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[Zac]

Yes, I know it's the DAP-2553 board, but I don't see any place for DAP-2590 specific messages.  Sorry.

I am experiencing random total disconnects (every client dropped at the same time) with my DAP-2590.  Tech support has suggested that I should:

* reduce power to as low as will still let me connect reliably
* turn off extra features (like short GI, IGMP snooping, bandwidth limits, &c)
* change from my preferred band at 5.2GHz to the over-crowded 2.4GHz band
* relocate the unit so it is not near so many 2.4GHz stations (my neighbours' several WiFi networks)
   (despite the fact that I use it in 5.2GHz specifically because of the local 2.4GHz clutter)
* try connecting with more clients
* try connecting with other brand or model WiFi adapters
   (have tried with Intel (two models) and Broadcom (one model), don't have any other brand WiFi adapters)

None of that has worked (I can not relocate it away from my neighbours, so I don't know if that would have worked, but I have tried nearly everything else that has occurred to me).  Windows 7 will not connect to it if I turn off WMM, but I have disabled all of the other features above basic wireless (except encryption and authentication, which I refuse to disable).

What I see in the logs looks like normal behaviour except that every so often (at least daily but in some cases it is only a couple hours apart) there will appear an entry "Initiate wireless success" that occurs within a few seconds of when the connections to all my clients are lost.  These "Initiate wireless success" log entries do not occur near other log entries that are indicative of the device rebooting entirely -- they are right in the normal flow of things, often it looks like this (omitting the MAC addresses):

Nov 17 05:26:20    [Wireless]   4-way handshake success:STA [mac address]
Nov 17 05:25:17    [Wireless]   Association Success:STA [mac address]
... omitting a bunch of association success with handshake fail pairs ...
Nov 17 05:17:00    [Wireless]   Initiate Wireless success
Nov 17 05:12:01    [Wireless]   Group key update success:STA [mac address]
Nov 17 05:12:00    [Wireless]   Group key update success:STA [mac address]
Nov 17 05:02:01    [Wireless]   Group key update success:STA [mac address]
Nov 17 05:02:00    [Wireless]   Group key update success:STA [mac address]

So it is operating along, doing its job, then suddenly the radio is restarted.  Clients eventually reconnect (usually must be told to disconnect and then reconnect) and then things seem normal for a while -- at least until it decides to reset the radio again.

Tech support claims to have "never heard of" an issue with the DAP-2590 dropping connections.

Eventually, I was told by tech support that this is probably the radio resetting because of all the nearby 2.4GHz stations (between seven and ten depending upon conditions and which PC is scanning), even though I specifically operate this unit in the 5.2GHz band to avoid that interference.  I am the only person within range using 5.2GHz.  Tech support asserts that the radio still *receives* at 2.4GHz even when it is set to 5.2GHz (the ability to turn the radio off on dual radio units only affects transmit, not receive, and the same applies to single radio units -- by setting the radio to use 5.2GHz I only set where it transmits, it still receives both bands).  Frankly, I think this assertion is bogus, and their pre-sales support seems to think so too; they sent me back to tier 3 support to get clarification about why I was deliberately looking for a unit that specifically DOES NOT HAVE THE ABILITY to work at 2.4GHz (to avoid the stupid radio reset from interference problem).

I have an older DLink 802.11a access point that I really like (a DWL-7100AP) and it has never suffered this sort of problem, even though it also can operate at 2.4GHz as an 802.11b/g access point (I still only use it at 5.4GHz, but have had it disconnected while trying to debug the problem with the DAP-2590).  I have another brand 802.11n unit (a router) that operates quite well, not suffering the radio problem (but it has problems dealing with my network since it is a router and not an access point).

I still normally use the DWL-7100AP, but was hoping to upgrade to support 802.11n.

I have tried multiple firmware versions and get the same problems.  I have iterated through a number of configurations, all different around some detail or other on the Wireless settings or Performance settings page, as well as turning off pretty much everything else.  I continue to get unwarranted "Initiate wireless success" log messages at about the time all my clients lose connectivity.

