RE: [PLUG] Response to your DCANet DSL Problems - WAS: Puzzling networking problem

["Andy Smith" <ajs@dca.net>]

Hello Gabriel,

To answer some of your questions:

> Really. So the ATM link isn't actually COVAD equipment?
> 
> (Or are you not a COVAD reseller? I thought you were...)

DCANet sells SDSL and ADSL service using both Covad and Verizon.  In
Center City Philadelphia and downtown Wilmington we can provision
point-to-point DSL service ourselves.

In this case, the user with the troubles has a Verizon ADSL circuit, so
I wrote about how the Verizon system works.  Covad's network is similar
to Verizon in that all traffic is aggregated via layer-2 ATM and then
handed off to the ISP.  Covad is nicer in that the ATM network is static
-- that is, the ATM PVC's do not change dynamically.  Also, Covad
provisions one PVC per customer, instead of one (or more) PVC's per
central office.  With Verizon ADSL there could be dozens or even
hundreds of subscribers in a single ATM PVC, with Covad there is only
ever one.  

Covad also provisions SDSL over dedicated copper pairs, which can
eliminate the problems of using 'line splitters' and having the DSL ride
on your dial tone.  But, Covad is more expensive, and in the end more
people choose Verizon simply because of price.

>> Sometimes in this whole process, and lately more frequently, Verizon
>> will re-provision which ATM PVC your particular traffic traverses.
This
>> happens with no warning to us or to anyone else.
>
> That's insane. I'll wager they notify their internal IP services
> when they do this. (Uh, well, actually, based on their quality of
> service, maybe not.)

Well, you have to remember that most ISP's who provide Verizon ADSL
service (including Verizon.net) also require the use of PPPoE or PPPoA.
PPP-over-Ethernet will automatically 'redial' in the event of a
connectivity loss, so in essence for users who have to use PPPo{E,A} the
underlying network reconfigurations are for the most part unnoticeable.


I know that some routers and firewalls which can be set to use DHCP for
external addressing will periodically ping the assigned default gateway.
If they don't get a response back, they will self release / renew.
Again, this would fix any unannounced changes in the network and the end
user probably would not notice.

> I think that may be my cue to point out that my Speakeasy-managed
> COVAD SDSL (768) line has had troubles a grand total of zero times
> in nearly two years of service. Note that I pay a little bit over
> three times as much as DCANet's ADSL subscribers do for this
> service.

Yep, Covad circuits are better circuits, for the reasons I pointed out
above.  Hopefully they'll be able to stay in business in the face of
competition from Verizon and cable.

-Andy


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