Comcast Pro: Where's my speed increase?

carage · Post by **carage** » Tue Jul 08, 2003 6:17 pm

I upgraded to Comcast Pro (3500/384) yesterday, the tech said it would probably take effect within an hour. However, according to the speedtests I did last night and today, I do not see ANY significant download speed increases.
According to the DSLReport speedtest, my upload is indeed increased from 2xx to 3xx kbps now, but my download is still around 11xx to 14xx which is pretty much the same before the upgrade.
Tests at bandwidthplace.com indicates I have a connection of about 1.3 Mbps and I got around 10xx to 14xx on the MSN test.
I called Comcast and they said they cannot guarantee the download speed, but typically I should be getting around 3.1 Mbps at any major speedtest easily.
I asked them to see if there is something over there, and they said the server indicates I am on the Comcast Pro program, but since I only upgraded for about 24 hours there is not enough data from the cable modem to ananlyze and asked me to let it sit for at least two or three days before I call back.
Are there any one on this board also using the Comcast Pro? What kind of speeds do you typically get?
I am not going to pay $50 extra just for increasing my upload by 100kbps.

The modem is a Motorola SurfBoard SB4200
NIC: 3com 905c-TX-M (no driver tweaks)
Windows XP Pro (I did set QoS to 0)
Modem self diagnostic is reporting s/n ratios of 35 db, the tech said that is almost ideal.
Anything I can do to get to the speeds I should be getting?
Thanks in advance.

carage · Post by **carage** » Tue Jul 08, 2003 6:20 pm

Here are my SG Analyzer stats
TCP options string = 020405b40103030301010402
MTU = 1500
MTU is fully optimized for broadband.
MSS = 1460
Maximum useful data in each packet = 1460, which equals MSS.

Default Receive Window (RWIN) = 513920
RWIN Scaling (RFC1323) = 3 bits
Unscaled Receive Window = 64240

RWIN is a multiple of MSS
Other values for RWIN that might work well with your current MTU/MSS:
256960 (MSS x 44 * scale factor of 4)
128480 (MSS x 44 * scale factor of 2)
64240 (MSS x 44)
bandwidth * delay product:

Your RcvWindow limits you to: 20556.8 kbps (2569.6 KBytes/s) @ 200ms
Your RcvWindow limits you to: 8222.72 kbps (1027.84 KBytes/s) @ 500ms
MTU Discovery (RFC1191) = ON
Time to live left = 51 hops

TTL value is ok.
Timestamps (RFC1323) = OFF
Selective Acknowledgements (RFC2018) = ON
IP type of service field (RFC1349) = 00000000

Anything hampering my performance?

mnosteele52 · Post by **mnosteele52** » Tue Jul 08, 2003 6:52 pm

Your RWIN is way too high for your caps, try the following:

Download the TCP Optimizer and try the following settings.

Settings tab:

select - cable modem
check - custom settings
network adapter selection - your NIC
check modify all adapters
maxmtu - 1500
TTL - 64
TCP Receive Window - 37960 or 64240
MTU Discovery - yes
Black Hole Detect - no
Selective Acks - yes
Max Dup ACKs - 3
TCP 1323 Options - uncheck both boxes

Other Settings tab:

Max Connections per Server - 10
Max Connections per 1.0 Server - 20
Lan Browsing Speedup - optimized

Then select "Apply Changes" and reboot to take effect.

carage · Post by **carage** » Tue Jul 08, 2003 7:58 pm

I set the RWIN to 64240, but wouldn't that be kind of small if I am supposed to get something like 3.1 mbps?

mnosteele52 · Post by **mnosteele52** » Tue Jul 08, 2003 10:15 pm

Originally posted by carage
I set the RWIN to 64240, but wouldn't that be kind of small if I am supposed to get something like 3.1 mbps?

No not at all, I guess you didn't even try 37960? Your RWIN is based on your caps and latency, depending on how low your latency is will determine what value your RWIN should be. A larger value DOES NOT mean more speed, in most cases it only means more retransmitted packets. Retransmitted packets = slower speed.

carage · Post by **carage** » Tue Jul 08, 2003 10:48 pm

Thanks, I guess I should try the lower value.
Hmm....so higher value does not mean faster?
Is the lower value the opposite around then?

mnosteele52 · Post by **mnosteele52** » Tue Jul 08, 2003 10:57 pm

Here you go.........