I have discussed the issue with DLink technical support three times, and their answer is to get another unit with dual radios.  I have tried to get DLink pre-sales support to suggest a unit that either does not have 2.4GHz capability or has the 2.4GHz and 5.2GHz antennae separate so that I can terminate the 2.4GHz antennae in a way that will prevent the unit receiving interference (or at least should sharply reduce the amount it sees) from the neighbours' networks that all operate at 2.4GHz, but they have no suggestions for such an alternative; the best idea they can offer is that I should try the DWL-2690AP.

I don't mind paying $300 for an access point (would rather pay less but the less expensive units are too often cheaply made router-only units), but do want it to work -- and nearly perfectly.  I am not willing to pay $600 or more for an access point, and particularly not from the same company whose $300 access point can't hold connections for several hours and whose support seems (perhaps) evasive.

DLink denies there is an issue with the unit, but too often when a little searching I see odd disconnection issues around this model, in addition to other bugs (for example, support for VLANs apparently does not work, but I do not need that).

I am not willing to let my money go to waste on a beta level product, so I will be returning mine if I can not resolve this problem shortly (within a few days, so I can still get a full refund from the seller).  Since DLink tech support suggests I avoid the 2.4GHz interference and DLink pre-sales support can not offer me a model where this is a possibility, I must unhappily seek other brands.

[Zac]

Rolling back to 1.13 firmware (from the 1.20 firmware) does not help.  I still get disconnects of all clients at once, and an 'Initiate wireless success' message at the same time in the log.

[FurryNutz]

Zac,
This seems like that the DAP is having problem due to over congestion of the surrounding area with other Wifi networks and radios. One guy is expereincing the same issues with his DIR-855 in a apartment complex:
http://forums.dlink.com/index.php?topic=41071.0

Have used InSSIDer to see what networks are surrounding you and what channels they are using and if there are any open ones?

It's seems like you have done alot to narrow down the cause of this and the DAP still seems to be having trouble. I really feel this could a due to external interferences and clutter.

Even in 5Ghz mode, the unit still cuts out? Are there any other 5Ghz radios around?
How about any phone devices that run 5Ghz or even 2.4Ghz?

Any chance of taking this DAP unit to a different location, like home, friend for families place for a temp test to see if it works else where?


Keep us posted.

[Zac]

This seems like that the DAP is having problem due to over congestion of the surrounding area with other Wifi networks and radios. One guy is expereincing the same issues with his DIR-855 in a apartment complex:
http://forums.dlink.com/index.php?topic=41071.0

Have used InSSIDer to see what networks are surrounding you and what channels they are using and if there are any open ones?

No, but I see a bunch (several to ten usually, depending upon which PC I use, the time of day, phase of the moon, alignment of the planets, &c) when I scan for wireless networks with the Intel tools or the built-in support from Windows XP or Windows 7.  I'm the only one running with SSID not broadcast, but this setting also has no apparent effect upon the DAP-2590 radio resets.  If I set the PC to limit itself to 2.4GHz (802.11b/g/n), I still see the other networks.  If I set the PC to limit itself to 5GHz (802.11a/n) then I see nobody else.

I'll look at some of these other tools, but have no idea what good it will do me to know who else is cluttering 2.4GHz when I want to operate exclusively at 5GHz.  Maybe there is somebody else at 5GHz, but 802.11b/g are 2.4GHz only and 802.11n 5GHz is not common yet (and may never be if people are put off by paying an extra $10 on a $1000 laptop for a dual-band card, but I'm not complaining about *that*).

It's seems like you have done alot to narrow down the cause of this and the DAP still seems to be having trouble. I really feel this could a due to external interferences and clutter.

Even in 5Ghz mode, the unit still cuts out? Are there any other 5Ghz radios around?
How about any phone devices that run 5Ghz or even 2.4Ghz?

