P2PRG S. Kamei
Internet-Draft NTT Communications
Intended status: Informational T. Momose
Expires: January 16, 2013 Cisco Systems
T. Inoue
T. Nishitani
NTT Communications
July 15, 2012
ALTO-Like Activities and Experiments in P2P Network Experiment Council
draft-kamei-p2p-experiments-japan-08
Abstract
This document introduces experiments to clarify how ALTO-like
approach was effective to reduce network traffic made by a Council in
Japan to harmonize P2P technology with the infrastructure. And this
also provides some suggestions that might be useful for ALTO
architecture learned through our experiments.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Background in Japan . . . . . . . . . . . . . . . . . . . . . 3
2.1. P2P traffic . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Impact on network infrastructure . . . . . . . . . . . . . 3
2.3. The object of P2P Network Experiment Council . . . . . . . 4
3. The details of the experiments . . . . . . . . . . . . . . . . 5
3.1. Dummy Node . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Hint Server ('08) . . . . . . . . . . . . . . . . . . . . . . 7
5. High-Level Trial Results . . . . . . . . . . . . . . . . . . . 11
5.1. Peer Selection with P2P . . . . . . . . . . . . . . . . . 11
5.2. Peer Selection with the Hint Server . . . . . . . . . . . 12
6. Considerations . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1. Next steps . . . . . . . . . . . . . . . . . . . . . . . . 13
6.2. Feedback to ALTO WG . . . . . . . . . . . . . . . . . . . 13
6.2.1. Hierarchical architecture for ALTO servers . . . . . . 13
6.2.2. Measurement mechanism . . . . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 14
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
10. Informative References . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
An overlay network, which is used by P2P and other applications,
offers the advantage of allowing flexible provision of services while
hiding the lower layer network. The downside is that inefficient
routes are often taken in the lower IP network, thereby increasing
the network load. Several proposals have been made to build an
overlay network that takes account of 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
optimize a network without the cooperation of network providers.
Recently, the controversy between the overlay network and the network
providers has been rekindled. Under these circumstances, some
researchers have studied overlay network control technology that
takes account of the network topology information obtained from
network providers.
One of the activities concerning this issue has been made by the P2P
Network Experiment Council in Japan. This document reports on the
issues addressed and experiments being made by the council, focusing
on the experiments made from 2007 to 2008.
2. Background in Japan
2.1. P2P traffic
As of 2008, the world most popular P2P file sharing application,
Bittorrent, isn't widely deployed in Japan. Instead, other Japan
specific file sharing P2P applications such as Winny [3], Share [4],
and so on, still occupy 40% of the Internet traffic in Japan even
though many those P2P users were arrested for sharing illegal files
with these P2P apps.
Each P2P file sharing application has a unique protocol and none of
them have a large market share therefore making it hard to
effectively control.
2.2. Impact on network infrastructure
One of the advantage of using P2P technology for content delivery is
that peers exchange content directly among themselves. This reduces
the load on servers. Also, P2P applications can reduce upstream
traffic from an original content server. This is significant that
the charge for upstream traffic is usually delay-sensitive for
content delivery services, and it is not negligible.
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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 with using P2P
technology for reducing server cost. Another problem for network
providers that an extremely inefficient routing may be selected has
been raised. It is 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 increases the
volume of traffic per user remarkably.
Faced with increase in the load on network infrastructure, network
providers are compelled to take actions to overcome the sudden
increase in facilities' cost. Representative actions include placing
content in internet exchanges or data centers, introducing bandwidth
control, and raising the access fees [5].
In the future, video posting sites, which has been delivered using
client-server applications, may adopt P2P system. The increase in
traffic arising from such a shift will be a great threat to the
network.
2.3. The object of P2P Network Experiment Council
In order to reduce Internet traffic and encourage legitimate use of
P2P technologies, the Japanese government led to establish a new
council called P2P Network Experiment Council conjunction with
commercial P2P application vendors and ISPs in 2006.
Then the council had started to develop regulations that include
several guidelines such like an advance notice to restrict bandwidth
to heavy traffic users. In accordance with the regulations, some
ISPs introduced solutions that reduce traffic caused by P2P file
sharing applications.
Besides this activity, the council also looked for new ways to
control traffic by commercial P2P applications with ISPs, carriers,
contents providers and P2P system vendors. In this work, the council
had experiments that introduced ALTO-like system and observed how the
traffic was reduced by redirecting to proper peers on the real
Internet in Japan.
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In our experiment, the council settled hint servers, which are
described in section 4. Hint servers have a protocol offering
network distance to peers, which is disclosed to P2P application
vendors.
