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]

[Andrew-G]

"This firmware seems to fix the BQM graphs and Puma6 checker, making it appear as though the issue is resolved when it is not. It smacks of deliberate deceit, much like the Volkswagen diesel defeat device."

And just like Volkswagen, Virginmedia experiment on monkeys.  Us, that is.

[stevedh2]

Is there any way to check latency without icmp.

The only ways I've found would require me to setup a remote server, also its a bit late as I wouldn't e able to do a before and after as I have already had the new firmware.

[RidingTheFlow]

Pingplotter allows TCP, and you can use any close-by reasonably fast webserver (TCP port 80) to ping.

For udp "ping" you can use any public close-by and fast DNS server.

[Piers]

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@Andrew-Gwrote:

"This firmware seems to fix the BQM graphs and Puma6 checker, making it appear as though the issue is resolved when it is not. It smacks of deliberate deceit, much like the Volkswagen diesel defeat device."

And just like Volkswagen, Virginmedia experiment on monkeys.  Us, that is.

---

Well, as a US-owned company, what do you expect? Look at what happened to Cadbury, Boots, et al.

[Wam7]

My first thoughts were that they've made a fix so the BQM meter looks more normal but the underlying problem was still there. Though to be fair I've definitely, beyond a shadow of a doubt noticed great improvements in 2 areas.

·  Uploading large files to filehost. Beforehand I would only ever get ~17Mb upload instead of the full 22Mb that I normally can get. Now I get the full 22Mb which it never did in the last year.

·  When the upload was being fully utilised then the internet was very slow and Skype calls would be nearly impossible but now the missus can talk to her sister in Latvia via Skype without her shouting to me "are you uploading something..." and there is now hardly a difference in loading web pages.

The peaks are where I'm uploading something. Before, those upload peaks would saturate the whole of the graph in blue.

So while the new firmware might not fix the intrinsic fault of the Puma6 chipset it does seem to go some way to alleviate some of the issues associated with it.

[Datalink]

@RidingTheFlow wrote:

Pingplotter allows TCP, and you can use any close-by reasonably fast webserver (TCP port 80) to ping.

For udp "ping" you can use any public close-by and fast DNS server.

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Actually that's not totally correct. 

 First problem is TCP/IP.  Pingplotter requires either Npcap or Win10pcap in order to run TCP/IP on Windows 10.  Here's a note on the issue from Pingplotter:

https://www.pingman.com/kb/115

For other Windows versions, Pingplotter indicates the requirement to use Winpcap:

https://www.pingplotter.com/manual/packetoptions.html

Note the requirement to run Pingplotter in Admin mode for the first time when you attempt to run TCP/IP.

 Personal opinion, load Npcap or Win10pcap.  I think I've actually used both with Pingplotter to run TCP/IP.  As I currently run Wireshark for plotting ping/query response instead, I'll usually have one or the other loaded anyway, so I wouldn't have any issues with Pingplotter and TCP/IP if I had decided to use it.  Here's the links for Win10pcap and Npcap:

Win10pcap:  http://www.win10pcap.org/

Npcap:  https://nmap.org/npcap/

When you have that finally set up, change the Pingplotter engine options to run TCP/IP to port 53 of Virgin Media's DNS.  Port 80 might not work.  If so, give Port 53 a try, and then port 7.  if none of those work then try google, using 8.8.8.8 or 8.8.4.4 using port 53.  I just checked the Virgin Media DNS address with all ports and had no success, most likely as I'm outside of the Virgin Media network.  Thats typical when you try to ping an ISP DNS and your not located within that ISP.  Google, using 8.8.8.8 or 8.8.4.4 using port 53 does work.  Ports 80 and 7 don't.  The Virgin Media DNS addresses that I tried are:

Primary DNS: 194.168.4.100

Secondary DNS: 194.168.8.100

@ Next point is UDP.  As @RidingTheFlow puts it, yes you can use a close-by DNS server.  Problem is, you really need a server set up to respond to a UDP ping.  Any other server, including a DNS will usually respond with an ICMP unreachable response.  Pingplotter will actually plot that but will not provide any warning that the outbound ping is UDP and the response is ICMP.  So, if you didn't know this, you would assume that the plot is accurate and true.  Not correct in this case.  

If your interested in plotting a UDP query and response to your DNS, have a look at the following post which is located in the DSLReports forum:

http://www.dslreports.com/forum/r31737637-

That will run a one second interval DNS query to your chosen DNS address, which in this case should be the VM DNS address.  The result is two way UDP traffic.  That instruction plan is only for a one second interval, so, kill the BQM and let this run for a 24 hour period to see if in fact there is any change in the UDP throughput.  As this only runs a one second interval query, you'll need the longer term test to see what the results look like.  I'm working on posting a faster scripted instruction set for ICMP, TCP/IP and UDP, all using Wireshark.  Wireshark plots the min and max values whereas Pingplotter uses data averaging on the plot, causing the plot to flatten all high pings as you move up in plot timeframes from 1 min to 24 hours and beyond.  With multi-hour plots, the data that is plotted looks pretty good as all of the high time responses disappear.  Pingplotter does not indicate the use of data averaging to the user. 

[RidingTheFlow]

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@Wam7wrote:

The peaks are where I'm uploading something. Before, those upload peaks would saturate the whole of the graph in blue.

So while the new firmware might not fix the intrinsic fault of the Puma6 chipset it does seem to go some way to alleviate some of the issues associated with it.

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This sounds more like better QoS/bufferbloat improvement. This is not really related to Puma 6 lag spikes - though if here in new firmware, improvement nonetheless.

Though I personally run my own router with infinitely better QoS than SH could ever hope to pull - therefore I never really cared about VM improving QoS. My BQM graph looks pretty much flat 24/7/365, and you will never see that I was doing several big uploads/downloads this day on the graph:

Lot of advanced customers with own gamer-grade routers and SH in modem mode are in same boat.

[ShadowOfDeth69]

@RidingTheFlow How is your minimum latency so low? My building is only feet from the cabinet but my minimum latency is in the high 20s.

[dasBOT]

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@RidingTheFlowwrote:

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@Wam7wrote:

The peaks are where I'm uploading something. Before, those upload peaks would saturate the whole of the graph in blue.

So while the new firmware might not fix the intrinsic fault of the Puma6 chipset it does seem to go some way to alleviate some of the issues associated with it.

---

This sounds more like better QoS/bufferbloat improvement. This is not really related to Puma 6 lag spikes - though if here in new firmware, improvement nonetheless.

Though I personally run my own router with infinitely better QoS than SH could ever hope to pull - therefore I never really cared about VM improving QoS. My BQM graph looks pretty much flat 24/7/365, and you will never see that I was doing several big uploads/downloads this day on the graph:

Lot of advanced customers with own gamer-grade routers and SH in modem mode are in same boat.

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you are just lucky of being in good area that's it

i'm useing sh3 in modem mode and netgear nighthawk x4s as router and internet is at best mediocre

[RidingTheFlow]

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@ShadowOfDeth69wrote:
@RidingTheFlow How is your minimum latency so low? My building is only feet from the cabinet but my minimum latency is in the high 20s.

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a) SH2AC in modem mode

b) Area without over-subscription

c) Good router with QoS properly set up. Note, that lot of people assume good router instantly should make bufferbloat better. Usually this is not the case, since you at least need properly setup QoS/SQM and normally sacrifice some max bandwidth for it (usually not more than 10%).