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modem weirdness
The fine folks at Telerama lent us a modem with which to test. (We've been having random short-term network lossage.) The test modem, however, is unhappy in new and novel ways.
With the test modem, pings and SSH connections get through just fine, but web browsing isn't happening. (I saw one page get to "transferring..." before failing, but most sites timed out at "resolving host". Reminder: other uses of name service were fine.) I cleared the cache and restarted the browser, which didn't make a difference. Dani reported the same behavior with a different browser on a different machine. Restoring the original modem made the problem go away.
So that was oddity #1. Oddity #2 presented itself when I picked up the phone to call tech support about oddity #1 -- and found a very noisy line. After switching to my cell phone, I talked to someone who suggested that the noise is due to a lack of filtering on the phone line and he has no clue why the selective network service would be happening. But the old modem doesn't produce noise on the line, and all I did was swap the cables to the new modem and turn it on. I definitely didn't change any configuration on our phone lines.
Could it be that some modems have this filtering built-in and others don't? That seems weird to me, as the person I talked to seemed to be saying that the filtering has to be done to all jacks, and I certainly got the noise on a different jack than the one supporting the modem (which is consistent with that). I know that BellAtlantic came in and did something to our phone line before installing DSL 5+ years ago, but it was a change at the box and not at the jacks.
Both modems are Westell, though of different vintages.
I am now officially perplexed.
With the test modem, pings and SSH connections get through just fine, but web browsing isn't happening. (I saw one page get to "transferring..." before failing, but most sites timed out at "resolving host". Reminder: other uses of name service were fine.) I cleared the cache and restarted the browser, which didn't make a difference. Dani reported the same behavior with a different browser on a different machine. Restoring the original modem made the problem go away.
So that was oddity #1. Oddity #2 presented itself when I picked up the phone to call tech support about oddity #1 -- and found a very noisy line. After switching to my cell phone, I talked to someone who suggested that the noise is due to a lack of filtering on the phone line and he has no clue why the selective network service would be happening. But the old modem doesn't produce noise on the line, and all I did was swap the cables to the new modem and turn it on. I definitely didn't change any configuration on our phone lines.
Could it be that some modems have this filtering built-in and others don't? That seems weird to me, as the person I talked to seemed to be saying that the filtering has to be done to all jacks, and I certainly got the noise on a different jack than the one supporting the modem (which is consistent with that). I know that BellAtlantic came in and did something to our phone line before installing DSL 5+ years ago, but it was a change at the box and not at the jacks.
Both modems are Westell, though of different vintages.
I am now officially perplexed.
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The newer version of ADSL technology doesn't require a house splitter, but requires low-pass filters on all the phone lines connected to analog devices, or there will be noise on the line. The nice thing is that they mail you a DSL intsall kit and flip a switch at the Central Office, and you have DSL. No house visit. (I'm waiting for them to mail my kit to me. I was pleasantly surprised that no one had to come to my house to give me DSL!)
The first of the two types is older and would explain why Bell Atlantic had to come to the house to install something 5 years ago. I wonder if somewhere along the line, your type of DSL was changed? But why it would manifest itself when you switch modems, I don't know. Unless the old modem was designed for the first type of DSL, and the newer modem is designed for the newer type.
For a slightly more techy explanation of it all, see:
http://www.techweb.com/encyclopedia/defineterm.jhtml;jsessionid=2J5XLVSZKVNR2QSNDBCCKHSCJUMEKJVN?term=dsl&x=0&y=0