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I am quite confused with networking and speeds and such. I want to buy something so its throwing Google off - if I type in the keywords I just get websites selling the products I want, not information about them. (Sometimes Google's too good for its own good!)


The product

So, I want to get a main's Ethernet power adapter like this one:

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Amazon product page: TP-Link TL-PA511KIT 500 Mbps Gigabit Powerline Adapter - Twin Pack
TP-Link product page: AV500 Gigabit Powerline Adapter Starter Kit (TL-PA511KIT)

  • HomePlug AV standard compliant, high-speed data transfer rate of up to 500Mbps, ideal for HD video or 3D video streaming and online gaming
  • Mains Filter for better powerline communication performance
  • No new wires, use existing electrical wiring
  • Up to 300 meter range over a home's electrical circuit for better performance through walls or across floors
  • Plug and Play, no new wires or configuration required
  • Patented Power-Saving Mode automatically reduces power consumption by up to 85%
  • 128-bit AES encryption ensures that the network is safe simply by pressing a button on paired devices
  • Built-in QoS assures the quality of bandwidth sensitive applications such as voice, video and online games
  • Supports IGMP managed multicast IP transmission, optimizes IPTV streaming


My Question:

It is refered as an "500 Mbps Gigabit Powerline Adapter".

What does this mean? In my head if its 500Mbps then its not Gigabit? Surely a Gigabit is 1000Mbps?

There is another, slightly cheaper model which is 500Mbps, but is NOT Gigabit. Well, what difference does this make? What's the point in getting a Gigabit one, when I'm only going to get speeds of 500Mbps anyway?

Also, what does 10/100, 10/100/1000, 100/1000 mean in relation to these? That's the Ethernet "description" or "specification" but it doesn't mean anything to me!

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6 Answers

up vote 15 down vote accepted

From the TP-Link product spec:
It has a Gigabit Ethernet Port - that's where you connect your your PC/laptop/whatever device) and it can transmit 500Mbps over powerline.

As for 10/100 and the rest - as you said, it's related to Ethernet standards, but in simple terms just tell you 'speed' a device can operate:
10/100 mean either 10Mbps or 100Mbps
10/100/1000 - 10Mbps or 100Mbps or 1000Mbps etc.
Now, when you connect two devices, they will operate at highest common speed (one is 100, one is 1000 -> operate at 100). If they do not support such (say one is set to only allow 10Mbps and other only 1000Mbps) they will fail to communicate.

Going back to your question - it's similar logic here: 1G/500M plug will limit you to max 500M, but 100M/500M (non Gigabit one) will be max 100M as that's lowest speed along the transmission path. If the price difference is small it makes sense to go for Gigabit one - unless you know that none of your devices will ever support Gigabit.

Edit: I have not used those devices, but just googled a bit and it looks those high speeds (over power) are a bit (cough) overinflated. So if you have a chance it would be best to actually try both and see what actual speed you get!

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I agree about the speed being inflated, I have used the older 200mbps devices and generally you get about half that if your wiring is good, less if it's not. –  Col Oct 3 '12 at 11:14
    
Thanks for the answer. So essentially, if I understand you correctly, its 500Mbps from the source power adapter to the client adapter. Then the 100/1000 means that its 100Mbps or 1Gbps from the client power adapter to the computer/NAS/whatever. So the only reason for getting a 500Mbps 10/100 over a 200Mbps 10/100 is if you have more than two of them connecting at once (assuming that the speeds are correct?). –  Thomas Clayson Oct 3 '12 at 12:18
    
@ThomasClayson Yes you're right –  wmz Oct 3 '12 at 13:02
    
And yet manufactures CON users by selling 500Mbps adapters with 10/100Mbps ports claiming 500Mbps speed! –  Mrchief Jan 3 '13 at 15:58
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It's a bit cheeky describing it as Gigabit but I think the gist of it is that the network port runs at 1Gbps but it can only send half that over the power lines. The one that doesn't mention gigabit only has a fast ethernet port for 100mbps so you wouldn't get the performance of 500mbps unless you were using more adapters. I think the 500mpbs is split amongst all the powerline adapters you have.

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+1, you were faster than me :-), and also for mentioning it's shared media –  wmz Oct 3 '12 at 11:03
    
Thanks for the answer. I think I understand now. I gave it to @wmz because his answer was a bit more descriptive, but this helps. :) Thanks! –  Thomas Clayson Oct 3 '12 at 12:18
    
No prob, his was definitely a more complete answer I gave it a +1 too –  Col Oct 3 '12 at 12:23
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Each of the standard Ethernet speeds, 10Mbit/sec, 100Mbit/sec (a.k.a. "FastEthernet"), and 1000Mbit/sec (a.k.a. "Gigabit Ethernet") have different signaling and negotiation methods.

So maybe this adapter supports the Gigabit Ethernet signaling standard but just can't do the full 1000Mbit/sec over the link layer.

Guess it's possible e.g. a FastEthernet interface to actually operate faster than 100Mbit/sec but still use FastEthernet signaling/negotiation. However, a Gigabit interface connected to it would negotiate down to FastEthernet, and still transmit at that maximum speed, so I don't know what is going on with that. It's entirely possible the specs are incorrect or written by non-knowledgeable people.

One advantage Gigabit Ethernet has even if you aren't getting a full 1000Mbit/sec is "jumbo frames" which increase LAN (not Internet, of course) speed by allowing bigger Ethernet frames (8000bytes instead of 1500bytes), which can mean a higher MTU, which means reduced packet header overhead.

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The specification states that the device supports IEEE802.3ab, which means that the Ethernet ports do support Gigabit Ethernet. The powerline transceivers, however, have a maximum rating of 500 Mbps in each direction (assuming full-duplex).

The actual total throughput will depend on a lot of factors, such as:

  • length of electrical cabling between powerline devices
  • whether or not the powerline devices are on different circuits, and if there are any circuit breakers between the devices
  • age of electrical cabling
  • interference/noise from other electrical equipment
  • the speed of other networking equipment

Note that the so-called "200 Mbps" powerline devices often have 100 Mbps Ethernet ports, and are therefore limited to 100 Mbps in each direction (which could sneakily be called 200 Mbps, in half-duplex). This would also be the case for the non-Gigabit version you refer to.

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Good answers by the other posters. Just an addition, in case you want to be happy with your device: to not buy the cheapest stuff. I tried several "value" manufacturers and even if they manage to give you acceptable performance under optimal circumstances, they will completely fail, when network conditions are not so fair, like when your washing machine is running, or you have to plug in your network device into an extension cable (maybe chained twice). Top manufacturers like Devolo (there may be others like AVM) really deliver way better results in real life conditions.

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Brill, thanks - I bought a pair of TP Links like in my question. They seem pretty good. They're going from extension to extension and they work pretty well. –  Thomas Clayson Oct 16 '12 at 8:09
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The AV200 vs AV500 and AV600 can reach the desired speeds in near perfect conditions. The fast ethernet 100M will reach around 180M on a AV500 segment. As posted earlier the speeds degrade very fast with interference and old wiring. TPlink and other mentioned products use the same chipset. So I am assuming it is the filters that probably giving superior performance in noisy environments.

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