How does third-party DSL work? [telecom]

I have telephone service from AT&T, and DSL from Earthlink.

A while back my DSL went totally dead. The modem indicated that there was no connection to the DSL modem at the other end. Eventually Earthlink had an AT&T man come by, who spent a lot of time checking the wiring in my house and eventually found that the trouble was somewhere out there in the telephone plant, believe he said pair gain equipment. He said there are cards in there that go bad sometimes, and he switched my line to a different pair and that fixed it all up.

Now I'm having a different problem - the DSL modem indicates that it has a solid connection to the DSL modem at the other end, but the Internet connection keeps going away and coming back. There's supposed to be an AT&T man coming to look at it again.

It would help if I understood how all this works. DSL modem on copper pair at my house goes somewhere out in the city to some apparatus but not direct to the telephone office. I don't know where the DSL modem at the far end is, nor whether it is owned by AT&T or by Earthlink, nor how the DSL modem out there connects to the Internet.

Reply to
Jim Haynes
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Typically, (at least how we have it with CenturyLink and the 3rd party ISP I am part of)... Although there are lots of different scenarios, this is probably the most likely.

Your line routes out either to the central office DSLAM, or more likely, to the remote terminal box where the remote DSLAM is located. There the line is split off to the DSLAM, and off to the POTS switch (which would be further along the line in a remote terminal).

The DSLAM back-hauls over data back to the CO, in CenturyLinks' case, all over ATM, either optical OC3c, or bonded IMA ATM T1s.

The ATM packets are switched onto the ATM backbone, and then feed off to the 3rd party ISP on some sort of ATM trunk lines, optical OC3c or potentially DS3s.

There the 3rd party ISP terminates the ATM signal back into layer-3 internet with their gear, and puts your packets onto the Internet proper, giving you your IP address, and doing all the IP packet routing.

Other telco arrangements would hand off on GigEthernet with a vlan per-customer (not happening for 3rd party ISPs in CenturyLink territory). Or even a 3rd party ISP just resells the ILEC service altogether.

So, if the signal is out altogether, your line is disconnected between your prem and the remote DSLAM box (or the remote DSLAM is down). If you train up to remote DSLAM, but you can't authenticate or pass IP packets, then there is a whole backbone stretching from the remote, through the COs of how many ever hops, and back out to the ISP to terminate.

Since the CO-to-CO trunks are usually pretty stable, and the 3rd party ISP is probably pretty stable (if they are still around this late in the game), the problem usually involves the environmental box where the remote terminal is, either the feed into the box from the prem, or the back feed out of the box however they handle it.

Reply to
Doug McIntyre

There are AT&T and Earthlink forums on

Your questions can/will be answered there.

Reply to
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