Mapping Network Devices to OSI Model - 1.1

Hub

Layer 1; broadcasts data to all ports; replaced by switches in modern networks

Repeater

Layer 1; purely amplifies signal, no addressing

NIC (Network Interface Card)

Layer 2; connects device to network; handles framing and MAC addressing

Access Point (AP)

Layer 2; connects wireless devices to wired network; uses MAC addresses

Bridge

Layer 2; older tech, largely replaced by switches

Switch

Layer 2 (or 3 if routing); forwards traffic using MAC or IP addresses

Router

Layer 3; Connects different networks and routes traffic using IP addresses

Firewall

Layer 3 (IP filtering) or Layer 4 (TCP/UDP ports); filters traffic based on rules

IDS/IPS (Intrusion Detection/Prevention System)

Layer 3; Monitors or blocks suspicious traffic

Load Balancer

Layer 4 (TCP/UDP) or 7 (application content); Distributes network traffic across multiple servers

Proxy Server

Layer 7; acts as an intermediary between a user's device and the internet, receiving requests from clients, forwarding them to the relevant server, and returning the server's response to the client.

Physical - 1

hardware + signals

defines physical aspects of network like media types (cables, connectors), voltage levels, signal frequencies, max cable length, bandwidth limits

specifies physical topology

Data link - 2

prepares data for physical transmission; handles framing, MAC addressing, and error detection

unit of data: frame

Sublayers:

1. Media Access Control - controls access to physical media (who can send data and when)

2. Logical Link Control - manages error checking and flow control

Common layer 2 protocols and techs:

• HDLC, PPP, PPTP, L2TP: used for WAN links and tunneling

• STP: prevents switching loops

• VLANs: segment networks logically

Network - 3

handles routing, which moves data between different networks

uses logical IP addresses, not MAC

Routing decisions determine best path for data to reach destination

Routing protocols allow routers to share and update path info

Routing can be

• static - manually configured by admin

• dynamic - automatically updated using routing protocols

fragment frames to traverse through networks

anything ip, router, packet, or subnet masking related

Transport - 4

moves data between devices efficiently and reliably

error checking, service addressing (delivers data to right app using port number), segmentation

Transmission Control Protocol - reliable, connection oriented guaranteed delivery

User Datagram Protocol - faster, connectionless not guaranteed delivery

buffering: temporarily storing data if receiver is slow or busy

windowing: sending chunks of data that require fewer acks

Session - 5

manages communication sessions between apps on different devices

establishes, maintains, terminates app level connections

Presentation - 6

responsible for translating data formats between application and network layer

handles data encoding, encryption, compression

Application - 7

interfaces directly with end users or apps to send or receive network data

exs: file access, printing, email, web browsing, time sync

common protocols: HTTP, FTP, DNS, POP3

Network Attached Storage (NAS)

dedicated file level storage device connected to network that allows users to store and retrieve data from a central location

Storage Area Network (SAN)

high speed specialized network that provides block level access to storage devices in large enterprise environments

Wireless LAN Controller (WLAN controller)

manages multiple wireless APs in a network; helps with performance and security monitoring

Content Delivery Network (CDN)

application layer; globally distributed network of proxy servers and data centers designed to delivery internet users fast

virtual private network (VPN)

network layer; creates safe and encrypted connection over less secure network

quality of service (QOS)

set of technologies and policies used to manage and prioritize network traffic to ensure performance of critical application and service