Not quite. In most exchanges, Telstra owns the DSLAM infrastructure and sells its ADSL service wholesale to the other ISP. This is the issue that have been before the ACCC recently.

Once the DSL services are aggregated at the exchange, Telstrs delivers the IP packets to the contracted ISP. I am only familiar with the Shasta BSN5000 they used to use, and in that box a trunk is established over any other supported connection media to the contracted ISP. This would often by ATM, but could be any supported service such as fast etherenet (I think telstra migrated off the BSN before GigE was available). But the BSN5000 is basically an ATM box at that point.

The areas of potential outage would be:

• Telstra copper cable infrastructure
• Telstra DSLAM and aggregation infrastructure
• Trunk to contracted ISP
• Contracted ISP's authentication process (usually RADIUS)
• Contracted ISP's network

In the early days of Telstra ADSL, one of their biggest problem areas was the authentication process. That problem would not affect other ISP's.

For me, the biggest issue in selecting an ISP is the capacity of their network and how well they peer with the big players (ie Telstra, Optus, Connect.Com) and how they trunk to the US. That is the area of most congestion and hence performance issues. And I run a lot of IP Telephony over my ADSL service, so the last thing I want is to be passing through a congested peering connection between my ADSL ISP and my IP telephony server.