HTTP (Hyper Text Transfer Protocol) is an application-layer protocol used to transfer web pages and data between a client (browser) and a web server.
It is the foundation of data communication on the World Wide Web.
👉 HTTP is the rule that allows your browser to talk to a website server.
When you open a website:
1️⃣ Browser sends an HTTP request
2️⃣ Server processes request
3️⃣ Server sends HTTP response
4️⃣ Browser displays webpage
Step-by-Step:
| Method | Purpose |
| GET | Retrieve data |
| POST | Send data |
| PUT | Update data |
| DELETE | Delete data |
GET /index.html HTTP/1.1
Host: www.example.com
| Feature | HTTP | HTTPS |
| Security | Not secure | Secure (encrypted) |
| Port | 80 | 443 |
| Encryption | No | SSL/TLS |
HTTPS (HyperText Transfer Protocol Secure) is a secure version of HTTP that encrypts communication between a client (browser) and a web server using SSL/TLS encryption.
It ensures that data transferred over the internet is confidential and secure.
👉 HTTPS = HTTP + Security
When you see 🔒 lock icon in the browser, → Website is using HTTPS.
1️⃣ Client sends a request to the server
2️⃣ Server sends digital certificate
3️⃣ Browser verifies certificate
4️⃣ SSL/TLS handshake occurs
5️⃣ Secure encrypted session is established
6️⃣ Data is exchanged securely
Data is converted into an unreadable format.
Verifies website identity using a digital certificate.
Ensures data is not modified during transmission.
| Feature | HTTP | HTTPS |
| Port | 80 | 443 |
| Security | No encryption | Encrypted |
| Data Protection | No | Yes |
| Certificate Required | No | Yes |
FTP (File Transfer Protocol) is an application-layer protocol used to transfer files between a client and a server over a network.
It allows users to upload, download, rename, delete, and manage files on a remote server.
👉 FTP is used to transfer files from one computer to another over a network or the internet.
Example:
FTP uses TCP protocol.
FTP uses two connections:
When a web developer uploads website files to a hosting server using FileZilla → FTP is used.
| Feature | FTP | HTTP |
| Purpose | File transfer | Web browsing |
| Port | 21 | 80 |
| Security | Not secure | Not secure (unless HTTPS) |
DHCP (Dynamic Host Configuration Protocol) is a network protocol that automatically assigns IP addresses and other network configuration details to devices in a network.
It eliminates the need to manually configure IP settings.
👉 DHCP automatically gives your device an IP address when you connect to a network.
Example:
When you connect your phone to Wi-Fi, it automatically gets an IP address — DHCP is doing that job.
Works over the UDP protocol.
DHCP follows a 4-step process called DORA:
1️⃣ Discover
Client broadcasts request:
“Is there any DHCP server?”
2️⃣ Offer
DHCP server replies with available IP address.
3️⃣ Request
Client requests that offered IP.
4️⃣ Acknowledge
Server confirms and assigns IP officially.
DHCP assigns IP for a limited time (called lease).
After lease expires:
Device assigns itself an APIPA address:
Range: 169.254.x.x
This indicates DHCP server is not reachable.
| Feature | Static IP | DHCP |
| Configuration | Manual | Automatic |
| Used For | Servers | Client devices |
| Risk of Conflict | Yes | No |
In the office network:
DNS (Domain Name System) is a network protocol that translates human-readable domain names (like www.google.com) into IP addresses (like 142.250.x.x) so that computers can communicate with each other.
It is often called the “Phonebook of the Internet.”
👉 Humans remember names (google.com).
👉 Computers understand numbers (IP addresses).
DNS converts names into IP addresses.
When you type www.google.com:
1️⃣ Browser checks local DNS cache
2️⃣ If not found → request sent to DNS resolver
3️⃣ Resolver contacts:
DNS works in a hierarchical structure:
| Record Type | Purpose |
| A | Maps domain → IPv4 |
| AAAA | Maps domain → IPv6 |
| MX | Mail server record |
| CNAME | Alias record |
| NS | Name server record |
| PTR | Reverse lookup |
nslookup google.com
Output:
Returns the IP address of Google.com
Example:
If ping 8.8.8.8 works but ping google.com fails → DNS issue.
Secure versions:
SMTP (Simple Mail Transfer Protocol) is an application-layer protocol used to send emails from a client to a mail server and between mail servers.
