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[Weaver]

An idea: do you think we could petition someone to commission an ultimate performance simple modem? Better than a combo device would be a small number of models: ADSL2 or ADSL2+, plus a VDSL2 model and a G.Fast model. Each needs to speak PPPoE on the LAN side of course. A second ethernet port for admin / stats might be worth considering.

Mine should have an optimisation option for long lines (7.3 km in my case) and a selectable bandwidth-limited, ultra-high-quality analog front end, and a decent PSU.

Perhaps someone important could persuade someone like BT to commission one, having specced it, and then test it. Or ISPA or somebody. Smaller ISPs could perhaps get together and push it through?

Something that ‘just works’, outstandingly well, and makes all ISPs, BTOR and BTWholesale etc look good.

[PhilipD]

Hi

Combo devices are just modems, and modems are combo devices.  For example HG612 is a combo device if unlocked and set that way, i.e. routes but is supplied as just a modem.  In fact I think it is true to say all "modem" only devices sold as such are just a checkbox away from being fully fledged router.

There is no advantage in a modem only device, as it's the same components found in routers.

A single box that works well on everything and makes everyone look good is already the aspiration of all manufacturers I would have thought, but the variable nature of such things means one device can't be optimal for every bit of hardware and type/condition of a phone line.

Mine should have an optimisation option for long lines (7.3 km in my case) and a selectable bandwidth-limited, ultra-high-quality analog front end, and a decent PSU.

 

I would think this is a dwindling market targeting longer lines, and I'm not sure what is "optimised for a longer line"?  You can already tweak the modem settings to optimise this yourself on most kit certainly Broadcom, but at the end of the day, it's physics, you can't make a line appear shorter no matter how much you spend on a modem.

All analog front ends are ultra quality, or as best as the manufacturer is willing to spend without running into the laws of diminishing returns.  The components for the analog front end are as cheap as chips anyway, fractions of a pence, throwing more money at exotic analogue front ends will made no difference, might up the price by 50p but have the exact same sync speed as the cheaper components.

The signal has traveled in your case of 7 Km, over cable never designed for that type of signal, the fact you get anything at all is testament to just how good these modems are, there is little more you can do to improve things except try a few different modems and use the one that works best on your line.

Regards

Phil

[Bowdon]

I think ISP's need to move away from the router/modem combo. If one part fails it takes the whole line down.

I did have a good router/modem combo with the Netgear DG834GT. It lasted me for 5 years with my custom firmware. Never had a problem with it at all.

The HH5 on the other hand tends to be a pile of smelly compost. It might function for the majority of people. But I wonder at what cost.

The more they try and do 'one size fits all', the more likely for issues.

Maybe bring out different versions of the modem. ADSL1/2+, FTTC + G.Fast, FTTP/H.

[nallar]

> A second ethernet port for admin / stats might be worth considering.

There's no need for that. You can run both PPPoE + normal IP over the single ethernet port. With pfSense you do this by assigning one interface as the ethernet port, and one as the PPPoE connection which is over the ethernet port. Doing this with a Vigor 130, but there's no reason why it shouldn't work with any modem.

[Weaver]

I realise that I shouldn't have used the word combo as it's totally unhelpful, it makes people think of modem/routers, or modem + router + firewall + nat translator + wap possibly also including teas-made and lawnmower. What I intended to say was devices that handle multiple xDSL protocols in one box (i.e. combo _DSL_ software), as opposed to models tuned for one the lower-frequency protocols only because they are bandwidth limited.

@PhilipD: I defer to your good self on design matters, input such as yours is always valued for a sanity reset. Do I take it you would not feel there's a need for a narrower frequency bandpass option in an analog front end for an ADSL1/ADSL2-only modem? (That is, no ADSL2+ frequencies, and certainly no VDSL2 capability.) This was something that Burakkucat mentioned to me just over a year ago, trying ADSL2 not ADSL2+ for those of us on ultra-long lines, to see if there is any tiny improvement to be had.

[ejs]

I think the main difference between ADSL2+ and ADSL2 on long lines is because the earliest BTW ADSL2+ MSANs do ADSL2+ badly on long lines, and much less about the technical standards and the science of the technology. There's even a difference in upstream performance between ADSL2 and ADSL2+ on those exchanges, yet the upstream frequencies are the same with ADSL2 and ADSL2+. On more modern exchange equipment, it seems to make little to no difference. But the poor performance of that earliest equipment has somehow been taken to mean that ADSL2+ in general works badly on long lines, rather than showing it was just that earliest equipment that doesn't do it well.

[Weaver]

The question is then, what makes a good modem? They certainly are not all the same in terms of aggression, from personal experience. Perhaps they offer similar performance on good lines. I wouldn't know.

