One document matched: draft-tschofenig-conex-ps-00.xml
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<rfc category="info" ipr="trust200902" docName="draft-tschofenig-conex-ps-00.txt">
<front>
<title abbrev="Congestion Exposure PS">Congestion Exposure Problem Statement</title>
<author initials="H." surname="Tschofenig" fullname="Hannes Tschofenig">
<organization>Nokia Siemens Networks</organization>
<address>
<postal>
<street>Linnoitustie 6</street>
<city>Espoo</city>
<code>FIN-02600</code>
<country>Finland</country>
</postal>
<phone>+358 (50) 4871445</phone>
<email>Hannes.Tschofenig@gmx.net</email>
<uri>http://www.tschofenig.priv.at</uri>
</address>
</author>
<!--
<author initials="B." surname="Aboba" fullname="Bernard Aboba">
<organization>Microsoft Corporation</organization>
<address>
<postal>
<street>One Microsoft Way</street>
<city>Redmond</city>
<region>WA</region>
<code>98052</code>
<country>US</country>
</postal>
<email>bernarda@microsoft.com</email>
</address>
</author>
-->
<author fullname="Alissa Cooper" initials="A." surname="Cooper">
<organization>Center for Democracy & Technology</organization>
<address>
<postal>
<street>1634 I Street NW, Suite 1100</street>
<city>Washington</city>
<region>DC</region>
<code/>
<country>USA</country>
</postal>
<email>acooper@cdt.org</email>
</address>
</author>
<date year="2009"/>
<area>Transport Area</area>
<workgroup>CONEX</workgroup>
<keyword>Internet-Draft</keyword>
<abstract>
<t> The availability of broadband connections together with flat-rate pricing has made new
types of peer-to-peer applications possible. From an Internet evolution and end user value
point of view 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 the usage of p2p systems
the observation can be made that a certain group of users, called high-consuming users,
decided to use their flat-rate contract excessively. This in turn seems to have caused
network operators to take actions.</t>
<t>This document illustrates a couple of techniques used by operators today to deal with
excessive bandwidth usage. More information can improve the decision making process.</t>
</abstract>
</front>
<middle>
<!-- ====================================================================== -->
<section anchor="introduction" title="Introduction">
<t>In 2006 K. Cho et al. <xref target="traffic"/> published a paper about the growth of
residential user-to-user traffic in Japan that indicates '... a small number of users
dictate the overall behavior; 4 % of high-consuming users account for 75 % of the inbound
volume, and the fiber users account for 86 % of the inbound volume.'. The same paper also
indicates a substantial increase in traffic growth, namely 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. </t>
<!-- <t>
<list style="empty">
<t>There is fewer detailed research data for other countries, such as in Europe or in the
US, available. [Editor's Note: Are there any reference to more recent data? How did the
traffic growth evolve in the last few years and how the traffic distribution with
respect to user-to-user traffic?] </t>
</list>
</t>
-->
<t> These numbers itself do not represent a problem as by themself and do not necessarily lead
to congestion. However, some operators very likely had different expectations about the
growth rates and traffic consumption of individual users and statistics (used for their
pricing models) did not work out too well for them. The profit margins for Internet access
are quite slim due to fierce competition. This puts a lot of pressure on operators to deal
with these high-consuming users who cost them a lot of money. Finally, some broadband
networks may not have the ideal characteristics (such as the topology for routing traffic)
for user-to-user traffic (e.g., Cable Networks). </t>
<t>
<list style="empty">
<t> Congestion is often mentioned in this context and as stated in RFC 5594 <xref
target="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.". </t>
<!-- <t>Furthermore, one has to consider how ISPs data traffic pricing works. [Editor's Note:
Add text here.]</t> -->
</list>
</t>
<t>To summarize in a simplistic way, those who produce a lot of traffic cost a lot.</t>
<t> Operators are now facing a range of options, see sections below, that can be taken and
there is a tradeoff between what is allowed (legally and from a public relation point of
view) and what is useful from a performance point of view. The latter aspect can be seen
from the point of view of a device performance (as many of the mechanisms actually slow down
the forwarding performance quite a bit) and consequently a cost challenge.</t>
<t> The existence of flat rate pricing contributes to some of the problems since the 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 the amount. As such, users that rarely utilize
the network pay the same amount as someone who uses P2p filesharing excessively. </t>
<t>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 <list style="symbols">
<t>Uncertainty in the bill: unpredicable costs that make planning difficult.</t>
<t>Uncertainty in the performance: performance degradation as part of the actions being
taken</t>
</list> True flat rate pricing avoids uncertainty in the bill. Unfortunately, most of the
solutions described below lead to some uncertainty and thereby increase unhappyness of
customers. </t>
</section>
<!-- ====================================================================== -->
<section title="State-of-the-Art Building Blocks">
<section title="Means of Identifying the Causes of Congestion">
<t> RFC 2975 <xref target="RFC2975"/> describes accounting as "The collection of resource
consumption data for the purposes of capacity and trend analysis, cost allocation,
auditing, and billing.".</t>
<t> 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 <xref
target="RFC2866"/> and <xref target="RFC2865"/>) and Diameter <xref target="RFC3588"/>,
has increased. The fact that standardized protocols have been available allowed different
AAA networks to be interconnected and their usage can be found in almost every enterprise
and operator network. The initial accounting mechanisms envisioned a rather non-real time
nature in reporting resource consumption but with mechanisms like like Diameter Credit
Control <xref target="RFC4006"/> allowed real-time credit control checks. </t>
<t> It has to be noted that 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.
