what causes the fluctuations in the cable modem

[Flasch186]

This morning, the internet is acting crazy. One second it pushes through files quick, and then 5 seconds later it bottlenecks to a standstill. What cuases this?

[gstelmack]

Bottleneck at the ISP (they could be having network issues anywhere from your street corner to the 'net itself). Maybe everyone on your street got highspeed internet for Christmas?

Problems with the cable line in your house itself. We upgraded to VOIP which puts more demands on the line and started having all kinds of connectivity issues (where the modem would spontaneously reboot). It turned out our cable run to the street was 149' in length and used a cable type rated to 150'. Since it was old and we had more demands on it, the cable just wasn't holding up and they replaced it with a heavier-duty cable. You could have troubles with any part of the cabling.

But I'd put my money on network issues. Check your ISP's network status page.

[chinaski]

Cable is pooled bandwidth, whereas DSL is dedicated. So like Greg said, if a bunch of people in your neighborhood got cable net over xmas, it will effect your bandwidth; but only of course if you are all online at the same time.

[DanGarion]

It is highly unlikely that you are having issues with bandwidth because there are too many customers in your neighborhood. Our network hasn't had an issue such as that in the Los Angeles area for well over three years.

DSL is pooled bandwidth (if that's what you want to call it) just like Cable modems, it's just the bandwidth is pooled at the switch instead of at the Hub/CMTS site. DSL is NOT dedicated, period.

Are there times when the Cable Link or Cable light flashes on the modem and you lose all connectivity?
There could be a number of reasons your cable can be fast one minute and slow another. What programs do you have running on your computer? Are you using an file sharing or peer-2-peer programs while you are doing your general browsing? Are you connected to a network behind your cable modem (like a router or switch)? Is your computer fully protected by both a firewall and virus software?

After those questions are answered. Your cable line could have some sort of defect or loss due to a cut or nick in the like. The jumpers or connectors could have corrosion. Are you noticing the problem happening when it's cold? how about when it's warm? have you called your cable company while the problem is happening and had them run whatever tools they have to check the signal level on them. Generally the SNR (signal to noise ratio) shoudl be at or above 30 (this does depend on your cable provider). The Modem's receive power RxP should be anywhere between 15 and -15, optimal range should be 9 to -9, but the 15's should still provide solid service. Transmit Power TxP should generally 31-54, anything over 54 could cause problems. Of course every cable provider runs their system differently and all I can do is provide you with our company guidelines here locally, but most of these are the DOCSIS standards.

[Desnudo]

This morning, the internet is acting crazy. One second it pushes through files quick, and then 5 seconds later it bottlenecks to a standstill. What cuases this?

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