7800N tweaking advice, does DLM mind, what about PhyR/SRA?

[slimgym]

Hi
I bought the Billion 7800N to be able to manage my SNRM as I have around 70dB attenuation (BT say). We have no prospect of FTTC and patchy 3G. My circuit is underground to the pole which is probably why my SNRM does not vary day to night. A 6dB SNRM gives me G.DMT 2MBPS on G.DMT with each 3dB losing me around 300kbps. At 6dB it is prone to disconnecting on occasions when the phone rings and anything less than 6dB the error rate is high enough to impact on throughput. At least now if that does happen I can re-apply the 6dB connect margin!

I wondered if anyone knows whether the re-sync that occurs when you change the SRNM is seen by DLM as a disruption, i.e. will this increase your connect margin by 3dB? I am very wary of messing with it too much as a day of power cuts saw my sync down to 896kbps once!

I have enabled PhyR both ways and SRA, but my DSLAM appears to be Infineon so (being as it is not Broadcom), is there any advantage or disadvantage to having these enabled at my end?

Many thanks
Dave

[Tomken]

Try changing the microfilters to see if that resolves the disconnects when the phone rings, but if you have an ADSL faceplate fitted then you should contact your ISP, also if changing the microfilters doesn't resolve.

DLMs wouldn't bother about the odd reset but if there are several in a short period of time, then it could see that as an unstable connection and knock you back.

With a Downstream Atten of 72, then a 6dB profile probably is too low to maintain a stable connection but the G.Dmt will help.

SRA should only be enabled it your ISP supports it and has it enabled at the exchange.

I found when PhyR was enabled it seemed to add to instability, as if it was keeping the SNRM too low so I never bother with that and Billion tech support don't advocate using it (don't know why as it's a feature of the router).

This program http://www.metageek.net/products/inssider/ will show who else is around you and if there's anyone on the same channel as you, either about the same RSSI or up to about -70dBm then you should change channels to give you a RSSI of about -50dBm (-70dBm is borderline conflict).

Channels 1, 6 and 11 are the only three that don't overlap but if using any of these aren't really suitable (because of the above), then try for something 2 or 3 away from the nearest channel/RSSI except channel 9 as that is the domain of microwaves, but over 10ft away from one should be okay as when they're on, they can disrupt your connection and try and avoid having a cordless base unit sited near to your router as they can also disrupt the WiFi.

If you log into your 7800N, click on Advanced/Status/ADSL Status it will display some of the stats which include the Attenuations.

[tinytim]

I'd concentrate on the disconnections caused by the phone ringing before anything else. That probably indicates equipment problems in the exchange. Contact your ISP about that as Tomken says.

Also is there any noise on the line? This is best tested with a corded phone , dialling 17070 & option 2. If there's any noise report it to BT (presumably) but don't mention broadband.

[slimgym]

Hi, thx for the replies I went through the wiring when I first moved in and put a faceplate splitter in so the other two slave sockets have the DSL signal filtered. Max sync was G.DMT 2.2MBPS on a HH2 but once the (intermittent) disconnects on ringing started my sync dropped to 1.8MBPS with quite a few CRC's. There is no difference with sync speed in the test socket. BT (India) and Newcastle escalations just say if my SNRM increases to 15dB (and my sync drops to 1MBPS) then that's where DLM has determined my circuit is most stable. They said to ring back if it drops below 500kbps. Currently I'm synced 1.4MBPS and get a few CRC's a day.

The line is very quiet - we are close we are to Brookmans Park MF transmitter but the faceplate splitter has an RF filter in it. The circuit is all u/g except the drop wire which comes off the first pole when the wire emerges from u/g.

I was interested to know if the DLM considers a resync request from the router as a disconnect event (like a power cut or whatever) and then start you off on the downward spiral. I don't mind playing by the DLM rules but the information on what they are is sketchy. At least now if I get an unexpected sync through phone ringing, power loss or whatever I can bring it back up without the enforced wait in DLM hell.

Might disable PhyR/SRA then, as for wifi we are very isolated with no other wifi visible for a good ten minute walk (hence why we're not on BT's list for FTTC!).

Better having some DSL than no DSL but would like to be able to get as much speed as possible.

[Tomken]

Sometimes using a High Speed ADSL cable between the master socket and the router can help a little with speed but ultimately, it depends on the length and quality of the wire and joints between you and the exchange, but if you continue to get drops when the phone rings and when connected to the master socket, then that's an ISP problem - but Good Luck !

[tinytim]

By "faceplate splitter" do you mean a filtered faceplate? If this is so & the wiring was done right then any extensions don't need filters.

I think BT is OK with SRA enabled but disabling PhyR is probably a good idea.

