70Mbps speed on "perfect" FTTC setup

We moved into our new place this time last year and the BT engineer fitted not only a new socket but also new wire from the pole. He told us the local exchange is literally a street away.

Three weeks ago we got Infinity 2 from BT and speedtests like Ookla and BT Wholesale are showing 70Mbps, on a Mac connected via Ethernet straight to the HomeHub. The HomeHub itself says the connection is 74.75 Mbps.

I'm not about to complain to BT but, all things considered, this doesn't seem as fast as it could be (and apologies to anybody who thinks I don't know I'm born).

Is this speed good or bad, and what can be done to improve it? I've already optimised the MTU to 1488, via ping tests.

EDIT: I'm guessing you might want to see this: https://imgur.com/a39lQbi
This is based on my address and not phone number, which comes up as not being in the database.

Edited by deleted (Wed 09-Mar-16 16:44:42)

In reply to a post by johnnny:

He told us the local exchange is literally a street away.

FTTC speeds are affected by distance to cabinet not distance to the exchange and the speed drops off more rapidly.

A line with 750m of cable to the exchange will run at full speed or near as damn it with ADSL2+.

If the same line has a cabinet that is 200m of cable from the exchange then the same line will be 500m of cable from the cabinet and will run significantly below full speed. Probably around 70Mb/s.

Edited by Andrue (Wed 09-Mar-16 16:47:27)

I think the cabinet is at the end of our street, which is around 200m away.

In reply to a post by johnnny:

I think the cabinet is at the end of our street, which is around 200m away.

Does your cable go the short route? Is it possible that it meanders a bit making the length between property and cabinet longer than it appears while having a shorter run to the exchange?

How recently did your cab go live? Another possibility here is that you're suffering from crosstalk. That's where other lines using that cabinet are interfering with yours. If it's a new cabinet that's less likely but on a cabinet that's been taking orders for several months the likelihood increases. And crosstalk being the nasty thing it is you could just be unlucky in getting interference from the only other person currently on that cabinet.

Edited by Andrue (Wed 09-Mar-16 16:50:22)

You're connected right near the upper end of the estimation. Nothing to be concerned about. You might find the speed does drop over time as more people take up the service. As long as you're above the lower estimation, there's no fault.

What type is your cabinet - Huawei or ECI?

What modem are you using? Type A or Type B ?

Your connection to the cabinet may go all the way up the other side of the street and back down to you on your side.

MTU should be 1500, the homehub properly supports pppoe with mini jumbo frames.

70mbps throughput on a 74.75 mbit sync looks about right to me.

BT actually recommend 1492 on a Business Infinity service. I cannot see any reason why that would not be the same on the residential equivalent.

MTU should always be 1500 so i've been told by talktalk but maybe it varies per service

Anyways

74.75 = 71Mbps real world max

If you had a perfect line you would sync around 80Mbps.

1492 is standard where PPPoE is involved as PPPoE has an 8 byte overhead. For many routers, this is all they will support, because it's PPPoE.

BTs kit does support mini jumbo frames of 1508, meaning that after the PPPoE overhead, you are left with a 1500 byte MTU. The issue is that your kit at home/the office needs to support this.

1492 is therefore a better blanket recommendation as it is more compatible. But a BT Homehub will work fine at 1500.

AAISP talk about this in their KB here : http://aa.net.uk/kb-broadband-mtu.html

You can ping from a client using various packet sizes to confirm what your MTU can be set to.

ping -f -l 1492 ip_adress

Perhaps I spoke too soon � I was getting 72Mbps last night consistently, on a sync of 75Mbps.

The MTU does seem to make a difference although I haven't exhaustively tested this. With 1488 I seem to eke out around 0.5Mbps faster speeds compared to either 1492 or 1500.

It looks like you really need more speed too....

In reply to a post by epyon:

If you had a perfect line you would sync around 80Mbps.

It used to be shown in the modem as 79999 back when I had such a line. Don't know if that's still the case but after six months my connection speed had dropped to 68Mb/s. Thankfully it's not dropped any further over the last couple of years.

It looks like you really need more speed too....

Well on the homehub i think it just shows in mbps

but yes on my router it says 79999/20000 or something like that i've not checked in a long while.