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]

[Sephiroth]

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@philjohnwrote:

There's no reason it shouldn't be able to support more with that processor, heck, a 1.5Ghz dual core ARM processor in my Netgear R7800 can handle over 900Mbps between the LAN and WAN with NAT, and that's not even using the 2 packet processing cores it also has as OpenWRT/LEDE doesn't support hardware NAT.

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... but the Hub 3 has a lame Intel Atom 4110, single core, 1.2GHz.  And there's more hitting that than a NATted router.  The entire VM node/segment data on the tuned channels hits that Puma 6, which has to discard those that do not match the particular session's BPI+ key. 

[Sephiroth]

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@Andrew-Gwrote:

Hi Seph - reading some of that linked discussion, there's a series of comments that suggest that the Puma 6 actually works a treat up to 60 Mbps, and then falls off a cliff in performance terms, on account of the puny CPU.  Have you seen any evidence of better performance of the Hub 3 when used at 50-60 Mbps?

Why I'm asking is that I really want reliable low latency, bandwidth is only a nice to have.  I'd happily take a 50-60 Mbps connection if that fixed the Hub 3 performance problems.  And I'd save a few quid a month.  

Cheers

A

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Yes - it is a fascinating discussion that goes into the guts of the problem.  On instinct, one could buy the 60 meg argument because the data arrival rate at the Hub 3 would be 1/5 that of a 300 meg connection.  It's the Puma 6 that remains the same, so it would be under less strain, one could say.

I got two takeaways from that discussion:

1.  The data arrival rate is a major factor;

2.  24 downstream channels makes the Puma 6 very busy.

[Guybrush85]

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@Sephirothwrote:

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@Andrew-Gwrote:

Hi Seph - reading some of that linked discussion, there's a series of comments that suggest that the Puma 6 actually works a treat up to 60 Mbps, and then falls off a cliff in performance terms, on account of the puny CPU.  Have you seen any evidence of better performance of the Hub 3 when used at 50-60 Mbps?

Why I'm asking is that I really want reliable low latency, bandwidth is only a nice to have.  I'd happily take a 50-60 Mbps connection if that fixed the Hub 3 performance problems.  And I'd save a few quid a month.  

Cheers

A

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Yes - it is a fascinating discussion that goes into the guts of the problem.  On instinct, one could buy the 60 meg argument because the data arrival rate at the Hub 3 would be 1/5 that of a 300 meg connection.  It's the Puma 6 that remains the same, so it would be under less strain, one could say.

I got two takeaways from that discussion:

1.  The data arrival rate is a major factor;

2.  24 downstream channels makes the Puma 6 very busy.

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The one thing that seems to be almost across the board is that more channels = increase in observed latency. Unless you're called WildWayz... which is then where the whole noise/load on the CMTS comes into play. 

[MS8]

Hello everyone. 

I have literally just got installed about an hour ago and I'd like to give an update. 

I have tested the Hub 3 (without the trial update) and I cannot see any hint of Lag... It is really smooth, as initially the latency was my main concern. But no, everything is running very smoothly.. 

In in area 22 if that helps 

[AneesHasan]

http://www.dslreports.com/tools/puma6

try this test and see what result you get

[MS8]

https://imgur.com/a/K9ffS

Here 

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@AneesHasanwrote:

http://www.dslreports.com/tools/puma6

try this test and see what result you get

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[Guybrush85]

Since you can see the result, you already know it has the issue, so take with that what you will.

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@MS8wrote:

https://imgur.com/a/K9ffS

Here 

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@AneesHasanwrote:

http://www.dslreports.com/tools/puma6

try this test and see what result you get

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[MS8]

I know it has a problem, but I cannot see any signs of it during gaming

[ShadowOfDeth69]

The imgur link does show something is wrong. What games are you currently playing?

[Andrew-G]

MS8: "I have tested the Hub 3 (without the trial update) and I cannot see any hint of Lag... It is really smooth, as initially the latency was my main concern. But no, everything is running very smoothly.. "

That's because the problems of the Hub 3 don't manifest as "lag", by which I mean significant and sustained high latency (that's the technical term for "ping").  

The problems are frequent regular but absolutely momentary peaks in latency, and what they show up as is things like being shot by players facing the wrong way, a higher miss rate on your own shots, much high lose rates on "corner confrontations", and even being shot by a player who should be visible but isn't (yet, for you).  It's a subtle degradation that you may struggle to actually see, but it is inherent in the Puma 6 chipset that underpowers the Hub 3.

My son is an avid gamer and sees no problem.  I'm also a gamer, and I can see the problem all too clearly.  It depends upon how observant and demanding the user is.  I'm paying many hundred of pounds a year, and I expect better - particularly when VM swapped out a much better Superhub 2 for one of their crapbag Hub 3s, and I found my gaming materially worse.