NETWORK DEVICESRONALD SHERGAOCTOBER 13, 2015LTEC 4550

HUBS

• Functions solely at the OSI physical layer 1.• Broadcasts any incoming signal out all ports. Allows increased devices

on network.• Increases size of collision domain.• Essentially, a repeater. All connected devices must be configured for

the same network to ensure all can communicate with one another.• Legacy device. Superseded by switches.

HUBS (CONT.)• Might see one on a small, old network to allow addition of

devices at low cost compared to a switch.• Can be found ranging in price from $5 for a basic splitter to $150 for a 4-

port. Keep in mind, this is a deprecated technology as switches are more abundant and can do the job better, so pricing can be all over the place.

• Devices connectusing straight cable,but connections vary..• Example

SWITCHES

• Function at OSI layer 2.• Hubs’ smarter counterpart. Switches effectively replaced hubs in the

market.• Each port on a switch creates a new collision domain. Switch knows

destination of information, so only sends out necessary ports.• Able to buffer packets, which eliminates possibility of collisions.• Can be seen in many different forms in most every network today. Often

integrated into SOHO routers.• A switch can cost under $10 all the way up to thousands of dollars,

depending on its intended application.

SWITCHES (CONT.)

• In any network, a switch can replace a hub.• A layer 2 switch cannot bridge two

networks, so all devices must belongto the same network to communicate.

ROUTERS

• Function at layer 3 of the OSI model.• Routers enable communication between two networks or more, directing

traffic based on destination IP addresses and a table that determines best path.• Commonly called “backbone of the Internet.”• Routers range from SOHO to Core types, and are priced accordingly.• A SOHO router can be as cheap as <$20, and a Core router costs tens of

thousands of dollars or more.

ROUTERS (CONT.)

• The router has knowledge of the directly connected networks. Even though they are different, the router is able to forward traffic between them.• A router can connect any network to any other, so they can

be found in small home networks, business server rooms, and in ISP routing centers, to give a few examples.

BRIDGES

• Function at layer 2 of OSI model.• Connect segments of a network to one another.• Keeps a table of MAC addresses for each port, so it can keep data

within each segment unless necessary to travel to another.• Good way to decrease number of collision domains.• Precursor to switches, which are basically multiport bridges.• A more modern type is a device that plugs into an ethernet port (e.g.

TV) and connects to a wireless network, bridging the two connections.• Full wireless bridging also common today.

BRIDGES (CONT.)

• Since many types of devices can providebridge function, their price can drastically vary.They can range from tens to hundreds of dollars,depending on their capability.• Diagram to the right: PC1 can communicate with

any other PC#. But if it wants to reach PC2, thetraffic never reaches HUB2.

GATEWAYS

• Function at various layers of OSI model, including layer 3.• Act as a border between networks that are using different

protocols (like TCP/IP, VOIP, or AppleTalk).• Mainly integrated into other hardware nowadays.• Price is variable. A SOHO solution would be home

router/modem ($10-$200+). Other more advanced gateways can run thousands of dollars.

GATEWAYS (CONT.)

• Diagram to the right shows gateway linking an IP network to a POTS network.• The gateway is necessary to

translate POTS analog signal to theIP signal and protocol.

FIREWALLS

• Function at OSI layer 3 or higher.• Block/allow traffic based on how it is configured.• Can be dedicated hardware or integrated into other devices.• Intended to protect against unwanted intrusions.• Software included in most PC operating systems, and

dedicated hardware can be found in enterprise infrastructures.

FIREWALLS (CONT.)

• The firewall is best placed closest to the public Internet so the local network cannot be reached by unauthorized traffic.• Pricing ranges from a few dollars for a home router, up to

over $100k for an enterprise solution.

WIRELESS AP

• Functions at layer 2 of the OSI model.• Basically, a wireless switch/hub.• Can be used both to extend network reach, and to segment

the network.• Often seen integrated into home routers; discrete devices are

more often found in enterprise/campus networks.• Pricing ranges from tens to hundreds of dollars.

WIRELESS AP (CONT.)

• Found anywhere a wireless network is present.• Grants wireless capability to an otherwise wired network.

NETWORK TOPOLOGY

• Below is a network with each device that has been covered in this presentation.