VDSL limited to 60mbps during daytime

Forums › Spark New Zealand (including Skinny and BigPipe) › VDSL limited to 60mbps during daytime

eldite

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#261936 23-Dec-2019 15:24

Our community of around 130 houses finally received Fibre to our cabinet and an upgrade to VDSL about 6 months ago. Prior to that we had ADSL1, 6mbps shared over 58 users. So it's a major upgrade!

I'm lucky in that my VDSL syncs at 122Mbps down. However unless it's between midnight to 6am, speed tests just jump to 60Mbps and sit there for the duration of the test.

After midnight, speeds jump to 96Mbps and sit at that for the duration of the test.

There is absolutely no question that is it being limited by either Chorus or Skinny during daytime hours. The behavior is consistent and reproducible.

I really don't care, 60Mbps is fine, but I'm interested if anyone else has seen this, or knows what's going on?

I'd love to see more transparency around these policies.

Also, wondering if anyone attained over 100Mbps on VDSL before? or if it's not possible? The spec for my Annex says max 100, but it's syncing in excess of that.

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#2380502 23-Dec-2019 15:44

its possibly to go all the way up to about 130mbps with VDSL.

Handle9

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#2380539 23-Dec-2019 17:39

Chorus or Skinny won't be limiting your connection. It will be a physical limitations either caused by back haul limitations or more likely cross talk.

Talkiet

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#2380550 23-Dec-2019 17:47

It's worth pointing this sticky (which is in the Spark forum admittedly)..

https://www.geekzone.co.nz/forums.asp?forumid=39&topicid=171109

It applies to Skinny and Bigpipe fixed BB as well.

Cheers - N

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cyril7

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#2380628 23-Dec-2019 19:22

Hi, have multiple customers on VDSL connections syncing over 100Mb/s, this is quite normal. I also have a couple of modems that sit in the same room as the Chorus ISAM with 10m max of jumper wire between the ISAM and modem, they sync around 130Mb/s with around 30Mb/s up.

As Neil (Talkiet) says Spark do not limit any connection in any way, and Chorus continuously monitor uplinks from cabinets for saturation and upgrade to eliminate congestion, so my guess is its more likely increased traffic in the local loop phone cabling taking a hit as users start streaming during prime time. Ths is where the VDSL connections between the cabinet and house start to have impacted performance.

But honestly, you get 60Mb/s during peak hour, is there more you need?, you do realise that 60Mb/s is waaay more than enough to successfully stream multiple HD or even 4K services plus not impact on any browsing

Cyril

eldite

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#2382316 28-Dec-2019 22:35

This is an example over a couple of days. You can see it's 60Mbps all the time, then it isn't. Times in UTC.

In my opinion it's unquestionably being limited. Congestion doesn't work like this and it can't be physical limitations because it's only certain times of day.

I guess no one else here has seen this, and the only problem I have with it is that it means that it isn't faster than my friends fibre like it ideally would be :)

Talkiet

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#2382320 28-Dec-2019 22:43

Skinny isn't doing any rate limiting on any fixed BB connections. If I can be any clearer, please let me know how.

Cheers - N

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#2382321 28-Dec-2019 22:46

You should be very happy with 60Mbps after putting up with ADSL1

raytaylor

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#2382329 29-Dec-2019 00:02

Crosstalk will affect DSL connections - multiple neighbors causing interference as the signals travel down the copper pairs next to each other in the trunk cable going down the road.

Some DSLAMs have some fancy noise cancellation which helps lower the effects and push higher speeds over longer distances when crosstalk causes problems. This is called "Vectoring"

Each VDSL connection has a CIR base rate which chorus guarantees. If the CIR (committed information rate) is not met, it is then considered a fault.
With the old ADSL it was 64kbps average over a 15 minute period (someone else can confirm)

With VDSL, it is still quite low - i think it might still be the same as ADSL, except that when capacity is available, it will go faster.

So if there are speed variances to your ISPs speed test server, it could be
- DSL tail slowing down due to crosstalk or other interference
- Backhaul fiber between the cabinet and the isp becoming congested (though chorus now over provision this in most areas)
- An issue at the ISP end

However 60mbits is more than the 2.6mbits required for HD netflix so its all good.

