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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

The following issues were resolved in release 9.1.93V:
2.3.1 TCP/UDP/DNS Latency Issues
Tracking No.
PD 24878
Description
Multiple latency issues have been observed:
- UDP upstream delays during rate-limited TCP traffic
- HTTP delays under heavy TCP Ack load
- Slow HTTP session initiation
- Slow DNS responsiveness
2.3.5 Ping Latency Intervals Too High
Tracking No.
PD 22502
Description
The time interval to receive a response to a transmitted ping is longer than required by subscribers with time-sensitive applications
2.3.7 DNS Latency Issue
Tracking No.
PD 23345
Description
Under certain conditions, the modem may drop DNS packets, causing the applications to retransmit and increasing latency of DNS queries.

An update has been released by Arris. What timeline can we expect for this to reach hub 3s?

Sorry if this is not the correct forum to post in, I have had VM broadband for many year and was on they (150mb download speed I think) up until very recently when I got a speed increase to 200mb with an upload of 10mb and I do get these speeds. As I have their complete package (TV/BB/Phone) but want to move my TV to Sky (for proper 4K/UHD content not just Netflix) I thought I would as part of removing the TV upgrade my broadband to their 200mb/20mb Gamer tier, I have read about the issues with the super hub 3 and am a little concerned by these jitter issues, it sounds like there could be a firmware fix (although has anyone/testers verified it actually works?)

So my question is, I dont game much but I do work from home and so want the quick upload speeds, should I be concerned about the current SH3 issue or would it not impact normal internet usage (ie where a ping of 150 instead of 25 is unlikely to impact what I am doing).

The other question I have is can I opt to keep the SH 2AC instead, or is the SH3 required for the quicker upload speeds?


@m15terd wrote:

The other question I have is can I opt to keep the SH 2AC instead, or is the SH3 required for the quicker upload speeds?


SH2ac is absolutely fine with the Gamer plan and this is what I am currently using. Currently getting 22Mbps up/~220Mbps down. The Hub3 (with it's current firmware) is utterly useless as a router and even in modem mode has issues with latency. 100ms delay to the modem (which is what I was seeing frequently) is not satisfactory IMHO.

Just tell VM to note that you'll be using the 2ac with your upgrade, as it would appear that they're sending out Hub3's for upgrades to the Gamer plan now.


Tom

It is brilliant news that arris has released the new firmware but now we play the waiting game with virginmedia......

Arris seem to have managed to acknowledge (and hopefully fix) all the issues that my Samknows White Box detected last September.

I'm still for waiting for an acknowledgement from Virgin Media to my problem report - but since they seemingly haven't informed their own front-line staff of the problem, I'll probably be waiting a while longer.

 

 

Philuk
Tuning in

Hopefully a moderator wouldn't mind just popping into this thread with an estimate on deployment.

MUD_Wizard
Superuser Emeritus
Superuser Emeritus

@m15terd wrote:

Sorry if this is not the correct forum to post in, I have had VM broadband for many year and was on they (150mb download speed I think) up until very recently when I got a speed increase to 200mb with an upload of 10mb and I do get these speeds. As I have their complete package (TV/BB/Phone) but want to move my TV to Sky (for proper 4K/UHD content not just Netflix) I thought I would as part of removing the TV upgrade my broadband to their 200mb/20mb Gamer tier, I have read about the issues with the super hub 3 and am a little concerned by these jitter issues, it sounds like there could be a firmware fix (although has anyone/testers verified it actually works?)

@m15terd Unless you're a serious FPS game player then you're unlikely to notice the jitter issues.

So my question is, I dont game much but I do work from home and so want the quick upload speeds, should I be concerned about the current SH3 issue or would it not impact normal internet usage (ie where a ping of 150 instead of 25 is unlikely to impact what I am doing).

Won't impact normal internet usage such as web browsing, streaming, including uploading, downloading, or non-jitter sensitive applications. Skype seemed to work just as good/badly on my Hub 3 as my SH2ac over the year or more I was testing it.

Average latency is usually just 3 ms above what you'd get with a SH2ac. The jitter we talk of here is spikes in latency once or twice every 100 seconds. i.e. not all the time. So hard to notice outside of Thinkbroadband BQM's or continuous ping's.

If you use a VPN for work then, depending on the type of VPN protocol used, the Hub 3 might or might not cause some issues by its implementation.

For most people, bufferbloat is more likely to cause greater grief and that should be handled by installing a 3rd party router with whatever VM Hub you're using: https://www.youtube.com/watch?v=C72c4B277Vg

The other question I have is can I opt to keep the SH 2AC instead, or is the SH3 required for the quicker upload speeds?


VM will require you to take a Hub 3 in order to apply the Gamer tier to it, then you will have to fight to return to your SH2ac but it is possible.

The Hub 3 is not technically required for quicker uploads, it's just required to apply the profile in the first instance.

Just to note, Firmware version 9.1.93V which will update the Arris SB6190 is one step towards the resolution of TCP/IP, ICMP and UDP latentcy for IPV4 and IPV6 (?).  It would appear that there is more work to do, however, there is no indication in the Arris thread of what remains to be done.  Its possible that VM may not do anything until the Intel/Arris group has finally declared all issues as finally resolved.  I hate to raise that possibility, but, that is something to consider.  If so, it will be several weeks before other updates will be ready for release for the SB6190 and possibly several weeks more until firmware updates for other Arris products are ready.   Not trying to be a grinch, but, it might be too early to declare victory at this point in time  😞

http://www.dslreports.com/forum/r31332206-

 

 


MUD_Wizard wrote: Average latency is usually just 3 ms above what you'd get with a SH2ac. The jitter we talk of here is spikes in latency once or twice every 100 seconds. i.e. not all the time. So hard to notice outside of Thinkbroadband BQM's or continuous ping's.

I don't if I agree with that 3ms figure. My own graphs of SH3 vs SH3 over various channel numbers show latency really climbs quite a bit. I'm up at least 11ms now compared to where I started on the SH3. There's arguments to have about what is noticeable or not and in what games, but the SH3 gets particularly ugly at high channel counts.

SH3 8x2 - 17ms average:

6345db8a8a6b9cba7c29b2d5e539ba72-20-11-2015 

 

SH3 24x2 - 28ms average: 

4e3908d6aa72046ea0c3e280c3517b1a-28-03-2017

Yup, two thumbs up! Thats a good example of the additional latency that occurs as you go up in channel count.  It will be noticeable for web cruising due to the UDP packet loss which kills a portion of the DNS lookups.  That results in successive DNS lookups until the browser finally has the data, slowing down page loading. Thats on top of the usual UDP latency which occurs and finally the TCP/IP latency which adds to the slow page loads as well.