Re: Tiscali Broadband

[Brian Candler <B.Candler at pobox.com>]

On Mon, Jun 23, 2003 at 01:48:42PM +0300, Mark Tinka wrote:
> I've been looking at your company's website, and I noticed your broadband
> service. Would you please tell me what technology you are actually using to
> deliver the broadband service? Is it it some form of xDSL [I should think
> so]?

Yep, ADSL: 512K down/256K up, 1M down/256K up, or 2M down/256K up.

In the UK, although 'local loop unbundling' technically exists (where the
ISP puts their own equipment in the telephone exchange and connects it to
the copper), nobody does it, including us. Rather, we use the BT wholesale
DSL service: BT installs DSLAMs in exchanges and connects to the lines, and
the ISP gets either an ATM or an IP interconnect from BT. (We do both).

> >From what I see, if a client has a phone line from the telco, all you do is
> add a splitter to which your client then connects his telephone and your
> broadband modem. In theory, this should be cheaper than installing a
> dedicated frame relay or TDM circuit like corporates would - I guess because
> the telco only knows about a phone line going to the client's place, which
> has already been provisioned, right?

Certainly it's cheaper. However typically DSL bandwidth is aggregated
between multiple customers onto a single ATM VP, which may mean that at peak
periods the full bandwidth is not available.

> However, what does the telco have to do to the line for it to modulate more
> than 3KHz [.256MHz +]?

DSL is designed to work over unconditioned copper. However the range is
limited - perhaps 3-5km depending on what data rate you want. You can select
'adaptive' data rate for longer lines, but the modems may train down to a
speed below 512kbps.

The line needs to have any loading coils removed, but apart from that it
should work. An engineer can use a meter to measure the end-to-end signal
loss.

> Does what they do make the cost of line/provisioning
> of Tiscali broadband more expensive for the client? What arrangement do you
> have with the telco to provision a broadband circuit to the client? What
> does it cost the telco to provision circuit bandwidth to the cleint's line,
> even though it's an existing phone line?

It's a wholesale arrangement between BT and the ISPs. The details and
pricing are available from BT's website, if you look hard enough. The
products are called "IPstream" (where the ISP gets an IP feed) and
"Datastream" (for ATM)

> In comparison to a main stream frame relay, TDM or other dedicated service,
> what is the savings in costs to Tiscali, BT and the client, you have
> realised?

Setting up a VPN customer with say 50 DSL lines is a whole lot cheaper than
50 TDM circuits. Balanced against this, DSL coverage is a long way from 100%
(that is, BT has only installed DSLAMs in the exchanges where there are at
least 250 broadband customers), so the more remote sites still need either a
leased line or ISDN dialup. DSL also seems to be a lot less reliable, so for
critical apps ISDN backup is important.

HTH,

Brian.

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