wdiff draft-tschofenig-conex-ps-00.txt draft-tschofenig-conex-ps-01.txt

CONEX H. Tschofenig
Internet-Draft Nokia Siemens Networks
Intended status: Informational A. Cooper
Expires: April 22, 29, 2010 Center for Democracy &
Technology
October 19, 26, 2009

Congestion Exposure Problem Statement
draft-tschofenig-conex-ps-00.txt
draft-tschofenig-conex-ps-01.txt

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Abstract

The increasingly ubiquitous availability of broadband connections broadband, together with
flat-rate
pricing has pricing, have made the use of new types kinds of peer-to-peer
applications possible. increasingly common. From an Internet the perspective of the
Internet's evolution and its contributions to end user value point of view value, this is
very exciting. As a consequence, an increase of user-to-user traffic
was observable all around the world over the last few years. With However, the uptick in peer-to-peer application usage of p2p systems
has also contributed to the observation can be made that a certain
group rise of users, called high-consuming users, decided to use "high-consuming users" who take
their flat-rate contract excessively. This in turn seems contracts to have caused
network the limit by continuously file-sharing
to the maximum extent possible. Network operators have responded to take actions.
this phenomenon in a number of different fashions.

This document discusses the problems created for operators by high-
consuming users and illustrates a couple number of techniques used by operators
today are
currently using to deal cope with excessive high bandwidth usage. More information can
improve the decision making process.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. State-of-the-Art Building Blocks . . . . . . . . . . . . . . . 5
2.1. Means of Identifying the Causes of Congestion Accounting . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Potential Actions Operators might take in Response Deep Packet Inspection . . . . . . . . . . . . . . 6 . . . . 5
3. Network Operator Responses to Congestion . . . . . . . . . . . 7
4. New Activities . . . . . . . . . . . . . . . . . . . . . . . . 8
4. 9
5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5. 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. 12
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
8. 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. 14
9.1. Normative References . . . . . . . . . . . . . . . . . . . 13
8.2. 14
9.2. Informative References . . . . . . . . . . . . . . . . . . 13 14
Appendix A. Example Policy Statement . . . . . . . . . . . . . . 15 16
A.1. Fair Usage Policy . . . . . . . . . . . . . . . . . . . . 15 16
A.1.1. What is the Fair Usage Policy? . . . . . . . . . . . . 15 16
A.1.2. How do I know I'm a very heavy user? . . . . . . . . . 15 16
A.1.3. I have Contract Option 3, does the Fair Usage
Policy apply to me? . . . . . . . . . . . . . . . . . 15 16
A.1.4. Peer to Peer (P2P) . . . . . . . . . . . . . . . . . . 15 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 18

1. Introduction

In recent years, network operators around the world have begun to
feel the affects of "high-consuming users" -- those who use the
maximum amount of bandwidth possible, usually for the purpose of
peer-to-peer file sharing. In 2006 K. Cho et al. [traffic] published a paper about the growth of
residential user-to-user traffic in Japan reported
that indicates '... a for residential Japanese broadband connections, "a small number
of users dictate the overall behavior; 4 % 4% of high-consuming users
account for 75 % 75% of the inbound volume, and the fiber users account
for 86 % 86% of the inbound volume.'. The same volume." A more recent paper published
December 2008, see [traffic2], confirms that the distribution has not
changed much. User-to-user traffic comprised 63% of overall
residential traffic volume. The authors noted not only a changing
traffic distribution, but also
indicates a substantial increase in overall
traffic growth, namely 37 % growth (37% per
year according, and not just a different distribution of traffic
among the users. At that time 63 % of the residential traffic volume
is contributed by user-to-user traffic.

These numbers itself do year). Operators in other countries have
experienced similar shifts.

This trend does not represent necessarily present a problem on its face, as by themself and
increased traffic volumes do not necessarily automatically lead to congestion.
However, in some cases where operators very
likely had different expectations about the were not expecting these
changes in growth rates and traffic
consumption of individual users and statistics (used for consumption, their pricing models) did not work out too well for them. The profit
margins for models
and congestion management architectures have proved inadequate. In
some countries, fierce competition among Internet access are quite slim due to fierce competition. providers
has yielded low profit margins. This puts a lot of has increased the pressure on
operators to find effective ways to deal with these high- consuming users
who cost them a lot more money than the bulk of money. Finally, their subscribers.
Furthermore, some broadband networks (such as cable networks) may not
have the ideal characteristics (such as
the topology for routing traffic) (routing topology, for example) to
support high volumes of user-to-user traffic (e.g.,
Cable Networks). traffic.