It is responsible for outgoing mail delivery.
👉 SMTP is the protocol that sends your email to the recipient.
When you click Send in Gmail or Outlook → SMTP is working in the background.
| Port | Usage |
| 25 | Default SMTP (server-to-server) |
| 587 | Secure email submission |
| 465 | SMTP over SSL (older secure method) |
Works over TCP protocol.
Example: You send an email to your friend.
1️⃣ Your email client connects to SMTP server
2️⃣ SMTP server verifies sender
3️⃣ Server finds recipient mail server (via DNS MX record)
4️⃣ Email is transferred to recipient’s mail server
5️⃣ Recipient retrieves email using POP3 or IMAP
👉 SMTP is only used for sending emails.
👉 For receiving emails, we use:
Basic SMTP ❌ Not secure (plain text).
Secure versions use:
When you send an email from:
SMTP handles the outgoing message delivery.
| Protocol | Purpose |
| SMTP | Sending email |
| POP3 | Downloading email |
| IMAP | Syncing email |
SNMP (Simple Network Management Protocol) is an application-layer protocol used to monitor and manage network devices such as routers, switches, servers, printers, and firewalls.
It allows network administrators to collect information, monitor performance, and detect faults remotely.
👉 SNMP helps administrators monitor network devices from a central system.
Example:
Checking CPU usage of a router remotely → SNMP is used.
| Port | Purpose |
| 161 | SNMP Requests (Manager → Agent) |
| 162 | SNMP Traps (Agent → Manager) |
Uses UDP protocol.
SNMP works using three main components:
1️⃣ SNMP Manager sends request to device
2️⃣ SNMP Agent reads information from MIB
3️⃣ Agent sends response back
4️⃣ If issue occurs → Agent sends Trap alert
| Version | Security |
| SNMPv1 | No encryption |
| SNMPv2 | Improved performance |
| SNMPv3 | Secure (Authentication + Encryption) |
👉 SNMPv3 is recommended for security.
In a company network:
ICMP (Internet Control Message Protocol) is a network-layer protocol used for error reporting and network diagnostics in IP networks.
It helps devices communicate information about network problems.
👉 ICMP is used to check whether a device is reachable and to report network errors.
Example:
When you use the ping command → ICMP is working.
❌ No.
ICMP does not use TCP or UDP ports.
It works directly at the Network Layer (Layer 3) with IP.
When you run:
ping 8.8.8.8
1️⃣ Your device sends ICMP Echo Request
2️⃣ Destination replies with ICMP Echo Reply
3️⃣ You see response time (latency)
| Type | Purpose |
| Echo Request | Sent by ping |
| Echo Reply | Response to ping |
| Destination Unreachable | Target cannot be reached |
| Time Exceeded | TTL expired |
| Redirect | Suggests better route |
✅ Used By:
🔹 Request Timed Out
No reply received.
🔹 Destination Host Unreachable
Routing problem.
🔹 TTL Expired
Packet exceeded hop limit.
If internet is not working:
1️⃣ Ping 127.0.0.1 → Check local TCP/IP
2️⃣ Ping gateway → Check router connectivity
3️⃣ Ping 8.8.8.8 → Check internet
4️⃣ Ping google.com → Check DNS
All use ICMP.
| Feature | ICMP | SNMP |
| Purpose | Diagnostics | Monitoring |
| Port | No port | 161/162 |
| Used For | Ping, error reporting | Device management |
| Protocol | Full Form | Port | Purpose |
| HTTP | Hyper Text Transfer Protocol | 80 | Web browsing |
| HTTPS | HTTP Secure | 443 | Secure browsing |
| FTP | File Transfer Protocol | 21 | File transfer |
| DHCP | Dynamic Host Configuration Protocol | 67/68 | IP assignment |
| DNS | Domain Name System | 53 | Name resolution |
| SMTP | Simple Mail Transfer Protocol | 25 | Send email |
| SNMP | Simple Network Management Protocol | 161 | Device monitoring |
| ICMP | Internet Control Message Protocol | No port | Diagnostics |
Common networking protocols include HTTP and HTTPS for web communication, FTP for file transfer, DHCP for automatic IP assignment, DNS for domain resolution, SMTP for email sending, SNMP for device monitoring, and ICMP for network diagnostics.
