wdiff rfc6875v1.txt rfc6875.txt

Internet Research Task Force (IRTF) S. Kamei
Request for Comments: 6875 NTT Communications
Category: Informational T. Momose
ISSN: 2070-1721 Cisco Systems
T. Inoue
T. Nishitani
NTT Communications
February 2013

ALTO-Like

The P2P Network Experiment Council's Activities and Experiments with
Application-Layer Traffic Optimization (ALTO) in P2P Network Experiment Council Japan

Abstract

This document introduces describes experiments to that clarify how ALTO-like an approach
similar to Application-Layer Traffic Optimization (ALTO) was
effective to reduce in reducing network traffic made traffic. These experiments were
performed in Japan by a the P2P Network Experiment Council in
Japan an
attempt to harmonize P2P peer-to-peer (P2P) technology with the network
infrastructure. And Based on what was learned from these experiments,
this
also document provides some suggestions that might be useful for the
ALTO architecture learned through our experiments. Especially, experiment and especially for application independent ALTO-like application-independent ALTO-
like server operation.

Status of This Memo

This document is not an Internet Standards Track specification; it is
published for informational purposes.

This document is a product of the Internet Research Task Force
(IRTF). The IRTF publishes the results of Internet-related research
and development activities. These results might not be suitable for
deployment. This RFC represents the individual opinion(s) of one or
more members of the Peer-to-Peer Research Group of the Internet
Research Task Force (IRTF). Documents approved for publication by
the IRSG are not a candidate for any level of Internet Standard; see
Section 2 of RFC 5741.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6875.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Background in Japan . . . . . . . . . . . . . . . . . . . . . 3
2.1. P2P Traffic . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Impact on Network Infrastructure . . . . . . . . . . . . . 4
2.3. Overview of the P2P Network Experiment Council . . . . . . 5
3. Objectives of the P2P Network Experiment Council . . . . . . . 5
4. Details of the Experiment . . . . . . . . . . . . . . . . . . 7
4.1. Dummy Node . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Hint Server ('08) Servers . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. High-Level Trial Results . . . . . . . . . . . . . . . . . . . 13
6.1. Peer Selection with P2P . . . . . . . . . . . . . . . . . 13
6.2. Peer Selection with the Hint Server . . . . . . . . . . . 13
7. Considerations . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Next Steps . . . . . . . . . . . . . . . . . . . . . . . . 14
7.2. Feedback to the ALTO WG . . . . . . . . . . . . . . . . . 15
7.2.1. Hierarchical Architecture for ALTO Servers . . . . . . 15
7.2.2. Measurement Mechanism . . . . . . . . . . . . . . . . 15
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
10. Informative References . . . . . . . . . . . . . . . . . . . . 16

1. Introduction

An overlay network, which is used by P2P and other applications,
offers the advantage of allowing flexible provisioning of services
while hiding the lower-layer network. The downside disadvantage is that
inefficient routes are often taken in routing without considering the lower IP network, thereby lower-layer network may
cause increasing the network load. Several proposals have been made
to build an overlay network that takes into account the information
about the lower-layer network [1] [2]. Since the management of the
Internet is highly distributed, it is difficult to implement such
proposals, and thus to optimize a network, without the cooperation of
network providers.

Recently, the controversy between the overlay network and the network
providers about network resource wastefulness has been rekindled.
Under these circumstances, some researchers have studied overlay-
network control technology that takes into account the network
topology information obtained from network providers.

One of the activities concerning research effort regarding this issue has been made were experiments planned and
performed by the P2P Network Experiment Council in Japan. We planned some experiments in
the council. This
document reports on these experiments and the issues addressed and they addressed.

These experiments being made by the council.

This experiment made were performed from 2007 to 2008, because P2P
traffic had
reduced due to revision of decreased after Japanese copyright law in Japan. And was revised. While
more recently, the dominant traffic is HTTP based flash streaming in Japan, U.S, the United States, and so
on. However, P2P
elsewhere has been HTTP-based flash streaming, a large amount of
traffic remains in large Asia (outside Japan) is still P2P traffic, like PPStreaming,
in Asia (except Japan)[3], P2P
streaming [3], and P2P technology is very useful in such a real-time
streaming area.

