Newbie problem with RCA Cable modem, thanks!

saobi · Post by **saobi** » Tue Feb 26, 2008 10:42 pm

Hi all, I'm a total newbie to broadband hardware. So thanks in advance!

Problem: tonight I am seeing dropped internet connectivity every 3 minutes or so, and each time, I have to unplug my cable modem, replug, then renew my IP, then it'll work for ~3 minutes, repeat....

I use time warner, so I called them up, they ran a diagnostic and said my "download power" was too high ( no details). And said they must send a technician over to "fix" it. Unfortunately, the earliest appointment is 2 weeks away. Is there anything I can check/try in the mean time that may help me fix it myself?

The modem I use is RCA. I connect my ethernet cable directly to it, no routers. And this is the first time in 2 years that I am seeing this problem.

I am happy to run any software tools and post the results here if needed. Again, thanks so much in advance!

YARDofSTUF · Post by **YARDofSTUF** » Tue Feb 26, 2008 11:08 pm

Wiggle the power cable to the modem, does the modem turn off and on or act eratic?

helter · Post by **helter** » Tue Feb 26, 2008 11:37 pm

saobi wrote:Hi all, I'm a total newbie to broadband hardware. So thanks in advance!

Problem: tonight I am seeing dropped internet connectivity every 3 minutes or so, and each time, I have to unplug my cable modem, replug, then renew my IP, then it'll work for ~3 minutes, repeat....

I use time warner, so I called them up, they ran a diagnostic and said my "download power" was too high ( no details). And said they must send a technician over to "fix" it. Unfortunately, the earliest appointment is 2 weeks away. Is there anything I can check/try in the mean time that may help me fix it myself?

The modem I use is RCA. I connect my ethernet cable directly to it, no routers. And this is the first time in 2 years that I am seeing this problem.

I am happy to run any software tools and post the results here if needed. Again, thanks so much in advance!

http://192.168.100.1 what are your modem diagnostics showing?

saobi · Post by **saobi** » Wed Feb 27, 2008 12:16 am

Here's the screen of the diagnostic page of the modem
(http://192.168.100.1 )

Thanks

helter · Post by **helter** » Wed Feb 27, 2008 9:03 am

saobi wrote:Here's the screen of the diagnostic page of the modem
(http://192.168.100.1 )

Thanks

While 9.8 is technically out of spec for an install its fine for the modem, and all he needs is a 3db attenuator on the back of it to put you at 6.8 and 49 so I'm not sure what he was trying to say...

9.8 will not cause dropped internet connectivity though.
BER is fine, so I'm guessing it is something else.
Is the problem still happening?

Check the event log and see what it says as well.

trogers · Post by **trogers** » Wed Feb 27, 2008 9:43 am

What speed did you pay your ISP to give you?

Post your TCP Analyzer report.

saobi · Post by **saobi** » Wed Feb 27, 2008 8:47 pm

Sorry, it looks like now my connection won't even stay on for more than 1 minutes, so I couldn't really run TCP analyzer with this connection. I'm posting in another location

Just to clarify, my time warner support guy told me that my "downstream power" was too high.

In any case, I just bought a new cable modem (Motorola) from radio shack. They said I just need to call my cable company and tell them the serial number of the new modem. Will the new modem fix the issue?

YARDofSTUF · Post by **YARDofSTUF** » Wed Feb 27, 2008 8:49 pm

If the old modem was the problem then yes a new one will fix it. Did you wiggle the power cable?

saobi · Post by **saobi** » Wed Feb 27, 2008 9:00 pm

Ok I managed to get onto that connection for 1 minute. Tried wiggling the cord, it does not seem to influence the modem lights.

Here's the TCP Analyzer results:

TCP options string = 020405b40103030101010402
MTU = 1500
MTU is fully optimized for broadband.
MSS = 1460
Maximum useful data in each packet = 1460, which equals MSS.
Default TCP Receive Window (RWIN) = 65700
RWIN Scaling (RFC1323) = 1 bits (scale factor of 2)
Unscaled TCP Receive Window = 32850

RWIN is not fully optimized (even though it is a comparatively large number). The unscaled RWIN value is lower than it should be. Also, RWIN being close to and above 65535 does not justify the header overhead of enabling TCP 1323 Options. You might want to use one of the recommended RWIN values below.