Other approaches, as documented in <xref target="I-D.livingood-woundy-congestion-mgmt"/>,
lead to similar results.</t>
<t>Deep packet inspection refers to inspecting traffic that passes through the operators
networks up to the application layer. Depending on the configuration of the device traffic
shaping, 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. </t>
<t>Determining the type of application that a subscriber is running was seen as necessary to
throttle only certain applications, instead of impacting the full range of traffic a
subscriber is using. A side-effect is the additional investment for the device and
operational costs. The process of inspecting traffic is performance intensive and
continous software updates are necessary to ensure that the detection engine recognizes
the latest protocol variants. Additionally, the attempt 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. </t>
</section>
<section title="Potential Actions Operators might take in Response">
<t>What actions are taken based on the collected information and in what time frame is
largely left to the choice of those who run the infrastructure. In the context of this
discussion the collected information may be used to charge the user per volume, per time
and in various different combinations. Additionally, the RADIUS and Diameter allow the
server side with a server-initiated message (see Change of Authorization in <xref
target="RFC3576"/>, and the functionality provided in the Diameter Base specification
<xref target="RFC3588"/>) to push decisions to the AAA clients, typically edge nodes,
acting as enforcement nodes. These decisions include actions like shaping or packet
marking. </t>
<t>
<list style="hanging">
<t hangText="Shaping:"> End user contracts often offer a combination of 'flat-rate'
scheme whereby a fixed price tariff is used up to a certain usage volume (typically
quite high for regular usage). Subsequently, if the consumption goes beyond a certain
threshold then the entire traffic is given lower priority and potentially shaped.
<list style="empty">
<t>In many countries operators have to offer a clear description of the service they
offer and since the term 'flat-rate' is already associated with a certain meaning
the term 'Unlimited Data Rate' is often used for this type of service. Contracts
typically contain statements that allow certain actions to be taken. An example of
such a fair use statement can be found in <xref target="policy"/>. </t>
</list> 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. </t>
<t hangText="Class-Based Assignment:"> In this technique users are classified into a set
of classes depending on their past behavior. Subsequently, the traffic is treated
according to the associated class. It is ensured that the traffic of lightweight
users, users that really rarely use their Internet connection, cannot be pushed away
by heavy users. This mechanism again requires some form of DiffServ marking to be in
place. </t>
<t hangText="Charging for Excessive Traffic:"> As a possible action a user might get
charged differently for traffic that exeeds a certain threshold compared to the
traffic that falls within the agreed limits. </t>
<t hangText="Discontinuing Contracts:">In some rare cases ISP also decided to cut
connectivity under certain condition. In fact this might be justified in certain
cases. For example, in case of new botnets malware distribution when the operator
recognizes an infected machine and hotlines the entire traffic of that particular
machine to a separate network and, like in WLAN hotspots, HTTP traffic is intercepted
to display further information. In some cases the same technique has been applied with
excessive usage of P2P traffic, either intentionally or due to a false alarm caused by
a statistical traffic analysis technique.<vspace blankLines="1"/> 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. </t>
</list>
</t>
</section>
</section>
<!-- ====================================================================== -->
<section title="New Activities">
<t> In response to the P2P infrastructure workshop in 2008 (with a summary documented <xref
target="RFC5594"/>) two working groups and one research group has been created that focus
on a certain area of the application space:<list style="empty">
<t> LEDBAT (Low Extra Delay Background Transport) <xref target="ledbat"/> is designed to
allow to keep the latency across the congested bottleneck low even as it is saturated.