TCPReceiveWindow(RWIN) - Determines how much data the receiving computer is prepared to get. A TcpReceiveWindow value that's too large will result in greater loss of data if a packet is lost or damaged. A too small of a value will be very slow, as each packet will have to be acknowledged before the next packet is sent. If each data packet had to be acknowledged before another could be sent, then performance could suffer due to the delay time needed for the data packet to reach the receiver plus the time needed for the acknowledgment packet to get back to the sender. To avoid this delay, the sender is allowed to keep transmitting data packets prior to receiving acknowledgments up to a maximum "window" size advertised by the receiver, normally large enough for several packets. The larger the window, the more packets that can be sent before needing an acknowledgment; however, larger windows can require more packets to be retransmitted when a transmission error occurs. Hence, the receive window size needs to be large enough to keep data flowing continuously, but not excessively large.

Here is the formula to find your optimum value:

TcpReceiveWindow (RWIN) Formula

(Maximum Bandwidth x Maximum Anticipated Latency) / 8

Example of my connection with a 3000 download cap with a maximum latency of 100 ms:

(3000 x 100) / 8 = 37500 To make it a multiple of MSS divide by 1460:

37500 / 1460 = 25.68 Then round up to the nearest even whole number:

26 x 1460 = 37960 - my RWIN

To find your maximum anticipated latency read here.

I hope this helps.

wee96 · Post by **wee96** » Wed Jul 09, 2003 12:20 am

There might be a problem with your rates on your account, Ive had this happen to alot of people I service. The guy or gal on the phone thinks they put the correct rates for the pro service, modem never pulls the pro boot file, and your stuck at regular service. Might wanna keep calling and have someone come to your house .

carage · Post by **carage** » Wed Jul 09, 2003 3:11 am

I guess I will until tomorrow afternoon then call back to see what is going on.
Is there anything I can do on my part though?
I've been though a lot of power cycles, manually renewing IPs (BTW, I think my IP is static now), and tweaking with SGOptimizer according Dr.Tweak.

carage · Post by **carage** » Wed Jul 09, 2003 3:16 am

Self-Diagnostic Page

Downstream Value
Frequency 645000000 Hz Locked
Signal to Noise Ratio 35 dB
QAM 64
Network Access Control Object ON
Power Level 3 dBmV 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

Upstream Value
Channel ID 1
Frequency 23000000 Hz Ranged
Ranging Service ID 633
Symbol Rate 2.560 Msym/s
Power Level 37 dBmV

Kip Patterson · Post by **Kip Patterson** » Wed Jul 09, 2003 7:32 am

All your numbers look great.

carage · Post by **carage** » Thu Jul 10, 2003 5:06 am

Just did another round of testing
DSLreports 1300/322
BandwithPlace 1.2 mbps
MSN 1220.5 kbps

It's 2AM now, so I guess it is probably not the time of the day issue.
I hope Comcast has a pretty good explanation tomorrow...
They are not going to make me wait forever...

joshjerm89 · Post by **joshjerm89** » Thu Jul 10, 2003 3:33 pm

try poweringcycling down the modem( turning it off andd off) for about 15 seconds

carage · Post by **carage** » Thu Jul 10, 2003 7:39 pm

Originally posted by joshjerm89
try poweringcycling down the modem( turning it off andd off) for about 15 seconds

I did that a lot of times....

carage · Post by **carage** » Fri Jul 11, 2003 2:11 am

Just installed a new SB 5100, unfortunately that doesn't improve the download speeds at all. I guess this rules out faulty modem as an issue.
What else could be wrong? This doesn't make sense at all...
I am seriously doubting whether Comcast put me on the right configuration boot file or not. I guess I am pushing for a service call this time.

carage · Post by **carage** » Fri Jul 11, 2003 2:21 am

BTW, it seems DSLreport speedtest no longer measures upload...Where can I find a credible speedtest for both upload and download?

