What are network protocols?

Network protocols are a set of rules that manage data exchange between multiple devices within a network.



How protocols works

Network protocols work on rules and procedures controlling data transmission and receiving across a network. They work with hardware or software irrespective of different devices and can communicate effectively.

Classifications of Network Protocols

Categorize network protocols based on their functions and OSI layer. They are 

1. Communication Protocols: Data exchange over a network.

2. Security Protocols: To protect data and communication over a network.

3. Routing Protocols: The best path for data to travel across networks.

4. Management Protocols: Monitor and maintain network devices and traffic.

5. File Transfer Protocols: Transfer of files across a network.

Types of Network Protocols

HTTP (Hypertext Transfer Protocol):

HTTP (Hypertext Transfer Protocol) enables data transfer, like web pages, over the internet.

Uses:

  • Requesting and sending web pages
  • Submitting forms
  • Uploading files
  • APIs (Application Programming Interfaces)

Testing Http with Commands:

Curl commands:

  • Download a web page: curl <URL>
  • Download a file: curl -o filename.txt <URL>
  • Send a GET request: curl <URL>
  • Send a POST request: curl -X POST -d "data=hello" <URL>
  • Send a GET request with headers: curl -H "Accept: application/json" <URL>
  • Check HTTP status code: curl -I <URL>

Wget commands :

  • Download a web page: wget <URL>
  • Download a file: wget -O filename.txt <URL>
  • Send a GET request: wget --method=GET <URL>
  • Send a POST request: wget --post-data "data=hello" <URL>
  • Send a GET request with headers: wget --header="Accept: application/json" <URL>
  • Check HTTP status code: wget --server-response --spider <URL>

Third-party Tools: Postman, HTTPiecurl

HTTPS (Hypertext Transfer Protocol Secure):

HTTPS is a secure extension of HTTP which encrypting data and authenticating websites.

Uses:

  • Secure online transactions
  • Protect sensitive data
  • Verify website authenticity

Testing Https with commands:

Curl and Wget

Third-party Tools: SSL Labs, Qualys' SSL

FTP (File Transfer Protocol):

FTP is a protocol for transferring files over the network.

Uses:

  • Upload/download files to/from a server
  • Manage files on a remote server

Testing FTP with commands:

FTP and Curl

FTP commands:

  • Connect to an FTP server: FTP [server address]
  • Log in to the FTP server: login [username]
  • Enter password: password [password]
  • List files and directories: ls
  • Change directory: cd [directory]
  • Download a file: get [filename]
  • Upload a file: put [filename]
  • Download multiple files: mget [filename1] [filename2] ...
  • Upload multiple files: mput [filename1] [filename2] ...
  • Quit the FTP session: quit
  • Same as quit: bye
  • Display FTP commands: help
  • Create a new directory: mkdir [directory]
  • Remove a directory: rmdir [directory]
  • Delete a file: delete [filename]
  • Rename a file: rename [old filename] [new filename]

Third-party Tools: FileZilla, WinSCP

SMTP (Simple Mail Transfer Protocol):

SMTP helps send and receive emails over the Internet.

Uses:

  • Send and receive emails
  • Relay emails between mail servers

SMTP commands:

  • Connect to SMTP server: telnet [mail server] 25
  • Identify yourself: ehlo [your domain]
  • Specify sender: mail from:<sender@example.com>
  • Specify recipient: rcpt to:<recipient@example.com>
  • Send email body: data
  • Exit: quit

Third-party Tools: Mailtrap

POP3 (Post Office Protocol version 3):

POP3 is a protocol for retrieving email messages from a mail server.

Uses:

  • Download emails from a mail server to a local device
  • Delete emails from the mail server after retrieval
  • Enable email clients to access email messages

POP3 commands:

  • Connect to POP3 server: telnet [mail server] 110
  • Login: user [username]
  • Enter password: pass [password]
  • List emails: list
  • Retrieve email: retr [email number]
  • Exit: quit

Third-party Tools: Mailtrap

IMAP (Internet Message Access Protocol):

IMAP allows us to check and organize our emails remotely, making it easy to stay connected.

Uses:

  • Access and manage emails on a mail server
  • Keep emails synchronized across multiple devices.
  • IMAP enables multiple clients to access a single mailbox simultaneously, facilitating collaborative email management and real-time synchronization across devices.

IMAP commands:

  • Connect to IMAP server (non-SSL): telnet [mail server] 143
  • Connect to IMAP server (SSL/TLS): openssl s_client -connect [mail server]:993
  • Using an IMAP testing tool: imaptest [mail server]

Third-party Tools:- Mailtrap

TCP (Transmission Control Protocol):

TCP helps devices communicate reliably over the internet, making sure data is sent accurately and in the right order.

