HomePlug FAQ *Part 2*

blacksheep99

I bought two pairs of the On Networks AV200 homeplugs to try and create a small home network.  I have my microserver sat upstairs, HTPC in the living room, router in the hall and my laptop is connected via wifi.

I did some initial tests and I am not impressed with the file transfer speeds.  I am running Win7 on the HTPC and my Laptop.  The NL40 microserver is running Windows server 2012 Essentials.  Via the plugs I am seeing a max read speed of 3Mb/s.  On the laptop it is 130Kb/s!  I compare I plugged the laptop directly in to the NL40 and was seeing 80Mb/s  Speed.  

As is usual in a house there were phone charges plugged in and lights on but I cant let the girlfriend she has to live without these thing.  Based on these results I will be looking at alternatives.  How would AV500 plugs fair?  I was hoping to see around 20Mb/s via the homeplugs.

berkeley384

Im sure this will have been discussed / answered but I haven't found the post that answers this ....

Aren't all these speed ratings a big con?

You can buy TP link homeplugs rated as 500Mbps both with and without a Gigabit Ethernet connection....

Doesn't that imply then that the connection on the homeplugs without a Gigabit Ethernet connection are using a Fast Ethernet (or worse Ethernet) connection that has a maximum capacity of 100Mbps (10Mbps for Ethernet)

If the above theory is correct - and Im not saying that it is, how exactly can you get 500Mbps

Thinking logically about this - this must be the case - as otherwise there would be no point in making them and advertising them with a Gigabit Ethernet connection as the standard ones would / cu could achieve the same thing

MilhouseVH

The 5th generation AR7420 chipset includes only a 10/100 Ethernet PHY so yes, it's limited to 100Mbps. However the original 4th generation 500-AV AR7400 ethernet PHY is genuinely rated at 10/100/1000 so best to avoid the AR7420-based devices. I believe the AR7420 is marketed as a lower cost alternative to the AR7400.

Fmrl

IMO, sort of - It would be nice if the manufacturers and retailers published "real world" performance figures instead of "theoretical"!

As I understand it, homeplugs create a "one wire" (half-duplex collision domain) network plus there's also noise, latency, encryption, conversion, etc. delays so the actual throughput is considerably less than the advertised rate.  For example, my 200mbps homeplugs max out at around 35mbps (so around 1/3rd of the actual). Also, I tend to have 3 or 4 homeplugs switched on at the same time so if more than one device is talking then there's added delays for this due to it being "one wire".

I think "real world" performance of a pair of 500mbps homeplugs would be around 170mbps (1/3rd of the actual) so I think it actually makes sense only to have 100mbps ethernet connectivity ports on them... IMO, better to have connected devices only expecting fast ethernet speeds rather than gigabit ethernet connected devices being bottlenecked by a comparatively slow link.

By the way, one of my Newlink 200s blew up at the weekend so I'm currently considering upgrading to 500mbps fast ethernet homeplugs.

MilhouseVH

With 200-AV I achieved 65Mbps "real world", and with 500-AV (based on AR7400 chipset) I achieve 135Mbps (both test results from iperf).

I disagree that having 100Mbps ports on 500-AV makes any sense. Although the additional throughput that I achieve beyond 100Mbps isn't much, it's better to have it than not. Artificially restricting 500-AV to a maximum 100Mbps throughput makes no sense when it is capable of more.

Fmrl

You have to take flow control into account though, two gigabit capable devices talking to each other over a much slower core network will force pause frames which potentially cause them both to perform slower as demand increases. You wouldn't get this scenario with fast ethernet devices as there wouldn't be a bottleneck on the network.

MilhouseVH

Maybe, but with GigE 500-AV I can achieve 135Mbps of actual throughput (with or without pause frames I have no idea - this is with both 500-AV connected through GigE switches, -~~~mains~~~-) and I wouldn't get that kind of throughput with 100Mbps ports.

berkeley384

But you cant have 500Mbps using a Fast Ethernet home plugs as Fast Ethernet has a maximum port speed of 100Mbps ...

This is is what I don't understand about these devices

Fmrl

But you don't get 500mbps! From what MillhouseVH has said, even with gigabit ethernet versions of homeplugs you only get 135mbps across your network (with possible flow control and congestion issues on your devices if the traffic ramps up).

I have 200mbps homeplugs at the moment and if I max out the network at around 40mbps then one of the homeplugs starts dropping packets (they don't appear to have any buffering, QOS, etc. but I wouldn't expect them to anyway - they're only layer 2 hubs). Too many dropped packets, pause frames, congestion, etc. and you'll end up with application problems.

Fmrl

It would be interesting to see what throughput you do actually get if you dropped the NICs down to fast ethernet. I'm not disagreeing with you about the speed increase but it's comparatively marginal ie. 1Gbps connections throttled down to 135mbps is quite a step down. I'm not sure how the homeplugs handle congestion (not very well I expect) so IMO you're not really getting much of a benefit.