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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

qpop
On our wavelength

My letter:

 

Hi Tom

 

I am a recent customer of Virgin, moving to your network on 15th March. The purchasing and installation process all went relatively smoothly. I opted for your 200mbps connection as I do a lot of latency-sensitive online gaming, video streaming, and workplace VPN usage, and believed this package would be a meaningful upgrade from the 50mbps BT fibre I moved from.

 

However, immediately following installation I noticed I was getting significant spikes in latency, resulting in unstable connections on VPN, and poor gaming/streaming performance.

 

I started investigating this issue, using Think Broadband’s “Broadband quality monitor”. I attach a picture of the latest output, demonstrating the problem.

 

On further investigation, I found out that I was not alone, and there is a 500+ post thread on Virgin’s own Community Support forum discussing the issue in much greater technical detail than I am capable of. Thread available here: https://community.virginmedia.com/t5/Gaming-Support/Hub-3-Compal-CH7465-LG-TG2492LG-and-CGNV4-Latenc...

 

To summarise my understanding of the issue: This is a flaw in the chipset within the Superhub 3 modem, which is exacerbated by higher speeds. This flaw has been acknowledged by the manufacturer who has released various firmware iterations to fix the problem, but none have solved it. It boils down to faulty hardware and is currently subject to a class action lawsuit in the US.

 

The great news for me and others similarly affected is that a ready solution exists – using the older Superhub 2AC instead.

 

This has resulted in four phonecalls to your support desk:

 

On the first call I was told that a 2AC could not be sent out.

 

On the second I was told that the support teams no longer have the ability to specifically order a 2AC, but a note would be added and they would try to get me one sent. I received a second Superhub 3.

 

On the third I was told there may be an alternative way to get a 2AC out to me. This never materialised.

 

The fourth I was told, under no circumstances would a 2AC be sent to me, and that as long as I was getting acceptable sync speeds, Virgin Media did not consider there to be a problem.

 

I disagree with the fourth caller – high latency means that  I cannot do what I purchased the contract to do. It is not a one-off issue or a local network fault, but a known hardware fault with a modem that you give me no alternative but to use.

 

I would really appreciate your help in resolving this problem, as follows:

  • To provide me with equipment that will allow me to use the network as intended (A Superhub 2AC).
  • To acknowledge the known issue with the Puma chipset and provide an update to your customers on the likely wait until a fix.
  • To consider training your technical support representatives on this problem and provide a path to customers receiving the short-term fix without the significant friction I (and others as per the forum thread) have experienced.

 

If Virgin Media are unable to provide me with any of the above, I would very much appreciate a reason why and the plausible next steps.

 

Thanks for your time

qpop
On our wavelength

I have also flagged this thread with Money Saving Expert via Twitter. Who else can we point this issue out to try and get things moving?

rio_w
Dialled in

I called Virgin Media Customer Support, 5 minutes on the phone having explained to them that I'm having latency issues with the Hub 3 they confirmed, I should receive the Hub 2ac within a few days. On my way to being a happy virgin media customer, I couldn't believe how easy and quick they complied with my wishes.

Wait and see what turns up before you get too excited.

My replacement is out for delivery today, but I was also told by Customer Retentions that despite them putting notes to the effect that I need a SH2(ac) there is still the possibility that it will be another Hub 3.0 sent out by the people in the warehouse. {sigh}

And in the meantime I can watch the pretty patterns as my latency issues seem to be on a 6 hour cycle:

b11824220199f7a5f912e31e88a0cc51-26-04-2017

 

 

 

_____________________________________________

Hub 3.0, 350Mb BB; TV 360, Maxit TV, Phone

wotusaw
Superfast

I feel sorry for the VM staff. Technically they are just not trained to deal with this. Who would be. I can't understand most of it even slightly.

Now that DOSPUMA6GATE has started it's going to get much worse.

Management needs to acknowledge the problem/communicate with it's customers on what action is being undertaken. Yes, right.Smiley Very Happy

My latency tests are worse than yours and don't seem to be on any cycle at all. Just bad all the time.

Virgin are supplying me with an excellent download/upload. No problems there. However, as can be seen the inherent problems of the 'puma 6 chipset' laugh at the wonderful connection speed. 

Think in my case the 'A'  'bufferbloat' is keeping me from being totally humiliated in 'Titanfall 2'.

Included my charts/tests. You can see the weird contradictions. I believe I'm stuck with the 24 downstream/2 upstream channels which apparently doesn't help the latency.

puma 6 tri test 2604.jpg

 

 

You're very luck rio_w.

I've rung them three times and been told every time getting a replacement Hub2 was impossible.  I even had a nice chat with second line and they explained they just don't have any left, so it's more can't rather than won't.

qpop
On our wavelength

I have also contacted the Register's newsdesk with a link to this thread, who have just responded to say they'll look into it.

to anyone stumbling on this forum thread right now...  the latest discovery from DSL forums is that your internet connection (through the SH3 VM modem) is completely vulnerable to a low bandwidth DOS attack. i.e. your connection will drop dead if attacked by script kiddies.

I believe you can thank Intel for their absolutely terrific puma 6 chip-set included in the SH3...!!

I have just run some tests to my own modem and the results are appalling.

I won't give much in the way of technical details in an open forum as this is a long way from being fixed ( if that's even possible)

What I can say is that even on the limited number of channels that VM utilise, its possible to kill a connection with WAY less bandwidth than is being reported.

This attack is trivial to execute. Even a modest DDoS attack could take down hundreds of thousands of Virgin customers.

Still expect zero response from Virgin, but should they want any more detail I'm happy to discuss over PM.

Puma 6 Test with almost no bandwidth:

puma6.jpg 


@qpop wrote:

I have also flagged this thread with Money Saving Expert via Twitter. Who else can we point this issue out to try and get things moving?


Nobody can speed up the fix, it will take intel as long as it takes them to resolve it, assuming they can even fully resolve it with a firmware update, its entirely possible that its just bad design and cannot be completely fixed, publicity can't fix a bad design, as the hub2's have been phased out they are likely either out of stock or at a very low stock level, getting one would be a lottery in itself, i'm dreading the day my hub2 kicks the bucket because i'll be stuck with a hub3 which won't be fun, my only hope is the hub 4 is out before that happens because at this point thats likely to be our best bet