Adam Bowden wrote:
>
> IMHO:
>
> This is what I thought happens - Just a guess (probably get flamed )
>
> DSL represents the connection between client and telecoms atm network. Which
> seems to establish some form of "ppp" type connection across telecoms ATM
> network. This represents the connection between client and ISP. Telecom
> charges the dsl user on a usage based system.
>

AFAIK, the ppp connection is between the RAN and the customer, not the
ISP and the customer.

> If the ISP did not connect to the client through the ATM network then they
> would probably need ISDN T-1 circuits to take the incoming modem calls and
> the appropriate modem hardware. Ie they need a modem and 1/24th of an T-1
> ISDN connection for each client. This is probably more expensive than the
> ATM type solution because they need hardware and fixed bandwidth per client
> ie each modem requires 64kbs.
>

T1 is just an Americanism. New Zealand uses the European standard 'E'.
The E1 is 2.048 MBit/s, whereas a T1 is 1.544 MBit/s. An E1 is just a
bunch of 64K multiplexed digital channels anyway.

> Now I assume what ISPs rely on is that not everybody thrashes there internet
> connection so they will "concentrate" all their clients going through one
> Internet pipe. The speed of this pipe only needs to be good enough to
> maintain their customers perception of Quality of service.
>

Yes, QoS or bandwidth shaping is pretty widely practiced. It would be
very hard for an ISP to guarantee the maximum available bandwith for all
its clients at once. For example frame relay has a CIR which, where I
work is 8K (no sniggers please). This bursts to a maximum of 64K.
Depending on how loaded the network over which the frame relay PVC runs
over, the Telco can set a switch which causes packets to be dropped
depending on how much restiction the burst can burst up to. Walker
wireless is the same. A typical connection of 64Kbit 'guarantees' you
that 64K but can burst up to 2 megs, and depending on how Walker
Wireless control their b/w, that burst is restricted.

Chris Hellberg

This message is part of the NZ Broadband mailing list.
see http://unixathome.org/adsl/ for archives, FAQ,
and various documents.
To unsubscribe: send mail to majordomo@unixathome.org
with "unsubscribe adsl" in the body of the message
Received on Fri Oct 6 10:40:03 2000