Muni fiber: L1 or L2?

Thu Feb 7 01:03:54 UTC 2013

Scott Helms wrote:

>> You miss ATM switches to connect the card to multiple modems.

> Most PPPoE L2TP setups have no ATM besides the default PVC
> between the modem and the DSLAM.

You still miss ATM switches to connect the card to multiple DSLAMs.

>>> You realize that most commonly the L2TP LAC and LNS are just routers
>> right?
>>
>> Who, do you think, operate the network between LAC and LNS?

> Most often the the LAC and the LNS are directly connected (from an IP
> standpoint) for purposes of PPPoE termination.

Most often? No, it merely means there aren't real competitors.

Assuming LACs are operated by a dominant carrier, there are 3
cases how LACs and LNSs are located.

1) Each CO has an LAC and an LNS of a CLEC, in which case the
CLEC should have its own DSLAMs (with Ethernet interface, of
course)  connected to its customer twisted pairs and the LAC
and the LNSs can be eliminated to eliminate unnecessary cost.

Or, if there are other CLECs doing otherwise, the LAC may
still be necessary. But, the CLEC does not have to pay the
cost for it.

CLECs operate their own network between COs.

The most competitive case.

2) Each CO has an LAC and a CLEC has one or more LNSs somewhere,
in which case, the LNSs must be attached to a network operated
by the dominant carrier.

CLECs may operate their own network between some COs.

Moderately competitive case.

3) An LAC is centralized that network between COs and the LAC
is operated by the dominant carrier, in which case LNSs of
CLECs will likely be located near the LAC, which should be
the case you silently assumed.

The dominant carrier operate all the network between COs.

The least competitive case.

>> The largest DSL operator in Japan directly connect their routers
>> in COs with dark fibers to form there IP backbone. There is no
>> LAC nor LNS.

> OK, that's great but that neither makes it right nor wrong.

The question to be asked is not "right or wrong?" but "how
much competitive?".

Worse, the following statement of you is wrong:

: You're not getting rid of boxes, you're just getting rid of
: the only open access technology that's had significant success
: in the US or Europe.

> The largest
> DSL provider in the US (ATT) does it how I've described and that again
> doesn't make it right or wrong.

The largest DSL operator in Japan is not NTT or its family companies.

Lack of competitor at L1 tends to make DSL more expensive, unless
strong regulation is applied to the dominant carrier.

So, it is better, right, to let inter CO networks operated by
CLECs.

>>> Smaller ISPs usually go for L2 services, provided by the
>>> infrastructure operator or another ISP already present on
>>> site. But some tends to stick to L1 service and deply
>>> their own eqipments for many reasons.

> Again, that's neither right nor wrong.  We do lots of things because of
> regulations.  I don't believe (could be wrong) that most of the people in
> this conversation have the same problems or solutions as the tier 1
> operators.

FYI, the largest DSL operator in Japan is not tier 1.

> Its simply a different world and despite your belief L2
> unbundling is not a poor alternative.

It's poor because it's less unbundled and needs extra equipments
unnecessary for real competitors.

						Masataka Ohta