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

[Datalink]

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]

[Shelke]

Looks more like someone is saturating their upstream, probably a lot of torrenting going on.

[plazma]

This is not exactly the same thing, for example one single steam download at full rate may not impact the issue as much as 200+ active connections, even if they are using much smaller bandwidth, its a lot of line chatter, which will impact things in different ways...

Im not saying thats the case here, im guessing, but from what ive seen already it would explain why its amplified for some and not others.

Think of it like dominos, the puma 6 chipset hickups and it effects all the dominos in the que, if there are not many in line the effect is less.

@Shelke, nope and nope, watching the traffic graph in pfsense, i can see my bandwidth out is frequently below 1.5Mbits per second... and so is my incoming bandwidth... So im saturating my 10-12Mbit upload with less than 1.5Mbit, even if i hit the threshold in peak times i should still be able to do 4.2Mbps. I think your assessment to be wrong.

[LiveWire]

@plazma

Interesting to see we both use x64 pfsense boxes and get near identical graphs - might have to do some digging around with that.

[plazma]

@LiveWire, was fine with the sh2, there are other people here who have posted similar looking graphs who i assume are not using pf-sense, between game traffic, ssh sessions, email, web, ftp, dropbox, voice traffic, etc etc i think the issue is due to number of sockets in use impacting the issue. Do you have traffic shaping turned on, as this will also impact the issue a little, but that what it suppose to do... but then the puma 6 hickuping every few seconds and bumping back delay north of 120ms just gets magnified.

[LiveWire]

@plamza

Ironically I do use traffic shaping - may have to turn that off and see if that makes a difference.

You're probably right regarding the number of sockets open not helping!

[wotusaw]

Livewire...Plazma...

I have done a lot of these Broadband graphs here...

http://thenitwitts.enjin.com/forum/m/28206608/viewthread/30648466-virgin-very-near-to-fixing-hub3-pu...

I use none of the stuff youv'e listed. Mine has always been an almost solid block of yellow. The new patch gave me a sort of wave effect I think maybe.

However I turn my modem off every day for an hour or so to cool it down so the wave may be something to do with that rather than the patch. I turn HUB3 off because a Virgin tech suggested doing that to someone else when he complained.

I'm on 300/20 gamer/whatever.

I'm not unhappy with Virgin. The enormous speed they pump out I think helps overcome this problem a tad. However I did play someone using Sky the other day in Titanfall 2 and he seemed invincible...maybe he's just better than me...but frankly find that inconceivable.

[boltedenergy]

---

@plazma wrote:

This is not exactly the same thing, for example one single steam download at full rate may not impact the issue as much as 200+ active connections, even if they are using much smaller bandwidth, its a lot of line chatter, which will impact things in different ways...

Im not saying thats the case here, im guessing, but from what ive seen already it would explain why its amplified for some and not others.

Think of it like dominos, the puma 6 chipset hickups and it effects all the dominos in the que, if there are not many in line the effect is less.

@Shelke, nope and nope, watching the traffic graph in pfsense, i can see my bandwidth out is frequently below 1.5Mbits per second... and so is my incoming bandwidth... So im saturating my 10-12Mbit upload with less than 1.5Mbit, even if i hit the threshold in peak times i should still be able to do 4.2Mbps. I think your assessment to be wrong.

---

There's definitely some truth in this, having a lot more open TCP/UDP connections appears (in my case) to make the latency problems much more apparent and it also eventually can leave the router in a 'hungover' state. When I say hungover state, I have observed slower opening of web sites and stream buffering issues. Completing a full reboot of the router is required for it to start behaving like 'normal' with the expected ping spikes and laggy response on time sensitive applications.

[PhilHornby]

---

@cje85 wrote:

Do you have something running automatically each hour to cause those spikes?

---

@Does seem to be Samknows - I switched it off @ about midday, and they've gone. I wonder if Samknows is also responsible for the 27GB per day of downloaded data?...(that being about 26GB more than I can account for!)

[Andrew-G]

I'm with WildWayz on this, I don't think that really nasty BQM from plazma is down to a bit of busy use of the router.  The BQM I posted had two gamers running different games all evening, another family member doing general browsing and downloading on a Chromebook and another streaming video for a couple of hours (plus four connected phones, a Chromecast, and machines doing periodic sync-ins with OneDrive and Google).  

What's more, if plazma's BQM was cause by other people using the connection, were they REALLY all hammering the connection continuously between midnight and 6 am, AND at a similar level ALL day and ALL evening?  I think there's more to it than the Hub 3, much as I loathe the device.

[Datalink]

The bottom line with the BQM or any other plot, UDP, ICMP, or TCP/IP, is that the lower the ping interval, the greater the number of latency spikes you will see on the plot.  As you drop the ping interval from a few seconds down to 1 second and then down to something like 10 to 20 ms, the plot goes from a hit and miss situation where the ping output or return occasionally coincides with the 1.9 second task timing, to one where you will see every latency spike as there is either an outgoing ping or response occurring during every task run time (every 1.9 seconds).  Take that plot and compress 24 hours of data into something like a BQM sized plot, and you have a solid mass of color that buries all of the individual latency spikes.  I don't believe there will be much difference in the plot when you take the modem throughput into consideration.  The 1.9 second task still runs no matter what load is running though the modem, but, if anything, I would suspect that the latency times might be higher due to the amount of data that is buffered while the task runs. Keep in mind that the number of channels also comes into the equation, the higher the downstream channel count, the higher the latency times.  

As a reminder, here is a plot from 2016, with a 32 channel Puma 6 modem.  This would have been done with a 2.5 second ping interval at the time, and with nothing running except for the ICMP ping from the modem to the CMTS and back again.  That's only 1 hour of plot time, so, multiply by 24 hours and then compress the plot so that you see all 24 hours and you end up with a solid mass where the individual ping responses are buried and can't be distinguished. 

http://communityforums.rogers.com/t5/media/gallerypage/user-id/829158/album-id/419/image-id/3685i250...

I suspect that if you were able to time your ping transmission to coincide with the modem task run times, you would end up with a high level response time which would probably be pretty constant.  Its just a question of how high that time would be, 80ms, 150ms, 250ms? That would also depend on the number of downstream channels of course. 

What does a BQM run at in terms of ping interval and is it adjustable?