Kitz Forum

Broadband Related => Broadband Hardware => Topic started by: Weaver on January 03, 2016, 03:48:46 AM

Title: DLink modem bitswap
Post by: Weaver on January 03, 2016, 03:48:46 AM: I have several DLink DSL-320B-Z1 modems (in bridge mode, modem-only). There is a page similar to the following in the web UI
http://www.support.dlink.com/emulators/dsl2540b/100/adslcfg.html
(That's for the wrong modem, but it gives an idea.)

Shouldn't "bitswap enable" be always ticked? As shown.
Title: Re: DLink modem bitswap
Post by: burakkucat on January 03, 2016, 03:25:49 PM: Yes. I would ensure that "Bitswap Enable", "SRA" and "ADSL2" are selected, everything else is deselected.
Title: Re: DLink modem bitswap
Post by: Weaver on January 03, 2016, 04:55:39 PM: The modems I have been using had this option unticked. What will this do to performance and reliability?
Title: Re: DLink modem bitswap
Post by: Weaver on January 03, 2016, 04:57:54 PM: I don't understand how I've been getting away without this?
Title: Re: DLink modem bitswap
Post by: aesmith on January 03, 2016, 05:06:27 PM: Is SRA supported by BT?
Title: Re: DLink modem bitswap
Post by: Weaver on January 03, 2016, 05:28:27 PM: I believe SRA is not supported by BT, hardly by anyone in the UK. Kitz mentioned UKOnline iirc.
Title: Re: DLink modem bitswap
Post by: Weaver on January 03, 2016, 05:31:50 PM: The help says
“By default the D-Link router will determine your best connection.”
in what looks like an attack of cut and pastry maybe. But there is no default, it's either off or on. So presumably unticked means disabled and ticked means default to on?
Title: Re: DLink modem bitswap
Post by: Weaver on January 03, 2016, 05:37:09 PM: The previous set of modems, Mode = auto, as opposed to Mode = default, were the same btw.
Title: Re: DLink modem bitswap
Post by: Weaver on January 03, 2016, 05:59:29 PM: Why would anyone want or need to disable bitswap? I wasn't even aware that you could do such a thing?
Title: Re: DLink modem bitswap
Post by: burakkucat on January 03, 2016, 06:23:11 PM: :shrug2:

You have three of those devices, each with its own circuit. Perhaps turn on bit swapping in the configuration for one modem only and see how the circuit behaves? Then, after examining the result so obtained, turn on bit swapping for the second and third modems. :-\
Title: Re: DLink modem bitswap
Post by: NewtronStar on January 03, 2016, 09:07:38 PM: The way it works is to swap spare SNR to tones that are not being effected by burst of noise though you would need plenty of non effected spare tones close by for it work well but it's better on than off it should make the line more stable.
Title: Re: DLink modem bitswap
Post by: Weaver on January 03, 2016, 09:14:43 PM: I'm afraid I went the whole hog, and asked Mrs Weaver to tick bitswap enable on all the modems.
Title: Re: DLink modem bitswap
Post by: Chrysalis on January 04, 2016, 01:46:22 AM: bitswapping can have a massive impact, it should always be on really unless its buggy to the point its detrimental (in which case the modem shouldnt be on the market) or for troubleshooting purposes.
Title: Re: DLink modem bitswap
Post by: Weaver on January 04, 2016, 01:54:15 AM: Unless I am misunderstanding some system of defaults, my ISP, Andrews and Arnold, appears to be sending out DLink modems with the bitswap tick box unticked! Is this not disastrously bad?
Title: Re: DLink modem bitswap
Post by: Chrysalis on January 04, 2016, 05:27:36 AM: are AAISP configuring it like that or is that the firmware default? seems very odd to disable it.
Title: Re: DLink modem bitswap
Post by: Weaver on January 04, 2016, 09:36:05 AM: @Chrysalis - Don't know the answer to that, but in any event it's A & A's bad bug if it does what it appears to do.
Title: Re: DLink modem bitswap
Post by: Weaver on January 04, 2016, 11:13:05 AM: Have reported this to A & A for investigation.
Title: Re: DLink modem bitswap
Post by: Weaver on January 04, 2016, 11:14:47 AM: Dopey question: what effects am I likely to see?
Title: Re: DLink modem bitswap
Post by: Weaver on January 04, 2016, 11:18:30 AM: Do I have to power-cycle the modem for this to take effect, I wonder?
Title: Re: DLink modem bitswap
Post by: Weaver on January 04, 2016, 01:01:51 PM: Have confirmed that A & A don't touch the tick box, it comes unticked by default and a non-A & A supplied owner said it's unticked on his device too. So it's nothing to do with A & A, but they are not "fixing it" either by ticking it.