I have one (probably would call it antique) cordless phone that (I think) runs at about 800MHz.  It far predates the gigahertz plus phones.

The DAP-2590 cuts out about the same in either band.  Not only that, it is slower in 2.4GHz mode because of all the nearby clutter (naturally).

I only want it in 5GHz mode, and don't care about 2.4GHz because of all the nearby clutter (besides, 802.11n in 2.4GHz is bogus -- 802.1n requires two clear non-overlapping 40MHz channels to actually get anywhere near its spec, and supposedly there are *exactly* two non-overlapping 40MHz channels in the US 2.4GHz range, but these channels overlap a bunch of the other channels used by 802.11b and 802.11g and cordless phones and RF remotes and probably bluetooth and almost certainly other stuff (not to mention microwave ovens!), so even finding a single clear 40MHz channel is nearly impossible).

As far as I can tell, I am the only person within range using *any* 5GHz WiFi devices, but I don't have a way to tell if there are *other types* of systems using the range (no, directional tunable RF meters are not part of my usual diagnostic kit).  This is the first time I've even thought I might need one.

I chose this unit because I *avoid* 2.4GHz like the plague (too crowded), and this unit has 5GHz capability without also paying extra (another $300!) for a second radio at 2.4GHz that I will almost certainly never use (in, for example, the DAP-2690).  I have been sitting happily in the 5GHz band for years without issues (fewer attempts at intrusion, wider selection of channels to avoid interference, less clutter, better bandwidth).

My 802.11a access point (an older DLink unit -- DWL-7100) has worked perfectly for years, and I have machines that connect to it and stay connected for *weeks* without problems.  Unplugging that AP and connecting the same devices to the DAP-2590 has them dropping every couple to few hours when the radio on the DAP-2590 resets, even if I force it to 802.11a mode, which certainly should not tax it even if there is nearby noise.

Any chance of taking this DAP unit to a different location, like home, friend for families place for a temp test to see if it works else where?

It *is* in my home network.

Unhappily no good chance to take it elsewhere and leave it long enough to get a good sample: nobody else I know has bothered to (pay extra in order to) buy devices that can speak either 802.11a or 802.11n at 5GHz (though a few of the not-too-expensive 802.11n devices can work at 5GHz, they still seem uncommon).

Amusingly I can run both the DAP-2590 and the DWL-7100 at the same time (firmware 1.13 on the DAP-2590 renders my 802.11a devices unable to connect to it unless the DAP-2590 is in '802.11a only' mode, but the DAP-2590 still resets even in this configuration), and while the DAP-2590 is collapsing under the stress of a single 802.11n client in the 5GHz band, the DWL-7100 happily purrs along without problems with its normal two clients, also in the 5GHz band (I turned off the 802.11b/g support on the DWL-7100 almost as soon as I opened its box).

I still have a little while before I have to decide to keep or return this DAP-2590.  I don't intend to loan it out to see if somebody else has problems with it.  Even if I would consider this, too many of my friends are running hardware that only supports the 2.4GHz band and are perfectly accustomed to wireless dropouts simply because of all the other stuff in that band, so they'd never notice it.

For a 'commercial grade' AP to collapse because of nearby noise in a different part of the spectrum seems wrong; so much so it definitely does not warrant a 'commercial grade' designation (I would hesitate to call it 'consumer grade' -- sounds more like 'beta test').  I also experimented with a 'consumer grade' 802.11n router (doesn't speak 802.11a but can speak 802.11n at 5GHz) that does not suffer this radio problem in the same place and with similar configuration, but it has other problems in my network because it is a router and I don't need another router.

I keep hoping the problem is something that can be addressed by configuration or firmware, but the way the DLink tech support people talk about the problem, it makes me think it is a design defect or firmware bug in the radio.  Thankfully, I think it might be the case that radio firmware is included in the unit firmware, because the 1.13 firmware and the 1.20 firmware show distinct differences that might be due to radio firmware in some places (for example, the signal strength indication on the clients page on 1.20 shows 100% for everything, but on 1.13 it shows 80% to 90% most of the time).  Unhappily I do not seem to have a firmware version that avoids the radio resetting.

