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Hub 3 / Compal CH7465-LG (TG2492LG) and CGNV4 Latency Cause

Datalink
Up to speed

Good Day Ladies and Gentlemen,

Greetings from the other side of the pond, so to speak.  Over the last few weeks I've been perusing various user forums across North America and Europe for issues related to Intel Puma 6 modem latency.  Of those forums, your Hub 3 stands out as yet another Puma 6 based modem where users see continuous latency no matter what site is used or what online game is played. Considering all of the problems that are on the go, the following information should be of interest to all Hub 3, Compal CH7465-LG and Hitron CGNV4 modem users.  There is much more to post regarding this, so this is a start, to alert VM users as to the real cause of the latency and hopefully engage the VM engineering staff, via the forum staff, with Arris.  I am surprised to see that there has been no mention on this board of users from other ISPs who are suffering the exact same issues with their modems, so, this may come as a surprise to some, and possibly old news to others.

So, the short story ........

The Hub 3 / Compal CH7465-LG (TG2492LG) & Hiton CGNV4 modems are Intel Puma 6 / 6 Media Gateway (MG) based modems.  These modems exhibit high latency to the modem and high latency thru the modem.  The latency affects all IPV4 and IPV6 protocols, so it will be seen on every internet application and game.  The basic cause is the processing of the data packets thru a CPU software based process instead of thru the hardware processor / accelerator.  It appears that a higher priority task runs periodically, causing the packet processing to halt, and then resume.  This is observed as latency in applications and in ping tests to the modem and beyond.  For the last several weeks, Hitron, along with Intel and Rogers Communications in Canada have been addressing the latency issue within the Hitron CGNxxx series modems.  To date, only the IPV4 ICMP latency has been resolved.  Although this is only one protocol, it does show that a Puma 6MG modem is capable of using the hardware processor / accelerator with good results.  Currently Rogers is waiting for further firmware updates from Hitron which should include an expanded list of resolved protocol latency issues.  For Arris modems, "Netdog" an Arris engineer indicated last week that Arris was onboard to address the issue for the Arris SB6190 modem.  That should be considered as good news for any Arris modem (read Hub 3) user as Arris should be able to port those changes over to other Puma 6/6MG modems fairly quickly.  This is not a trivial exercise and will probably take several weeks to accomplish.  Note that there is no guarantee at this point that it is possible to shift all packet processing to the hardware processor / accelerator without suffering from any packet loss side effects.  Time will tell if all of the technical issues can be resolved with the current hardware included in the Puma 6/6MG chipset.  Last night, Netdog loaded beta firmware on selected test modems on the Comcast Communications network.  As this was only done last night, it's too soon to tell what this version resolves and if it was successful or not.  Netdog has contacts with staff at Comcast, Rogers, Charter and Cox Communications to fan out beta versions and modifications for testing.  I'd say its time to add Virgin Media and/or Liberty Global to that group as well.

Recent activity:

Approx three weeks ago a DSLReports user, xymox1 started a thread where he reported high latency to an Arris SB6190 and illustrated that with numerous MultiPing plots.  This is the same latency that I and other users with Rogers communications have been dealing with for months so it came as no surprise.  As well as reporting via that thread, xymox1 took it upon himself to email several staff members at Arris, Intel, Cablelabs and others.  The result of that campaign was Netdog's announcement, last week, that Arris was fully engaged at resolving the issue.  That has led to last nights release of beta firmware, although as I indicated its too early to determine what the beta firmware resolves, if anything.


The original thread that xymox1 started is here:

https://www.dslreports.com/forum/r31079834-ALL-SB6190-is-a-terrible-modem-Intel-Puma-6-MaxLinear-mis...


Yesterday, DSLReports issued a news story covering the thread:

https://www.dslreports.com/shownews/The-Arris-SB6190-Modem-Puma-6-Chipset-Have-Some-Major-Issues-138...


Today, Arris responded:

https://www.dslreports.com/shownews/Arris-Tells-us-Its-Working-With-Intel-on-SB6190-Puma6-Problems-1...