Using hint server, P2P application vendors can introduce ALTO
concepts easily to their P2P distribution systems. Because the
protocol provided of hint servers is independent on specific P2P
application vendors like Bittorrent, the council defines the protocol
to be able to use any P2P application vendors. It needs to gather
network information from ISPs to offer network distance to peers,
however many ISPs dislike to disclose such information to others.
Therefore, hint servers are designed to offer little information
about ISPs' network architecture to P2P application vendors.
To monitor traffic of peers, the council also settled dummy node,
which are described in section 3.1.
This memo describes the overview of the experiments.
3. The details of the experiments
The council has already learned that the server cost could be reduced
with using P2P technology for contents delivering by investigating
data offered by the members of the council. For example, the data
brought by the vendors shows as follows:
90% of traffic was reduced with UG Live by Utagoe Inc [6].
The costs of delivering to tens of thousand subscribers was
reduced to 1/5 with BBbroadcast with TV Bank Corp. [7]
On the other hand, these reduced server costs may affect network
load. One of the goals of our experiments is to visualize the
impacts and propose an architecture to reduce network load caused by
these new technologies.
To satisfy the above goals, the framework to be proposed should be
well generalized as possible that doesn't rely specific P2P
application behaviors because multi P2P application vendors join
these experiments. In addition, the traffic should be captured
beyond multi ISPs.
3.1. Dummy Node
As mentioned before, while the effect of delivery using P2P
technology on reducing the traffic and the load on servers is well
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known, traffic behavior in the inter-ISP is not known. In Japan,
there is a backbone traffic report cooperated with ISPs and IXes [8].
However, this measurement requires to capture packets on subscribers
line to know end user's activity. 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 and P2P
applications are running on the nodes. Every P2P node provided by
participating vendors in the experiment was configured so it always
contacted the hint server.
By introducing dummy nodes, we can observe and evaluate how much P2P
applications have affected networks by measuring the traffic on dummy
nodes. Since this method can't measure every subscriber's traffic,
the accuracy would be less than other methods. But this make it
possible to adapt to situations many different P2P applications
coexist on a network. We can say this is suitable for these
experiments.
A dummy node consists of Intel PC server, Linux(CentOS), VMWare and
Windows XP works on VMWare. With this configuration, all packets can
be captured without any impacts to the network, nodes and application
behaviors. And it enable 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 packets are transmitted through it.
In these experiments, we captured source/destination address, port
number, amount of traffic and start/end time to see flow information.
60 Dummy nodes are put on access networks that are closest subscriber
as possible in different 40 networks.
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+----------------------+
|+--------------------+|
||+------------------+||
||| P2P Application |||
||| WindowsXP |||
||| +--+ |||
||+--------|N |------+||
|| VMware |e | ||
|+---------|t |-------+|
| Linux |IF| capture|
+----------| |--------+
+--+
Dummy nodes
Figure 1
4. Hint Server ('08)
In Japan, bottleneck in IP networks have been shifting from access
networks to backbone networks and equipments, such as bandwidth
between ISPs and capacity in IXs, since FTTH has rapidly spread all
over Japan. Under these circumstances, the Council proposed a less
restrictive and more flexible cooperation between ISPs than existent
P4P experiments [9]. The proposed method consists of the following
elements: (1) P2P clients, (2) P2P control servers, and (3) a hint
server: a peer selection hint server. (1) and (2) are existing
systems but whether (2) exists depends on each application. (3) is a
server that provides a hint as to the selection of a peer, and plays
a role equivalent to that of 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 through
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&#
12288;the hint server. The hint server calculate network distance
between peers (P2P client) 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 can be made publicly, the above procedure can
produce a result which is close to overall optimization. However,
some information held by ISPs can often be confidential. Besides, in
some cases, the volume of calculation required to process all
information can be excessive. To avoid these problems, it is planned
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to conduct experiments with a limited set of functions, analyze
experiments 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 difficulties to achieve
coordination among providers. In consideration of these
difficulties, the council has been limiting the implementation and
experiments to the following scope since 2006.
Figure 2 shows an outline of the hint server.
+---------+ GetLocation +-------------GeoIP DB Server---------+
| | +-----------+ | +----------+ +-----------+ |
| |--|IP Address |-->| | GeoIP DB | |Quagga etc | |
| | +-----------+ | +----------+ +-----------+ |
| | | +-------------+ +----------------+ |
| | +-----------+ | | District | | Routing | |
| |--|AS Code: |---| | information | |information(DGP)| |
| | |Regional | | | | | | |
|P2P Peers| |Information| | | Range of | |AS Code(origin) | |
| or | +-----------+ | | IP address | | | |
| Contro| | | +-------------+ +----------------+ |
| Server | +-------------------------------------+
| | | ^
| | PeerSelection v |
| | +-----------+ +--------------------------------------+
| |--|IP Address |-->| +--Priority Node Selection System--+ |
| | | List | | | | |
| | +-----------+ | | Peer candidate ranking | |
| | +-----------+ | | | |
| |--| Ranking |-->| +----------------------------------+ |
| | +-----------+ +--------------------------------------+
+---------+
Peer selection hint server
Figure 2
The network information used by the hint server is not information
solicited from individual ISPs but the AS number and district
information, which are more or less already public. 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, to achieve the above. A peer can select a peer based on
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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 ratio of peers within the same AS or the same
prefecture calculated from the distribution of ASs and prefectures in
the IP address space from one-day data on a Winny network.