j79zlr · Post by **j79zlr** » Fri Jul 11, 2003 2:25 am

http://nyc.speakeasy.net/
http://chi.speakeasy.net/
http://wdc.speakeasy.net/
http://sfo.speakeasy.net/
http://den.speakeasy.net/
http://dfw.speakeasy.net/
http://atl.speakeasy.net/
http://bos.speakeasy.net/
http://www.phl.speakeasy.net/
http://lax.speakeasy.net/
http://cle.speakeasy.net/
http://mia.speakeasy.net/
http://msp.speakeasy.net/
http://sea.speakeasy.net/
http://hou.speakeasy.net/

carage · Post by **carage** » Fri Jul 11, 2003 2:43 am

Thanks...
Speakeasy Seattle
DL: 1364 kbps

UL: 361 kbps

j79zlr · Post by **j79zlr** » Fri Jul 11, 2003 2:48 am

I do find speakeasy's test to be the most accurate, speed test that is. The best way to actually test your connections Download is to download a file from a realiable fast server like the OOL FTP test. ftp://ftp1.optonline.net/pub/test64

I personally think that you need to light a fire under well ya know, to get your premium service uncapped. It looks like you are still at 1800. Complain, you can usually get a free month or so for your trouble.

carage · Post by **carage** » Fri Jul 11, 2003 3:01 am

Yeah, but the strangest thing is the upload cap has been raised, but not the download cap... They say a situation like this is very odd, because the Pro boot file contains both the upload and the download.
If the modem is not using the Pro boot file, then the upload cap would have remained at 256 kbps. They never heard of a situation which only half of the cap is lifted.

mnosteele52 · Post by **mnosteele52** » Fri Jul 11, 2003 9:25 am

carage you have completely lost me, your upload is fine. I don't see what you are complaining about. Please post a TCP/IP Analyzer test and a speed test from the OOL ftp link that j79zlr gave you.

carage · Post by **carage** » Fri Jul 11, 2003 1:58 pm

um...I never complained about the upload...
It is just that how is it possible that they changed the upload but not the download?

carage · Post by **carage** » Fri Jul 11, 2003 2:14 pm

OOL FTP:
64 MB in 5 minutes 55 seconds
184 KBps = 1472 kbps

carage · Post by **carage** » Fri Jul 11, 2003 2:22 pm

TCP options string = 020405b401010402
MTU = 1500
MTU is fully optimized for broadband.
MSS = 1460
Maximum useful data in each packet = 1460, which equals MSS.

Default Receive Window (RWIN) = 64240
RWIN Scaling (RFC1323) = 0 bits
Unscaled Receive Window = 64240

RWIN is a multiple of MSS
Other values for RWIN that might work well with your current MTU/MSS:
513920 (MSS x 44 * scale factor of 8)
256960 (MSS x 44 * scale factor of 4)
128480 (MSS x 44 * scale factor of 2)
bandwidth * delay product:

Your RcvWindow limits you to: 2569.6 kbps (321.2 KBytes/s) @ 200ms
Your RcvWindow limits you to: 1027.84 kbps (128.48 KBytes/s) @ 500ms
MTU Discovery (RFC1191) = ON
Time to live left = 51 hops

TTL value is ok.
Timestamps (RFC1323) = OFF
Selective Acknowledgements (RFC2018) = ON
IP type of service field (RFC1349) = 00000000

carage · Post by **carage** » Fri Jul 11, 2003 2:25 pm

Speakeasy Seattle:
1444/363 kbps

Bandwidth Place:
1.4 mbps

MSN:
1332.5 kbps

carage · Post by **carage** » Fri Jul 11, 2003 3:46 pm

After bouncing me through 5 different reps (which means I have to describe the same problem 5 times), they finally offered to schedule a service visit this Sunday between 12-4.
I'll see how it goes...

joshjerm89 · Post by **joshjerm89** » Fri Jul 11, 2003 5:55 pm

thats weird cuz my dl is always at ~225 for 1800 and 255 upload

carage · Post by **carage** » Fri Jul 11, 2003 10:33 pm

Originally posted by joshjerm89
thats weird cuz my dl is always at ~225 for 1800 and 255 upload

I guess you are lucky...

Kip Patterson · Post by **Kip Patterson** » Sat Jul 12, 2003 5:09 pm

I can't see what good a service call will do. For whatever reason, their system doesn't seem to be able to deliver the bandwidth. I would cancel and go back to the standard service.

