Network Devices

Network Devices

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A physical network may be composed of a number of different devices in order to function as needed. Many of these devices are described in the following pages.

In this video, we’ll talk about some devices operating at the different layers of the Open

Systems Interconnection, also known as the OSI model. A switch is a data link layer

device. It is available either as a standalone or integrated with other devices, such as

wireless routers or modems that can plug in physical devices. A switch keeps the traffic

between the source and destination ports from interfering with other devices in the

network. A router operates at the network layer and can connect your home network to

the Internet. Or, in a business or institutional scenario, a router can connect your

webserver to your database server. Firewalls can operate at multiple layers of the OSI

model, including data link, network, transport, session, and application - and in certain

circumstances, presentation as well. At the data link and network levels the firewall

defines what traffic should go between two networks. For example, your home network

and the Internet are two different networks with two separate ports, and therefore two

different data link layers. You can use the firewall to filter traffic between these

networks based on individual IP addresses or a range of them. At the transport layer, the

firewall filter settings are port-based. For example, you can allow or block traffic from a

port like the Transmission Control Protocol, also called TCP or the User Datagram

Protocol, often called UDP. You can also filter traffic using a range of ports or a

combination of IP addresses and ports. The firewall that operates at the network and

transport layers is called the Layer 4 firewall, and the one that works at the session,

presentation, and application layers is the Layer 7 firewall. The Layer 7 firewall is also

smart enough to decrypt and analyze the content flowing through, thereby adding one

more level of filtering to the IP address and port combination. A firewall is thus a

powerful tool that can help prevent malicious attacks like Structured Query Language,

also known as SQL injection, or other malware. Firewalls can be software devices that run

inside a virtual machine or physical server or can also be hardware devices like Fortinet's

Fortigate device. Both the software and hardware firewalls work towards the same

result. The cost of a firewall varies depending on its features, capabilities, and speed. In

this video, we discussed the different devices like a switch, router, and firewall that

operate at the different layers of the OSI model.