That response was also picked by Multichannel.com

http://www.multichannel.com/news/distribution/intel-arris-working-firmware-fix-sb6190-modem/409379

This is more news likely to appear in the next few days as additional tech and news staff pick up on this issue.


Hub 3 observations:

Like many others using a Puma 6/6MG modem, Hub 3 users are experiencing latency when they ping the modem, or ping a target outside of the home, game online or use low latency applications.  The common misconception is that this is Buffer Bloat. It's not. Its most likely a case of the packet processing stopping while the CPU processes a higher priority task.  The packet processing is done via the CPU no matter what mode the modem is operating in, modem mode or router mode and no matter what IPV4 or IPV6 protocol is used.  Normally, the latency is just that, latency.  The exception are UDP packets. In this case there is latency and packet loss.  The result of that is delayed and failed DNS lookups, and poor game performance for games that use UDP for player/server comms or player/player comms.


Can this be fixed?

So far, it appears that the answer is yes.  Rogers Communications issued beta firmware to a small group of test modems in October.  This version shifted the IPV4 ICMP processing from the CPU to the hardware processor / accelerator, resulting in greatly improved performance in ping latency.  At the present time we are waiting for the next version firmware which should shift other protocols over to the hardware processor / accelerator.  That can be seen in the following post:

http://communityforums.rogers.com/t5/forums/forumtopicpage/board-id/Getting_connected/message-id/369...

The details and results of last nights beta release to the Comcast group have yet to be seen.

At this point there is enough reading to keep most staff and users busy.  My intention is to post some of the history leading up to this point and instructions on how to detect the latency and packet loss.  This is not thru the use of a BQM.  I had hoped to post this all at once but events are moving much faster than I had thought they would.  For now this should suffice to get the ball rolling.

Below is a link to a post with a couple of HrPing plots from my 32 channel modem to the connected CMTS.  This shows the latency that is observed and reflects what others have posted in this forum using Pingplotter and HrPing.

https://www.dslreports.com/forum/r31106550-

HrPing is one of the freebie applications that can be used to monitor the latency to and thru the modem. 

Pingplots with Pingplotter which show the latency from my modem to the CMTS can be found in the first two to three rows of my online image library at Rogers Communications, located below.  They are essentially what the BQM would look like if you were able to zoom into the plot to the point where you could see the individual ping spikes.  Those ping spikes are common to Puma 6 and Puma 6MG modems.

http://communityforums.rogers.com/t5/media/gallerypage/user-id/829158

 

 

 [MOD EDIT: Subject heading changed to assist community]

4,478 REPLIES 4,478


@Luke_113 wrote:
More than a little, your graph is superbly clean for a Virgin line. you're on the newer firmware right?
https://www.thinkbroadband.com/broadband/monitoring/quality/share/7230b3a8dca0229a6fcab8d7a9aef17efc...



Yes, contacted VM to upgrade to Vivid 350 yesterday as I was missing the 20Mbps upload I had previously (all computers in the house backup offsite to Backblaze, and I also have a VPN server running here so I can remote back into my home network), and when the new config file was pushed it upgraded me at the same time - as can be seen from the following network log entries:

2018-04-19 23:32:37.00	notice	SW Download INIT - Via Config file
2018-04-19 23:41:14.00	notice	SW download Successful - Via Config file

I'm still on 20 bonded channels though, as I'm pretty sure I'm the only house in the street connected, and uptake of VM isn't massive, as we also have full whack 80/20 FTTC available throughout the estate. It was a project lightning infill as the top end of the estate, and most estates around us already had VM, so could just be I'm on a super empty segment!

Loui79
On our wavelength

@philjohn wrote:

Having a decent router, with decent firmware, behind also helps a little I believe.


Possibly for the internal connection to the outside world and maybe to reduce the loading on the hub but I don't think it makes a huge difference to the BQM. I've had 3 different routers behind my hub at various times, one of which was a business grade multiwan router, and there's very little difference in them. 

