more on worth reading

[David Farber <dave () farber net>]

Begin forwarded message:

From: Sean Donelan <sean () DONELAN COM>
Date: January 8, 2006 7:09:01 AM EST
To: CYBERTELECOM-L () LISTSERV AOL COM
Subject: Re: FW: [IP] worth reading
Reply-To: Telecom Regulation & the Internet <CYBERTELECOM- 
L () LISTSERV AOL COM>

The are all big companies with hundreds of thousands of people, its
amazing they manage to keep things as organized as they do.  I have
enough trouble just trying to get my family to agree what movie to
go see.

Since the service is now being sold to the public, at least in limited
quantities, folks should be seeing what's happening soon for themselves.
This is just what the public could/will discover for themselves using  
the
service now.

Start with the assumption you are buying a fractional IP line. When
I ordered Internet service for my ISP, the local telco installed an
OC12 line and mux on my premises.  But they didn't give me access
to the entire OC12, instead they used the mux to break out individual
TDM circuits as I ordered more bandwidth.  The rest of the OC12 line
was used for other services, and sometimes even other customers because
it was actually a fiber ring that just passed through the cabinet.

With "fractionalized IP" access (VDSL2 or FTTX), instead of fixed TDM
channels on a OC ring, you are buying a fraction of the bandwidth on  
an IP
connection for "Internet" access, not the entire circuit.  The Internet
portion works just like the Internet you use today, up to the data rate
(3Mbps, 6Mbps, etc), you bought to anywhere on the Internet, using any
IP protocol you want (modulo the usual AUP conditions such as no sending
spam, etc). The more Internet bandwidth you want, the more expensive it
is. The "Internet" charge includes both the local access line bandwidth
and also  a portion of the regional and backbone transit networks costs.
The telco's used to call this the GSP (Global Service Provider) charge,
now its just part of your Internet bill.

If you buy Internet access, you can still use it for VOIP or IPTV  
service
with any other provider on the Internet, within the constraints of the
bandwidth you bought for Internet access.  It works just as well or
poorly as it works on today's Internet.

The other part of the "fractionalized IP" VDSL2 bandwidth (e.g. 25Mbps
minus the 6Mbps used for Internet, which you didn't pay for) is used for
other carrier services.  If you just want video or voice service, you
don't need to buy any Internet access bandwidth at all.  If you only
wanted carrier IPTV service, your set-top box would get IP access to the
carrier's local video servers, not the Internet. If you only wanted
carrier voice access, your ATA would get IP access to the carrier's  
local
voice servers, not the Internet. Its no different than today if you
ordered cable TV service, but not cable modem service.  Or order
telephone service, but not DSL Internet service.

The fractionalized IP access line functions like two or three parallel
access networks over the access line, just at the IP layer instead of
separate ATM PVCs or cable RF channels. People are  buying access to
different "virtual" networks. You can buy access to the video network,
the voice network or the Internet network. Just because you buy  
access to
one of the networks, doesn't mean you get access to all of the bandwidth
on the physical circuit.

The x-PON used for FTTX may have a separate lambda for downstream video
broadcast.  In that case, it has a separate layer 2 network in addition
ot the two-way video IP traffic over the IP network.  Folks can get very
confused about what traffic goes through the broadcast lamda and which
traffic goes over the two-way lambdas.

You don't "see" the bandwidth being used for carrier's IPTV or  
IPVoice any
more than your PC "sees" the bandwidth being used for your cable video
channels or telephone POTS lines today. Your PC can't go above the
Internet access rate you bought on the fractionalized IP line, just like
you buy DSL/Cable service today.  The difference is instead of the
line rate being controlled by the DSL sync rate or DOCSIS configuration,
the Internet access rate is controlled by a leaky bucket IP queue set to
your purchased access rate (e.g. 3Mbps, 6Mbps, etc) for each virtual
network over the fractionalized IP circuit.

If you don't buy/use the carrier's voice or video service, the
Internet service is effectively the only service on the VDSL2 access
link, so QOS just acts as a bandwidth limiter based on the access rate
you bought.  In that case, there is nothing to "prioritize" beyond
a few link management messages.

If you have multiple services on a 25Mbps access line.  For example,
15Mbps to the carrier's video servers, 512Kbps to the carrier's voice
servers, and 6Mbps anywhere else (i.e. the Internet). In case the line
sync rate crashes through the floor, e.g. drops to only a few hundred
Kbps because the line is bad, QOS is important so your phone still works
(has first priority on the remaining hundred Kbps) when you call the
carrier to fix the line. Cable companies reserve bandwidth for their
"Digital Voice" services for the same reason. Again, if you don't use  
the
carrier's voice or video service, if the line sync rate crashes whatever
bandwidth available up to the maximum you bought for Internet access is
available for whatever service you can push through the remaining
bandwidth.

Once you go above the reserved bandwidth for Internet access and
also use other services from the carrier, you have oversubscribe
the line, and you are faced with choices.  Regardless of how big you
make the line (remember when 56K DDS circuits where considered fast),
bandwidth needs always expand and you always face the problem of
oversubscription and how to pay for upgrades.

The carrier could offer "burstable" Internet access up to the link rate,
but would people understand what happens when they use more bandwidth
than exists on their access line when they are sharing bandwidth among
all the services instead of reserving fixed amounts of each service?
Tech savvy people may understand they have a total of X-Mbps of
bandwidth. When they turn on 10 HD video streams, will they be surprised
if they see macroblocking. Other people probably will call their service
provider to complain their TV doesn't work or they aren't getting the
full X-Mbps downloads at the same time as watching HD sports on their  
TV.
In the near term, under-promising so you can over-deliver seems a safer
path.  That's probably why 6Mbps (instead of 25Mbps) is the top Internet
access rate now for VDSL2 and 30Mbps (instead of 100Mbps) is the top
Internet access rate for FTTP.

The carriers have probably changed their plans 10 times since I left, so
I have no idea what they are planning to do.


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