I'll check out the tool you mentioned and let you know if it helps or tech support lets me know they have an idea or I figure something else out.

Thanks.

[FurryNutz]

I like your sense of humor man, you got have some in dealing with this things. LOL.

You mentioned that you had older HW running A modes with out issue. One test I would do is try Single mode A or N if you can and see if it exhibits the same issues on 5Ghz. Try playing with channels.

I agree that the collapse of the connections should probably not happen however, again, this is probably not something FW can or would fix by using any update. I feel the wireless is probably encountering some sort of interference on some level and it's trying to maintain signals and connection and something is stopping that from being reliably maintained. I presume that most any WiFi devices will have problems dealing with a situation like this. This issue seems to be coming more prevalent the more people get WiFi's going and being such a populated and congested area, the channels are being more used up and the radios going, there is just to much interference to maintain a clean signal.

You probably proved that this isn't a FW issue as you've gone from the latest back to an older one and it's still producing the issue.

How long do you have before you return the unit?
One thing you could try, go get a different device, try a router, or access point something different. I might bet that device would exhibit the same problem. Just a suggestion.

Keep us posted on what you see on InSSIDer.

[Zac]

I like your sense of humor man, you got have some in dealing with this things. LOL.

Sometimes humour is all I have to keep me from going crazy.

You mentioned that you had older HW running A modes with out issue. One test I would do is try Single mode A or N if you can and see if it exhibits the same issues on 5Ghz. Try playing with channels.

One thing you could try, go get a different device, try a router, or access point something different. I might bet that device would exhibit the same problem. Just a suggestion.

It's a pain to find something that supports 5.2GHz.  Bleagh.  Found two, picked up one, trying it now.

Keep us posted on what you see on InSSIDer.

There are 13 other networks in my area according to inSSIDer in the 2.4GHz range, a plurality of networks with 40MHz blocks can be found on channel 1 (five of them), another cluster on channel 6 (four of these), one on channel 10; two 80MHz blocks exist on channels 6+10 and one on channels 1+5.  I am running the only networks showing up in the 5.2GHz band at all.

I have tried a few configurations, using the units alone or in various groupings, and the results are the same.  When used alone, they are placed in about the same place; when used together, I place them several feet apart but in the same area as when using them alone.  Uplink is always autosensing 10/100/1000 switch, with them all using the expected speed to the switch (1000Mb/s for the 802.11n boxes, 100Mb/s for the 802.11a box), all over Cat5e cabling.  I do not have any of the units set to drop wireless on loss of uplink.  All units are powered by their discrete power converters (no Power over Ethernet) and all units plus the switch are plugged into an APC SmartUPS 1000XL.

I have tried max transmit power, -3dB, and -6dB.  Signal at the clients seems to start to drop noticeably starting at -6dB, but none of these settings has any effect on the problems.

I have three client systems, all laptops, usually powered from line and often docked, connecting to these devices.  I may have a Broadcom WiFi card around here somewhere but it is not mounted and the drivers are a pain (since it seems only Dell officially used that particular card, the drivers have to be tricked to install to anything but a certain model Dell laptop that I have never owned).  All three clients are using Intel WiFi cards, which is what my limited testing has found to be most solid:

  Lenovo ThinkPad W700, Intel 5300AGN, Windows 7 Ultimate, native WiFi controls
  Toshiba Tecra M3, Intel 2915ABG, Windows XP Pro, native WiFi controls
  IBM ThinkPad A31p, Intel 2915ABG, Windows XP Pro, Intel WiFi controls

Signal column is 'about average value' at client with the base station at full output.