Our experience in this experiment might be useful for ALTO
architecture, especially for application-independent and multi-
application ALTO-like server operations. We suggest that a generic
measurement mechanism is important because each application has
different mechanism, which makes it difficult to compare their
effectiveness.

This document is a product of the P2P Research Group (RG). The views
in this document were considered controversial by the P2P RG, but the
RG reached a consensus that the document should still be published.

2. Background in Japan

2.1. P2P Traffic

As of 2008, the world's most popular P2P file-sharing application,
BitTorrent, was not widely deployed in Japan. Instead, other file-
sharing P2P applications specific to Japan, such as Winny [4] and
Share [5], still account for 40% of the Internet traffic in Japan,
even though many those P2P users were arrested for sharing illegal
files with these P2P applications.

Each P2P file-sharing application has a unique protocol and none have
a large market share, therefore making it hard to control them
effectively.

2.2. Impact on Network Infrastructure

One advantage of using P2P technology for content delivery is that
peers exchange content directly among themselves without server
bottleneck. This reduces the load on servers. Also, P2P
applications can reduce upstream traffic from an origin content
server. This reduces server cost dramatically.

It is also known that server cost could be reduced with P2P
technology. However, the story is quite different for network
providers. From the viewpoint of network providers, the traffic that
content servers generate has shifted to the edge network and the
amount of traffic has not necessarily been reduced by using P2P
technology for reducing server cost. Another problem for network
providers is that extremely inefficient routing may be selected
because overlay network systems are configured without any regard to
the structure of the lower-layer network or network geometry.

In some cases, the total amount of traffic on the Internet used to be
limited by the capacity of servers. For those cases, P2P technology
can improve the scalability of servers; however, it may exhaust
network resources. Moreover, using P2P applications remarkably
increases the volume of traffic per user.

Faced with an increase in the load on network infrastructure, network
providers are compelled to take actions to overcome the sudden
increase in facilities' costs. Representative actions include
placing content in Internet Exchanges (IXs) or data centers,
introducing bandwidth control, and raising access fees [6].

As mentioned above, the dominant traffic currently in Japan, the US,
and elsewhere, is HTTP-based flash streaming. However, a large
amount of traffic in Asia (outside Japan) is P2P traffic, like
PPStreaming P2P
Streaming [3], and P2P technology is very useful in such real-time
streaming. The increase in traffic arising from such a shift may be
a great threat to the network.

2.3. Overview of the P2P Network Experiment Council

In order to reduce Internet traffic and encourage legitimate use of
P2P technologies, in 2006 the Japanese government established a new
council called the P2P Network Experiment Council, in conjunction
with commercial P2P application vendors and ISPs.

The council developed regulations that include guidelines such as
giving advance notice to heavy traffic users before restricting their
bandwidth. In accordance with the regulations, some ISPs introduced
solutions that reduce traffic caused by P2P file-sharing
applications.

In addition, the council, along with ISPs, carriers, contents
providers, and P2P system vendors, looked for new ways to control
traffic by commercial P2P applications. In this work, the council
performed experiments that introduced an ALTO-like system and
observed how the traffic was reduced when it was redirected to proper
peers on the real Internet in Japan.

In our experiment, the council deployed hint servers, which are
described in Section 5. Hint servers run a protocol that offers
network distances to peers, and these distances are disclosed to P2P
application vendors.

Using hint servers, P2P application vendors can introduce ALTO
concepts easily into their P2P distribution systems. Because the
protocol used by hint servers, as defined by the council, is
independent of specific P2P application vendors like BitTorrent. The
protocol needs to gather network information from ISPs so it can
provide network distance to peers. However, many ISPs dislike
disclosing such information to others. Therefore, hint servers are
designed to offer little information about an ISP's network
architecture to P2P application vendors.

