| Layer | Name | Data Unit | Function | Examples |
|---|---|---|---|---|
| 7 | Application | Data | Network process to application | HTTP, FTP, SMTP, DNS |
| 6 | Presentation | Data | Data representation, encryption | SSL/TLS, JPEG, MPEG |
| 5 | Session | Data | Dialog control, synchronization | NetBIOS, PPTP, RPC |
| 4 | Transport | Segment | End-to-end communication | TCP, UDP |
| 3 | Network | Packet | Path determination, logical addressing | IP, ICMP, ARP |
| 2 | Data Link | Frame | Physical addressing, error detection | Ethernet, Wi-Fi, PPP |
| 1 | Physical | Bit | Media, signal transmission | Cables, hubs, repeaters |
| Layer | Name | Protocols | Function | Comparison to OSI |
|---|---|---|---|---|
| 4 | Application | HTTP, FTP, SMTP, DNS, DHCP | Process-to-process communication | Combines OSI layers 5-7 |
| 3 | Transport | TCP, UDP | Port-to-port communication | OSI layer 4 |
| 2 | Internet | IP, ICMP, ARP, IGMP | Host-to-host communication | OSI layer 3 |
| 1 | Network Access | Ethernet, Wi-Fi, PPP | Network media access | Combines OSI layers 1-2 |
| Protocol | Layer | Port | Description | Characteristics |
|---|---|---|---|---|
| TCP | Transport | N/A | Transmission Control Protocol | Connection-oriented, reliable, ordered |
| UDP | Transport | N/A | User Datagram Protocol | Connectionless, fast, unreliable |
| HTTP | Application | 80 | HyperText Transfer Protocol | Web page transfer |
| HTTPS | Application | 443 | HTTP Secure | Encrypted HTTP |
| FTP | Application | 20, 21 | File Transfer Protocol | File transfer |
| SMTP | Application | 25 | Simple Mail Transfer Protocol | Email transmission |
| POP3 | Application | 110 | Post Office Protocol | Email retrieval |
| IMAP | Application | 143 | Internet Message Access Protocol | Advanced email access |
| DNS | Application | 53 | Domain Name System | Name to IP resolution |
| DHCP | Application | 67, 68 | Dynamic Host Configuration Protocol | Automatic IP assignment |
| SNMP | Application | 161, 162 | Simple Network Management Protocol | Network device monitoring |
| Class | Range | Default Subnet Mask | Network Bits | Host Bits | Max Networks | Max Hosts |
|---|---|---|---|---|---|---|
| A | 1.0.0.0 - 126.255.255.255 | 255.0.0.0 | 8 | 24 | 126 | 16,777,214 |
| B | 128.0.0.0 - 191.255.255.255 | 255.255.0.0 | 16 | 16 | 16,384 | 65,534 |
| C | 192.0.0.0 - 223.255.255.255 | 255.255.255.0 | 24 | 8 | 2,097,152 | 254 |
| D | 224.0.0.0 - 239.255.255.255 | N/A | Multicast | Multicast | Multicast | Multicast |
| E | 240.0.0.0 - 255.255.255.255 | N/A | Experimental | Experimental | Experimental | Experimental |
| Subnet Mask | Binary | Wildcard | Networks | Hosts | Useful IPs |
|---|---|---|---|---|---|
| 255.0.0.0 | 11111111.00000000.00000000.00000000 | 0.255.255.255 | 1 | 16,777,216 | 16,777,214 |
| 255.128.0.0 | 11111111.10000000.00000000.00000000 | 0.127.255.255 | 2 | 8,388,608 | 8,388,606 |
| 255.192.0.0 | 11111111.11000000.00000000.00000000 | 0.63.255.255 | 4 | 4,194,304 | 4,194,302 |
| 255.224.0.0 | 11111111.11100000.00000000.00000000 | 0.31.255.255 | 8 | 2,097,152 | 2,097,150 |
| 255.240.0.0 | 11111111.11110000.00000000.00000000 | 0.15.255.255 | 16 | 1,048,576 | 1,048,574 |
| 255.248.0.0 | 11111111.11111000.00000000.00000000 | 0.7.255.255 | 32 | 524,288 | 524,286 |
| 255.252.0.0 | 11111111.11111100.00000000.00000000 | 0.3.255.255 | 64 | 262,144 | 262,142 |
| 255.254.0.0 | 11111111.11111110.00000000.00000000 | 0.1.255.255 | 128 | 131,072 | 131,070 |
| 255.255.0.0 | 11111111.11111111.00000000.00000000 | 0.0.255.255 | 256 | 65,536 | 65,534 |
| Protocol | Type | Algorithm | Update Method | Use Case |
|---|---|---|---|---|
| RIP (v1/v2) | Distance Vector | Distance Vector | Periodic updates | Small networks, simple configuration |
| OSPF | Link State | Dijkstra's Algorithm | Triggered updates | Large networks, complex topologies |
| EIGRP | Hybrid | DUAL Algorithm | Partial updates | Cisco networks, fast convergence |
| BGP | Path Vector | Path Vector | Incremental updates | Internet backbone, inter-AS routing |
