Basic Internet Connectivity And Modem Help

[kumatan]

Just as many of you on this forum, I'm scratching my hair over the horrible connectivity and frequent modem reboots since the beginning of June.

My specs to start with...
Comcast Tier: Blast (Internet Only)  30Mbps/6Mbps 
Modem:  Motorola SBG 6121
Wireless Router: MediaLink (Wireless-N Broadband)
Average Daily Usage: 3.5-5GB in residential (due to heavy video streaming)
Area: San Francisco, CA

I stream videos quite heavily on daily basis watching international TV channels using Sony's LocationFree device (the base-station is set in Tokyo).

The streaming image gets so blurry during 17:00-23:00 on every business days, then it gets worse during holidays and weekends.

Here's what my ShaperProbe returns at different hours of the day (during the high traffic hours).

Tested with video streaming: 

Last login: Thu Jun 21 16:03:37 on ttys000
Connected to server 74.63.50.40.
Estimating capacity:
Upstream: 6391 Kbps.
Downstream: 35083 Kbps.
The measurement will last for about 2.5 minutes. Please wait.
Checking for traffic shapers:
Upstream: Burst size: 9738-9816 KB; Shaping rate: 4237 Kbps.
Downstream: Measurement aborted due to high packet loss rate.

Last login: Thu Jun 21 17:31:54 on ttys000
Connected to server 74.63.50.40.
Estimating capacity:
Upstream: 6403 Kbps.
Downstream: 35804 Kbps.
The measurement will last for about 2.5 minutes. Please wait.
Checking for traffic shapers:
Upstream: Burst size: 9268-9340 KB; Shaping rate: 4256 Kbps.
Downstream: Measurement aborted due to high packet loss rate.

Last login: Thu Jun 21 19:22:40 on ttys000
Connected to server 38.107.216.47.
Estimating capacity:
Upstream: 6437 Kbps.
Downstream: 35898 Kbps.
The measurement will last for about 2.5 minutes. Please wait.
Checking for traffic shapers:
Upstream: Burst size: 9063-9138 KB; Shaping rate: 4218 Kbps.
Downstream: Burst size: 17626-17955 KB; Shaping rate: 26077 Kbps.

Tested with all video streaming SHUT OFF.

Last login: Thu Jun 21 17:41:30 on ttys000
Connected to server 217.163.1.87.
Estimating capacity:
Upstream: 6288 Kbps.
Downstream: 34654 Kbps.
The measurement will last for about 2.5 minutes. Please wait.
Checking for traffic shapers:
Upstream: Burst size: 10089-10164 KB; Shaping rate: 4256 Kbps.
Downstream: Burst size: 20382-20666 KB; Shaping rate: 26394 Kbps.

Last login: Thu Jun 21 18:22:47 on ttys000
Connected to server 80.239.142.215.
Estimating capacity:
Upstream: 1326 Kbps.
Downstream: 35324 Kbps.
The measurement will last for about 3.0 minutes. Please wait.
Checking for traffic shapers:
Upstream: No shaper detected.  Median received rate: 1008 Kbps.
Downstream: Burst size: 19840-20139 KB; Shaping rate: 26656 Kbps.

Last login: Thu Jun 21 19:09:03 on ttys000
Connected to server 74.63.50.34.
Estimating capacity:
Upstream: 6399 Kbps.
Downstream: 29288 Kbps.
The measurement will last for about 2.5 minutes. Please wait.
Checking for traffic shapers:
Upstream: Burst size: 9797-9873 KB; Shaping rate: 4274 Kbps.
Downstream: No shaper detected.  Median received rate: 28746 Kbps.

Are these speeds powered enough for my tier?  
Estimated caps seem okay, but why am I getting so many high packet loss on downstreams when streaming videos, and even when not streaming, around / less than 20MB burst sizes whereas I'm supposed to get 30MB PowerBoost?   

Also, why are my downstream shaping rates often much higher than burst sizes?  Please correct me if I'm wrong, but isn't "shaping" the corrected rate of burst size?  

Before anyone asks, I've also done several power cycles, coaxial checks, modem (& wifi router) factory resets, and all other magical steps listed here: 
http://forums.comcast.com/t5/Connectivity-and-Modem-Help/Connection-Troubleshooting-Tips/td-p/125357...

Reading too many horror stories of comcast techs here on forums, I dread to call them and rather troubleshoot or better understand the situation all by myself. 

Any help of experts out there is greatly appreciated.

[bnaughty]

MediaLink? Ummm.... that's either some super high end stuff I've never heard of or its the Sam's choice model... I know you need the router and all but have you bypassed it as a troubleshooting step?