Congestion is often mentioned in this context and as cost are closely related. As stated in RFC 5594 [RFC5594]
[RFC5594], "... congestion can be viewed merely as a manifestation of
cost. An ISP that invests in capacity could be considered to be
paying to relieve congestion. Or, if subscribers are charged for
congesting the network, then cost and congestion could be viewed as
one and the same. The distinction between them may thus be
artificial.".

To summarize in a simplistic way, The upshot for network operators is: those who produce
a lot of traffic cost a lot.

Operators are now facing a range of options, see sections below, that
can be taken and there is a tradeoff between options for addressing this
problem. There are many factors to consider for each kind of
solution, including how the solution performs, its cost, what is allowed (legally
and from a the
public relation point relations impact of view) using a particular solution might be, and
what is useful from a
performance point of view. The latter aspect can be seen from legal framework exists to support the
point of view use of a particular
solution. The performance considerations must take into account the
balance between device performance (as and forwarding performance (since
many of the solution mechanisms
actually slow down the forwarding performance quite a bit) performance),
and
consequently a cost challenge.

The existence of flat rate pricing contributes this determination is intimiately related to measuring a
solution's overall cost.

In some of cases, the
problems since popularity of flat-rate pricing plans exacerbate
the congestion problem because an individual's bandwidth usage in total needs to be covered by
the money obtained from broadband customers but the usage of
individual users is not reflected in
tied to his or her monthly bill, creating an incentive to use as much
bandwidth as possible and leaving operators to cover the amount. As such, costs of all
their users with essentially equal payments from each. Operators
know that
rarely utilize users appreciate the network pay certainty of having the same bill amount as someone who uses
P2p filesharing excessively.

However, from a psychological point of view humans tend to strive to
avoid uncertainty and hence offerings that reduced uncertainty. For
a user there are essentially two aspects to worry about

o Uncertainty in
remain the bill: unpredicable same for each billing period, allowing users to plan their
costs accordingly. But while flat-rate pricing avoids billing
uncertainty, it creates performance uncertainty: users cannot be sure
that make planning
difficult.

o Uncertainty in the performance: performance degradation as part of
the actions their connections is not being taken

True flat rate pricing avoids uncertainty in altered or
degrated based on how the bill. network operator manages congestion.
Unfortunately, most of the solutions described below lead to create some
uncertainty
performance uncertainty, and thereby increase unhappyness of customers. thus users are unlikely to view them as
ideal solutions, despite users' well known preference for flat-rate
pricing.

2. State-of-the-Art Building Blocks

2.1. Means

Two means of Identifying learning about the Causes of Congestion resource consumption and the traffic
traveling through the network that are in use today are accounting
and deep packet inspection.

2.1. Accounting

RFC 2975 [RFC2975] describes accounting as "The collection of
resource consumption data for the purposes of capacity and trend
analysis, cost allocation, auditing, and billing.".

Over the years the number of information elements that can be sent
from an accounting client to an accounting server using standardized
protocols, such as RADIUS (see [RFC2866] and [RFC2865]) and Diameter
[RFC3588], has increased. The fact that existence of standardized protocols have
been available
has allowed different AAA networks to be interconnected
and their usage can be found interconnect. These protocols
are now used in almost every enterprise and operator network. The
initial accounting mechanisms envisioned a rather non-
real non-real time
nature in reporting resource consumption but with mechanisms like
like Diameter Credit Control [RFC4006] allowed real-
time real-time credit
control checks.

It has to be noted that

Although they are popular, RADIUS and Diameter are not the only
protocols that can be used to collect usage information and to
trigger certain actions, even they are fairly popular. responses. Other approaches, as documented in
[I-D.livingood-woundy-congestion-mgmt], lead to similar results.

2.2. Deep Packet Inspection

Deep packet inspection (DPI) refers to inspecting the observation and analysis
of traffic that passes through the operators operator networks up to the
application layer. This allows operators to determine the
applications and/or application-layer protocols that subscribers are
using and respond on a per-application or per-protocol basis.

The process of inspecting traffic, particularly in real time, can be
highly performance-intensive. DPI equipment may also require
continous software updates to ensure that the detection engine
recognizes the latest protocol variants.

There may be a number of other factors that contribute to a network
operator's decision to use DPI, including potential user backlash,
privacy impact, and legal concerns.

Depending on the configuration of the device traffic shaping, doing the inspection,
packet dropping/blocking and other usages might be applied. For
example, content sharing p2p applications maintain many simultaneous
TCP connections with other nodes for the purpose of simultaneous
downloads. An operator may, for example, limit the number of
connection setups from a single subscriber. . Certain end user
contracts may also allow operators to ban servers from residential
access.

