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]

[DarkBahamut]

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@Andrew-G wrote:

@ alecgrist

"Now to see how this goes, it's already noticable."

It shouldn't be.  The problems affect Intel Puma 5, 6 and 7 chipsets.  The SH 2ac is by all reports I've seen a Puma 5 device.  Virginmedia have been foisting  garbage on customers since the days before time.

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Yes, the 2ac will be better.

The issue is made worse by having more connected downstream channels, and as the 2ac can only connect to 8 it substantially less affected by the issue. The same is true on the Hub 3. We have graphs of that on 8DS channels too is it's not far of a 2ac in those situations.

[alexgrist]

Regardless of whether it's affected by a similar or the same issue doesn't matter right now if I can reduce it, I have another engineer coming today about my current problem but after trying 2 Superhub 3's the issue was consistently worse compared to the 2ac so I chose to go back to that until VM finish their tral of the update firmware.

Although interestingly like an engineer told me 2 days ago, Superhub 4 should be coming pretty soon because of this problem.

[theoven]

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@alexgrist wrote:

Regardless of whether it's affected by a similar or the same issue doesn't matter right now if I can reduce it, I have another engineer coming today about my current problem but after trying 2 Superhub 3's the issue was consistently worse compared to the 2ac so I chose to go back to that until VM finish their tral of the update firmware.

Although interestingly like an engineer told me 2 days ago, Superhub 4 should be coming pretty soon because of this problem.

---

I hope the hub 4 come before I leave.

Explain the issue upload speed is low, you receive packet fast but send back dealy.

[dasBOT]

The solution is simply .. end any cooperation with Intel and Arris.

Introduce SH4 not based on Intel rubish or allow us to use 3rd party routers.

It is really that simple

[Grumpy101]

I only hope Broadcom can churn out enough chips in the future to support alternative modems.

Intel currently has a massive market share in the cable modem market and for cable companies worldwide to switch en masse to Broadcom may well be problematical.

It honestly wouldn't suprise me if the mythical Hub4 turned out to be a Puma 7.

[ShadowOfDeth69]

I read on the American forum this first came on that the Puma 7 has the same issues as the 6 but uses a faster processor that may mitigate the effects somewhat.

Virgin need to cut this proprietary BS and go the way of some American ISPs and allow the use of personal equipment at least from a pre-approved list of manufacturers. American companies are NOTORIOUS for being anti-consumer yet they allow the use of your own kit.

If we could just follow suit with the Americans on this and maybe legalise weed while we're at it 🙂

[d4v34]

Looks like a problem in the US

https://www.theregister.co.uk/2017/04/11/intel_puma_6_arris/

If VM keep their relationship with Arris, their new cable modem (8200 in the States) uses a Broadcom chip so there's hope that the whole Puma 6 debacle will disappear with the Super Hub 4.

[Andrew-G]

Let's hope that the SH4 (or whatever it will be called) uses Broadcom, but as some others have suggested, Virginmedia/Liberty Global have previous form for snatching defeat from the jaws of victory.  The whole SH3 is a farce, not merely because of the technical faults of Puma 6, but because VM committed to this DOCSIS 3.0 device at the same time that they were making the investment and technical decisions to invest in DOCSIS 3.1 upgrades to the network, and long after the DOCSIS 3.1 standards were agreed in 2013.  As a result they are going to have to replace large numbers of SH3 to make use of DOCSIS 3.1.

As usual, the commercial strategy for 3.1 (as publicly reported) will be another premium product costing a further £10-£15 a month.  Potentially VM hope to use the poor performance of their own crummy hardware to force unhappy SH3 customers to pay more in order to get the new cable modem.  I wouldn't put anything past Virginmedia - a company that milks its customers, provides poor service.  I dislike Virginmedia, I recommend others avoid, and as soon as there's a credible broadband alternative offering 100 Gbps, I shall be off.  Just because VM can do the highest speeds, I simply don't need them, and I think they'll find that selling 500 Mbps is an uphill struggle..

[cje85]

Are Openreach based fibre services (BT/Sky etc) available in your area? They are usually considered better than cable for gaming and other latency sensitive activities, as the DOCSIS platform naturally suffers from more jitter than VDSL.

[Andrew-G]

@cje85

Yep, Openreach FTTC is available, but round here most people are connected to Openreach services in preference to Virginmedia (I can see this from the wifi SSIDs and router brands, via Wifi Analyzer).  As a result, although I'd get a nominal 78 Mbps, there are poor contention ratios, and I doubt I'd get an acceptable speed at peak times - the few speed checker results available for OR connections in the area are not good, with the highest reported test result 45 Mbps..