Networking - Network Protocols and Services

1. What Are Network Protocols and Services?

  • Network Protocols are rules and standards that define how data is transmitted, formatted, and processed across a network.

  • Network Services are applications or functions that rely on these protocols to provide features like email, web browsing, file transfer, and domain name resolution.

Example:
When you open a website:

  • HTTP/HTTPS = protocol used to request and receive web pages.

  • DNS = service that converts domain name → IP address.

  • TCP/IP = protocol suite that ensures data delivery.

2. Types of Network Protocols

Network protocols can be divided into three main categories:

Type Examples Purpose
Communication Protocols HTTP, HTTPS, FTP, SMTP, POP3, IMAP Enable data exchange between devices
Network Management Protocols DNS, DHCP, SNMP, NTP Manage and control network operations
Security Protocols SSL/TLS, IPsec, SSH Secure communication

3. Common Network Protocols & Services

A. HTTP & HTTPS (Web Browsing)

  • HTTP (HyperText Transfer Protocol) → Transfers data between browser and web server.

  • HTTPS (HTTP Secure) → Same as HTTP but encrypted using SSL/TLS.

Feature HTTP HTTPS
Port 80 443
Security Not secure Encrypted
Use Basic web browsing Secure transactions

Example:

http://example.com   → Not secure  
https://example.com  → Secure connection

B. FTP & SFTP (File Transfer)

  • FTP (File Transfer Protocol) → Used to upload and download files.

  • SFTP (Secure FTP) → Uses SSH encryption for secure file transfers.

Feature FTP SFTP
Port 21 22
Security No encryption Encrypted
Use Case File sharing Secure file transfers

C. SMTP, POP3, and IMAP (Email Services)

Protocol Function Port Use Case
SMTP (Simple Mail Transfer Protocol) Sends email from client → mail server 25 / 587 Sending emails
POP3 (Post Office Protocol v3) Downloads emails from mail server → client 110 Offline email storage
IMAP (Internet Message Access Protocol) Accesses and manages emails directly on the server 143 / 993 Online email access

Example:

  • SMTP: Sending an email via Gmail.

  • IMAP: Reading emails on multiple devices.

  • POP3: Downloads emails to one device.

D. DNS (Domain Name System)

  • Converts domain names into IP addresses.

  • Without DNS, you would need to remember IPs like 172.217.160.78 instead of google.com.

Feature Details
Port 53
Protocol UDP/TCP
Function Resolves domain names to IP addresses

Example:

google.com → 172.217.160.78

E. DHCP (Dynamic Host Configuration Protocol)

  • Automatically assigns IP addresses to devices in a network.

  • Without DHCP, IPs must be configured manually.

Feature Details
Port 67 (server), 68 (client)
Protocol UDP
Function Assigns IP, subnet mask, gateway, and DNS

Example:
When you connect your laptop to Wi-Fi, DHCP assigns you an IP like 192.168.1.10.

F. SNMP (Simple Network Management Protocol)

  • Used by network administrators to monitor and manage network devices like routers, switches, and servers.

Feature Details
Port 161
Protocol UDP
Function Monitors and controls network devices

Example:
SNMP can collect data like:

  • CPU usage of routers

  • Network bandwidth

  • Interface errors

G. NTP (Network Time Protocol)

  • Synchronizes time and clocks across devices in a network.

Feature Details
Port 123
Protocol UDP
Function Ensures accurate timestamps for logs and transactions

Example:
Bank servers and payment gateways use NTP for time synchronization.

H. SSH & Telnet (Remote Access)

Protocol Port Security Use Case
Telnet 23 No encryption Remote device access
SSH 22 Encrypted Secure remote access

Example:

ssh [email protected]

  • Logs in securely to a router or server.

I. IPsec & SSL/TLS (Security Protocols)

  • IPsec → Secures VPNs by encrypting packets.

  • SSL/TLS → Secures web traffic (used in HTTPS).

Feature IPsec SSL/TLS
Use VPN security HTTPS encryption
Protocol Works at Layer 3 Works at Layer 7
Port UDP 500 TCP 443

4. Summary Table

Protocol Function Port Layer Service Type
HTTP Web browsing 80 App Layer Web
HTTPS Secure web browsing 443 App Layer Web
FTP File transfer 21 App Layer File sharing
SFTP Secure file transfer 22 App Layer File sharing
SMTP Send emails 25 / 587 App Layer Email
POP3 Download emails 110 App Layer Email
IMAP Read emails online 143 / 993 App Layer Email
DNS Name resolution 53 App Layer Management
DHCP Assign IP addresses 67/68 App Layer Management
SNMP Network monitoring 161 App Layer Management
NTP Time synchronization 123 App Layer Management
SSH Secure remote login 22 App Layer Security
Telnet Remote login (insecure) 23 App Layer Security
IPsec VPN security 500 Network Layer Security
SSL/TLS Secure encryption 443 App Layer Security

5. Diagram

   [User] → [Browser] → HTTP/HTTPS → [Web Server]
         ↓
       DNS → Resolves "example.com" → 93.184.216.34
         ↓
   DHCP → Assigns IP address dynamically
         ↓
   SMTP/IMAP → Emails exchanged securely
         ↓
   SSH → Secure remote access to servers
         ↓
   NTP → Keeps time synchronized

6. Key Takeaways

  • Protocols define how data is sent, received, and secured.

  • Services like DNS, DHCP, NTP, and SNMP make networks functional and manageable.

  • Security protocols like HTTPS, SSL/TLS, SSH, and IPsec protect data.