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]

[ShadowOfDeth69]

@supernovi No. It absolutely has not been confirmed at all. Just a few people parroting what other people say without knowing 100% for sure.

[RidingTheFlow]

I can confirm it has not been confirmed 🙂

And will not be until trials are over. As Phil rightfully pointed out, trialists are under NDA so you won't see any public reports of truly cutting-edge firmware performance from 100% genuine trialist - only from people who have no actual clue (or on older update which were (semi)public)

[Datalink]

CM700 and SB6190 firmwares rolling out:

http://www.dslreports.com/forum/r31903462-CM700-and-SB6190-firmwares-rolling-out

Now the interesting part starts. Has Intel managed to find a permanent solution that addresses both latency and DOS problems, or are the Puma 6 modems a permanent write-off?

http://www.dslreports.com/forum/r31903596-

Cox is rolling out new firmware 9.1.103AA36 for SB6190:

(Link as included above:)

http://www.dslreports.com/forum/r31903462-CM700-and-SB6190-firmwares-rolling-out

Also updating Puma 6 based Netgear CM700

[deasmi]

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@Sephiroth

wrote:

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@Demostrike

wrote:

I have the new firmware and my graph looks better. What tests on UDP and tcp would you like done?

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Just to remind - the firmware update is a sticking plaster to make the BQM look good.  It doesn't actually fix the underlying problem.  Ping responses are diverted to another processor (I'm told the hardware accelerator) and the improvement in Puma 6 processing capacity is not given when not doing these pings.

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That still remains to be seen/proven, please don't remind people as if it's factual.

My BQM is much better with the new firmware but so is my dslreports test, which some take as a real manifestation of the issue.

Here is mine currently, which looks nothing like the old firmware which had red every 2 seconds. Note this is not a clean single PC modem mode test, it's normally totally green when I do that.

I've also use the the ping plotter test seen on the dslreports forums a lot, which is UDP port 53 not icmp, and it's clean as well. No packet loss, some one off latency spikes.

So if this is a sticking plaster it's also fixed DNS traffic loss and the DSL reports test. That's not impossible, but it's not as simple as offloading ICMP from the CPU.

Until someone has full patch information or a repeatable test that shows the issue is still there (or not) with the new firmware your comments remain speculation I'm afraid, which helps no one really.

 Firmware: 9.1.116.603  And I'm not a trialist, so am quite able to discuss, signed nothing.

[Datalink]

You can't use Pingplotter as an accurate measurement for UDP response times and losses.  Pingplotter uses UDP outbound to a co-operating server, which would respond with a UDP ping if it was set to do so.  Unfortunately, unless you have your own server available, the response from every other server, including Pingplotter's own server is an ICMP destination port unreachable response, so, UDP outbound, ICMP inbound.  After you see the ICMP response times from an ICMP two-way test, you can generally surmise what the UDP response time might be, but that's not entirely accurate given the outbound and inbound protocol mismatch. 

[deasmi]

I understand that, but folks over at dslreports have horror show pingplotter output with puma 6 modems. May well have changed for the same reason as BQM as you say.

The actual dslreports modem test however I believed is understood to demonstrate the issue with UDP packets.

[philjohn]

You can try iperf3 - there are public servers available and it shows you packet loss AND jitter, e.g.

iperf3 -c ping.online.net -p 5207 -u -R

for downstream

iperf3 -c ping.online.net -p 5207 -u

for upstream

You can also up the time the test runs for with the -t option (e.g. -t 120 for 2 minutes of testing)

Bare in mind the public servers can only run one test total at a time, so you may get a message that the server is busy, you can retry with -p 5200 all the way through -p 5209

[SonarUK]

its been a while since the Trails Team last posted.

http://community.virginmedia.com/t5/Gaming-Support/Hub-3-Compal-CH7465-LG-TG2492LG-and-CGNV4-Latency...

[francisuk1989]

Guessing are next modems are going to be on of the hitron CGNxx model is funny how the business users didnt get the hub 3 but got the Hub 2/1 in the past

85.236.100.68 is one of the multiplay game server's if useful what should hit tclo > linx route giving 8 hops

[Andrew-G]

"Guessing are next modems are going to be on of the hitron CGNxx model"

Aren't those all DOCSIS 3.1 Puma 6 efforts?  It seems very unlikely there will be a new DOCSIS 3.0 hub issued - if VM/Liberty Global had planned to do that then they needed to get it into circulation 18 months ago, and they would have needed to choose a non Puma 6 model.  If some component part has to be changed due to an old part going out of production then it is remotely possible (but still IMHO unlikely) that there might be a Hub 3.1.

VM know full well the Hub 3 is a dog, and that it is barely fit for purpose.  But they didn't care when specifying it, they don't care now, and they won't care when they eventually choose a 3.1 hub.