General

Best of the ISP-Lists

Troubleshooting PM3 Disconnects

Members of the ISP-Tech list discuss dealing with disconnect problems. They suggest that there are other possible problems to consider before you start second-guessing the quality of your downstream connection.

On the ISP-Tech list in December, JR asked,

"We're a small ISP using primarily PM3 modems; lately we've gotten a lot of calls about dropped connections. I've got a coworker who's convinced it's because our T1 is getting over-saturated. Will a PM3 just randomly disconnect users if their network requests are timing out because of an over-saturated pipe?"

A number of respondents suggested that the first thing to check is the modem:

[JM explained] "The only time our PM3 kills a call is if we turn it off, or if our multiple login checker finds an account logged on more than once. 99% of the time, the problem is on the client's end. See if they have a software-based modem. If they do, have them get a hardware-based modem; that solves it every time."

[TNA agreed] "Pretty soon, the manufacturers will include a cup and a string as a modem and still blame it on the ISP. We should sue computer manufacturers for using software modems."

[CS advised] "Familiarize yourself with the modem information at www.808hi.com. You will be able to fix most of your disconnect issues by having your users install the latest firmware for their modems, or by limiting their connect rate, or by giving them a string to define a protocol. Even many with 'five dollar' modems will be satisfied." Others noted that there are a wide and colorful variety of other factors to consider:

[JT observed] "The trouble is, no two connections are the same, or follow the same route through the telco's circuits and switches. I have three dialup locations in my city for my customers; some work good for some, others are better for someone else. People in older neighborhoods have more trouble-but not always."

[DH advised] "PM3s are very sensitive to traffic loads on their Ethernet port. If you are using a 10BaseT hub, then Lucent recommends only two PM3s on that LAN. If you need more, they recommend using a 100BaseT switch. I had numerous disconnect problems with six PM3s on a 10BaseT network. I had to convert to a 100BaseT switch to get rid of them."

[RS added] "Remember, there are lots of reasons for disconnects. We see customer line issues pop up every fall, when woodpeckers peck holes in the cable sheaths."

Finally, TKS offered a balanced view of the situation:

"Most problems are line-related. In order of probability: line noise, corrosion in the box outside their home, noise from other telephone devices on the same line, and, of course, the modem. The downside is that the telco will claim to test the line and tell the customer his line is good. I had a customer who had to call them six times, and the sixth time they miraculously found a problem—he now gets no drops."

—End

 

Related article:
	[Oct. 4, 2000]	No Busy Signals?