Determining the type of application that a subscriber is running was
seen as necessary

3. Network Operator Responses to throttle only certain applications, instead Congestion

Once they have collected congestion information using either of
impacting the full range of traffic
techniques described above or others, network operators have a subscriber is using. A side-
effect is the additional investment number
of options for the device and operational
costs. The process how to respond. For all of inspecting traffic these options, it is performance intensive
and continous software updates are necessary up to ensure that the
detection engine recognizes the latest protocol variants.
Additionally,
the attempt operator to selectively deal with applications (even
though these applications might be the reason for the high traffic
volume) has not been received well by the users.

2.2. Potential Actions Operators might take in Response

What actions are taken based on decide the collected information breadth and in what
time frame is largely left to the choice of those who run the
infrastructure. In the context depth of this discussion the collected
information may its response: which
users will be used to charge affected, the user per volume, per time and frame in various different combinations. Additionally, the RADIUS which congestion will be
managed, whether specific applications or protocols will be targeted,
and
Diameter allow the server side with a server-initiated message (see
Change of Authorization in [RFC3576], so forth. Operators can chose from both technical and the functionality provided
in the Diameter Base specification [RFC3588]) to push decisions to
the AAA clients, typically edge nodes, acting as enforcement nodes.
These decisions include actions like shaping or packet marking.

Shaping: pricing/
contract-based options. Technical options include:

Wholistic traffic shaping:

End user contracts often offer a combination of 'flat-rate'
scheme whereby a fixed price tariff is used up to provide users with a certain threshold
for baseline usage volume (typically (which is typically quite high for regular usage). high).
Subsequently, if
the consumption goes beyond a certain threshold then the entire threshold, all of the
user's traffic is given lower reduced priority and potentially shaped.

In many countries operators have to offer vis a clear description
of the service they offer and since vis other users on
the term 'flat-rate' is
already associated with network. Some operators may only shape traffic during times
of congestion or peak usage periods (even if a certain meaning user has exceeded
his or her baseline threshold).

Per-application or per-protocol shaping:

Network operators that can identify particular applications or
protocols creating congestion may decide to throttle only those
applications or protocols. They may also take indirect steps that
result in the term 'Unlimited
Data Rate' is often used for this type shaping of service. Contracts
typically contain statements that allow only certain actions to be
taken. applications, such as
limiting the number of simultaneous TCP connection setups from a
single subscriber (to handle peer-to-peer traffic), or preventing
users from hosting servers on residential connections. An example
of such a an ISP's fair use statement can be found usage policy describing how it manages specific
protocols is included in Appendix A.

Note that traffic shaping is often only applied to high-consuming
users (since they are known based on the accounting procedures) or
the effect becomes only visible during peak hours when the network
fills up.

Class-Based Assignment:

In this technique users are classified into a set of classes
depending on their past behavior. Subsequently,
the their traffic is
treated according to the their associated class. It is
ensured that the traffic of classes. This may prevent
lightweight users, users that really
rarely use their Internet connection, cannot be pushed away by from feeling the effects of sharing network
capacity with heavy users. This mechanism again requires some form of DiffServ
packet marking to be in place. able to differentiate light users from heavy
users.

Pricing/contract-based options include:

Charging for Excessive Traffic: As a possible action a user might
get charged Network operators may charge
users differently for traffic that exeeds a certain threshold
compared to the traffic that falls within below the agreed
limits. threshold.

Suspending or Discontinuing Contracts: In some rare cases ISP also decided ISPs
may decide to cut
connectivity under certain condition. suspend or terminate the contracts of heavy
users. In fact some cases this might response may be
justified in certain cases. For example, in case of new botnets
malware distribution associated with a
security issue; when the an operator recognizes an infected a botnet-infected
machine and hotlines generating excessive traffic, it may hotline all the entire
traffic of that particular machine to a separate network and, like in WLAN hotspots, HTTP traffic is
intercepted to display further information. network, and
ultimately suspend or terminate the machine's connection. In
some cases the same technique has been applied with excessive usage of to users engaged
in heavy P2P
traffic, usage, either intentionally or due to a false
alarm caused by a statistical traffic analysis technique.

In France the HADOPI law adopted in parliament that allowed an
'independent authority' to punish copyright violators with a
temporary suspension of their Internet access has raised
discussions within Europe about the fundamental right to
'communicate and express' and its applicability to the Internet
access. Although this discussion is still ongoing the French
Supreme Court had striked down portions of the law arguing that
any restriction of such a right can only be decided by a judge.

3. analysis.

