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pflog
Bueller? Bueller?
Premium,MVM
join:2001-09-01
El Dorado Hills, CA
kudos:3
reply to pflog

Re: [Business] [POLL] Do you have the new 15/3 or 27/7 business

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New boot files were released apparently. Is anyone seeing improved behavior of the speeds on 27/7 on SMC devices? I power cycled mine, but still getting the same erratic speeds after PB.

It does look like upstream PB is back, albeit less than before.

Powerboost results #1 (re-ran due to 'high packet loss' thing on download):

Estimating capacity:
Upstream: 14081 Kbps.
Downstream: 34882 Kbps.

Upstream: Burst size: 9717-9951 KB; Shaping rate: 7466 Kbps.
Downstream: Measurement aborted due to high packet loss rate.

Powerboost results #2:

Upstream: 13751 Kbps.
Downstream: 34769 Kbps.

Upstream: Burst size: 9574-9792 KB; Shaping rate: 7466 Kbps.
Downstream: Burst size: 18692-18878 KB; Shaping rate: 29008 Kbps.

Wireshark I/O graph attached (will re-attach, that previous one was the packets/s not bytes/s).


ropeguru
Premium
join:2001-01-25
Mechanicsville, VA

Click for full size
Click for full size
All of my stats are the same (ie. still no power boost). My graph isn't quite as bad as yours but does have som hiccups. I have power cycled the SMC multiple times too.

hhahn

join:2011-06-25
Marlton, NJ

I also still don't have Powerboost. I tried rebooting the modem today, but no change. It's completely gone on both the download and upload.

This sucks.



NetFixer
Snarl For The Camera Please
Premium
join:2004-06-24
The Boro
Reviews:
·Cingular Wireless
·Comcast Business..
·Vonage

said by hhahn:

I also still don't have Powerboost. I tried rebooting the modem today, but no change. It's completely gone on both the download and upload.

This sucks.

I had to buy a managed switch so that I could limit the negative effects of Comcast's PowerBoost, and you get Comcast to do it for you for free.

This really sucks.
--
We can never have enough of nature.
We need to witness our own limits transgressed, and some life pasturing freely where we never wander.

hhahn

join:2011-06-25
Marlton, NJ

said by NetFixer:

said by hhahn:

I also still don't have Powerboost. I tried rebooting the modem today, but no change. It's completely gone on both the download and upload.

This sucks.

I had to buy a managed switch so that I could limit the negative effects of Comcast's PowerBoost, and you get Comcast to do it for you for free.

This really sucks.

Yeah, it really sucks when you're working over a VPN and every time you save, it takes 10-15 seconds to finish a save command.

Maybe if Comcast would simply offer halfway decent upload speeds, especially on their god damn business tiers, there wouldn't be as much of a demand.


ropeguru
Premium
join:2001-01-25
Mechanicsville, VA
reply to pflog

Looks like they have really fubar'ed something in the config now. When I run a shaper probe it is intermittently failing on too much packet loss. Pinging from the inside out I see the loss and when pinging from the outside to the default gateway IP on the SMC, it also starts throwing timeouts, which tells me the SMC is having issues.

Update: Even when pinging the WAN DHCP IP address on the SMC, it also starts timing out along with the other IP's. So this is definitely a SMC issue all around not just a router processing issue within the SMC.



pflog
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join:2001-09-01
El Dorado Hills, CA
kudos:3

1 edit

Click for full size
Looks like unfortunately the Netgear device doesn't help with this 27/7 issue. Although the speeds are more sawtooth and less erratic now with the Netgear, there's clearly still an issue with the speeds after power boost ends.

However, the tech said something about pulling the boot file and config from my SMC and then pushing one or both to the Netgear, so perhaps he wasn't supposed to do that, not sure.

On the plus side, my SNR was sitting between 35 and 35.5 on the 4 channels on the SMC, and this Netgear's 8 channels are sitting at 37+, so I can't complain about that.

*edit* Adding shaperprobe results:

Estimating capacity:
Upstream: 10800 Kbps.
Downstream: 35398 Kbps.

Upstream: Burst size: 9795-9915 KB; Shaping rate: 7429 Kbps.

Downstream: Burst size: 20208-20442 KB; Shaping rate: 28560 Kbps.