Unit          Mode    Band            Signal   Free (<=20%)   Loaded (>20%)
-----------   -----   -------------   ------   ------------   -------------
DWL-7100AP    a       5.2GHz          -50dB    no problems    no problems
DWL-7100AP    b,g     2.4GHz          0dB      no problems    no problems
DWL-7100AP    a,b,g   2.4GHz,5.2GHz   (above)  no problems    no problems
-----------   -----   -------------   ------   ------------   -------------
TL-WR1043ND   b       2.4GHz          -40dB    no problems    no problems
TL-WR1043ND   g       2.4GHz          -40dB    no problems    no problems
TL-WR1043ND   b,g     2.4GHz          -40dB    no problems    no problems
TL-WR1043ND   n       2.4GHz          -40dB    no problems    no problems
TL-WR1043ND   b,g,n   2.4GHz          -40dB    no problems    no problems
-----------   -----   -------------   ------   ------------   -------------
DAP-2590      a       5.2GHz          -50dB    problem 1      problem 2
DAP-2590      n       5.2GHz          -50dB    problem 1      problem 2
DAP-2590      a,n     5.2GHz          -50dB    problem 1      problem 2
DAP-2590      b,g     2.4GHz          -35dB    no problems    no problems
DAP-2590      n       2.4GHz          -35dB    no problems    no problems
DAP-2590      b,g,n   2.4GHz          -35dB    no problems    no problems
-----------   -----   -------------   ------   ------------   -------------

inSSIDer is confused by the DWL-7100AP in dual-band mode: it alternates it between showing up in 2.4GHz and 5.2GHz, but clients attached to it show no such confusion or any traffic interruption that would seem related.  Maybe this has to do with it claiming the same MAC address in both bands (despite different SSIDs)?

Problem 1: Radio resets randomly, usually between 1 and 8 hours between resets, disconnecting all clients and requiring intervention (clients can not reconnect automatically and must be forced to dissociate before they can reconnect).  When the radio resets, it pops back up on an apparently randomly chose channel.

Problem 2: Radio appears to keep working but control interface seems to become confused -- log disappears (page 1 of zero) and WiFi stats mostly stick at zero (maybe other symptoms I have not yet noticed).  This seems to happen after several hours.  The box must be restarted before the logs show up again (and any logs that did exist are lost).

On the DAP-2590, firmware 1.13 seems to show more credible stats for the wireless clients (particularly signal strength, which is often 80% to 90% but sometimes varies outside of this range for short intervals, and reduces if I reduce power at the client), but it seems flaky about connecting both 802.11n and 802.11a clients at the same time.  While firmware 1.20 does not seem to have problems with having both 802.11n and 802.11a clients, it usually shows what I think are pretty bogus signal levels (almost invariably 100%, and does not seem to reduce until I set the client power very low).  I do know the ThinkPad A31p antennae were designed for 2.4GHz radios, but the 5.2GHz card works fine with it at slight cost of signal strength on both client and access point end, so basically it should probably never show up as 100% at the AP (sits around 60% according to the DWL-7100AP).

The DAP-2590 signal strength according to inSSIDer is pretty stable in 5.2GHz mode, sitting around -50dB, but in 2.4GHz mode it hops about, from -85dB to -10dB or better, often swinging wildly between samples, though it seems to tend toward -35dB.  Maybe this has to do with all the clutter in 2.4GHz that does not appear in 5.2GHz, but it's a touch unnerving and yet another reason I would prefer to stay in the 5.2GHz range.  A number of the other networks in the 2.4GHz band have similar behaviour, but my DWL-7100AP seems pretty steady at around -50dB in the 5.2GHz band (but curiously shows up at 0dB in the 2.4GHz band).

Despite the 'improved' signal level, performance in 2.4GHz is awful.  The DAP-2590 usually transfers data at between 20% and 60% of the claimed speed, and in the 2.4GHz band more often the 802.11n client claims speeds in the range of 11Mb/s to 40Mb/s (though sometimes as high as 130Mb/s, even though inSSIDer claims it is always using an 80MHz channel).  In 5.2GHz it consistently provides nominal speeds of 200Mb/s and up, usually toward 300Mb/s.  Perhaps due to the 2.4GHz clutter?