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yitz

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#2382332 29-Dec-2019 00:42

Do Spark/Skinny/Bigpipe still use xDSL port line rate data passed on from Chorus to do some sort of traffic policing at their BNGs? I recall at one stage Bigpipe offered some fancy prioritisation functionality through their app. On Spark Retail connections they also did something to improve good throughput??

Also that slight difference in latency is interesting, I assume you are testing to the same server. I recall when I used Spark personally the connection would stop passing traffic for a few seconds at the same time most (every?) early evening and at the same time there would be a slight bump in latency, I put it down to them load balancing paths within their core network. I don't recall there being any association with connection performance in terms of throughput/speed, but it was only a ADSL2+ connection.

As for why it is capping out at 95 Mbps would that be because you have equipment that is only capable of 100 Mbps Ethernet or do you have a gigabit LAN.

toejam316

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#2382334 29-Dec-2019 04:57

eldite:

This is an example over a couple of days. You can see it's 60Mbps all the time, then it isn't. Times in UTC.

In my opinion it's unquestionably being limited. Congestion doesn't work like this and it can't be physical limitations because it's only certain times of day.

I guess no one else here has seen this, and the only problem I have with it is that it means that it isn't faster than my friends fibre like it ideally would be :)

One thing I'm noticing is your latency is dropping too, pretty consistently. Have you had a squizz at your modem stats to see what if anything is changing between these periods?

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#2382340 29-Dec-2019 08:12

Hey folks. There are a few comments above to the effect of "why are you complaing? 60 is good enough".

The OP says "I really don't care, 60Mbps is fine, but I'm interested if anyone else has seen this, or knows what's going on? "

I am not reading the post as a complaint - just a query about a curious connection issue.

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#2382341 29-Dec-2019 08:15

your results dont exactly line up to being limited during the day. 23rd at 7am is 57mbps, the the following day at 6am its 95mbps. it doesnt seem consistent, more like its resynced at a lower speed. check the connection log.

the latency change to me seems like something else is happening, because it it was rate limited the latency shouldnt change.

can you provide more info? modem stats for the slower and faster times?

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#2382346 29-Dec-2019 08:41

Talkiet:

Skinny isn't doing any rate limiting on any fixed BB connections. If I can be any clearer, please let me know how.

Just to reiterate this, @Talkiet knows the answer to this. There is no rate limiting going on.

As others have already noted, there is a correlation between increased latency and decreased throughput, but only on the downstream. Given upstream remains unaffected, I'd suggest that the common issue of upstream saturation due to cloud services is unlikely the culprit here. From the brief numbers you have provided, it looks to change behaviour about once per day. This is consistent with DLM resyncing the line, and changing to a different profile. I suggest looking at the modem you are using, ensure that firmware is current, and monitor the VDSL line stats over several days; specifically sync rate, noise margin and line profile. If your modem has a log, check for line sync drops.

Post those line stats here if you need help interpreting them.

sbiddle

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#2382353 29-Dec-2019 08:58

As others have indicated speedtest results only show a part of the picture.

Sync rate is what is critical here, and based on the very limited information the OP has shown so far my best guess would would be that ddDLM is dynamically changing this which is also why the latency is increasing.

yitz

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#2382420 29-Dec-2019 12:28

Jase2985:

your results dont exactly line up to being limited during the day. 23rd at 7am is 57mbps, the the following day at 6am its 95mbps. it doesnt seem consistent, more like its resynced at a lower speed. check the connection log.

Even accounting for UTC+13 just shows that conditions changed early evening on the 24th.

23/12 2.29p limited
24/12 10.46a limited
23/12 8.12p limited
24/12 1.26p limited
24/12 2.15p limited
24/12 3.10p limited
24/12 7.28p full speed
24/12 10.46p full speed

I would say points toward ddDLM and sync rates.

Would be good if Chorus provided a public API to query port stats now they are always collecting data but I assume it still have to be done through ISP helpdesk.

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