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I was reading the HowStuffWorks article on ethernet. From the article, I understand that bridges are just like repeaters, but with the added benefit of not cluttering up other collision domains.

So I understand that we can use a bridge wherever we can use a repeater. My questions is, if that's the case, why do repeaters still exist?

Does it have to do with:

1) Bridges cost more than repeaters?

2) Bridges introduce a higher overhead?

  • Bridge == Switch, Repeater == Hub. Nobody makes hubs anymore. Fundamentally, repeaters are simple electrical devices with virtually no understanding of the protocol. – Ricky Beam Oct 29 '15 at 20:07
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I would argue that repeaters hardly do exist today.

A repeater amplifies the electric signal but is a completely analogue device and does not in any way interpret the signal. A repeater is the same thing as a 2-port hub although I've seen some companies starting to use the term repeater for equipment that resembles a switch more than a hub.

Contrast this with a switch that receives a frame, interprets it and extracts the destination MAC address which it then acts upon to forward the frame to it's correct destination. A bridge is the same thing as a 2-port switch.

Due to the low cost of switches and their support for higher speeds, the market for hubs/repeaters is slim to none.

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  • Ethernet repeaters are not "completely analogue devices". They operate above the PHY (which handles the wire level encoding) but they don't do any medium access control or packet buffering themselves. – Peter Green Mar 30 '16 at 4:17
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In general, repeaters are no longer needed or used in modern networking. This section of the article dedicated to repeaters is largely there to provide historical background, and a big hint that this is the case is that it also mentions thicknet (a long defunct network technology).

Repeaters operate on L1 of the OSI model and simply "regenerate" the signal allowing it to cover a longer distance than it would otherwise. Being a relatively simple device, they were considerably cheaper at the time than bridges. They were quite common at one point and as such there were even rules for their deployment (reference the 5-4-3 Rule if interested).

Today repeaters are limited to a couple of roles. First, carriers/ISPs will sometimes use repeaters when they are covering very long distances or using a technology that will benefit from strong signal strengths (for example xDSL).

Second, and more commonly known to general users, are repeaters that are sold to extend the coverage of consumer 802.11 wireless. Some of these truly are repeaters, while some are more advanced than simple signal repeaters.

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Repeaters works on Layer 1 of OSI model and Bridges works on Layer 2. The main thing that repeaters does is to REPEAT the signal from one side to other, it no taken on mind destination or something else, it just repeat the signal to the other ports.

On the other hand, bridges conmunicate 2 networks from different topologies. This one also works matching the destination MAC address, to send or not, the transmition to that network segment.

Bridges are more like a switch, a small switch, a 2 port switch.

I´m not have any price, but i think bridges DO NOT cost more that repeaters, the contrary, because, with the repeaters you can connect a lot of equipments, it have about 8, 16 ports, and bridges only have 2 interfaces, on the way to EXTEND and separate a collision domain into 2.

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to be aware of the whole image this topic is technical speaking about logical items accomplish certain tasks not existed devices , where bridge is the device which has two ports , those two ports will share the same collision domain and the repeaters are the devices which detect certain signal (which suffered from some degradation) and amplify it and send it again . now a days the existing device are the switches which is multi port bridge (share the same broadcast domain on the base of VLANs) and when you read any configuration guide of any product some time you can see its describe the switch as abridge .repeaters are existing only on the wireless setup (actually it is Access point configured as repeater) where it can spread the coverage on a far location than which the access point is setup.

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A repeater (aka hub) is a relatively simple device. It decodes and regenerates the wire-level encoding and participates in a minor way in collision enforcement but it does not buffer frames or make any descisions about where a frame is destined for.

A bridge (aka switch) is a far more complex device that works on a scale of full frames and keeps a table of MAC addresses so it can send packets where they need to go.

if that's the case, why do repeaters still exist?

Because it takes decades for legacy equipment that was made in massive volume to completely go away.

1) Bridges cost more than repeaters?

They used to but the economics have shifted over the years. The digital electronics that form the core of a switch became dirt cheap so the cost advantages of hubs went away.

2) Bridges introduce a higher overhead?

It depends on how exactly you define "overhead". A frame in a bridge will spend a little longer in transit than a frame in a repeater. On the other hand bridges allow the use of full duplex links which eliminate the overhead of CSMA/CD.

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