This allows applications that send large amounts of data, particularly upstream on home
connections, such as peer-to-peer application, to operate without destroying the user
experience in interactive applications. <vspace blankLines="1"/> LEDBAT is a promising
approach when applied widely in P2P clients. This solution has been focused P2P applications, and its applicability to other applications, such as video using H.264, is unclear.</t>
<t>ALTO (Application-Layer Traffic Optimization) <xref target="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 to be a viable solution. However, a lot of the content
being distributed in P2P filesharing networks today is not legal and caching such
content by operators could turn out problematic for them. </t>
<t>Peer to Peer Research Group <xref target="p2prg"/> aims to provide a discussion forum
for resarchers related to all sorts of challenges of P2P systems in general, such as P2P
streaming, interconnecting distinct P2P application overlays, security and privacy, etc.
<xref target="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. </t>
</list>
</t>
</section>
<!-- ====================================================================== -->
<section title="Summary">
<t> Heavy 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 <xref
target="I-D.livingood-woundy-congestion-mgmt"/> have demonstrated one way of taking
congestion information into consideration. </t>
<t> 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).</t>
<t> 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. </t>
</section>
<!-- ====================================================================== -->
<section title="Security Considerations">
<t>This document highlights approaches for dealing with heavy network usage and all of them
raise security and privacy concerns. This document does, however, not introduce new
mechanism and hence the reader is referred to the description of the respective
mechanism.</t>
</section>
<!-- ====================================================================== -->
<section title="IANA Considerations">
<t>This document does not require actions by IANA.</t>
</section>
<!-- ====================================================================== -->
<section title="Acknowledgments">
<t> The authors would like to thank Alan DeKok, Jens-Peter Haack, Jouni Korhonen, 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 it was used as a starting point). </t>
</section>
</middle>
<!-- ====================================================================== -->
<back>
<references title="Normative References"> &RFC2119; </references>
<references title="Informative References"> &RFC5594; &RFC2975; &RFC3588;
&RFC3576; &RFC4006; &RFC2866; &RFC2865;
&I-D.livingood-woundy-congestion-mgmt; &I-D.irtf-p2prg-mythbustering; <reference
anchor="traffic">
<front>
<title>The impact and implications of the growth in residential user-to-user traffic</title>
<author initials="K" surname="Cho" fullname="Kenjiro Cho">
<organization/>
</author>
<author initials="K" surname="Fukuda" fullname="Kensuke Fukuda">
<organization/>
</author>
<author initials="H" surname="Kato" fullname="Hiroshi Kato">
<organization/>
</author>
<author initials="A" surname="Kato" fullname="Akira Kato">
<organization/>
</author>
<date year="2006"/>
</front>
<seriesInfo name="SIGCOMM Comput. Commun. Rev." value="36"/>
<format type="HTML" target="http://doi.acm.org/10.1145/1151659.1159938"/>
</reference>
<reference anchor="alto" target="http://www.ietf.org/dyn/wg/charter/alto-charter.html">
<front>
<title/>
<!-- The title's extraneous quote marks in the text ouput will be removed before
publication, unless you want to add a title to this reference. -->
<author>
<organization/>
</author>
<date/>
</front>
</reference>
<reference anchor="ledbat" target="http://www.ietf.org/dyn/wg/charter/ledbat-charter.html">
<front>
<title/>
<!-- The title's extraneous quote marks in the text ouput will be removed before
publication, unless you want to add a title to this reference. -->
<author>
<organization/>
</author>
<date/>
</front>
</reference>
<reference anchor="p2prg" target="http://www.irtf.org/charter?gtype=rg&group=p2prg">
<front>
<title/>
<!-- The title's extraneous quote marks in the text ouput will be removed before
publication, unless you want to add a title to this reference. -->
<author>
<organization/>
</author>
<date/>
</front>
</reference>
</references>
<section anchor="policy" title="Example Policy Statement">
<section title="Fair Usage Policy">
<section title="What is the Fair Usage Policy?">
<t>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 %). </t>
</section>
<section title="How do I know I'm a very heavy user?">
<t> 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. </t>
</section>
<section title="I have Contract Option 3, does the Fair Usage Policy
apply to me?">
<t> 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. </t>
</section>
<section title="Peer to Peer (P2P)">
<section
title="I'm noticing slower P2P speeds at peak times even though I'm not a
very heavy user, why is this?">
<t> 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. </t>
<t>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. </t>
<t>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. </t>
</section>
<section title="Does this mean I can't use Peer-to-Peer (P2P) applications?">
<t> 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. </t>
</section>
</section>
</section>
</section>
</back>
</rfc>
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