RWIN is a multiple of MSS
Other RWIN values 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)
64240 (MSS x 44)
bandwidth * delay product (Note this is not a speed test):

Your TCP Window limits you to: 2628 kbps (329 KBytes/s) @ 200ms
Your TCP Window limits you to: 1051 kbps (131 KBytes/s) @ 500ms
MTU Discovery (RFC1191) = ON
Time to live left = 114 hops
TTL value is ok.
Timestamps (RFC1323) = OFF
Selective Acknowledgements (RFC2018) = ON
IP type of service field (RFC1349) = 00000000 (0)

Here's my modem's event log, over two days:

Thu Feb 28 01:49:09 2008 Critical (3) SYNC Timing Synchronization failure - Failed to receive MAC S...
Thu Feb 28 01:48:50 2008 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Thu Feb 28 01:48:17 2008 Critical (3) Started Unicast Maintenance Ranging - No Response received - ...
Thu Feb 28 01:45:32 2008 Critical (3) SYNC Timing Synchronization failure - Failed to receive MAC S...
Thu Feb 28 01:45:13 2008 Critical (3) No Ranging Response received - T3 time-out
Thu Feb 28 01:45:03 2008 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Thu Feb 28 01:44:30 2008 Critical (3) Started Unicast Maintenance Ranging - No Response received - ...
Thu Feb 28 01:44:26 2008 Critical (3) Started Unicast Maintenance Ranging - No Response received - ...
Time Not Established Critical (3) No Ranging Response received - T3 time-out
Time Not Established Critical (3) Started Unicast Maintenance Ranging - No Response received - ...
Time Not Established Critical (3) No Ranging Response received - T3 time-out
Thu Feb 28 01:35:22 2008 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Thu Feb 28 01:34:50 2008 Critical (3) Started Unicast Maintenance Ranging - No Response received - ...
Thu Feb 28 00:02:47 2008 Critical (3) No Ranging Response received - T3 time-out
Thu Feb 28 00:02:40 2008 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Thu Feb 28 00:02:08 2008 Critical (3) Started Unicast Maintenance Ranging - No Response received - ...
Thu Feb 28 00:01:46 2008 Critical (3) No Ranging Response received - T3 time-out
Thu Feb 28 00:01:31 2008 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Thu Feb 28 00:00:58 2008 Critical (3) Started Unicast Maintenance Ranging - No Response received - ...
Thu Feb 28 00:00:06 2008 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Wed Feb 27 23:59:33 2008 Critical (3) Started Unicast Maintenance Ranging - No Response received - ...
Wed Feb 27 23:59:04 2008 Critical (3) DHCP FAILED - Discover sent, no offer received
Wed Feb 27 23:58:51 2008 Critical (3) Started Unicast Maintenance Ranging - No Response received - ...
Wed Feb 27 23:58:47 2008 Critical (3) DHCP FAILED - Discover sent, no offer received
Wed Feb 27 23:58:46 2008 Critical (3) Started Unicast Maintenance Ranging - No Response received - ...
Wed Feb 27 23:58:38 2008 Critical (3) DHCP FAILED - Discover sent, no offer received
Wed Feb 27 23:58:16 2008 Critical (3) REG RSP not received
Wed Feb 27 23:58:16 2008 Critical (3) Started Unicast Maintenance Ranging - No Response received - ...
Wed Feb 27 23:58:13 2008 Critical (3) REG RSP not received
Wed Feb 27 23:58:13 2008 Critical (3) Started Unicast Maintenance Ranging - No Response received - ...
Wed Feb 27 23:58:10 2008 Critical (3) REG RSP not received
Wed Feb 27 23:58:10 2008 Critical (3) Started Unicast Maintenance Ranging - No Response received - ...

trogers · Post by **trogers** » Wed Feb 27, 2008 9:28 pm

You are using Vista. Check and see if you need to upgrade the firmwares of your Nic, modem, etc. to work with Vista.

saobi · Post by **saobi** » Wed Feb 27, 2008 9:30 pm

No, I'm using XP, SP2. Not Vista.

trogers · Post by **trogers** » Wed Feb 27, 2008 9:35 pm

saobi wrote:No, I'm using XP, SP2. Not Vista.

Then your TCP Window set to 65700 is inefficient.

Try the following with TCP Optimizer:

General Settings tab:
Custom settings - check
Modify All Network Adapters - check
network adapter selection - your NIC
MTU - 1500
TTL - 64
TCP Receive Window - 64240
MTU Discovery - Yes
Black Hole Detect - No
Selective Acks - Yes
Max Duplicate ACKs - 2
TCP 1323 Options:
Windows Scaling - uncheck
Timestamps - uncheck

Advanced Settings tab:
Max Connections per Server - 10
Max Connections per 1.0 Server - 20
LocalPriority - 1
Host Priority - 1
DNSPriority - 1
NetbtPriority - 1
Lan Browsing speedup - optimized
QoS: NonBestEffortLimit - 0
ToS: DisableUserTOSSetting - 0
ToS: DefaultTOSValue - 80
MaxNegativeCacheTtl - 0
NetFailureCacheTime - 0
NegativeSOACache Time - 0
LAN Request Buffer Size - 32768
Then select "Apply Changes" and reboot to take effect

saobi · Post by **saobi** » Wed Feb 27, 2008 9:56 pm

Hmm, I just disconnected the co-axial cable from my modem, and reconnected it. Now the connection has been alive for more than 20 mins! Maybe that fixed the problem?

Here's the new diagnostic page, after I re-connected the co-axial cable.