Faster broadband through bonding
Does doubling up your DSL really work?
Sex, money and chocolate are supposed to be the three things you can't have too much of. There is a fourth: Bandwidth. One way to have twice as much bandwidth is to have two lines, but getting them to work together isn't simple. Sharedband, a spin-off from BT Martlesham, is poised to launch a UK service to do just this.
An ugly truth about broadband is that the speed you get falls far short of what's advertised. But while complaining might change the ISPs advertising, it won't change the physics. In the past, networks have relied on everyone being so happy with the upgrade that it didn’t matter what the true speed actually was. If you went from dial-up with a rated 56kbps (in reality usually closer to 30kbps) to 512kbps (in reality 300kbps) and "always on", it was such an improvement it seemed churlish to complain. So the claim "up to 24Mb/s" really means 15Mb/s on a good day. Five means three, and three means one.
But you can do something about the speed. I know of one person who chose his house by drawing 1km circles around telephone exchanges on a map, and only looking at properties inside the circles where he knew he'd get the fastest connections. And I know another person who pulled out of a deal to move house when he found that the new place didn't support the 100Mb/s broadband he enjoyed in his previous house. He said that moving from regular broadband to 100Mb/s was as big a difference as going from dial-up to ADSL.
You know that the speed isn't going to be what's promised, and that uploading will be even slower. And that you’ll want more of it
So what's a speed-hungry surfer to do?
Well, if you are dedicated then you can tweak the performance. Try disabling the ring circuit on the phone line, make sure you have filters in all the right places, and run a diagnostic tool like DMT. It's the bandwidth equivalent of blueprinting an engine, but even with a huge amount of this tweaking, my friend with the circles on his map only gets 21Mb/s out of his 24Mb/s line.
Then there's bonding. Using a second DSL line is a bit like fitting a second engine - but it has similar transmission problems. Getting the speed to one computer has been a mess. If you had two lines, two routers and two network cards you couldn't aggregate the speed. You'd get greater reliability - if one line went down you had the other - but you couldn’t download files faster.
The solution adopted by Sharedband is not to aggregate the channels in the PC but in the router. Sharedband has code which runs in the best selling ADSL routers which gives one router control over the other. This manages the biggest problem, which is skew between the two lines. There are limitations: there's a limit to the speed of lines which can be aggregated, and the processors in the routers might not be able cope with two 24Mb/s lines. For those applications Sharedband is investigating a PC-based solution.
At a demonstration in their Ipswich office - with the poetic postcode of IP4 - the start-up showed downloads of between one and a half and close to two times the single line speed. It was also fault-tolerant: one router could be unplugged and although of course the speed dropped correspondingly, the download continued. The resilience is improved if you use two ISPs, ideally through two different exchanges, although this might be hard to arrange. There is no need to have both lines through the same ISP - indeed Sharedband recommend that you don't.
Sharedband is concentrating on wholesale deals and already has reseller agreements with BT Wholesale and Netgear.
Trial installations have shown that it's the increase in upload speed which is often most attractive. An installation at Mallory Park race circuit for the British Superbike Grand Prix allowed the attending journalists to upload stories and pictures at three times the speed they had the previous year. As a robust, high-speed solution Sharedband is concentrating on the small business market, but it might also be just the thing for the dedicated surfer, or enthusiastic home user.
Sharedband says it will go live in the next few weeks - the company's FAQ is here. ®
@several of you
Here's some info on how it works, straight from the mouth of someone who worked there for a while last year:
"Would be great if you could use cable on one router and ADSL on the other" - I don't think there's any technical obstacle to this. I don't know what's available in product form though.
"The problems start *because* you have two different WAN (ADSL) connections, and therefore two different IP addresses" - Sharedband handles this by giving you a completely new IP address from a pool that they own themselves. The two separate Internet-visible IP addresses of your two ADSL lines aren't used to communicate with the sites you visit. As a result your publically visible IP address stays the same no matter which of the bonded lines your packets happened to travel through.
"Several UK ADSL ISPs support this", "Unless this is something other than multilink PPP" - It's not multilink PPP, it works at the IP level. The bit that's new is the ability to bond together DSL lines _from different providers_ which as far as I know isn't possible with multilink PPP.
"all packets first have to travel to a 3rd party host before being reassembled and going on to their final destination" - correct, this is exactly how it works. The latency impact is unnoticably small (this isn't speculation, I measured it) because the 3rd party hosts are located in ISP data centres with fast, low-latency connections to high speed backbone pipes. The "single point of failure" issue here is addressed by integration with BGP; if any of the "3rd party hosts" goes down, another can take over by re-routing the affected block of customer IP addresses.
I'm considering buying a Draytek 2820
1 x ADSL WAN port, and 1 x Ethernet WAN port for either cable or into another ADSL router.
Anyone had experience with this?
Beware what you ask for
We recently moved to an ISP who's giving us a "2mb" circuit (two bonded T1s). All is fine except if you have one misbehaving circuit.
We had one of our T1s bouncing frequently for a short while. It basically killed all of our network traffic because individual sessions would have to go through a TCP timeout. We would have been better off if that bad T1 had just dropped completely and stayed down.
We ended up unplugging the bouncing circuit until the Telco fixed the problem.