FTTC jitter (some pings over 900ms)

[robpalmer]

I have FTTC Fibre 2 which is rated at 50mbit download, 10mbit upload (the maximum offered by BT to my house). Bandwidth is fine. Latency is mostly fine. The problem is jitter - the median ping time is fine, but sometime it goes very high - up to 900ms.

The consequence is that I look terrible on video calls for work.

An engineer was sent out who confirmed the line is fine. The Smart Hub 2 has been replaced. I am using ethernet cable direct into the router - it's not a WiFi issue.

Sync speed is good at 9.7mbps upload. I get 9mbit upload speeds.

I have compared the ping times to my 4g phone on BT Mobile. The mobile connection always has ping times less than 100ms according to... 

https://speed.cloudflare.com/

What is the cure for jitter? 

[robpalmer]

 

 

 

[robpalmer]

 

 

[robpalmer]

 

[robpalmer · Accepted solution]

Finally figured it out - the source of the jitter was the Smart Hub 2.  The solution was to switch back to my Home Hub 5.

BT sent me a replacement Smart Hub 2 and this also suffered from jitter just like the first Smart Hub 2 did. So I believe this is a flaw in the firmware which is common to both units.

Both Smart Hubs 2s suffer from latencies spikes of 500-1000ms approximately one per second. So the median ping time is good (15ms) but the jitter is terrible. Google Meet outgoing video quality is particularly sensitive to this type of latency.

The old Home Hub 5 shows a solid 15ms nearly all the time. Occasionally it spikes at 30ms. Video quality on Google Meet is now excellent.

I found this latency tester to be very useful when diagnosing this issue: https://test.webrtc.org/?test_filter=Network%20latency