For my dream modem I have a wish list of features

- correct input bandwidth, unless someone is going to tell me this is a non-issue
- please santa, monitoring of unused tones
- SRA, just in case (can but dream)
- retx (supported with ADSL2?), just in case (dream on)
- on LAN-side, use Ethernet flow control to keep queuing under control and let the router manage queues rather than the modem. Perhaps all modems already do this, I’m ashamed to say that I wouldn't know. Job for wireshark
- (having considered previous point) dear developers, pls implement QoS in L3, with sensible architecture of multiple queues, while I'm on a software development spending spree. - could do nice things such as prioritising DNS queries and TCP ACKs

For some reason I was rather disappointed with the Draytek Vigor 130 because of its less aggressive sync speed. Maybe I should retest it, because I certainly wouldn't mind getting back the free ~3% extra speed from the use of PPPoA, if my spreadsheet is not in error. Assuming TCP with 1500 byte IP MTU so L3/L4 overheads of IPv4+TCP headers, I compared the efficiency of a PPPoEoA with that PPPoA in terms the ratio of bytes over ATM to TCP SDU payload. (IPv6 comes out the same in this case.) Even if I could get the Draytek to simply match the sync rate obtained with the current Dlink DSL-320B-Z1 devices, it would be about 200kbps faster downstream - a free lunch.

(Although PPPoEoA is invariably bad news, in this case I could get a lot of that speed back if I went down to an MTU of 1492 because that would save me one whole ATM cell, 32 cells instead of 33, the only remaining difference being the reduction in efficiency because of the increased number of IP+TCP headers sent per byte of TCP payload due to the reduced MTU, but other than that, packets over PPPoA and over PPPoEoA would produce sequences of ATM cells of the same length. Of course PPPoEoA would still be worse, even worse, for short packets.)

It may be that the Draytek Vigor is not a “bad” modem on my line, it's just that the reliability vs speed tradeoff is set differently. If I could somehow tweak a Draytek to run at the same SNRM as the current DLinks, then it would be more of a fair comparison, comparing like with like.

[Weaver]

@ejs - I didn't know that. Some models of MSAN, or some firmware releases? Did they ever get fixed?

When Burakkucat was discussing this with me - I should let him speak for himself - if I recall correctly, would have to dig back to old threads or PM or both, the idea was concerning width of  bandpass at the input stage. If I understood correctly, some modems might reject more noise with narrower input filtering if they have a different configuration when in ADSL2 mode as opposed to ADSL2+.

[burakkucat]

When Burakkucat was discussing this with me - I should let him speak for himself - if I recall correctly, . . .

I can't recall!    But your recollection seems to be in the right area.

[ejs]

I think it is unlikely that somehow filtering off the top half of the ADSL2+ DS frequency range would somehow reduce noise on the remaining frequencies. There will be very little or no signal being transmitted on those frequencies on such long lines. There wouldn't be anything there to filter off.

Did they ever get fixed?

No. I think it's the ones with the TSTC vendor code that are the oldest and worst. Since they were the earliest ones installed, there is almost certainly some better technology available in those areas (LLU ADSL, FTTC). The IFTN ones auto switch between ADSL2 and ADSL2+ depending on whether any of the higher ADSL2+ tones end up being used or not, and even then, I don't think it makes much difference to the speeds attained. The newest BDCM ones don't even bother to auto switch, it makes little difference.

[PhilipD]

Hi Weaver

I think what you are really asking for is a custom made modem for your line to eek a bit more speed out of it whilst adding to it's reliability.   

Such a modem would be possible to commission, but you would find it was cheaper to have fibre installed or a leased line.

You can do no more than you have already done, and that is try a selection of modems and see which works best, even then it's a trade off, go for one with a bit more sync speed but less reliable and more prone to resync's or have less overall speed for something more reliable.  In many cases you can change the parameters to achieve this yourself without changing the hardware (SNR adjustment).

How much does it make any difference to you really with the small gains to be had, it's still a slow internet speed?  On your line it seems to me you would struggle streaming most things and something like 4K streaming would be impossible regardless of how well the modem performed.

"You can't make a silk purse out of a sows ear".

Other options, is it feesable to move to somewhere better connected?  Could you get a Wi-Fi point to point link from someone nearer to the exchange or FTTC cabinet for faster speeds.  What about bonding and have a second line installed to double your speeds?  Can you petition to bring FTTC to your village?

Regards

Phil

[RealAleMadrid]

@PhilipD, it may come as a shock to you but Weaver has got 3 bonded ADSL2+ lines giving him around 7Mbps total download speed, he is a very long way from the exchange!

[Dray]

Would satellite give more bandwidth?

[PhilipD]

Hi

@PhilipD, it may come as a shock to you but Weaver has got 3 bonded ADSL2+ lines giving him around 7Mbps total download speed, he is a very long way from the exchange!

In that case I would think looking for a dream modem is just clutching at straws, they've done all they can.

Not a cheap option but moving house is probably the only way to get faster speeds, or move to satellite, or maybe 4G with an external aerial might be possible, certainly now 800MHz is being used with 4G giving it extended range, there was only an article this morning about that Ispreview.

Regards

Phil

[Dray]

@PhilipD I'm quite sure moving house isn't a solution for the OP