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]

[cje85]

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@shanematthews wrote:

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i might actually get paid, as i said, VM broadband IS FTTC (Fibre to the cabinet) which is a fact, like it or not i didn't actually say anything wrong, all i did was correct your incorrect use of terminology which is pretty important when you're advising people on a tech forum, i never said it wasn't better, i just told you that you're actually talking about DOCSIS vs xDSL both of which operate FTTC and FTTP

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VM actually isn't FTTC. The fibre goes to a local node, which is connected by coaxial to all the street cabinets it serves, which are connected by coaxial to your home. the closest 'FTT_' for VM is FTTN (Fibre to the node/neighbourhood). 

[boltedenergy]

"there isn't a massive market for the modems themselves and you would likely end up paying massively over the odds for another compliant device that was likely also puma based which would actually not fix the issue and infact leave you even more out of pocket for the same level of service,"

That's is a highly subjective opinion of yours Shane which you should not disguise as being factual. as follows:

1) There's no market for modems because you are not allowed to use your own modem according to VM (the only major cable operator - monopoly?), if you are allowed to the market would then exist. This is a basic economic principles which you are choosing to ignore.

2) Cable modems would be and roughly are of similar pricing to ADSL modems so you won't need to pay "massively over the odds".

3) Anyone who has visited this thread or knows of this particular issue would DEFINITELY make an effort to buy a non puma device

4) Buying the non puma device would SOLVE their issue in this context of dodgy latency.

5) With the right chipset modem, you would get to the expected level of service you are already paying for but not receiving! (SH3 doesn't cut it)

[RockerSBM]

Hi All

My graph with the Hub3

cheers

shaun

[wotusaw]

shadowofdeth69@

"Is it weird for a BQM graph to seem to be getting "better" like in my link? Seems to be clearing up a little."

Same thing happening to mine. No one here seems to be interested in this strangeness. Before the 'update' I didn't have these dips in latency..and they are increasing in size.

[ShadowOfDeth69]

New firmware?

[ShadowOfDeth69]

Last time I checked my firmware I was it ended with V at the end. I can't see any significant packet loss to suggest a stealthy update... Fingers crossed it continues to improve.

[wotusaw]

shadowofdeth69@

"New firmware?"

Yes... I have the new firmware. The dips in the latency started after it was applied. They run on a cycle. Getting larger then returning to a smaller length but with each cycle the dips get slightly larger. Odd. 

I'd check your firmware again. It does look like you have the update.

[ShadowOfDeth69]

Although I can't explain what seems like a slight improvement I doubt it was the update. Unless they can push it without the Hub needing a reboot?

[nallar]

This could be related to the sampling rate of the thinkbroadband graphs and some process on the hub occuring at intervals.

It's like the interference pattern of two waves with frequencies which are not quite the same.



https://www.wolframalpha.com/input/?i=sin(x)+-+sin(x*1.1),+sin(x),+sin(x*1.1)+from+0+to+32pi

If TBB pings every second exactly and the hub 3 has a latency spike every 1.1 seconds you would see a pattern a bit like this.

It could also not be anything like that at all and this entire post is a load of nonsense. 😄

[ShadowOfDeth69]

Maybe. But my BQM has been running nearly a week now and for my personal graph that's the biggest change I've seen. I'm not a though so you might be right!