How do multiple ISPs serve their DSL customers using the same telco DSLAM?

Posted on 2004-11-23
Last Modified: 2008-01-16
let's make the following assumptions..
1. i have a phone line from Verizon at home,
2. My DSL Internet provider is Earthlink.
3. My neighbor also has a Verizon phone line and has DSL Internet access provided by AOL.
4. Earthlink and AOL don't have DSLAMs at the Verizon central office which serves me/my neighbor.
5. Both AOL and Earthlink have ATM WAN interfaces to Verizon's ATM backbone network, and the Verizon CO DSLAM also has interfaces connecting it to the same ATM backbone

How does Verizon configure the connection for the two customers here - me and my neighbor, who have different ISPs? I can think of the following options...

1. (Bridged?) VLAN
my phone loop lands on a particular DSLAM port A. This port is part of a VLAN which is specific to my ISP, and the VLAN spans multiple locations (other central offices) and includes the ISP WAN interface port (at the boundary Verizon ATM switch that connects to the ISP).
This would be a (bridged?) VLAN over an ATM WAN.

Similarly, my neighbor's port on the DSLAM would be part of a different VLAN.

my port on the DSLAM maps to an ATM PVC between the DSLAM and the ISP's ATM equipment. The one reason i can see this happening is for giving me a static IP address. I dont think option 1 can give me a static address, though i can't explain how.

My questions..
1. any wrong assumptions made in the statements above?
2. how is a VLAN over multiple locations mapped to ATM transport? I mean, how can the simultaneous use of a WAN ATM link be controlled?
3. How does the ISP router(which has an ATM interface with Verizon) see the multiple customers connected to the same DSLAM distinctly, so that they can each be assigned an IP address?


Question by:manisridhar
    LVL 9

    Accepted Solution

    I saw a company (ABC) provides resale DSL to end users through local Telco. User -> DSLAM (local telco) -> ATM PVC -> Company ABC's ATM interface -> Company ABC's cloud.

    Not sure if this is what you are asking ...

    Author Comment

    thanks. what you said is similar to what i thought. Would you know how exactly PPPoE terminated is different from Bridged Virtual LAN?

    LVL 32

    Assisted Solution

    Also, if the provider has a relationship with the telco why couldn't that connection be engineered to the provider's premise where the DSLAM is located? When I say relationship I mean the provider can purchase conectivity to the telco or they could co-locate equipment at the telcos premise. Either way this can be done quite easily


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