[slimgym]

Hi, I tried two faceplate DSL splitters, Austin Taylor and BT's NTE5 V10, no difference in sync speed between them, I have no splitters on the extension sockets as the faceplate feeds them all. I re-kroned all the extensions as they looked a bit iffy. I made a telephone extension with good quality UTP cable and crimped on RJ11's. This runs from the master socket (which is in an upstairs bedroom) to the living room and no difference in sync speed with the router either in the test socket, through the filter at the master jack, or at the end of the extension cable so I don't think any of that is at fault. I also tried a 12" pigtail of UTP with an RJ11 which I connected (still twisted) to the A/B terminals behind the master and again no gain in sync speed. The walls are thick so putting the router by the master jack means restricted wifi and the gigabit switch isn't where you want it. I tried to get as few joints as possible but with DLM acting between re-syncs you can't easily get any useful comparison measurements each time you make a change but so far nothing I have added or done has made it better or worse than in the test socket.

The length of the line is definitely the issue - we are 1.2 miles from the PCP (hence why FTTC was pointless) and 3.8 miles from the exchange. Frankly it's surprising anything works at all, I just want to optimize things as much as I can in my domain - it would be nice to get BT to do the same in theirs. At one time you could get an SFR to check all the joints along the route but these days BT are content to let DLM do it or rely on automatic tests showing NFF. It's more a case of prove it off their kit rather than do a proper investigation.

I shall probably knock off PhyR then when I next resync which will be a few days to avoid waking the DLM devil who keeps hold of the IP profile key I don't have

The Billion is a wonderful bit of kit though. Whilst Netgears and Home Hubs lock up, freeze or reboot on occasions when you're configuring within the interface (or pulling stats through telnet on RouterStats), this thing just keeps running, the uptime is the week since I plugged it in first. I have now setup some PRTG sensors using SNMP to monitor stuff over time and configured the VPN so I can enjoy my slow speeds when I'm out and about too

One thing I wondered if anyone else had noticed, not just with this router but with all I've tried, I lose 0.5dB SNRM when the phone is being used. I can see when the OH is on the phone as the PRTG graph drops a little - which was around 7pm tonight

[Tomken]

I've used Routerstats once to monitor my line for a short while but couldn't be chewed to leave my laptop on continuously and it's advised not to do that with laptops anyway.

My SNRM usually drops on an evening as most users do, but unless it causes me problems I just leave the router to get on with it rather than worrying about what's happening on the line.

If it isn't broken then I don't try to fix it and I think you can become too obsessive with line stats - just enjoy the Internet

Are you sure that's 3.8miles and not kms as that would give you an Attenuation of ~84dB and probably no broadband, which would certainly justify fiber.

I have a son who because of the distance he lives from the exchange, ADSL is not possible and so BT ran the cables into the area for FTTC

If your internal set up is sound and you've checked for wifi interference with the help of inSSIDer and you still get the disconnects, then there must be a fault on your line as the DLM would have knocked you back by now as it sets the SNRM for the most stable connection.

Can you try a different phone as it could be the cause of the fault and do you still get these disconnects (or drop in SNRM) from the phone when plugged into the test socket ?

[slimgym]

Yes it is 3.8 miles, just mapped it out on a google maps down the roads the wire runs to the exchange via the SCP, PCP, thankfully all underground. BT put the attenuation at 75dB and I am amazed it works at all. The PCP (LNPOT:PCP44) has 140 properties on it and covers a wide rural area all of which are a distance from it. We're not in the middle of nowhere - 15 miles from Central London as the crow flies. Potters Bar exchange migration is complete and FTTC is available for those who have been done. Now the council are canvassing resident power to fund something but that's 18 months off, if at all. I can see it from BT's point of view. We have no cable provider. If BT did put something in they would gain no additional revenue or win new customers. It's pointless from a business perspective except for customer satisfaction. Probably like most people around here I would dump BT in a heartbeat if I could.

It's only a few months since I replaced the cordless and the problems existed before and after. There are no physical phones plugged in, but if they are, it doesn't matter which one is lifted the SNRM drops a bit. It's only 0.5dB, I just wondered if I was alone. It might be more noticeable because of the loop loss.

As you say, some broadband is better than no broadband, but like someone on 20 meg upgrading to 40 you still want the uplift!

[Tomken]

Just checked your exchange with Sam Knows and Potters Bar was LLU enabled on 13 05 2006 which enables other providers to supply their own broadband down BT's lines rather that it being restricted to BT's Ipstream.

While band width is always determined by the length and quality of the wire and joints from the exchange, the likes of TalkTalk can push more down the line than BT's capped 8meg, so a phone around the various ISPs could prove fruitful if you're not tied to BT.

At least these days, they have to quote more realistic speeds for the line and attenuation, but it's still always quoted as "Up to...." and if you tell the ISPs how far away you are from the exchange, then those who are honest and understand what you're talking about, may give you what you could expect from your line and 3.8miles equates to ~6.08kms for those of them that don't know £ s d