1.
OSI MODEL

2.
INTRODUCTION
• OSI model is a conceptual model that defines a
networking framework to implement protocols in layers,
with control passed from one layer to the next. A layer
serves the layer above it and is served by the layer
below it. It conceptually divides computer network
architecture into 7 layers in a logical progression.

3.
The image below gives a brief description of OSI
model…

4.
DEVICES ON LAYERS
• Devices used in each layer are….
1.Physical layer or below : Hubs, Repeaters, Cables, Fibers, Wireless..
2.Data-link layer: Bridges, Modems, Network cards, 2-layer switches.
3.Network layer: Routers, Brouters, 3-layer switches.
4.Transport layer: Gateways, Firewalls.
5.Session layer: Gateways, Firewalls, PC’s.
6.Presentation layer : Gateways, Firewalls, PC’s.
7.Application layer: Gateways, Firewalls, all end devices like PC’s,
Phones, Servers..

5.
What are layer1, layer2, and layer3 devices and give
example of each?
• The layers you are referring to are the first three layers of the OSI model better known as
the hardware layers.
• Layer one is the physical layer. On this layer, the object of concern are wires, connectors,
signaling, etc. If this layer fails, the items using this also fail to connect.
• Examples layer one are:
• Category Cables (5e, 6, 6a, 7, 8), RJ45 connectors
• Layer two is the data link layer ( & the LLC). The hardware interface layer. This layer
contains the Logical Link Control and the Media Access Control better known as MAC
address; the 48-bit address that is burned into an EPROM at the factory making Network
adapters. It is the layer where networking protocols that operate only on the local network
segment (link) that a host is connected to. This is what most people think of when they
refer to a Network adapter.
• Examples for layer two: Ethernet Network Adapter.
• Layer three is the Network layer. This is the layer where Routers operate on. Where one
connects discontiguous networks.
• Example: Ethernet router.