To monitor the traffic of peers, the council also deployed a dummy
node, which is described in Section 4.1.

The remainder of this memo provides an overview of the experiments.

3. Objectives of the P2P Network Experiment Council

The Japanese Ministry of Internal Affairs and Communications, which
has jurisdiction over information and communication systems in Japan,
held meetings of an advisory panel on network neutrality in 2006 and
2007 in order to study issues related to next-generation networks,
such as how to ensure fairness in the use of networks and how to
define fairness in the cost burden. The panel took an interest in
P2P technology as a solution to the impending traffic saturation in
the backbone network resulting from the rapid expansion of broadband
access in Japan, and it formed a "Working Group on the P2P Network",
which carried out an intensive study of P2P networks.

The working group reported that it would be necessary to undertake
the following four activities, which are intended to encourage the
government to adopt relevant policies [7]:

o Formulate guidelines on P2P file-delivery applications to be self-
imposed by the industry.

o Promote feasibility tests of P2P networks.

o Study the current state of traffic control and promote the sharing
of information.

o Hold working group meetings about traffic control.

The first two proposals led to the establishment of the P2P Network
Experiment Council, supported by the Japanese Ministry of Internal
Affairs and Communications [8]. [8] [9]. The Council, with membership
from P2P delivery providers, content holders, and network providers,
began a variety of delivery experiments, which were expected to
strengthen cooperative control between different layers. In contrast
to P4P (Proactive Network Provider Participation for P2P), which
takes a relatively top-down approach of adopting an architecture
based on a proposal from a university, the Council is characterized
by its bottom-up approach. The aim of establishing the Council has been was
described as follows. follows (translated from [10]).

The rapid growth of broadband access enables content delivery
system
systems to deliver high-quality and high-volume videos securely
and efficiently. Although P2P technology is an effective
technology for this requirement, it still has some issues to be
coped with. Therefore, the "P2P Network Experiment Council" was
established with the support of the Japanese Ministry of Internal
Affairs and
Communications Communications, with its secretariat set up within the
Foundation for MultiMedia Communications (FMMC) (FMMC), in order to
formulate guidelines for providers and conduct feasibility tests
so that users can receive video delivery services safely.

The activities of the P2P Network Experiment Council can be
classified into two categories. The first is formulating guidelines
for promoting the commercial use of P2P technology. These guidelines
will enable users to use P2P technology safely and will give
providers clear rules they must observe. The second is feasibility
testing of P2P technology. Section 4 describes experiments conducted
in 2007 and 2008.

4. Details of the Experiment

The Council investigated data offered by the members of the Council
and learned that the server cost could be reduced by using P2P
technology for content delivery. For example, the data from the
vendors showed the following:

Traffic was reduced by 90% with UGLive by Utagoe, Inc. [9]. [11].

The cost of delivering to tens of thousands of subscribers was
reduced by 1/5 80% with BBbroadcast with TV Bank Corp. [10] [12]

On the other hand, these reduced server costs may have affected the
network load. One of the goals of our experiments was to visualize
the impact and propose an architecture to reduce network load caused
by these new technologies.

In order to visualize the reduction of network cost, we modeled P2P
applications and a multi-ISP environment. This model was also needed
for visualizing the effectiveness of the ALTO-like approach.

4.1. Dummy Node

As mentioned above, while the effect of using P2P technology to
reduce the traffic and the load on servers is well known; however,
traffic behavior in the inter-ISP area is not known. In Japan, the
ISPs and IXes cooperated to create a backbone traffic report [11]. [13].
However, the measurements gathered for that report required capturing
packets on subscribers' lines in order to determine the end users'
activities. It is not realistic to measure the behavior of P2P
applications at user terminals connected to the Internet because that
would require a large-scale arrangement for measurement, such as
using deep packet inspection (DPI) on aggregated lines.

To solve these problems, we put several nodes called 'dummy nodes' in
the ISP's networks. The dummy nodes emulate an end user's PC running
P2P applications. Every P2P node provided by participating vendors
in the experiment was configured so it always contacted the hint
server.

