Packet loss on FTTC - Lantiq vs Broadcom modem chipsets

[g67575]

I've been getting fairly consistent packet loss (1-3% recently) using the last couple of router/ modems that I've used to connect to my FTTC line. Both of these kits have had either Broadcom or Mediatek chipsets.

I have an older router/modem that has a Lantiq chipset, called the Archer VR200. My FTTC street cabinet uses an ECI chipset, which may or may not be relevant... This router has been put away in the loft (probably 1-2 years ago), as tends to happen to most useful things in my household .

Is it worth trying to get hold of it again, to see if it will solve the packet loss issues on my FTTC line?

I've seen some people discuss how different chipsets can affect line stats on FTTC. But I have no idea if this could lead to differences in packet loss also. Link here:
https://forum.kitz.co.uk/index.php?topic=23419.0

P.S. I don't mind if it syncs at a lower downstream rate, I'm more interested in reducing packet loss to a minimum (if this is even possible on most FTTC lines). Even just small amounts of packet loss seem to have quite a large effect on online streaming services like Google Stadia. I think it probably has effected online video calls too.

 

[g67575]

So, in case anyone is curious, I managed to fix the packet loss (retransmission in this case) of my FTTC connection, by limiting the upload speed. Here are my results in Mlab's Speed test:

The Telnet command I used to do this limits the frequency range of the upstream. The command is:

wan vdsl2 set us_tone 0 950

You have to do a modem resync after inputting this command for it to take effect.

This is with a DSL-N16 Router /modem.

If I set the upstream frequency any higher, I get anywhere between 1-10% packet loss.

Also, if UBPO if disabled, this causes the upstream bitrate to increase, which causes packet loss.

Bitswap can also cause packet loss if enabled, but was useful for troubleshooting the connection...

I'm pleased to have finally found a workaround. I might still test the other router, but I suspect packet loss is common on many FTTC lines. Looks like another thing Openreach won't fix

I also tested my connection in Google Stadia and it's working perfectly now, at least at 1080p resolution

 

[g67575]

Anyone else tried doing something like this? Or, do you consider lowering your upstream sync rate to be not worth the significant reduction in packet loss?

 

[Orcvader]

Depends on how big the speed loss is. If it's a tiny loss then I'll take it since packet loss is more frustrating for online gaming.

I swapped my Huawei modem for a Draytek Vigor 130 modem since I'm on an ECI cabinet too, and I found it offered better sync speeds with no packet loss. No idea what chipset it uses but maybe something to look into if you want to try recover the lost speed.

EDIT: Quick Google says the Vigor uses a Lantiq chipset.

 

[g67575]

Thanks for the info. I tried my VR200 router (Lantiq chipset), but the upstream packet loss was often worse and the modem synced at a lower downstream rate.

So, I think the only option on my line is to limit the upstream frequency, as higher frequencies on VDSL2 always have a lower SNR (and therefore, less useful signal is actually received).

I think if vectoring is applied, this problem is avoided upto a certain range but Openreach apparently thought it wasn't worth it.

G.INP might've helped too, according to it's designers, "Broadcom claims that retransmission technology provides up to ten times higher impulse noise resilience and significantly lower residual BER or packet-loss".
Source: https://kitz.co.uk/adsl/retransmission.htm

Unfortunately, according to Kitz the "Lantiq VRX-268 chipset...didn't fully support g.inp". Which is the chipset still used in many FTTC street cabinets.

Embarrassing for Openreach, considering that "G.998.4 - The ITU name for the technology which was standardised & approved in 2010".

Could be anywhere between 2026 and 2029 when many of these lines will be upgraded to 'full fibre' / FTTP by Openreach.

 

[g67575]

Does the ISP you use (for FTTC/VDSL2) actually have any impact on line stats and specific things like packet loss?

I'm on Cuckoo broadband FTTC, they use Talktalk Business as network backhaul apparently.

 

[g67575]

Does anyone know if any routers/modems allow the upstream SNR Margin to be increased? Presumably, that would reduce errors and packet loss also, and I'd probably be able to increase the upstream rate (up from ~1mbps).

It's generally around 6dB for the upstream bands.