Re: Skype asks FCC to open up cellular networks

[David Farber <dave () farber net>]

This has gotten to be one of the most "nasty" discussions on IP n a  
while. (not just the "nasty" noted below but emails I have not  
posted. Reminds me of the net neutrality discussions. Too much emotion.

Dave


Begin forwarded message:

From: Brad Templeton <btm () templetons com>
Date: February 26, 2007 6:19:34 PM JST
To: David Farber <dave () farber net>
Cc: dpreed () reed com, brett () lariat net
Subject: Re: [IP] Re: Skype asks FCC to open up cellular networks

> Skype  does nothing magic here.   If you  "call somebody" on your
> Skype connection,  the bits sent are (strangely and wonderfully)
> exactly those bits needed to send your voice to his machine.
>
> > technical --
> > is that Skype works by "robbing" bandwidth from its users and their
> > ISPs. Skype does not buy enough bandwidth to route or connect all
> > of the calls placed via its network.


The real answer is somewhere between Brett's point and David's
surprisingly nasty rebuttal.

VoIP is generally a peer 2 peer application, using the net exactly
as it was intended.   A VoIP phone company does not need to buy
more than a trivial amount of switching bandwidth in order to
operate in the ideal end to end internet, so the line about Skype
"not buying enough bandwidth" is perhaps the source of confusion.

The problem occurs when users are behind NAT, which happens by
their own choice, or the choice of their facility, or because their
ISP does not provide them with enough routable IP addresses (or for
example, IPv6 which some P2P apps can use though I am unsure if
Skype does.)

In this situation sometimes the P2P applications are forced to
not route the traffic end-to-end as they would like to.   Many
companies took the path of installing relay servers and buying
bandwidth to relay the traffic when the two endpoints can't reach
one another directly.  Skype took the more unusual approach of
using other computers running Skype on reachable machines as the
relays.   While this is fairly well known, and I think spelled
out in the Skype EULA, it is true that many Skype users are not
aware their machine is doing this, and that the bandwidth they
have paid for is going to this purpose.     Because Skype reveals
this on their web site, it's not really stealing, but because
many people are unaware, it often feels that way.   Skype claims
they limit bandwidth used by relays to 1kb/second per channel,
and about 5kb/second total, which suggests that they must use
multiple relays simultaneously, as a single GIPS voice channel
needs at least 2kb/second, I believe.

It's clear that they could be more explicit about this, however.

For most ISPs, having the relay be on the same ISP is a big
win for the user and causes minimal trouble for the ISP.  Brett
runs an unusual ISP which is based on wireless.  For him, it is
not a win.   I must admit that sometimes Brett seems to act as
though all network applications should be designed with the
constraints of a wireless ISP in mind.  While I don't think it
is bad to think about those constraints, it is wrong to declare
applications as evil because they are designed with the
constraints of wired ISPs.   Wireless ISPs do not have full
duplex transmission, they can't do upstream and downstream at
the same instant, and traffic between peers is often particularly
expensive because it goes to an access point and back, and in
the case of a relaying peer goes through once again.

These constraints lead Brett to wish to run his ISP differently,
and this is as it should be.  I believe he is fairly open with
his customers that he can't sell them the sort of service that
would be no problem on a wired network.


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