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The OSI (Open Systems Interconnection) model simplifies how devices and protocols collaborate to transmit data across the globe. Let’s explore its 7 layers, along with the devices and protocols involved:
1️⃣ Physical Layer 🛠️
Where raw binary data travels over physical media.
➡️ Devices: Hubs, Modems, Ethernet cables
➡️ Protocols: USB, Bluetooth, Ethernet
2️⃣ Data Link Layer 🔗
Ensures node-to-node communication with error detection and MAC addressing.
➡️ Devices: Switches, NICs
➡️ Protocols: ARP, PPP, IEEE 802.11 (Wi-Fi)
3️⃣ Network Layer 🌍
Routes data between networks, managing IP addressing.
➡️ Devices: Routers, Layer 3 switches
➡️ Protocols: IPv4/IPv6, ICMP, OSPF
4️⃣ Transport Layer 📥
Handles reliable data delivery through segmentation and flow control.
➡️ Devices: Firewalls
➡️ Protocols: TCP, UDP
5️⃣ Session Layer ✅
Manages connections between applications.
➡️ Devices: Application Gateways
➡️ Protocols: NetBIOS, PPTP
6️⃣ Presentation Layer 🌄
Formats, encrypts, and compresses data for applications.
➡️ Devices: Encryption devices
➡️ Protocols: SSL/TLS, JPEG, ASCII
7️⃣ Application Layer 📱
Provides user-facing interfaces and services.
➡️ Devices: Computers, Mobile Phones
➡️ Protocols: HTTP/HTTPS, FTP, SMTP, DNS
You Should Know:
Linux & Windows Commands Related to OSI Layers
Physical Layer (Layer 1)
- Check network interfaces in Linux:
ip link show
- View Ethernet details (Linux):
ethtool <interface_name>
Data Link Layer (Layer 2)
- Show MAC addresses (Linux):
ip neigh
- View ARP cache (Windows):
arp -a
Network Layer (Layer 3)
- Check routing table (Linux/Windows):
ip route Linux route print Windows
- Test connectivity (ICMP – Ping):
ping google.com
Transport Layer (Layer 4)
- Monitor TCP/UDP connections (Linux):
ss -tulnp
- Check open ports (Windows):
netstat -ano
Session Layer (Layer 5)
- Check active NetBIOS sessions (Windows):
nbtstat -S
Presentation Layer (Layer 6)
- Test SSL/TLS handshake:
openssl s_client -connect example.com:443
Application Layer (Layer 7)
- Query DNS records:
dig example.com Linux nslookup example.com Windows
- Test HTTP/HTTPS connectivity:
curl -I https://example.com
What Undercode Say:
The OSI model remains fundamental in networking, cybersecurity, and IT infrastructure. Understanding each layer helps in troubleshooting, penetration testing, and securing networks.
- For Ethical Hackers: Mapping attacks to OSI layers (e.g., ARP spoofing at Layer 2, DNS poisoning at Layer 7) is crucial.
- For Network Engineers: Mastering
tcpdump,Wireshark, and `nmap` helps analyze traffic across layers. - For SysAdmins: Commands like
netstat,ss, and `ip` provide deep insights into network behavior.
Expected Output:
A structured understanding of network communication, enabling efficient debugging, security hardening, and protocol analysis.
(Note: Telegram/WhatsApp URLs and unrelated comments were removed as requested.)
References:
Reported By: Surya Prakash – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