By introducing dummy nodes and measuring the traffic on them, we were
able to observe and evaluate how much the P2P applications affected
the networks. Since this method can't measure every subscriber's
traffic, the accuracy is less than other methods. However, using
dummy nodes makes it possible to adapt to situations in which many
different P2P applications coexist on a network. We decided that
using dummy nodes was suitable for these experiments.

A dummy node consisted of an Intel PC server running Linux (CentOS),
VMWare, and Windows XP on VMWare. With this configuration, all
packets can be captured without any impact on the behavior of the
network, nodes, or applications. Also, this configuration enabled us
to use different P2P applications for Windows and evaluate them
generally.

To see behaviors of the node, incoming and outgoing packets are
captured on Linux because every packet is transmitted through it. To
see flow information in these experiments, we captured the source and
destination addresses, port number, amount of traffic, and start and
end times.

We placed 60 dummy nodes on access networks of 40 different ISPs.
They were placed as close as possible to the subscriber in each
network.

+----------------------+
|+--------------------+|
||+------------------+||
||| P2P Application |||
||| Windows XP |||
||| +--+ |||
||+--------|N |------+||
|| VMware |e | ||
|+---------|t |-------+|
| Linux |IF| capture|
+----------| |--------+
+--+

Figure 1: Dummy node

5. Hint Server ('08) Servers

Since fiber to the home (FTTH) has rapidly spread all over Japan,
bottlenecks in IP networks have been shifting from access networks to
backbone networks and equipment, such as bandwidth between ISPs and
capacity in IXs. Under these circumstances, the Council proposed
less restrictive and more flexible cooperation between ISPs than
existent P4P experiments [12]. [14]. The proposed method consists of the
following elements: (1) P2P clients, (2) P2P control servers, and (3)
a hint server (specifically, a peer selection hint server). P2P
clients and control servers are existing systems, but whether the P2P
control servers exist is application dependent. The hint server is a
server that provides a hint for peer selection and plays a role
equivalent to that of the ALTO server. Note that this proposal was
based on results of experiments using dummy nodes. The results
showed that it was possible to reduce unnecessary traffic that flows
across the boundaries of geographical districts or ISPs by providing
information about the physical network to P2P applications.

When a peer joins the network, it registers its location information
(IP address) and supplementary information (line speed, etc.) with
the hint server. The hint server calculates the network distance
between peers (P2P clients) based on network topology information
obtained from the ISP and generates a priority table for peer
selection. The hint server returns the table to the peer.

If all information is public, the above procedure can produce results
that are nearly optimal. However, some information held by ISPs is
often confidential. Also, in some cases, the volume of calculation
required to process all information can be excessive. To avoid these
problems, the plan is to conduct experiments with a limited set of
functions, analyze the results, and gradually expand the scope of
optimization.

A control mechanism that makes use of all possible information is
difficult not only technically but also because it requires
coordination among providers. In light of these difficulties, the
council has been limiting the implementation and experiments to the
following scope since 2006.
technical scope.

Figure 2 shows an outline of the hint server.

+---------+ GetLocation +-------------GeoIP DB Server---------+
| | +-----------+ | +----------+ +-----------+ |
| |--|IP Address |-->| | GeoIP DB | |Quagga etc.| |BGP daemon | |
| | +-----------+ | +----------+ +-----------+ |
| | | +-------------+ +----------------+ |
| | +-----------+ | | District | | Routing | |
| |--|AS Code: |---| | Information | |Information(DGP)| |Information(BGP)| |
| | |Regional | | | | | | |
|P2P Peers| |Information| | | Range of | |AS Code(origin) | |
| or | +-----------+ | | IP Addresses| | | |
| Control | | +-------------+ +----------------+ |
| Server | +-------------------------------------+
| | | ^
| | PeerSelection v |
| | +-----------+ +--------------------------------------+
| |--|IP Address |-->| +--Priority Node Selection System--+ |
| | | List | | | | |
| | +-----------+ | | Peer Candidate Ranking | |
| | +-----------+ | | | |
| |--| Ranking |-->| +----------------------------------+ |
| | +-----------+ +--------------------------------------+
+---------+

Figure 2: Hint server for peer selection

The network information used by the hint server is not information
solicited from individual ISPs but is the Autonomous System (AS)
number and district information, which are more or less public
already. Routing tables are not generated. Instead, peers within
the same ISP or the same district are selected with higher priority
in order to confine traffic to within the same ISP or the same
district.

