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Author Topic: Hybrid Speed Boost at no extra cost, BT business broadband ADSL only.  (Read 454 times)

meritez

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https://newsroom.bt.com/bt-cranks-up-broadband-speeds-for-thousands-of-small-businesses-on-copper-lines/

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Hybrid Speed Boost is included at no extra cost for new BT business broadband customers taking ADSL broadband plans.

And

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Average upload speeds can be uplifted to 10Mbps

Sounds impressive, anyone aware of the cost?

I'm wondering if people like Weaver would benefit from moving one line to this service, apparently it only benefits TCP services as it uses mptcp for the higher speeds.
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Alex Atkin UK

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I'm kinda surprised AAISP do not already offer something like this.
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meritez

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I'm kinda surprised AAISP do not already offer something like this.

They do but in a pay as you use billing method per MB:
Quote
1.75p +VAT per MB upload/download
https://www.aa.net.uk/voice-and-mobile/
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Alex Atkin UK

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They offer 4G data sure, but I was referring to bonding DSL and 4G.  I'm not aware of them doing that.
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Weaver

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You can, as far as I can see, already bond 4G and wireful lines with AA and I thought about this but as far as I know thereís no one doing it. I suspect it would be a disaster because of the large difference in latency between 4G and wireful lines, just confusing TCP by causing out-of-sequence packet ordering. I suspect there might be problems with mismatched MTUs too.

In AAís control panel for linesí behaviour (clueless.aa.net.uk) you can just define a bonded set of lines by ticking a tick box next to each line you want to include in the bonded set, and the UI makes no distinction between 3G/4G Ďlinesí and wireful Ďrealí lines, so if you tick a mixture of different link types then thatís all you need to do. I have several Ďlinesí that are actually 4G SIMs. Most are not part of any bonded groups; these are for iPadsí 4G interfaces. One Ďlineí though is my Firebrick 3G USB dongle failover interface and that is set up with the appropriate clueless.aa.net.uk tickbox choices to make it a failover link associated with my main bonded set of DSL links, and AAís servers just know a rule about switching to the chosen failover link to the Firebrick if every single one of the DSL links goes down. The Ďonly if all downí rule prevents me from racking up a huge massive 3G/4G data bill.

You could simply have a 4G link live all the time within a bonded set with wired links, racking up a huge bill unless you used a cheap 4G service and a tunnel, so more MTU problems. That would do failover anyway because if any links go down the traffic just always gets redirected to the other links in the bonded set, with no concept of failover even being needed.

Iíve been thinking about it for some time, but since reliability is more important than speed then I will take some convincing that such a setup wonít just muck things up.

My Apple devices already can use MPTCP. Appleís Siri voice command interface races the upstream of 4G and wifi to get the userís audio up to the analysis servers or database severs or whatever they are (donít know how much of the processing is local and how much remote). I presume Apple has exposed MPTCP in the o/s rather than just making it confined to Siri - that would be madness - so I would hope any application can use it.
« Last Edit: May 27, 2022, 01:56:43 AM by Weaver »
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jelv

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I suspect there might be problems with mismatched MTUs too.

Wouldn't automatically using the smallest MTU from all the lines being used take care of that?
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kitz

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Hybrid Speed Boost from BT is underpinned by MultiPath TCP (MPTCP) technology from Tessares. MultiPath TCP is an enhancement to TCP, and enables the efficient, selective combining of existing network assets. It takes TCP based traffic and is able to split the traffic over multiple paths (such as fixed and mobile networks) to deliver increased speeds to customers.  More info about Tessares Hybrid access.

https://www.youtube.com/watch?v=R8RHr8mz_KM&t=115s
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Weaver

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@jelv - indeed, thatís the kind of thing that Iím already doing now with my failover to 3G; Iím already limiting IPv6 IP MTU to 1408 bytes all the time in order to deal with the limited MTU of the 3G USB dongle NIC that I have for failover. The IP MTU of my DSL lines is 1500, PPP MTU 1508. Iíve left the IPv4 MTU at 1500 bytes so there will probably be some fragmentation during failover and that may or may not be a really bad thing. Depends on how well fragments are handled.

I donít know how many systems misbehave when using IPv4 if the far end of some path theyíre accessing canít get an IPv4 MTU of 1500. I hope there wonít be too many, especially given that so many links are restricted to an IP MTU of 1492.

I always made it a priority to get an IPv4 MTU of 1500, but I donít know how important that is in practice, if at all. Being over-cautious, maybe.

