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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


@Datalink wrote:

@philjohn, the fact that you use a caching DNS resolver on your network results in very minimal impact, if any on your web browsing.  GRC's DNS benchmark can show up to a 10 % loss in DNS lookups, and the anecdotal comments from Puma 6 users who have switched to a Broadcom modem indicate that there is a noticeable web cruising improvement with the Broadcom or non-Puma 6 modems.  Speed in this case is irrelevant, its simply a matter what you're attempting to do, if for example you happen to be web cruising when the constant 1.92 second (interval) task runs, stopping traffic thru the modem (latency) and causing UDP losses (most likely due to the UDP packets timing out within the modem).  This should be easy to confirm with Wireshark.


Was hoping to see you on actually... How do you find some of the results coming out of the latest firmware over this side of the pond and are there any specific tests we could be doing? Honestly giving your knowledge in this area, it would be good to prove or disprove how 'fixed' the latency is. Of course the DOS is still yet to be tested on this newer firmware, I don't believe it's been done as of yet.

--------------------------------------------------------
Look behind you, a three-headed monkey

 wrote:

@philjohn, the fact that you use a caching DNS resolver on your network results in very minimal impact, if any on your web browsing.  GRC's DNS benchmark can show up to a 10 % loss in DNS lookups, and the anecdotal comments from Puma 6 users who have switched to a Broadcom modem indicate that there is a noticeable web cruising improvement with the Broadcom or non-Puma 6 modems.  Speed in this case is irrelevant, its simply a matter what you're attempting to do, if for example you happen to be web cruising when the constant 1.92 second (interval) task runs, stopping traffic thru the modem (latency) and causing UDP losses (most likely due to the UDP packets timing out within the modem).  This should be easy to confirm with Wireshark.


Since HTTP is a TCP based, rather than UDP based, protocol, UDP packet loss won't affect that. TCP can handle lost packets and just resend when it doesn't get an ACK back - being a guaranteed delivery, and very chatty protocol.

As for a caching DNS resolver, if 10% of DNS lookups fail because of UDP packet loss (DNS is UDP) and you have the most frequently accessed entries in a LRU cache, then it will make a tangible difference. Coming from a FTTC to Cable I didn't notice any serious problems with browsing, so either there are other things at play (congested node) or I just can't detect them - which is a distinct possibility. But I didn't have any pages failing to load at all, which some people were claiming. Likewise I don't put much stock in anecdotes about people noticing a night and day difference on Broadcom chipsets.

Finally, I put about zero trust in any of GRC's tools - just google him and look at many of the outlandish claims he's made over the years.

@Mike86UK

From my experience I would advise against switching to the SH3 for FPS gaming.

Over the years playing mostly the COD franchise I found:

SH1 was fine

Then I was switched to the SH3 and some time later when I bought the latest game I found the gameplay to be woeful.  I didn't connect the two events for a while, just gave up gaming.  When I started checking to see if there was an issue with my service I came across this thread.

Eventually I managed to get a SH2ac from Virgin and that was certainly better.

Now I'm on 40mb Sky fibre with low latency and gaming as it should be.

Sometimes if things are working fine then its best to just leave it alone.

 

Think I will leave it then. 

Ive got BT Sport with BT and my 18month contract ends in 10 days, so im going to see what offers they have on the Broadband and see if I can get a bundle and then maybe ditch Virgin. 

Max speed I can get on BT is 73Mb so I would take a small hit in speed, but if I can save a worthwhile amount then it would be worth it. 

 

 

well as someone who left virgin media for bt i am regretting it because bt's customer service is a complete joke and their broadband is even worse they keep sending me engineers and threaten me with £129.99 charges if an engineer needs to do work yesterday i rung up and the person i talked to said your broadband is supposed to not work for 5 days that how it is which i found amusing so basically for 5 days my services will not work so i signed up for bt broadband for no internet for 5 days 

https://uk.trustpilot.com/review/bt.com

https://www.landlinesaver.co.uk/broadband-reviews/bt

Boygroucho
On our wavelength

nad223

"well as someone who left virgin media for bt i am regretting it because bt's customer service is a complete joke and their broadband is even worse"

 

Unfortunately there is no "one ISP fits all".   In my case our estate got Virgin 20 odd years ago so a large number of homeowners have their service and we all suffer from over utilisation.   While BT only upgraded our cabinets to FTTC a couple of years ago, so you can imagine my Sky Fibre is pretty good.

Having a popular service is hardly much of an excuse for Virgin not investing in their infrastructure to provide a decent service for gamers though.

No reason why Virgin's BQM shouldn't look something like this:


03e460025bc6a2ac87218954b58faa4457566d12-02-05-2018

 

 

 


@Boygroucho wrote:

nad223

 

Having a popular service is hardly much of an excuse for Virgin not investing in their infrastructure to provide a decent service for gamers though.

 


It's totally an excuse - if they aren't losing more customers than are joining, then minimal investment makes perfect sense - especially if they are looking to sell up any time soon - low capex on the balance sheet, healthy and growing subscriber base etc. etc.

8Ace
On our wavelength

So I lost all Virgin services this morning and phoned 150. I got an automated message advising there were upgrades being done in my postcode (Salford). After the services were restored I checked and the firmware still hadn't been upgraded so I tried a factory reset. The Hub3 then pulled down the firmware upgrade (9.1.116.603) and I then dropped it back into modem mode. Not had much chance for real-world testing yet, but initially, it seems much better.

2018-05-02 12_03_12-Cable modem Puma 6 chipset test _ DSLReports, ISP Information.png2018-05-02 12_52_19-Share Broadband Quality Monitor _ thinkbroadband.png2018-05-02 12_55_40-Command Prompt.png

cje85
Trouble shooter

Are you on 300/350Mb? If not hopefully they have started making the new firmware more widely available.

Best Puma test I've seen so far - need to redo mine via an ethernet cable soon