study_admin_l10_topic

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- **Created on**: 2025-05-24 16:39:40

Application (7): User interface for network services (email, browsers).
Purpose: Lets users access network resources easily.
Presentation (6): Formats data (encryption/compression).
Purpose: Ensures systems understand exchanged data.
Session (5): Manages communication sessions.
Purpose: setup and manage and terminate sessions
Transport (4): Provides reliable data transfer (TCP/UDP).
Purpose: complete data delivery and error detection and segmentation
Network (3): Handles addressing/routing (IP).
Purpose: Finds best path across networks (routing) .
Data Link (2): Manages physical addressing (MAC).
Purpose: Ensures error-free local network delivery.
Physical (1): Transmits raw bit streams.
Purpose: Connects devices physically.

192.168.1.0/28:
Calculation: 2^(32-28) - 2 = 14 hosts
Explanation: 4 host bits → 16 total, minus network/broadcast.
172.168.1.0/22:
Calculation: 2^(32-22) - 2 = 1022 hosts
Explanation: 10 host bits → 1024 total, minus 2 reserved.
10.0.0.0/8:
Calculation: 2^(32-8) - 2 = 16,777,214 hosts
Explanation: 24 host bits → massive address space.

DHCP:
What: Automatically assigns IP configurations.
Why: Simplifies network setup and management.
DNS:
What: Converts domain names to IP addresses.
Why: Makes internet navigation user-friendly.
ARP:
What: Maps IP addresses to MAC addresses.
Why: Enables local network communication.
NAT:
What: Translates private IPs to public IPs.
Why: Conserves IPv4 addresses and adds security.
PAT:
What: Maps multiple devices to one IP using ports.
Why: Maximizes public IP address usage.

Subnetting: Dividing 172.16.0.0/16 into /24 subnets → 256 subnets with 254 hosts each.
ARP Process: PC broadcasts "Who has 192.168.1.1?", target replies with MAC.
NAT vs PAT: NAT (1-to-1 IP mapping), PAT (many-to-1 with port numbers).