS finds IP for a name. DHCP gives an IP to a device.

5. Remote Access — Telnet, SSH, RDP

Security comparison is frequently asked

Telnet

23 Insecure

Remote terminal access in plain text. Passwords can be sniffed. Mostly obsolete for secure use.

SSH

22 Secure

Secure Shell — encrypted remote login and command execution. Modern replacement for Telnet. Also used by SFTP.

RDP

3389

Remote Desktop Protocol — graphical remote desktop access, commonly associated with Windows.

Classic pair: SSH = 22 (secure). Telnet = 23 (not secure).

6. Management & Directory — SNMP, LDAP

SNMP

161 / 162

Simple Network Management Protocol monitors and manages network devices (routers, switches, servers).

  • Uses MIB (Management Information Base)
  • Agent data on 161; traps/notifications often 162
  • Admins check uptime, traffic, errors, alerts

LDAP

389 / 636

Lightweight Directory Access Protocol accesses directory services (users, groups, authentication directories).

  • Common in enterprise login systems
  • 389 plain LDAP; 636 often LDAPS
  • Related exam neighbour: Active Directory concepts

7. Other High-Yield Protocols (Short Notes)

ICMP

Error/diagnostic messages. Used by ping and traceroute-related functions.

ARP

IP → MAC address mapping on a LAN. RARP (MAC → IP) is mostly historical.

NTP

Network Time Protocol — synchronises clocks (port 123).

TCP vs UDP (Transport Layer Base)

Almost every protocol MCQ set includes this

TCP

Transmission Control Protocol — reliable, connection-oriented.

  • 3-way handshake
  • Ordered, acknowledged delivery
  • Flow & congestion control
  • Used by: HTTP, HTTPS, FTP, SMTP, POP3, IMAP, SSH, Telnet

UDP

User Datagram Protocol — fast, connectionless, no delivery guarantee.

  • Lower overhead, lower latency
  • No connection setup like TCP
  • Good for speed-sensitive apps
  • Used by: DNS queries, DHCP, SNMP, streaming/VoIP style apps
Exam line: TCP = trustworthy courier (slower but sure). UDP = postcard (fast, may be lost).

Must-Memorise Port Summary Table

Highest ROI revision block for competitive exams

Memorise
Port Protocol Purpose Mnemonic / tip
20 / 21FTPFile transfer (data / control)20 & 21 = two parts of file transfer
22SSH / SFTPSecure remote login / secure file transferSecure 22
23TelnetInsecure remote accessTele-net 23
25 / 587 / 465SMTPSend email25 = mail on the way
53DNSName → IP5-3 letters idea / phonebook
67 / 68DHCPAuto IP (server / client)67 gives, 68 receives
80HTTPWeb pagesHighway 80
110 / 995POP3 / POP3SDownload email110 post office
143 / 993IMAP / IMAPSSync email143 multi-device
161 / 162SNMPNetwork management161 ask, 162 trap
389 / 636LDAP / LDAPSDirectory servicesEnterprise user directory
443HTTPSSecure webLocked 443
3389RDPRemote desktopWindows remote screen
123NTPTime syncClock protocol

High-Frequency Comparisons

Compare Choose / remember
HTTP vs HTTPS HTTPS = HTTP + TLS/SSL encryption; ports 80 vs 443
SMTP vs POP3 vs IMAP SMTP sends; POP3 downloads; IMAP syncs on server
FTP vs SFTP FTP plain (20/21); SFTP secure over SSH (22)
Telnet vs SSH Telnet 23 insecure; SSH 22 secure
DNS vs DHCP DNS resolves names; DHCP assigns IPs
TCP vs UDP TCP reliable/connection-oriented; UDP fast/connectionless
A vs AAAA vs MX A=IPv4, AAAA=IPv6, MX=mail server

One-Glance Quick Revision

Read this block the night before the exam

HTTP

Web pages · Port 80 · Stateless

HTTPS

Secure web · Port 443 · TLS/SSL

FTP

File transfer · 20 data / 21 control

SFTP

Secure files · via SSH 22

SMTP

Send mail · 25/587 · Push

POP3

Download mail · 110/995

IMAP

Sync mail · 143/993 · Multi-device

DNS

Name → IP · 53 · A/AAAA/MX

DHCP

Auto IP · 67 server / 68 client

SSH

Secure remote · 22

Telnet

Insecure remote · 23

SNMP

Device management · 161/162 · MIB

RDP

Remote desktop · 3389

LDAP

Directory access · 389/636

TCP

Reliable · connection-oriented

UDP

Fast · connectionless

Practice MCQs on Common Protocols

Tap any option to reveal the correct answer and a short explanation. Answers stay hidden until you choose.

60 Questions
Score: 0 / 0 attempted

Exam Tips for Protocol Questions

Port first, story second

If options include numbers, match port → protocol before overthinking the wording.

Send vs receive mail

SMTP sends. POP3/IMAP receive/access. Never mark POP3 as “sending protocol”.

Secure twins

HTTP→HTTPS, Telnet→SSH, FTP→SFTP. Secure version usually adds encryption.

DNS record letters

A = IPv4, AAAA = IPv6 (longer), MX = Mail eXchange.

Full forms must be exact

HyperText (not Hyperlink), Domain Name System (not Server), Secure Shell (not System).

Layer placement

HTTP/FTP/SMTP/DNS = Application. TCP/UDP = Transport. Easy 1-mark questions.

GyanDesk tip: Revise the port table + email comparison first, then attempt “High probability” MCQs. Related notes: HTTP methods · DNS resolution · ARP & RARP · RIP OSPF BGP · Network Topologies · All IT notes

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Related notes

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