The tech brought up a good point. Powerboost fluctuates based on the load in the CMTS right? Could it be as simple as my CMTS thinking "powerboost is still uncapped" but the boot file is capping it? If the CMTS is "leaving the flood gates open", but the modem is clamping it, couldn't it cause exactly this behavior (packet loss, which causes the TCP stack to back off, then ramp back up, etc etc)?


espaeth
Digital Plumber
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join:2001-04-21
Minneapolis, MN
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1 recommendation

said by pflog:

The tech brought up a good point. Powerboost fluctuates based on the load in the CMTS right? Could it be as simple as my CMTS thinking "powerboost is still uncapped" but the boot file is capping it? If the CMTS is "leaving the flood gates open", but the modem is clamping it, couldn't it cause exactly this behavior (packet loss, which causes the TCP stack to back off, then ramp back up, etc etc)?

Not really. This is a rate shaping vs rate limiting problem. TCP automatically rate limits itself in relation to RTT and packet loss.

Rate shaping is about exploiting that function of TCP and implementing a "leaky bucket" mechanism where you start discarding packets even before the rate threshold is crossed. This causes TCP to back off on how quickly it tries to scale the ACK window and when you zoom out a bit on the IO graph you get that relatively smooth line you're accustomed to seeing.

Rate limiting is generally implemented as a strict threshold limit. All packets under the "bucket" threshold are accepted, everything above the threshold is dropped. This creates problems for TCP because each time it scales the window it sees 0 drops while still under the threshold which causes it to continue to be aggressive with the scaling. Eventually it scales pass the threshold, loses more than a few % of a congestion window's worth of packets, and kicks in congestion avoidance by cutting the TCP window to 1/2 of what it was. That process results in the sawtooth graph you see above.

Given that you're seeing the same behavior with 2 different CPE devices, I would speculate they are probably implementing the downstream shaping on the CMTS (this is logically the best place to do it anyway). I suspect either the CMTS profile for the 27/7 offering is incorrect, or the configuration may have found a code bug that causes rate shaping to not operate correctly with these specific parameters used.


pflog
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El Dorado Hills, CA
kudos:3

Yeah it seems pretty clear that the CMTS and 27/7 profiles are not playing nicely together in some areas, while they're ok in others.

I'm not even sure who needs to address this at this point? It seems like a localized issue that the CMTS engineers would need to fix/update, but how we get their attention is unknown to me.

ComcastDJ See Profile and jlivingood See Profile were/are both looking into this, but they were hoping the new Netgear modem would fix it. I'm not sure if they have the means or "authority" to push for CMTS updates in various places or if that all has to be driven locally.
--
"Women. Can't live with 'em, pass the beer nuts." -Norm



ropeguru
Premium
join:2001-01-25
Mechanicsville, VA

Off topic, but does the Netgear allow for native IPv6? If so, are you seeing it available at your location?



pflog
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join:2001-09-01
El Dorado Hills, CA
kudos:3

said by ropeguru:

Off topic, but does the Netgear allow for native IPv6? If so, are you seeing it available at your location?

It's listed as not supporting IPv6 on the comcast site here:

»mydeviceinfo.comcast.net/

Don't see any IPv6 stuff in the Gateway Summary -> Network tab. But I imagine it does support it, just not configured/setup yet?
--
"Women. Can't live with 'em, pass the beer nuts." -Norm

n_w95482
Premium
join:2005-08-03
Ukiah, CA
reply to pflog

Click for full size
Yay!
I made a post in the direct forum last week about the missed upgrade, and SteveTeow See Profile contacted me this morning saying it had been escalated to corporate. They called and emailed me during lunch to say it should be all fixed now. I then RDP'ed to my PC and tested it.

Those two small spikes in the picture were from me dragging windows around.

DiffProbe release. January 2012. Build 1008.
Shaper Detection Module.
 
Connected to server 38.102.0.111.
 
Estimating capacity:
Upstream: 21943 Kbps.
Downstream: 115656 Kbps.
 
The measurement will take upto 2.5 minutes. Please wait.
 
Checking for traffic shapers:
 
Upstream: Burst size: 9483-10018 KB;
Shaping rate: 7429 Kbps.
 
Downstream: Burst size: 18061-19830 KB;
Shaping rate: 28746 Kbps.
 
For more information, visit: http://www.cc.gatech.edu/~partha/diffprobe
 

--
KI6RIT


pflog
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join:2001-09-01
El Dorado Hills, CA
kudos:3

They never responded to my post in the direct forum.

I wish Comcast's left and right hands would talk to each other...

You're getting massive PB like we were before AND your speeds are consistent. Looks like your CMTS is configured correctly.

