dir-655 lan speed


Aug 6, 2003

I bought a d-link dir-655 (gigabit) router a few days ago. I connected it and I got it to work pretty quickly, however LAN-speed is a bit disappointing. I can't seem to get more then 6-8 MB / second, wheverever I copy files (see below for devices connected).
This happens when copying large files (500+ Megabyte) with total commander or flashFxp (ftp-client).

The router is connected to 4 devices
- PC A with GBit Intel Pro 1000ct network card (reported under winxp as being "1Gpbs - connected)
- PC B with GBit Intel Pro 1000gt network card (reported under winxp as "1Gbps - connected)
- QNap 209 NAS (with 1GBit connection)
- Buffalo Linkstation D300GL (should also have Gbit connection, lighting blue which means gbit connected)

When doing a ping from PC A to PC B, it's with a reply <1ms ttl=128.

I had cat5/cat5e cables (not entirely sure which it was), so I went and got cat6 cables (since they should definately support GBit connections).

However that didn't increase the speed either, and I'm at a loss... Why do I only get 5-6MB/sec?
From browsing through the QNap forums I read that 20MB/sec can be expected - but I'm far from that. At work when copying files with GBit ethernet, I get 30MB/sec.

Update: I tested using IPerf with the following two batch-files
server: iperf -s -u -w2m -i1
client: iperf -c -u -b400M -w2m -i1 -t60
result on client: [1920] 0.0- 1.0 sec 5.46 MBytes 45.8 Mbits/sec...

Shouldn't it more be like 600-700Mbit/second (1000 would be theoretical max, which probably cannot be reached)

Does anyone have suggestions what to try now?



Feb 9, 2009
Hi here is a few things that is overlooked by a lot of people

Check what speed Hard drives you are using in your pc's if you are using 4800rpm or less then you will experiance a delay with transfer speeds as the hard drives become a bottleneck not your network I recommend at least 7200rpm for IDE or SATA. I have tested with my laptop on 1gb and with my PC my PC has 2 7200rpm sata drives and the laptop has a 5400rpm drive and my average speed transfer was 30-40 mb a sec 800mb file took 15 secs to transfer 10gb took under 10 mins

Also make sure you have enough memory in both machines or windows is going to use the Hard Drives to make up the memory it doesnt have and that will kill your speed of the computers and no matter how fast your network your network only runs as fast as the slowest link in the chain.

Have you run defrag on your hard drive recently you will find that badly fragmented drives will cause delay in network speed.

Have you tried looking for firmware updates for your network equipment updated your drivers for your Network Cards, check that full duplex is on in network connections for all your network cards

Check your network cables are not running to close if possible to power cables power cables which can create Electromagnetic interfernance and degrade the transmission speed making TCP/IP resend data constantly because of data loss also be aware that air con units, microwave ovens, flouresent tube lighting can cause interfernace too I dont know if all this applys to you but they can all degrade network signals.


Jan 7, 2010
Let's see if we can breathe new life into this question. I am having the exact same problem.
When connected directly to the cable modem I get 16 MBps. When I connect behind the DIR655
it limits me to 8. I have the latest Firmware.

Any ideas out there?



Jan 17, 2010
Try going into advanced and adjusting your QoS (Traffic shaping) options. the traffic shaping is designed to prevent slowdowns due to congestion. however, you'll lose some bandwidth in the process...

if you disable your Traffic Shaping engine, retest and see if that helps. you may have to restart the router to see a difference.

just to explain: Traffic Shaping basically limits the maximum possible usable bandwidth on your Wide Area Network connection (WAN, or Internet connection), to less than full bandwidth, this allows for there to always be SOME free bandwidth for the purposes of making new connections. It also, very often, prevents the need for a lot of TCP retransmissions by always having enough bandwidth available to accept incoming packets.

This reserve, should be only 5 or 10 percent of the total available throughput (in this case, approximately 400-500KBps should be more than enough). however, depending on what algorithm the Automatic traffic shaping system uses, you could end up permanently degrading your internet connection (because it could never learn to increase the maximum)...

Good luck, I hope this does the trick.


Sep 25, 2006
Has anyone had any success here?

I thought my dlink 323 NAS was dying as transfer rates were HORRIBLE (4-8 hours to transfer system images of about 8 gigs) so went out and upgraded my NAS to a qnap 219P.

Was very impressed with the new nas until I went to restore data to it.

Transfer rates hovered around 1mbs. I found my win7 driver to be out of date, updated that and transfer rates about tripled to 2.5 average mbs but everything i read says it should be getting over 30mbs.

I do have bittorrent downloads running on it and I intend to test without them running but it doesn't seem right that having them run would cripple all other transfers.


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