You might wish to run some trace routes and post them.

Kip

carage · Post by **carage** » Sat Jul 12, 2003 6:06 pm

My friend suspected it could be the cable...
So we went out to get some cable higher than 750MHZ, unfortunately the cable frequencies were unmarked, so we ended up buying Radio Shack's best cable, the Fushion AV.
However that doesn't seem to be the case... Performance is the same.

My condo was built in 1996, could it still be using the old 500MHZ cable?

joshjerm89 · Post by **joshjerm89** » Tue Jul 15, 2003 10:17 am

i use pcpitstop.com's internet test. it works perfect for me. after tweaking my conection. 1800/256 i got 17** dls and 25* uls on the tests

carage · Post by **carage** » Wed Jul 16, 2003 5:41 pm

After a week of trying and a 3rd technician visit, I gave up on the idea and reverted back to the usual 1800/256.

If it wasn't because chaning my e-mail would be a hassle and I just bought a SB 5100 , I would have deflected to DSL.

Speakeasy's 3m/768 for $29 for the first three months and $69 afterwards looks like a great deal compared to Comcast Pro's 3.5m/384 at $95

illestdynasty · Post by **illestdynasty** » Thu Jul 17, 2003 2:12 am

To put it simple, for some reason or another the Config file that your modem recieved wasn't correct. When your modem boots it pulls a file that tells it operating paramiters, important IPs, and most importantly your speed caps. When you update to Pro, they are supposed to delete your standard 1800/256 config file and update your account with the 3500/384 file.

If they don't do it right, you won't get the right speed. Since you diagnostics were in spec, that looks to be the only problem. If you use DocsDiag, you should be able to see your cable modem config file.

Here are the results I pulled from a Customer using the standard 1800/256. Toshiba Modem

DocsDiag v020714 Copyright 2001-2 Robin Walker rdhw@cam.ac.uk

Verifying host 10.xxx.xxx.xxx ...
MAC address xxxxxxxxxxxx verified.

Thomson DCM235 Cable Modem serial no. xxxxxxxxxxxx, HW_Version 025, SW_Version
ST01.0A.01, Bootloader_Ver 3.5, OS: PSOS 2.5.0

System up time = 5 days 13h 19m 37.74s
Ethernet single-collision errs.1 = 6329
Ethernet multiple-collision errs.1 = 4780
Ethernet deferred xmits.1 = 3349
Ethernet other recv errors.1 = 254
Downstream channel ID = 2
Downstream channel frequency = 633007779 Hz
Downstream received signal power = 1.1 dBmV
Upstream channel ID = 3
Upstream channel frequency = 23000000 Hz
QoS max upstream bandwidth = 256000 bps
QoS max downstream bandwidth = 1800000 bps
SigQu: Signal to Noise Ratio = 36.4 dB
Cable modem status = Operational
Upstream transmit signal power = 45.0 dBmV
Date and Time = 2003-04-13,23:19:37.0+06:00
Configuration filename = hsd1.5M.cfg
Press any key to continue . . .

holden mcgrion · Post by **holden mcgrion** » Sat Jul 26, 2003 5:59 am

the same thing happened to me when i first got the comcast pro my speeds where the same 1500 d etc etc so i called back and first person didnt fully get me hooked up i stayed on line with second person till we got it it was cool i went from 1500 to 1700 d 256 up i dont no close to that anyway to i get now any where from 2900 d to 3150 d 375 up but in games my pings have not changed a hell of a lot some are same as before grrrrrr 100 bucks cnot that good cause pings is what i did this for thinking of going back to stantard hope this helps

Betauser · Post by **Betauser** » Sat Jul 26, 2003 1:56 pm

ok, im one of those ppl who upgraded to pro too and i got atleast 2.0mbs->up (doesnt go down) and 306kps->up and it doesnt go down either.. so i guess they did it right when i upgraded my connection..

holden mcgrion · Post by **holden mcgrion** » Sun Jul 27, 2003 8:55 am

i disagree at 2mb/300 or whatever it looks like your missing a mb or so should be better than than dont seem like pro to me looks like still in the minors.