Networking Fundamentals

Jump to bottom

abk edited this page Nov 13, 2019 · 1 revision

Networking Fundamentals

7-layer OSI model (Published in 1984).
- Application layer (7)
  - Protocols
  - HTTP
  - SSH
  - FTP
  - Sometimes uses Layer6.
  - Users typically interface here. (Browser).
- Presentation layer (6)
  - Conversion
  - Encryption (TLS)
  - Standards
- Session layer (5)
  - Introduces sessions
  - Both initiating and response traffic. SG understand, if you are allowing incoming traffic, it allows outgoing traffic.
- Transport layer (4)
  - TCP
    - Reliable transport
    - Uses Segments
    - Segments will be received in right order.
    - Adds ordering
    - Adds error checking
    - Adds concept of ports
    - Unique Individual ports for different functions.
  - UDP
    - Faster
    - Adds concept of ports
- Network layer (3)
  - Layer3 utilizes layer2.
  - Introduces IP addresses.
  - IP packet
  - Source IP, Destination IP
- Datalink layer (2)
  - Layer2 devices operate over layer1.
  - MAC address sits here. Unique address for a device.
  - Every networking device has a MAC address
  - Vendor / Physical Network Equipment and device itself.
  - Layer2 uses Frames
    - Contains source MAC address
    - Contains destination MAC address
- Physical layer (1)
  - Layer 1 is like dark room with multiple people talking.
  - Multiple devices can talk but no standards.

HOW TO REMEMBER THESE LAYERS ?

Please Do Not Throw Sausage Pizza Away - (1 - 7)
All People Seem To Need Data Processing - (7 - 1)

IP addressing

Version 4
- 32 bits binary values
- 4 bytes (octets).
- IPs are split into network part and node/host part
- Subnet mask or prefix shows where the split occurs.

Version 6

Subnetting

Process of breaking network down into smaller sub-networks.
10.0.0.0/16
- Single network from 10.0.0.0 to 10.0.255.255 and offers 65536 addresses.
10.0.0.0/17 AND 10.0.128.0/17
Multiple subnets will need to use CIDR.