Uses:

  • Reliable data transfer
  • Error detection and correction
  • Connection-oriented communication

TCP Commands:

  • Display TCP connections: netstat -t
  • Test TCP connection using telnet: telnet [host] [port]
  • Test TCP connection using netcat: nc [host] [port]
  • Capture and analyze TCP traffic: tcpdump

Third-party Tools:- Wireshark

UDP (User Datagram Protocol):

UDP is a transport-layer protocol that enables fast, connectionless data transfer between devices over IP networks.

Uses:

  • Fast data transfer
  • Connectionless communication
  • Real-time applications (e.g., video streaming, online gaming)

UDP with commands:

  • Display UDP connections: netstat -u
  • Test UDP connection using netcat: nc -u [host] [port]
  • Test UDP connectivity using udpcast: udpcast [options]

Third-party Tools:- Netcat, Wireshark

IP (Internet Protocol):

IP helps devices communicate online by giving them unique addresses and directing data packets.

Uses:

  • Assign unique addresses to devices
  • Route data packets between networks
  • Enable communication between devices on different networks

IP Commands:

  • Test connectivity: ping [IP address]
  • Display IP configuration (Windows): ipconfig
  • Trace route to IP address: traceroute [IP address]
  • Display IP addresses (Linux): ip addr show

Third-party Tools: WhatIsMyIP, IP Chicken

DHCP (Dynamic Host Configuration Protocol):

DHCP simplifies network setup by automatically assigning IP addresses and settings to devices, getting them online quickly and easily.

Uses:

  • Assign IP addresses to devices.
  • Assign subnet masks, gateways, and DNS servers.
  • With DHCP, devices can automatically obtain necessary network settings, connecting and communicating seamlessly without tedious manual configuration.

DHCP Commands:

  • Release current IP address: ipconfig /release
  • Request new IP address: ipconfig /renew
  • Test DHCP server: dhcping [server address]

Third-party Tools: Wireshark

DNS (Domain Name System):

DNS helps us access websites using easy-to-remember domain names instead of hard-to-remember IP addresses.

Uses:

  • Translate domain names to IP addresses
  • Enable web browsing and online communication
  • Provide domain name resolution

DNS Commands:

  • Query DNS records: nslookup [domain name]
  • Query DNS records: dig [domain name]
  • Test DNS resolution: ping [domain name]

Third-party Tools: IntoDNS

SNMP (Simple Network Management Protocol):

SNMP is a protocol for managing and monitoring network devices like routers, switches, and servers.

Uses:

  • Monitor network device performance
  • Configure network device settings
  • Receive alerts and notifications
  • -Manage network device firmware updates

SNMP Commands:

  • Retrieve device information: snmpwalk [device IP]
  • Retrieve specific data: snmpget [device IP] [OID]
  • Set configuration: snmpset [device IP] [OID] [value]

Third-party Tools: SolarWinds SNMP Tool

SSL/TLS (Secure Sockets Layer/Transport Layer Security):

SSL/TLS ensures data confidentiality, integrity, and authenticity, protecting users from eavesdropping, tampering, and man-in-the-middle attacks.

Uses:

  • Encrypt data in transit
  • Authenticate websites and servers
  • Establish secure connections (HTTPS)

Test SSL/TLS Commands:

  • Test SSL/TLS connection: openssl s_client -connect [host]:443
  • Scan SSL/TLS configurations: sslscan [host]:443

Third-party Tools:- Qualys SSL Test, DigiCert SSL Test

ICMP (Internet Control Message Protocol):

ICMP is a network protocol that provides error-reporting and diagnostic functions for IP networks.

Uses:

  • Error reporting (e.g., "Destination Unreachable")
  • Diagnostic functions (e.g., ping, traceroute)
  • Network congestion control

Test ICMP Commands:

  1. Test website: ping [host]
  2. Trace route to host: traceroute [host]
  3. Send ICMP echo requests: icmpush [host]

Third-party Tools: SolarWinds ICMP

BGP (Border Gateway Protocol):

BGP is a routing protocol that manages how data is routed between autonomous systems on the internet.

Uses:

  • Interconnects autonomous systems
  • Routes data between autonomous systems
  • Provides scalable and flexible routing

Test BGP Commands:

  • Display BGP routing table: show ip bgp
  • Display BGP summary: show ip bgp summary
  • Connect to a router and run BGP commands: telnet [router IP]

Third-party Tools: BGPmon, RIPE NCC BGP Toolkit

RIP (Routing Information Protocol):

RIP is a distance-vector routing protocol that manages how data is routed within a network.

Uses:

  • Routes data within a network
  • Provides simple and easy-to-configure routing
  • Suitable for small to medium-sized networks

Test RIP Commands:

  • Display RIP routing table: show ip rip database
  • Display RIP configuration: show ip rip
  • Debug RIP routing: debug ip rip

Third-party Tools: SolarWinds RIP Test, Cisco RIP Simulator










ASR

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