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FTTC Bonding

Posted: Wed Nov 21, 2012 7:09 pm
by dominicbatty
I'm after any pointers with the following if anyone fancies a challenge ... download bandwidth is roughly specified for information but you'll get the gist.

I've tried an RB493G and a VMWARE based RouterOS installation with the following and found the same results.

2x FTTC lines, 150m from cabinet.
ISP is Andrews and Arnold.
Both lines according to BT man will sync way in advance of the 80/20 they are currently limited to.

A laptop plugged directly into an individual line will speedtest at close to 80/20, I've tested this on both lines.

2x Laptops plugged into a line each and tested at the same time as separate links also speedtest at close to 80/20 each so they can clearly run at full rate at the same time without affecting each other.

Plugging the Openreach FTTC modems into either my RB493G or RouterOS on VMWARE with download from A&A routed down to me on either line individually will give full downstream bandwidth as expected of 80. This is fine for either line I choose to route down.

Bonding the upstream lines using route-marking in RouterOS gives close to expected bonded performance of upstream bandwidth, about 38 ish.

Now for the confusion ....

If I select to have A&A send me packets down alternate lines it all goes horribly wrong. You would expect roughly double the download (less the obvious overhead) but I end up lucky to receive anything over 20 from a potential of 160 available.

The router receiving the traffic has a very simplistic configuration with eveything I can find turned off so I don't think it is doing anything odd and the CPU does not seem to top out or anything like that.

I'm aware of other users, using RouterOS and A&A to achieve the same thing so you could argue it's not FTTC, it's not A&A and it's not BT but it's definitely something as I'm paying for an 80mbps line I'm barely using.

A&A were going to send me a Firebrick to prove the lines work fine on the basis if I plug a Firebrick into my two lines at this end and get 160/40 (ish) or at least not (20/40) then clearly it's a RouterOS issue but at the moment this does not appear like it's going to happen.

I'm after any advice or help anyone might be able to offer?

Many thanks, Dominic.

Re: FTTC Bonding

Posted: Wed Nov 21, 2012 10:32 pm
by CelticComms
A diagram and relevant config info would help. How are the 2 modems hooked in to the router. What are the relevant Ip settings on those interfaces?

Re: FTTC Bonding

Posted: Thu Nov 22, 2012 11:46 am
by dominicbatty
Hi Celticcomms,

RouterOS with three ethernet interfaces at 1500 MTU, 2x interfaces linked into the BT Openreach provided FTTC modems using ethernet cables, the other linked into the LAN. 2x PPPoE connections at 1492 connected via the BT modems to A&A (ISP).

Single IP block (/29) at A&A selected to route down both FTTC lines with equal measure.

Outgoing traffic to A&A is mangled and a routing-mark applied to alternate packets to route up alternate lines hence we round robin the outgoing packets up the A&A lines.

Masquerade outgoing traffic to the correct outgoing IP address.

Cheers, Dominic.

Re: FTTC Bonding

Posted: Mon Nov 26, 2012 12:21 am
by CelticComms
If you use Torch do you see packets coming down both links back to you? If the packets coming down via one link were failing and causing retries that might get you to the throughput numbers you mentioned.

Re: FTTC Bonding

Posted: Wed Nov 28, 2012 7:25 pm
by dominicbatty
Hi, yes I see packets coming down both links but I csannot tell if either are causing retries, I know if the download lines work individually then they are fine, I'm not sure if there is something wrong with the download logic at the A&A end but then if that was the case why are my lines not working and others with the same configuration are working fine.