| IS-IS | Link State | SPF Algorithm | Link state updates | Service provider networks |
| Device | Layer | Function | Use Case | Advantages |
|---|---|---|---|---|
| Repeater | Physical | Amplify signals | Extend cable length | Signal amplification |
| Hub | Physical | Connect multiple devices | Simple network connections | Low cost, simple |
| Bridge | Data Link | Connect network segments | Segment collision domains | Filter traffic |
| Switch | Data Link | Connect devices with MAC learning | Modern network connections | Fast, intelligent filtering |
| Router | Network | Connect networks, route packets | Connect different networks | Path selection, traffic control |
| Gateway | Application | Protocol conversion | Connect different network types | Protocol translation |
| Firewall | Network/Application | Security filtering | Network security | Security, access control |
| Topology | Description | Advantages | Disadvantages | Use Case |
|---|---|---|---|---|
| Bus | Single cable connects all devices | Easy to install, low cost | Single point of failure, difficult to troubleshoot | Small networks |
| Star | All devices connect to central hub/switch | Easy to install and manage, failure of one device doesn't affect others | Requires more cable, hub failure affects all | Most LANs |
| Ring | Each device connects to two others forming a ring | Equal access, predictable performance | Single break affects entire network | Token Ring networks |
| Mesh | Every device connects to every other device | High reliability, multiple paths | Expensive, complex | Critical networks |
| Tree | Hierarchical structure with root | Scalable, easy to manage | Root failure affects entire network | Large networks |
| Hybrid | Combination of topologies | Flexible, scalable | Complex, expensive | Large enterprise networks |
| Technology | Function | Description | Advantages | Disadvantages |
|---|---|---|---|---|
| Firewall | Access Control | Filters network traffic based on rules | Prevents unauthorized access | May block legitimate traffic |
| VPN | Secure Communication | Creates encrypted tunnel over public network | Secure remote access | Performance overhead |
| IDS | Intrusion Detection | Monitors network for suspicious activity | Real-time threat detection | False positives |
| IPS | Intrusion Prevention | Blocks detected threats | Prevents attacks in real-time | May impact performance |
| AAA | Authentication/Authorization/Auditing | Network access control framework | Comprehensive access control | Complexity |
| 802.1X | Port-based Network Access Control | Authenticates devices before network access | Secure network access | Requires infrastructure support |
| Standard | Frequency | Max Speed | Range | Year | Characteristics |
|---|---|---|---|---|---|
| 802.11a | 5 GHz | 54 Mbps | Shorter range | 1999 | OFDM, more channels |
| 802.11b | 2.4 GHz | 11 Mbps | Longer range | 1999 | Lower speed, longer range |
| 802.11g | 2.4 GHz | 54 Mbps | Longer range | 2003 | Backward compatible with b |
| 802.11n | 2.4/5 GHz | 600 Mbps | Improved range | 2009 | MIMO, 40 MHz channels |
| 802.11ac | 5 GHz | 6.9 Gbps | Shorter range | 2013 | Multi-user MIMO, beamforming |
| 802.11ax (Wi-Fi 6) | 2.4/5 GHz | 9.6 Gbps | Improved efficiency | 2019 | OFDMA, improved density |
| 802.11be (Wi-Fi 7) | 2.4/5/6 GHz | 46 Gbps | Enhanced range | 2024 | 320 MHz channels, 4K QAM |
| Command | OS | Purpose | Common Use |
|---|---|---|---|
| ping | All | Test IP connectivity | Check if host is reachable |
| tracert (traceroute) | Windows (Unix) | Trace route to destination | Identify network path and delays |
| ipconfig (ifconfig) | Windows (Unix) | Display IP configuration | View network settings |
| netstat | All | Display network connections | Check active connections and ports |
| nslookup (dig) | All | DNS lookup | Resolve domain names to IPs |
| arp | All | ARP table management | View MAC address mappings |
| telnet | All | Test port connectivity | Check if port is open |
| route | All | Display/modify routing table | View routing information |