[EG]

What do the modem's signal stats look like ?  Get them here; http://192.168.100.1

Please post the *Downstream Power Level*, the *Upstream Power Level*, and the *SNR* (Signal to Noise Ratio) numbers.

[kumatan]

EG, 

The connection was so sluggish just as usual weekend, I gave up watching videos or even surf pages during the peak hours.  I tried to read modem, but the signal page didn't even refresh, so I give you the reading as of now, 0:21am PST (off-Peak hours):

Downstream Bonding Channel Value

Channel ID	2	1	4	5
Frequency	711000000 Hz	705000000 Hz	723000000 Hz	729000000 Hz
Signal to Noise Ratio	36 dB	36 dB	37 dB	37 dB
Downstream Modulation	QAM256	QAM256	QAM256	QAM256
Power Level The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading	-3 dBmV	-2 dBmV	-3 dBmV	0 dBmV

Upstream Bonding Channel Value

Channel ID	8	7	9
Frequency	30600000 Hz	25300000 Hz	37000000 Hz
Ranging Service ID	2854	2854	2854
Symbol Rate	5.120 Msym/sec	2.560 Msym/sec	5.120 Msym/sec
Power Level	43 dBmV	43 dBmV	44 dBmV
Upstream Modulation	[3] QPSK [3] 64QAM	[3] QPSK [2] 16QAM	[3] QPSK [3] 64QAM
Ranging Status	Success	Success	Success

Signal Stats (Codewords) Bonding Channel Value

Channel ID	2	1	4	5
Total Unerrored Codewords	652802809	652805571	652805748	652803110
Total Correctable Codewords	17	0	0	0
Total Uncorrectable Codewords	755	534	501	496

Also, here's the reading from ShaperProbe at today's peak hour (around 8:00pm): 

Last login: Sat Jun 23 19:55:57 on console
Shaper Detection Module.

Connected to server 217.163.1.87.

Estimating capacity:
Upstream: 1760 Kbps.
Downstream: 42 Kbps.

The measurement will last for about 2.5 minutes. Please wait.

Checking for traffic shapers:

Upstream: No shaper detected.
Median received rate: 1642 Kbps.

Downstream: No shaper detected.
Median received rate: 74 Kbps.

For more information, visit: http://www.cc.gatech.edu/~partha/diffprobe

Only good thing from today's reading is, no high packet loss...

But 42 Kbps downstream was a jaw-dropper.  

[kumatan]

I purchased MediaLink after seeing high reviews by comcast users on Amazon, especially for its compatibility with Modem SBG6121.

http://www.amazon.com/Medialink-Wireless-Router-802-11n-Internal/dp/B0044YU60M

I've definitely tried connecting my PC or video streaming device directly to modem w/ ethernet, but at every attempt, it just doesn't discriminate the speed from WiFi, or improve the quality of video streaming. 

[Murphy]

Do the shaper measurements with a computer connected directly to the modem.

Turn the modem off while you make the connection.

Check the routers setup for QOS and disable it if it is enabled.

[EG]

The stats as read at the modem level at that moment in time were good so no smoking guns there, sorry. There are two additional signal stats which can't be read at the modem level. They can only be read from their end by them polling the CMTS (Cable Modem Termination System) at the local headend facility.

They are the 'Upstream Receive Power Level' and the 'Upstream uSNR' (upstream Signal To Noise Ratio). Both of these are as equally important in diagnosing connectivity issues as are the modem's stats.

You can call in and ask what these figures are. The Upstream Receive Power Level should fall within the range of -10dB to +10dB with 0dB being in the middle and perfect.

The Upstream SNR should be least 30dB, and the higher it is the better. You could have a noise ingress issue in the upstream channel.

[kumatan]

Sorry for the pause.

It seems that all speed issues with my SBG 6121 are solved since the latest firm push.  One night on last month I noticed the streaming visuals got suddenly clear and never went back to blurry.  But with my past experiences, I thought this was just happening by chance.  Then I turned the streaming on again next evening, then boom!! the visual and the speed I hoped for over a year were there again, and continued flawlessly.  I went back to the forum to find out why and learned some firm-up miracles happened.

With tears of joy, I'm enjoying comcast finally.  I just hope it will last throughout my subscription.

Thanks all experts for your help!! 

[EG]

Glad it worked out for you ! Not to be a downer, but this firmware push seems to have caused boatloads of problems for many others. Take a look around this board and specifically this lengthy thread;

http://forums.comcast.com/t5/Connectivity-and-Modem-Help/Having-issues-with-your-Motorola-SB6121-Ple...