# [or-cvs] r18879: {projects} clean up the economics discussion i'm done with the first dr (projects/performance)

arma at seul.org arma at seul.org
Wed Mar 11 10:55:21 UTC 2009

Author: arma
Date: 2009-03-11 06:55:21 -0400 (Wed, 11 Mar 2009)
New Revision: 18879

Modified:
projects/performance/performance.tex
Log:
clean up the economics discussion

i'm done with the first draft! woo!

Modified: projects/performance/performance.tex
===================================================================
--- projects/performance/performance.tex	2009-03-11 10:38:01 UTC (rev 18878)
+++ projects/performance/performance.tex	2009-03-11 10:55:21 UTC (rev 18879)
@@ -1459,8 +1459,8 @@

{\bf Risk}: Low.

-{\bf Plan}: Overall, it seems like a risky move, but with potentially
-quite a good payoff. I'm not convinced either way.
+{\bf Plan}: Overall, it seems like a delicate move, but with potentially
+quite a good payoff. I'm not convinced yet either way.

\section{The network overhead is still too high for modem users}

@@ -1564,7 +1564,8 @@
\subsection{Lessons from economics}
\label{sec:economics}

-Imagine the solutions above double the effective capacity of the Tor
+Imagine we implement all the solutions above, and it doubles the effective
+capacity of the Tor
network. The na\"{\i}ve hypothesis is that users would then experience
twice the throughput.
Unfortunately this is not true, because it assumes that the number of
@@ -1620,60 +1621,62 @@
then everyone gets a 50\% improvement, which matches the na\"{\i}ve
hypothesis.
More realistically, the number of users increases, so the performance
-gain is less and the shallower the curve gets, the smaller the performance
+gain is less. The shallower the curve gets, the smaller the performance
increase will be.
For demand curve B, there is a 18\% increase in the number of Tor users
-and a 27\% increase in throughput; whereas with curve C there are 33\%
+and a 27\% increase in throughput. On the other hand, with curve C there
+are 33\%
more users and so only a 13\% increase in throughput for each user.

-In an extreme case where the demand curve points down (not shown),
-as the network bandwidth increases, performance for users will fall.
-Products exhibiting this type of demand curve, such as designer clothes,
-are known as Veblen goods.
-As the price increases, their value as status symbols grows, so more
-people want to buy them.
-I don't think it is likely to be the case with Tor, but there could be
-a few users who might think that the slower the network is, the better
-it is for anonymity.
+%In an extreme case where the demand curve points down (not shown),
+%as the network bandwidth increases, performance for users will fall.
+%Products exhibiting this type of demand curve, such as designer clothes,
+%are known as Veblen goods.
+%As the price increases, their value as status symbols grows, so more
+%people want to buy them.
+%I don't think it is likely to be the case with Tor, but there could be
+%a few users who might think that the slower the network is, the better
+%it is for anonymity.

-To keep the explanation simple, I have made quite a few assumptions,
-some more reasonable than others.
-For the supply curve, I assume that all Tor's bandwidth goes into
-servicing user requests, it is shared fairly between users, there is
-no overhead when the number of Tor clients grows, and the performance
-bottleneck is the network, not clients.
-I don't think any of these are true, but the difference between the ideal
-case and reality might not be significant enough to nullify the analysis.
-The demand curves are basically guesswork -- it's unlikely that the true
-one is as nicely behaved as the ideal ones shown.
-It more likely will be a combination of the different classes, as
-different user communities come into relevance.
+%To keep the explanation simple, I have made quite a few assumptions,
+%some more reasonable than others.
+%For the supply curve, I assume that all Tor's bandwidth goes into
+%servicing user requests, it is shared fairly between users, there is
+%no overhead when the number of Tor clients grows, and the performance
+%bottleneck is the network, not clients.
+%I don't think any of these are true, but the difference between the ideal
+%case and reality might not be significant enough to nullify the analysis.
+%The demand curves are basically guesswork -- it's unlikely that the true
+%one is as nicely behaved as the ideal ones shown.
+%It more likely will be a combination of the different classes, as
+%different user communities come into relevance.

-I glossed over the aspect of reaching equilibrium -- in fact it could
+The above analysis glosses over many topics. One interesting analysis
+is reaching equilibrium -- in fact it could
take some time between the network bandwidth changing and the user
population reaching stability.
If this period is sufficiently long and network bandwidth is sufficiently
volatile it might never reach equilibrium.
-I've also ignored effects which shift the demand curve.
+We might also consider effects which shift the demand curve.
In normal economics, marketing makes people buy a product even though
they considered it too expensive.
Similarly, a Slashdot article or news of a privacy scandal could make
Tor users more tolerant of the poor performance.
Finally, the user perception of performance is an interesting and complex
-topic, which I've not covered here.
-I've assumed that performance is equivalent to throughput, but actually
+topic. In this analyis
+we assumed that performance is equivalent to throughput; but actually
latency, packet loss, predictability, and their interaction with TCP/IP
congestion control are important components too.

-\subsubsection{Differential pricing for Tor users}
+So what does all this tell us?

The above discussion has argued that the speed of an anonymity network
will converge on the slowest level that the most tolerant users will
consider usable.
-This is problematic because there are is significant variation in levels
+This is problematic because there is significant variation in levels
of tolerance between different users and different protocols.
Most notably, file sharing users are subject to high profile legal
-threats, and do not require interactive traffic, so will continue to use
+threats, and do not require interactive traffic, so they will continue to use
a network even if the performance is considerably lower than the usable
level for web browsing.

@@ -1687,8 +1690,8 @@
Alternatively, the network could be configured to share resources in a
manner such that the utility to each user is more equal.
In this case, it will be acceptable to all users that a single equilibrium
-point is formed, because its level will no longer be in terms of simple
-bandwidth.
+point is formed, because its level will no longer be characterized in
+terms of simple bandwidth.

\prettyref{sec:too-much-load} is an example of the former strategy.
Web browsing users will be offered better performance, so we should