When the hint server receives an IP address, it returns its attribute
information, in order to confine the traffic to achieve within the above. nearer ISP
or district. A peer can select another based on the returned
information. This operation is called GetLocation. However, in
preparation for the time when it becomes necessary to hide topology
information, an interface is provided through which a priority order
is returned in response to an input of a list of candidate peers.
This operation is called PeerSelection.

Although the target node is selected based on the criterion that it
is within the same ISP or the same district, this type of selection
is not very effective if the number of participating peers is small.
Table 1 shows the percentage of peers within the same AS or the same
prefecture calculated from the distribution of ASes and prefectures
in the IP address space from one-day data on a Winny network.

+--------------------+------------+
| Conditions | Percentage |
+--------------------+------------+
| AS matches | 6.70% |
| Prefecture matches | 12.76% |
| Both match | 2.09% |
| Neither match | 78.45% |
+--------------------+------------+

Table 1: AS and prefecture distributions

Because, in addition to the above, the presence or absence of content
affects the results, controlling peer selection within the same
district may be inadequate. Therefore, it is necessary to introduce
the weight of a continuous quantity that reflects the physical
distance or the AS path length as an indicator of the proximity of
the areas involved.

In consideration of this, the following two measures are used to
evaluate the proximity of peers in a hint server.

o AS path length (distance between ISPs)

AS path length is calculated from BGP full routes. Since a full
routing table retrieved at an ISP can show only a best path, it
may not get an accurate length if the AS hop count of both ISPs is
too large. To avoid this, we use BGP information received from
different ISPs and combine them. Based on this concept, we used
BGP routing information offered by three ISPs operated by big
telecommunication couriers and made a topology tree. Then, we
were able to calculate the shortest path between two given ASes.

o Geographical distance

Distances between peers are measured using the physical distance
between the capitals of the prefectures to which the peers belong.
Distances between prefectural capitals are sorted into ascending
order, and then into bands, with weights 1 to 15 assigned to them
so that each band contains roughly the same number of "capital
pairs". If either of the peer's locations is indefinite, the
distance is equal to 15; if they are in the same prefecture, the
distance is equal to 0.

Evaluation of distances between peers showed that the distribution
of distances was almost uniform when distances between peers are
normalized. This result suggests that using normalized distances
expands the area where the control by a hint server is effective.
The geographical distance is used only when the AS path length is
the same. same between some candidates.

An example of the request and the response

o Request

POST /PeerSelection HTTP/1.1
Host: ServerName
User-Agent: ClientName
Content-Type: text/plain; charset=utf-8

v=Version number
[application=Application identifier]
ip=IP address of physical interface
port=Port number of physical interface
[nat={no|upnp|unknown}]
[nat_ip=Global IP address using UPnP]
[nat_port= Global port number using UPnP]
[trans_id=transaction ID]
[pt=Flag of port type]
[ub=upload bandwidth]
[db=download bandwidth]

o Response

HTTP/1.1 200 OK
Date: Timestamp
Content-Type: text/plain; charset=utf-8
Cache-control: max-age=max age
Connection: close

v=Version number
ttl=ttl
server=hint server name
...
trans_id=transaction ID
pt=Flag of port type
client_ip=Peer IP address observed from server
client_port=Peer port number observed from server
numpeers=number of respond peer responding peers
n=[src address] dst address / cost / option

6. High-Level Trial Results

6.1. Peer Selection with P2P

Table 2 shows the result of the analysis of communication in a node
of an ISP in Tokyo, as an example of measurement results.