4. New Activities

In response to

Following the P2P infrastructure workshop IETF Workshop on Peer-to-Peer (P2P) Infrastructure in
2008 (with a
summary documented [RFC5594]) (see [RFC5594]), two working groups and one research group has been were
created that focus on a certain area of relate to the congestion issues created by peer-to-peer
application space: usage: :

LEDBAT (Low Extra Delay Background Transport) [ledbat] is designed
to allow to keep the latency across the a congested bottleneck low even as it
is saturated. This allows applications that send large amounts of
data, particularly upstream on home connections, such connections (such as peer-to-peer application, peer-to-
peer applications) to operate without destroying the user
experience in interactive applications.

LEDBAT is a promising approach when applied widely in holds substantial promise should P2P clients. clients adopt it
widely. This solution has been focused on P2P applications, and
its applicability to other applications, such as video using
H.264, is unclear.

ALTO (Application-Layer Traffic Optimization) [alto] aims to
design and specify mechanisms that will provide applications,
typically P2P applications, with information to perform better-
than-random initial peer selection to increase their performance
and at the same time to avoid excessive cross-domain traffic that
tends to be more expensive for the operator. For legal content ALTO mechanisms with the ability for ISPs to deploy proxies appear services may
take different approaches at balancing factors such as maximum
bandwidth, minimum cross-domain traffic, or lowest cost to be a viable solution. However, a lot of the content being
distributed
user, but in P2P filesharing networks today all cases the goal is not legal to expose information that can
ameliorate the interactions between peer-to-peer usage and
caching such content by operators could turn out problematic for
them. other
usages of shared networks.

Peer to Peer Research Group [p2prg] aims to provide a discussion
forum for resarchers related to all sorts of challenges of presented
by P2P systems in general, such as P2P streaming, interconnecting
distinct P2P application overlays, security and privacy, etc. privacy. Current
work on exposing myths about peer-to-peer filesharing
[I-D.irtf-p2prg-mythbustering] provides a number of literature references to
support some of the claimed benefits of ALTO solutions mechanisms,
such as the expected decrease in cross- domain traffic.

5. Summary

Heavy

High-consuming users are a reality. Operators that would like to
counteract the impact of heavy users on their networks have a fair
number of tools at their disposal. These tools may allow operators
to identify heavy users, collect performance and usage indications,
and choose from a variety of mitigating steps depending on the
operator's preferred business practices. Subscriber-specific
information, including policies, resource consumption information,
and details about the current network attachment point, may be
available in accounting servers. Information about the network
topology and the state of particular topology elements may be
available in the network management infrastructure. Solution
approaches similar to [I-D.livingood-woundy-congestion-mgmt] have
demonstrated one way of taking congestion information into
consideration.

The currently available mechanisms for identifying and mitigating
congestion largely run wholly within an operator's network and
without a lot of information exchange about congestion information to
or from end hosts or other network operators. Exposing this
information may allow end devices to make more informed decisions
(although policy enforcement would still be required by the
operator).

The collection of congestion information poses the challenge of
deciding where in the network to put the metering agents to ensure
that enough information is collected at the right point in time.
Distributed collection and the correlation of the information across
different nodes is a complex task. An approach that collects this
congestion information along the path of the data packet (via inband
signaling) would simplify this task. Regardless of the technical
solution utilized for collecting information, certain users will
undoubtedly observe the effects of decisions that operators make
about how to handle congestion. Allowing users to understand these
decisions will be crucial and having a channel to send feedback to
the end device and/or subscriber would be a helpful step towards
increased transparency.

6. Security Considerations

This document highlights approaches for dealing with heavy high-consuming
network
usage users and all of them raise security and privacy concerns. This
document does, however,
It does not introduce new mechanism and hence the
reader is referred to the description of mechanisms. The security considerations
for the respective mechanism.

6. existing mechanisms mentioned apply.

7. IANA Considerations

This document does not require actions by IANA.

8. Acknowledgments

The authors would like to thank Alan DeKok, Jens-Peter Haack,
Alexander Bachmutsky, Jonne Soininen, Joachim Charzinski, Hannu
Flinck, Joachim Kross, Jouni Korhonen, Mayutan Arumaithurai, Richard
Woundy, Daniel Correa Lobato, Luca Caviglione, Tommy Lindgren, Lars
Eggert, for their time to discuss the topic. Additionally, we would
like to thank Marcin Matuszewski for his help with the P2P
infrastructure workshop paper (as (since it was used as a starting point).

8. point
for the work on this memo).

9. References

8.1.

9.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

8.2.

9.2. Informative References

[I-D.irtf-p2prg-mythbustering]
Marocco, E., Fusco, A., Rimac, I., and V. Gurbani,
"Improving Peer Selection in Peer-to-peer Applications:
Myths vs. Reality", draft-irtf-p2prg-mythbustering-00
(work in progress), August 2009.