In the 2.4GHz band, with no traffic other than basic ambient fluff, pings between wireless and ethernet take somewhere between 4ms and 5000ms (maybe averaging about 500ms), and about half of them are dropped.  More to do with 2.4GHz clutter?  The TL-WR1043ND and DWL-7011AP do not exhibit this at 2.4GHz (or the DWL-7100AP at 5.2GHz), though; both of them show a tighter time range (3ms to 100ms, averaging about 15ms) and drop less than 1%.  The DAP-2590 provides better (but still not the best of the three) results at 5.2GHz.

Interestingly, I have not seen it reboot the radio in 2.4GHz...  I wonder if they test it at 5.2GHz in the lab...?

So after all this, the tech support claim that it is resetting in 5.2GHz mode because of 2.4GHz interference, despite supposedly only operating on a single band, is sounding more bogus.  I have had 802.11a (5.2GHz) connections to the DWL-7100AP stay up for weeks.  Seems to be little point in mentioning I have had 802.11n (2.4GHz) connections to the TL-WR1043ND also stay up for weeks.

But despite the DAP-2590 apparently working in 2.4GHz, it is not working where I wanted it to work, as I specifically purchased it to have 802.1n in the 5.2GHz band.

I need to return the DAP-2590 by early December.

If I can find something that does not (apparently randomly) drop all connections when running at 5.2GHz (and otherwise works well and does what I want), I will probably keep it.  Otherwise I'll skip 802.11n (go back to old faithful 802.11a) or wait for something that does work the way I want.  As for the DAP-2590, I'm not willing to pay commercial grade prices for beta grade product, so will probably send it back in a few days, with minimal additional tinkering, if nothing particularly inspiring comes along.

[Zac]

A new device was placed in same physical location as the DAP-2590 had used, and is now at 26 hours continuous without a radio reset or loss of connectivity to any client systems, in the 5.2GHz range.  I have varied the load from near idle to as much traffic as I could get across it (and back), with no glitches.

Unhappily the new device does not speak 802.11a and 802.11n both at the same time properly (first client to connect succeeds and clients speaking the other mode fail), but I can live with this since the old 802.11a access point and it seem to coexist peacefully.  The performance is also not as good as I would hope (seems to top out at 35% of the nominal stated connection speed, and average about 30% -- so if it says connected at 300Mb/s, I can get about 100Mb/s data across it with a gigabit connection to my wired network).  I would like to find something that can hold 45% or so with good encryption and security.  I have long suspected the 802.11* 'connection speed' is counting both halves of full duplex (so 100Mb/s ethernet would be written as 200Mb/s in this mode) and even on full duplex circuits it is hard to exceed 90% of one direction or the other (but usually can get close to 90% total if two streams pass in opposite directions).

However, the new device has now been running without a glitch longer for than the DAP-2590 has ever gone in 5.2GHz without a radio reset, so this makes two devices running nicely in the 5.2GHz spectrum (confirmed by inSSIDer) without radio reset problems.  And still, I have the only networks in the 5.2GHz range nearby; there are still all those others near me in 2.4GHz.

Oh, and pings: average from ethernet to either wireless is about 2ms (usually 1ms with an occasional spike to the teens), and either 802.11a or 802.11n to the other (which crosses ethernet and two access points right now) is about the same, so it's probably a measurement limitation that I am encountering.

[FurryNutz]

Ok Zac. After getting some additional 2ndary opinion on this. I'm going to recommend that you return this DAP unit and try another. We feel that this unit is defective with the 5Ghz radio. If your getting good singal now with a different unit then I would presume that the 2590 needs to be returned. I would recommend you try another of the same model if you can. If the next unit exhibits the same then I'll forward this on to my contact at DLink and let them know there 2590s are having problems.

I wish more forum users were like you like man. Your very thorough and detailed. Thanks for that and all the information. I hope I was helpful some and wish we could have resolved it.

Keep us posted.