This seems to be a complete red herring. Perhaps it's set to auto on anyway and the UI does nothing, a UI bug. Perhaps DLink just thought it was a useless idea but accidentally left the web UI in for it. Lots of speculation.

Notice that the pic earlier has it ticked (for wrong device model).
Title: Re: DLink modem bitswap
Post by: Weaver on January 04, 2016, 01:12:41 PM: I tried to find a way to report this issue to DLink, but I found their www UI bewildering. If anyone knows of a more civilised way to get in touch with real humans at DLink, then I would be grateful.
Title: Re: DLink modem bitswap
Post by: Chrysalis on January 04, 2016, 07:09:03 PM: A resync would be needed but a reboot of modem should not be needed.

If you able to monitor the bitloading of each tone, and the bitloading shifts about then bitswapping is working.
Title: Re: DLink modem bitswap
Post by: Weaver on January 04, 2016, 07:26:30 PM: @chrysalis - don't yet have the technology, three modems hidden behind a router. But maybe in the foreseeable future. See http://forum.kitz.co.uk/index.php/topic,16700.0.html
Title: Re: DLink modem bitswap
Post by: Weaver on January 04, 2016, 07:36:30 PM: I had better luck when I reported it straight to RevK via a tweet. Thanks Adrian. I suspect he will look into it.
Title: Re: DLink modem bitswap
Post by: NewtronStar on January 04, 2016, 09:36:16 PM: Here is my bitswap per tone graph it's only been running for 10 minutes and you will see each tone that is being effected by noise on this xDSL circuit.
Title: Re: DLink modem bitswap
Post by: Weaver on January 04, 2016, 09:40:56 PM: That's a very slick tool there.
Title: Re: DLink modem bitswap
Post by: NewtronStar on January 04, 2016, 10:08:36 PM: Quote from: Weaver on January 04, 2016, 09:40:56 PM
That's a very slick tool there.

It is slick tool by Roseway one just needs an unlocked HG612 or compatible modem/router but the graphs won't persuade your OR engineer visit to go deeper when looking for a fault unfortunately they won't understand what they are seeing in those graphs they only look at their JDSU no amount of printed graphs will help, it's only for personal use.
Title: Re: DLink modem bitswap
Post by: Weaver on March 21, 2017, 06:53:23 AM: I wrote
> This seems to be a complete red herring. Perhaps it's set to auto on anyway and the UI does nothing, a UI bug. Perhaps DLink just thought it was a useless idea but accidentally left the web UI in for it. Lots of speculation.

I can't remember what evidence I based the idea on that this was a red herring. Has DLink been sending these out with bitswap turned off by default according to the UI at least? Think so. Because we can factory reset one. And if the UI actually does anything, then AA has not been 'fixing' it, which is a real shame. I failed to persuade AA to change their config.

How would I actually test it? What kind of proof do I need to get as an outcome from ticking it, doing the right thing, to show it actually gives an improvement of reliability or speed or both? (Given that it could be that the UI does nothing, because it has a bug in it, and it just does the right thing anyway.)
Title: Re: DLink modem bitswap
Post by: ejs on March 21, 2017, 08:24:46 AM: I think you'd need evidence that the modem has done some bitswaps, which would imply recording the bits per tone data at different times, and seeing if it has changed. Of course if no bitswaps have happened, that might be because none were needed, but over several days, there are going to be changes in conditions from day to night, so it would be very unlikely for no bitswaps to ever be needed, especially on a long line.
Title: Re: DLink modem bitswap
Post by: Weaver on March 21, 2017, 10:42:24 AM: I don't recall offhand whether user g.dmt worked out how much in the way of stats can be extracted from these modems. I would have to isolate one temporarily because my router acts as a barrier between the modems and the main Lan, and then pick its brains using telnet.
Title: Re: DLink modem bitswap
Post by: Weaver on May 03, 2018, 07:22:13 PM: I notice that AA has now agreed to fix the config in the modems that they send out so that bitswap is turned on. (See http://forums.thinkbroadband.com/aaisp/4580060-aa-shipping-dlink-modems-with-bitswapoff-do-fix-yours.html)

I pestered them a lot over it. Thanks go to Andrew Hearn for making it happen. I wrote an article about these modems on the AA support wiki and included some instructions on fixing the config.

[Moderator edited to correct the auto-correct correction. (s/destructions/instructions/)]