If only we could get the engineers from your area to talk to the engineers in other areas where the CMTS isn't working correctly with the 27/7 profile.
--
"Women. Can't live with 'em, pass the beer nuts." -Norm


n_w95482
Premium
join:2005-08-03
Ukiah, CA

I forgot to mention in my above post that I'm using an SB6120 modem that I own. Also, it posted the config file in the log (SW Download INIT - Via Config file d11_m_sb6120_bciwidebandpremium_c05.cm) when they forced it. I think it's the same as before.
--
KI6RIT



pflog
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join:2001-09-01
El Dorado Hills, CA
kudos:3

said by n_w95482:

I forgot to mention in my above post that I'm using an SB6120 modem that I own. Also, it posted the config file in the log (SW Download INIT - Via Config file d11_m_sb6120_bciwidebandpremium_c05.cm) when they forced it. I think it's the same as before.

It'd be interesting to see if the Netgear works with 27/7 properly in your location...I don't suppose you know any other business class people in your area?
--
"Women. Can't live with 'em, pass the beer nuts." -Norm

mario02423

join:2004-06-09
Berwyn, IL
Reviews:
·Comcast
reply to pflog

Re: [Business]Do you have the new 15/3 or 27/7 business spee

This has been all sorts of mess. After the upgrade, I dropped from 93/30 PB to 35.9/7.8 consistent which, granted, is more than my contracted rate (12/2, or whatever the new one is).

On top of that, my service has been out for two days and I'm told that the technicians are a bit stumped.

I worked with Comcast_John on the CCBCI forums, but he didn't seem to get anything accomplished. When I call tech support, they tell me there's no such thing as Power Boost. Where do I go from here? How did you guys get in touch with Corporate Escalation?

Thanks!



NetFixer
Snarl For The Camera Please
Premium
join:2004-06-24
The Boro
Reviews:
·Cingular Wireless
·Comcast Business..
·Vonage

said by mario02423:

I call tech support, they tell me there's no such thing as Power Boost.

If only that were really true for business class (at the very least as a user selectable option). I would dearly love to see my d11_m_sb6121_bciwidebandstarter_c05.cm config file replaced by a d11_m_sb6121_bciwidebandstarter_noboost_c05.cm config file. PowerBoost totally screws up any applications/devices that try to use auto-sensing QoS.
--
We can never have enough of nature.
We need to witness our own limits transgressed, and some life pasturing freely where we never wander.

mario02423

join:2004-06-09
Berwyn, IL
Reviews:
·Comcast

said by NetFixer:

said by mario02423:

I call tech support, they tell me there's no such thing as Power Boost.

If only that were really true for business class (at the very least as a user selectable option). I would dearly love to see my d11_m_sb6121_bciwidebandstarter_c05.cm config file replaced by a d11_m_sb6121_bciwidebandstarter_noboost_c05.cm config file. PowerBoost totally screws up any applications/devices that try to use auto-sensing QoS.

If only there was a way to extract our config files. I'd send you mine, and I'd use yours.

n_w95482
Premium
join:2005-08-03
Ukiah, CA
reply to pflog

Re: [Business] [POLL] Do you have the new 15/3 or 27/7 business

said by pflog:

It'd be interesting to see if the Netgear works with 27/7 properly in your location...I don't suppose you know any other business class people in your area?

I know of two other business-class installs in town here, but I have little/no say in getting them to have their modem replaced (both are using SMC 8014s). One of them appears to be on an old 6/1 config file. I didn't even know the Netgear was an option until you mentioned it in an earlier post. Now if only they would approve an 8x4 conventional modem...
--
KI6RIT

n_w95482
Premium
join:2005-08-03
Ukiah, CA
reply to mario02423

Re: [Business]Do you have the new 15/3 or 27/7 business spee

said by mario02423:

How did you guys get in touch with Corporate Escalation?

All I did was post in the Comcast Direct forum here about being stuck on the old 22/5 tier. The issue was then forwarded to corporate by one of the Comcast staff that monitors that section, SteveTeow See Profile. I thought that having corporate deal with it themselves was a bit excessive at first, but they dealt with it very quickly (four hours from Steve's post to resolution).

That's the first time I've had an issue forwarded up to corporate. I don't know how common it is for that to happen.
--
KI6RIT

mario02423

join:2004-06-09
Berwyn, IL
Reviews:
·Comcast

said by n_w95482:

said by mario02423:

How did you guys get in touch with Corporate Escalation?

All I did was post in the Comcast Direct forum here about being stuck on the old 22/5 tier. The issue was then forwarded to corporate by one of the Comcast staff that monitors that section, SteveTeow See Profile. I thought that having corporate deal with it themselves was a bit excessive at first, but they dealt with it very quickly (four hours from Steve's post to resolution).

That's the first time I've had an issue forwarded up to corporate. I don't know how common it is for that to happen.

Thanks, n_w95482. I've set up a thread. My fingers hurt!