I just wish that all links and NICs had an actual IP MTU and L2 MTU of something more like 1600 bytes, then all machines could use an IP MTU of 1500 bytes with no problem, even if thereís tunnel overhead, say also PPPoE overhead, and possible other underlying L2 overhead. BT seems to do the right thing, with a large L2 MTU; they can of course handle things such as PPPoE 1508 byte PDUs. I presume the answer is in a BT SIN somewhere.
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noddy

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Re: Hybrid Speed Boost at no extra cost, BT business broadband ADSL only.
« Reply #8 on: August 02, 2022, 07:33:00 PM »

https://newsroom.bt.com/bt-cranks-up-broadband-speeds-for-thousands-of-small-businesses-on-copper-lines/

And

Sounds impressive, anyone aware of the cost?

I'm wondering if people like Weaver would benefit from moving one line to this service, apparently it only benefits TCP services as it uses mptcp for the higher speeds.
BT have been contacting me about going over to this according to them it's going to cost me approx £ 20 a month more and I'll lose my BT mobile deal so think I'll give it a miss
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Weaver

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Re: Hybrid Speed Boost at no extra cost, BT business broadband ADSL only.
« Reply #9 on: August 02, 2022, 08:51:17 PM »

Ironic that BT is trying to sell people MPTCP just as TCP is finally, thank god, being phased out in favour of the modern transport QUIC. ;)  And we are told QUIC traffic is already at 25% - is that right? (Disclosure: I hated TCP the moment I first ever saw it 30 years ago.) MPTCP does a great job for Apple SIRI though, to be fair. Given that the designers of QUIC have made such a large effort in doing attachment point mobility already, allowing a change of source address on the fly, then I wonder if they already have some of the pieces ready that are needed to do bonding properly. Iím not sure though, as they need to flow control and congestion control both in place separately over each sub-L4 per-path sub-connection or what on earth one is supposed to call it. And you need overall flow control to control the application processes to stop senders overwhelming the ingress to the links and overwhelming a slow receiver process.
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Chrysalis

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Re: Hybrid Speed Boost at no extra cost, BT business broadband ADSL only.
« Reply #10 on: August 03, 2022, 05:42:12 PM »

@jelv - indeed, thatís the kind of thing that Iím already doing now with my failover to 3G; Iím already limiting IPv6 IP MTU to 1408 bytes all the time in order to deal with the limited MTU of the 3G USB dongle NIC that I have for failover. The IP MTU of my DSL lines is 1500, PPP MTU 1508. Iíve left the IPv4 MTU at 1500 bytes so there will probably be some fragmentation during failover and that may or may not be a really bad thing. Depends on how well fragments are handled.

I donít know how many systems misbehave when using IPv4 if the far end of some path theyíre accessing canít get an IPv4 MTU of 1500. I hope there wonít be too many, especially given that so many links are restricted to an IP MTU of 1492.

I always made it a priority to get an IPv4 MTU of 1500, but I donít know how important that is in practice, if at all. Being over-cautious, maybe.

I just wish that all links and NICs had an actual IP MTU and L2 MTU of something more like 1600 bytes, then all machines could use an IP MTU of 1500 bytes with no problem, even if thereís tunnel overhead, say also PPPoE overhead, and possible other underlying L2 overhead. BT seems to do the right thing, with a large L2 MTU; they can of course handle things such as PPPoE 1508 byte PDUs. I presume the answer is in a BT SIN somewhere.

I had a weird issue on my line that uses baby jumbo frames to hit a 1500 byte MTU.

I noticed on two endpoints I was getting stalling issues. One of them was FreeBSD distribution servers, a simple http fetch would fail at a very high rate by just sitting there for ages with a very high timeout.  Occasionally (sub 5%) it would establish the connection and download.
Another was a server I manage myself, this one because I controlled both endpoints I fiddled with lots of thinks like the new TCP based MSS negotiation, and orphan timeout.  On this one the issue was downloads would always start normally, proceed at normal speed, but when the file was almost complete it would stall until the ftp client times out and then resume with no problems and carry on, I found raising the orphan timeout made it recover by itself after a few seconds.  So would then stall, but then carry on after 5-10 seconds and finish with no timeout in the client.

I eventually discovered dropping my MTU to 1492 PPPoE standard fixed both endpoints, yet on most endpoints I could see 1500 byte MTU was working fine, and also if I downloaded from FreeBSD on a native 1500 byte MTU connection was also fine so a very strange issue.

I ended up for now adding my own custom patch to pfsense so when it generates the rules, it sets a lower outgoing MSS using a scrub mss clamp rule for end points I define in a variable, of which I added all the FreeBSD dist servers and my problematic server.  I of course would rather just ditch PPP and have native 1500 bytes.  I did the patch because when I dropped it to 1492 globally I was noticing longer waits on web browsing, confirmed via dev tools, I assume maybe due to MSS negotiation.
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