In these two experiments, we evaluated different P2P applications.
In the first experiment, the P2P topology was generated by a tree
algorithm; in the second experiment, it was generated by a mesh
algorithm. Both resulted in similar performance.

+-----------------------------------------+------------+------------+
| Conditions | Experiment | Experiment |
| | 1 | 2 |
+-----------------------------------------+------------+------------+
| Peers selected within the same ISP | 22% | 29% |
| | | |
| Peers selected within the same district | 19% | 23% |
| | | |
| Peers selected within the same district | 5% | 7% |
| and the same ISP | | |
+-----------------------------------------+------------+------------+

Table 2: Percentage of communication within the same ISP

Table 2 shows that the probability of communication with peers in the
same ISP is proportional to the population size and the share of the
ISP in each district. The data show that peers were selected at
random. Note that the vendor of a P2P application used in these
experiments explained demonstrated that the mechanism for selecting a peer
using network information can be implemented. However, peer
selection is normally based on past information because users often
cannot actually perceive the effect of using network information.

6.2. Peer Selection with the Hint Server

The main objective of these experiments was to verify the operation
of the hint server and P2P applications. The distances between a
dummy node and a peer were obtained from data on the dummy nodes. An
examination of the distances between a dummy node and a peer revealed
that the mean value of distance after the hint server was introduced
was reduced by 10% and that the 95th percentile was reduced by 5%.
The results show that introducing a hint server can reduce the
network loads that result from P2P applications.

7. Considerations

We clarified the following during our experiments.

1. Dispersed dummy nodes can figure out determine the behavior of peers and
traffic between inter-ISP networks, which peers are selected by networks and can determine the peer
that each peer. peer selects. Therefore, this result proves the
importance of the peer-selection control mechanism that is
proposed by ALTO.

2. Using our peer-selection control mechanism, called hint servers,
can result in significant differences. Hint servers can lead
each peer to select a closer peer.

3. The 10% reduction of network cost is not satisfactory for ISPs,
but the controllability of P2P applications is the most important
point. When ISPs apply this mechanism to their real networks,
they will set a very large cost for the most expensive network
link.

In the experimental results for peer-selection control, the selection
is smaller in intra-ISP traffic than in other experiments [13]. [15]. We
think this is because there are fewer peers in each area of traffic
control. When there are many peers in one ISP, it is easy to select
peers in the same ISP. However, when there are fewer peers in one
ISP, it is difficult to select peers in the same ISP. In our
experiments, most of the ISPs had many peers in their networks, i.e.,
there were a small number of ISPs that had few peers in their
networks.

Moreover, we didn't force P2P vendors to limit their implementation
policy; therefore, we observed differences in how each implementation
weighs the information from the hint servers. Specifically, in P2P
applications when a tree topology is used, the hint-server mechanism
is very effective; on the other hand, when a mesh topology is used,
it less effective.

7.1. Next Steps

In recent research, we've changed to an ALTO-based communication
protocol on hint servers because the requirements of ALTO are
documented in RFC 6708 [16] and the ALTO protocol is nearly standardized. a work in
progress [17]. In our implementation, protocol identifiers (PIDs)
and the cost value are mapped to ISP subnets and to ISP distance,
respectively. We also implement services for compatibility required
by ALTO such as Service
Capability and Map Services. Services and Endpoint Cost Service. The Endpoint
Cost Service (defined in
[14]) [17]) is mainly used because of backward
compatibility with our experiments.

We are also studying a hierarchical structure of hint servers, in
order to control traffic at a coarse level (in inter-ISP areas) and
at a finer level (in intra-ISP areas). It is also effective for
limiting the areas where information is disclosed.

7.2. Feedback to the ALTO WG

This section describes what the authors learned from these
experiments that might be useful to the ALTO WG.