[Zac]

Received a new unit two days ago and configured it from scratch.  Decided against using my old config or anything else, for fear of some kind of contagion (have had a bad setup propagate a problem *once* with some device long ago, but that was too many times).

New unit seems to be working properly in the 5.2GHz range.  Don't know (or particularly care) about the 2.4GHz range.  Basically, I have had a machine connected (without automatic reconnect) to it since a couple hours after plugging it in and setting it up.  I've loaded it fairly well and let it sit at little load, connection has not dropped yet; no indication of radio resets in the logs either.

Overall, looking much better now.

Now, can somebody tell me why it *shipped* with firmware 1.15, but the download website does not offer this version?  I can download 1.00, 1.10, 1.13, and 1.20, but not 1.15...?  Frankly, since it works with 1.15 and does not support downloading the current firmware for backing it up, I'm afraid to upgrade it to 1.20, even though 1.20 claims some improvements I'd like.

Thanks!

[FurryNutz]

Good to hear the new unit is working better for you.
Not sure why 1.15 isn't listed anywhere. I would run it for now and see how it works for you.

If you do upgrade i would recommend configuring from scratch again since this seems to be a major update from 1.15 to 1.20.

Keep us posted.

[Zac]

Unhappily, the new unit has now begun acting the same way as the first one -- all clients are disconnected simultaneously, and the usual 'Initiate Wireless Success' entry appears in the logs at that time.  Started doing it occasionally, then at least daily, now more than twice per day.  Nearby (older D-Link AP in 5.2GHz band) does not suffer any apparent issue.

Even 1.25 firmware behaves the same way, so that's every firmware version I on which I can lay hands from 1.00 through 1.25, including the unreasonably hard-to-find 1.15.

Will see if D-Link will repair/replace it under the 'lifetime' warranty (a footnote in the warranty information seems to indicate the warranty is only one year in USA???).  Either way I'm dumping it on someone else who doesn't mind regular client disconnects or recycling it.  I'll replace it with an AP from another brand.

I will post an update about whether D-Link repairs it.

[FurryNutz]

Any other 5Ghz radios near by besides the other AP unit?
Is the DAP working in auto scan or manual channel?
Has this unit been working ok since a year ago?

Does the unit disconnect if all other 5Ghz APs turned off?
Does the AP seem warm to the touch? Wondering if there could be a heat issue maybe.

Keep us posted on how it goes with DLink replacement.

[Zac]

Any other 5Ghz radios near by besides the other AP unit?

No.  There's a thingy that speaks Bluetooth, but IIRC, that's more 2.4GHz clutter.

Is the DAP working in auto scan or manual channel?

Auto.  Setting manual has not helped, so I put it back to auto, where it has been most of the year.

Has this unit been working ok since a year ago?

Worked fine until about a month ago.  Then started dropping occasionally (maybe a couple times per week), increased to daily, now more than twice per day (and I think the intervals are still shrinking).

Does the unit disconnect if all other 5Ghz APs turned off?

Yes.  Also even if it and the other AP are forced to channels with some gap between them.

Does the AP seem warm to the touch? Wondering if there could be a heat issue maybe.

Warm is relative.  It is 'warm' to me, but it is not 'hot' (so probably case temperature between 100 and 120 Fahrenheit).  I don't think it has ever been 'cool' to the touch except after it has been unplugged for a while.

Keep us posted on how it goes with DLink replacement.

[FurryNutz]

I would try it at a different location as a test.

I would check the manual to see if there is operating temps listed. Some manuals have it listed.

I know that the DIR-857 is listed at working the mid 90f's, however actual is 100F -low 120F. 

I might try leaving it off for a while and see how it does after you turn it on.

Seems like something is causing it to disconnect... 

[FurryNutz]

I see this newer version of FW listed:
v1.25   10/8/2012 12:00:00 AM
Release Notes:
Enable ht20/40 coexistence in 2.4Ghz
Support DNS client for SNTP
   


Not sure if this would help any.