[I-D.livingood-woundy-congestion-mgmt]
Bastian, C., Klieber, T., Livingood, J., Mills, J., and R.
Woundy, "Comcast's Protocol-Agnostic Congestion Management
System", draft-livingood-woundy-congestion-mgmt-01 (work
in progress), September 2009.

[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, June 2000.

[RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.

[RFC2975] Aboba, B., Arkko, J., and D. Harrington, "Introduction to
Accounting Management", RFC 2975, October 2000.

[RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
Aboba, "Dynamic Authorization Extensions to Remote
Authentication Dial In User Service (RADIUS)", RFC 3576,
July 2003.

[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
Arkko, "Diameter Base Protocol", RFC 3588, September 2003.

[RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J.
Loughney, "Diameter Credit-Control Application", RFC 4006,
August 2005.

[RFC5594] Peterson, J. and A. Cooper, "Report from the IETF Workshop
on Peer-to-Peer (P2P) Infrastructure, May 28, 2008",
RFC 5594, July 2009.

[alto] "",
<http://www.ietf.org/dyn/wg/charter/alto-charter.html>.

[ledbat] "",
<http://www.ietf.org/dyn/wg/charter/ledbat-charter.html>.

[p2prg] "", <http://www.irtf.org/charter?gtype=rg&group=p2prg>.

[traffic] Cho, K., Fukuda, K., Kato, H., and A. Kato, "The impact
and implications of the growth in residential user-to-user
traffic", SIGCOMM Comput. Commun. Rev. 36, 2006.

[traffic2]
Cho, K., Fukuda, K., Esaki, H., and A. Kato, "Observing
slow crustal movement in residential user traffic, in
International Conference On Emerging Networking
Experiments And Technologies, Proceedings of the 2008 ACM
CoNEXT Conference, Madrid, Spain, Article No. 12", ,
2008.

Appendix A. Example Policy Statement

A.1. Fair Usage Policy

A.1.1. What is the Fair Usage Policy?

The Fair Usage Policy is designed to ensure that the service received
by the vast majority of our customers is not negatively impacted
because of extremely heavy usage by a very small minority of
customers. This is why ISP X continuously monitors network
performance and may restrict the speed available to very heavy users
during peak time. This applies to customers on all Options. Note if
you are a heavy user we will only restrict your speed, service will
not be stopped so ability to upload and download remains. No
restrictions will be imposed outside of the peak times. Only a very
small minority of customers will ever be affected by this (less than
1 %).

A.1.2. How do I know I'm a very heavy user?

There is no hard and fast usage limit that determines if you are a
heavy user as the parameters that determine heavy use vary with the
demands placed on the network at that given time. If you have a
query about fair usage related restrictions on your line please call
us.

A.1.3. I have Contract Option 3, does the Fair Usage Policy apply to
me?

Yes, the Fair Usage Policy applies to all customers on all Options,
including Option 3. Option 3 allows unlimited downloads and uploads
inclusive of the monthly rental price, so you will not be charged for
over-use, however this does not preclude ISP X from restricting your
speed at peak times if you are a heavy user. If you are an Option 3
heavy user this does not prevent you from continuing to use your
service, nor does it cost you any more but it ensures that you do not
negatively impact the majority of our customers who share the
available bandwidth with you.

A.1.4. Peer to Peer (P2P)

A.1.4.1. I'm noticing slower P2P speeds at peak times even though I'm
not a very heavy user, why is this?

P2P is the sharing and delivery of files amongst groups of people who
are logged on to a file sharing network. P2P consumes a significant
and highly disproportionate amount of bandwidth when in use even by
small numbers of users.

This is why we have a peak time policy where we limit P2P speeds to
manage the amount of bandwidth that is used by this application in
particular.

Without these limits all our customers using their broadband service
at peak times would suffer, regardless of whether they are using P2P
or not. It's important to remember that P2P isn't a time-critical
application so if you do need to download large files we advise you
to do this at off-peak times when no restrictions are placed, not
only will you be able to download faster but your usage will not
negatively impact other users.

A.1.4.2. Does this mean I can't use Peer-to-Peer (P2P) applications?

No, we are not stopping you from using any P2P service, P2P will just
be slowed down at peak times. Again, P2P is not generally a time-
sensitive application.

Authors' Addresses

Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo FIN-02600
Finland

Phone: +358 (50) 4871445
Email: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at

Alissa Cooper
Center for Democracy & Technology
1634 I Street NW, Suite 1100
Washington, DC
USA

Email: acooper@cdt.org