7.2.1. Hierarchical Architecture for ALTO Servers

In our experiments, we present the possibility of traffic control
among multiple ISPs and multiple P2P applications using an ALTO
mechanism. We found several problems when ISPs try to adopt the
mechanism. One is the granularity of network information from
Council members. Among inter-ISP areas, it is relatively easy to
handle information for public purposes by using BGP full routes. On
the other hand, among the intra-ISP areas, it may be difficult to
disclose the private information of each ISP. Kiesel [15] [18] proposes
some modifications for the ALTO protocol in order to hide ISP
information. We propose hierarchical structures. From the viewpoint
of cooperation between ISPs, fine-grained information is not
necessarily required. Moreover, it is difficult to exchange the
fine-grained information between ISPs. Considering this situation,
we used only coarse-grained information to control backbone traffic
in these experiments; however, in the future, there may be a demand
for controlling traffic within an ISP using fine-grained information.
Therefore, we decided to introduce hierarchical structures into ALTO
in order to cope with both situations. Actually, adopting a
hierarchical control mechanism that includes the following two steps
will be useful.

o First, use coarse-grained information about whole the network to
select ISPs.

o Second, use fine-grained information within the ISP to select a
peer.

7.2.2. Measurement Mechanism

In these experiments, there were two difficulties as follows.

o Evaluating the effect of introducing a hint server was difficult
because the P2P applications had their own measurement mechanisms.

o How to treat the priority order of peers suggested by a hint
server could not be predetermined for P2P applications.

From these experiences, the authors consider that clarifying the
requirements about measurement mechanisms for P2P applications is
necessary in ALTO.

8. Security Considerations

This document does not propose any kind of protocol, practice, or
standard.

9. Acknowledgments

The P2P Network Experiment Council was established thanks to strong
support by the Japanese Ministry of Internal Affairs and
Communications. These experiments were performed with cooperation
among the P2P Network Experiment Council members. DREAMBOAT Co.,
Ltd., Bitmedia, Inc., Utagoe, Inc., and Toyama IX have especially
supported the analyses of the experiments. The authors appreciate
Tohru Asami, Hiroshi Esaki, and Tatsuya Yamshita for their
constructive comments.

The authors would also like to thank Martin Stiemerling, Stefano
Previdi, and Vijay K. Gurbani for their comments on this document.

10. Informative References

[1] Kawahara, R., Lua, E., Uchida, M., Kamei, S., and H. Yoshino,
"On the Quality of Triangle Inequality Violation Aware Routing
Overlay Architecture", INFOCOM 2009, pages 2761-2765.

[2] Li, Z. and P. Mohapatra, "QRON: QoS-aware routing in overlay
networks", IEEE Journal on Selected Areas in
Communications, Vol. 22, No. 1, January 2004.

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[11]

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[13]

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[14]

[16] Kiesel, S., Previdi, S., Stiemerling, M., Woundy, R., and Y.
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[15]

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Authors' Addresses

Satoshi Kamei
NTT Communications Corporation
Granpark Tower 17F, 16F, 3-4-1 Shibaura
Minato-ku, Tokyo 108-8118
Japan

Phone: +81-50-3812-4697
EMail: skame@nttv6.jp

Tsuyoshi Momose
Cisco Systems G.K.
9-7-1 Akasaka
Minato-ku, Tokyo 107-6227
Japan

Phone: +81-3-6738-5154
EMail: tmomose@cisco.com

Takeshi Inoue
NTT Communications
3-4-1, Shibaura
Minato-ku, Tokyo 108-8118 Corporation
Kuredo Hakushima Building 3F, 14-15 Higashihakushimacho
Chuo-ku, Hiroshima-City, Hiroshima 730-0004
Japan

Phone: +81-3-6733-7177 +81-82-563-5030
EMail: inoue@jp.ntt.net

Tomohiro Nishitani
NTT Communications Corporation
1-1-6, Uchisaiwaicho
Chiyodaku, Tokyo 100-8019
Japan

Phone: +81-50-3812-4742
EMail: tomohiro.nishitani@ntt.com