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]

[horseman]

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@Sephiroth wrote:

For what my opinion is worth, a subjective view in this case is not invalid.

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Thanks - Too many of us it's worth a lot and so is any opinion irrespective of technical aptitude but still depends whether the OP is willing to "objectively" pursue with further diagnostics/effort?  Clearly I failed to give a balanced post so edited to attempt some "balance"....  😉

[dusktilldawn6]

Quick question I'm on the old firmware still 9111.6v im a new customer since 3rd may 2018 ,im on the 350 virgin package not an upgrade ,how do i get the new firmware thanks

[imzrex]

You need to factory reset the hub for them to push the new firmware to the hub

[dusktilldawn6]

Done that on previous hub and faulty hub showed software failed download or install under log,and engineer replaced faulty hub ,and have hard reset current hub 3,i signed up for 350 new connection not upgrade and  i see upgraded people get it instantly ,do i just wait, or request it or any thing i can do ,any input welcome thanks

[mercuryin]

For me these spikes are still a big problem. The problem is just fixed partially.

[nad223]

Software version

: 9.1.116.603

[Datalink]

@mercuryin, looks like you have packet loss from the second hop all the way to your selected target. Assuming that you have the modem running in router mode, or, the modem running in modem mode with a follow on router, the second hop is the CMTS. The 10.166.192.1 address is unusual as it falls within the private addres range, but, if that is what Virgin Media is using for the CMTS address, ok, it is what it is. Use that CMTS address as the ping target, not bbc.co.uk. For the purposes of detecting ping spikes from a Puma 6 modem, you don't have to go any further than the CMTS. In fact, if you do, that will usually mask the issue and result in a final plot that looks better than it really is.

So, for the present time, use 10.166.192.1. Drop the ping interval by overwriting the default time in the interval window down to 0.1 or 0.05 seconds or possibly further if you prefer. Usually the response time to the CMTS varies between 0.008 to 0.013 seconds, give or take a few milli-seconds. Drop the ping plot time down to 60 seconds. Right click on the plot and select 60 seconds. That should easily show if you still have issues with ICMP ping spikes that are attributable to the modem. Look for packet loss as well. Its possible for Pingplotter to generate false packet loss indications for the CMTS hop. To confirm whether or not you are actually seeing packet loss, run a command line ping and let that run for a few hours: ping -t 10.166.192.1

Use Control^C to bail out of the ping test and look at the results for any packet loss. If there is no packet loss in the ping test, then for some reason, in your particular case Pingplotter is generating false packet loss indications. Disregard any packet loss indications from hop two if that is the case.

If you don't see any ping spikes as the plot is rolling along, then the ping spikes that you see in your current plot are not attributable to the modem. If your modem is running the newer firmware version that would make sense.

Note that Pingplotter uses data averaging but doesn't advertise that fact. With low ping intervals you end up with a large amount of ping data. As you go up in plot time scales, from 60 seconds to 5 min, 10 min, 24 hours, etc, you are compressing more data into a fixed horizontal size display. Pingplotter has chosen to average the data for the number of data points which lie within a horizontal pixel or pixel range instead of preserving the low and high data points. As you go up in time plots that data averaging makes the plot look pretty good, even if you have high latency points in the data, so, that forces you to use the 60 second and perhaps 5 minute display to see the high latency points on the plot.

Pingplotter does display more than one plot. If you click or double click on the hop #2 IP address, that will bring up a second plot, stacked vertically on the display. That will allow you to compare the 2nd and final hop for latency spikes. If they are generated by the modem, you will usually see a one to one latency spike correspondence between the two plots. If you don't have that, then the latency spikes at the target are not caused by the modem.

One setting that is worth changing is to display the MAX return time in the text data. Your max plot times and max text data don't match. I assume that's due to the fact that the MAX time column is not displayed. Right click on the title bar for the columns, select MAX to display the maximum times and drag that column to the right so that it sits beside the MIN column. With that column displayed, you can see the maximum response times across all hops and easily determine if ping spikes from the modem is still an issue.

If you happen to be running a BQM as well, stop the BQM and set the modem so that it does not respond to WAN pings while you're running a Pingplotter test.

I'd be interested in seeing another post, using the CMTS as the target instead of bbc.co.uk, just to see what the end result looks like.

Hope this helps.

[cje85]

It's not possible to ping the addresses starting with 10 that VM uses for the CMTS.

My first hop (after router) is:

10.250.64.1 (10.250.64.1) 14.126 ms 14.561 ms 14.851 ms

But pinging it does not work:

PING 10.250.64.1 (10.250.64.1): 56 data bytes

--- 10.250.64.1 ping statistics ---
5 packets transmitted, 0 packets received, 100% packet loss

[Datalink]

Very interesting.  So it shows up in the pingplotter output, but you can't ping the CMTS with a command line ping?  In that case, ping the next hop IP address.  That's not entirely ideal, but it does work for the purposes of detecting high latency returns thru the modem. 

[Sephiroth]

Just to explain about the 10.xx address.

When the modem last initialised, it was a DHCP client to the CMTS and was allocated the 10.xx IP address as a client of the CMTS. Just to square the circle, the modem, acting then as a DHCP server to the router, binds with the router on 192.168.100.20 (usually) and sets up the gateway and WAN IP address.

There is no path from a router's client to the 10.xx address which is only visible to the modem.