The biggest difference I get on mine is when I go from modem mode to router mode on the hub.. I get less yellow, the same top end for the blue but a higher base ping. So where the green area is pretty flat in modem mode, it follows the blue in router mode. I've got a hunch that my current problem is a dodgy hub (more dodgy than the usual) but so far they've never tried changing it out. The last engineer saying it was all "within spec"....

 

My results look much more like your BT line.

I am verging on believeing they have actually improved matters above ICMP only.

Vivid 350 - Modem Mode - 9.1.116.603

iperf1.PNGiperf2.PNG

I certainly think there are improvements beyond ICMP, whether there are still performance issues that are less obvious remains to be seen.

There are so many knobs and levers that can be tweaked on Linux running on a modern SoC - for instance, the R7800 that I use has had some issues with odd latency spikes on the stock firmware AND OpenWRT - however - the latest development version (which I'm running) has had some patches applied that have stopped them altogether.

Still, should never have been an issue in the first place, but happy I'm on the new firmware and it seems to alleviate my issues. I'll be doing a lot of video conferencing next week (I went into the office today, of all days!) so I'll have a better idea then.

Just wanted to chime in on my experiences more recently.

I've always said that I haven't noticed any latency drops, but I did perform tests before and I was getting the odd large spike between myself and the modem, via my R7800. Also my BQM used to be massive spikes, same as everyone, I just wasn't seeing the effect in games. Now I have the new firmware (well, have had for about a month or more) and my BQM shows like this:

Also worth mentioning I'm a single user, with 2 devices at most at any one time, on 350/20, with a brand new line installed. Not sure how many of the people at my neighbourhood are on Virgin either.  

Boygroucho
On our wavelength

So after 17.5 years with Ntl/Virgin, I finally called it a day.

I have 25 days days left comparing my 38mb Sky (Now Tv) Fibre service to my 100mb Virgin Cable.

So far its a solid 37mb and great latency from Sky Fibre. Noting that we high high Virgin utilisation on our estate, which definitely affects Virgins performance.

Anyway...for this thread I've adding my data point (SH3 on old firmware):

sh3.png

 

sh2.png

 

Nowtv.png

 

nowspeed.png

 

puma6.png

 

speed2.png

 

 

 

 

 

 


@philjohn wrote:

@tonycv51 wrote:

These recent graphs are making me optimistic - just need the new firmware myself now. Queue multiple fruitless factory resets and power re-cycles this weekend....Smiley Sad


I kept doing this, but looking at the network log on my hub, the upgrade was triggered by the switch to Vivid 350 - what tier are you on? It could be that they're only trying it out with 350 customers as they will usually be on more bonded channels, and hence highlight the problem more.


Tried a re-cycle and factory reset earlier  - still on 116V.  200 is highest VM package in my area/postcode

Oh and I'm on 24 channels - so if one of the VM mods can get me prioritised for the new firmware I'd be extremely grateful ! 


@tonycv51 wrote:

Oh and I'm on 24 channels - so if one of the VM mods can get me prioritised for the new firmware I'd be extremely grateful ! 


^^^ Good luck with that I have been on 24 downstream channels for months and also have possibly one of the worst connections to the Virgin Network and they STILL have not given me ANY test firmware just look at the state of my BQM.

My area is no longer taking on new customers and max speeds are capped at 200/20 even though I can cross over the road and get 350/20 due to me being on the fringe of two CMTS areas.


@tommey wrote:

@tonycv51 wrote:

Oh and I'm on 24 channels - so if one of the VM mods can get me prioritised for the new firmware I'd be extremely grateful ! 


^^^ Good luck with that I have been on 24 downstream channels for months and also have possibly one of the worst connections to the Virgin Network and they STILL have not given me ANY test firmware just look at the state of my BQM.

My area is no longer taking on new customers and max speeds are capped at 200/20 even though I can cross over the road and get 350/20 due to me being on the fringe of two CMTS areas.


My BQM is not as bad as yours....e.g. last night 2 PS4s were being used and watched films on Now TV & Netflix with only a slight bump in the blue as you can see.  Used to be worse but luckily there were some network improvements earlier this year

82dbc3153fc1c76c0ba31a92edf4eb1fc5efd408.png