+--------------------+--------+
| Conditions | ratio |
+--------------------+--------+
| AS matches | 6.70% |
| Prefecture matches | 12.76% |
| Both match | 2.09% |
| Neither match | 78.45% |
+--------------------+--------+
Table 1: AS and prefecture distributions
Since, in addition to the above, the presence/absence of content
affects the result, the control of selecting a peer 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 the above, the following two measures are used
for the evaluation of proximity between peers in a hint server.
o AS path length (distance between ISPs)
AS path length 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 of both ISPs is too
large. To avoid this, we use multiple BGP information received
from different ISPs and combine them. Based on this concept, we
used BGP routing information's offered by three ISPs operated by
big telecommunication couriers and made a topology tree. Then it
enables to calculate the shortest path between given two ASes.
o Geographical distance
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Distances between peers are measured using physical distance of
prefectural capitals that target peers belong to. The distance
between prefectural capitals is used to calculate physical
distance. Distances between prefectural capitals are sorted into
ascending order, and then into bands, with weights 1 to 15
assigned to them so that there are a more or less equal number of
"capital pairs" in each band. If either of their location is
indefinite, distance is equal to 15 and, if they are in the same
prefecture, 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 only used when the AS path length is
same.
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=transcation ID]
[pt=Flag of port type]
[ub=upload bandwidth]
[db=download bandwidth]
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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
n=[src address] dst address / cost / option
5. High-Level Trial Results
5.1. Peer Selection with P2P
Table 2 shows the result of the analysis of communication in a node
of an ISP installed in Tokyo, as an example of measurement results.
In these two experiments we evaluate different P2P applications, in
1st experiment, the P2P topology is generated by tree algorithm, and
in 2nd experiment, it is generated by mesh algorithm. Both of them
result in similar performance.
+-----------------------------------------+------------+------------+
| Conditions | Experiment | Experiment |
| | 1 | 2 |
+-----------------------------------------+------------+------------+
| *Peers selected within the same ISP | 22% | 29% |
| *Peers selected within the same | 19% | 23% |
| district | | |
| *Peers selected within the same | 5% | 7% |
| district and the same ISP | | |
+-----------------------------------------+------------+------------+
Table 2: Percentage of communication within the same ISP
The table shows that the probability of communication with peers in
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the same ISP is proportional to the number of population 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 that the mechanism of selection 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.
5.2. Peer Selection with the Hint Server
The main objective of these experiments was to verify the operations
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 mean value of distance after the hint server was introduced was
reduced by 10% and that 95% value of that was reduced by 5%. The
results show introducing hint server can reduce network loads by P2P
applications.
6. Considerations
We clarified followings throughout our experiments.
1. Dispersed dummy nodes can figure out the behavior of peers and
traffic between inter-ISP networks, which peers are selected by
each peer. Therefore it proves that the importance of peer
selection control mechanism proposed in ALTO.
2. Using our peer selection control mechanism, called hint server,
could achieve significant differences. Our hint server can lead
each peer to select nearer peer.
In the experimental result of peer selection control, it is smaller
in intra-ISP traffic than other experiments [10] We think that it is
because there are smaller 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 small peers in one ISP, it is
difficult to select peers in the same ISP. In the situation of our
experiments, there are many ISPs of peers belonging, and there are
relatively smaller peers exist in same ISP.
Moreover, we didn't force P2P vendors to limit their implementation
policy, therefore we can observe differences how each implementations
weigh the information from the hint servers. Especially, in tree
overlay topology P2P applications, such mechanism is very effective,
on the other hand, in mesh overlay system, less effective.
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6.1. Next steps
The experiments are on going as of 2011. Current experiments in
2011, we've changed the communication protocol to hint servers to
ALTO based because it is nearly standardized. In our implementation,
PIDs and the value of cost are mapped to ISP subnets, and ISP
distance respectively. We also implement services for compatibility
required by ALTO such as Service Capability and Map Services. But
the Endpoint Cost Service is mainly used because of backward
compatibility of our experiments.
We also study hierarchical hint server structure, in order to control
in coarse inter-ISPs and in detail intra-ISP. It is also effective
for limiting the area of information disclose.
6.2. Feedback to ALTO WG
This section describes what the authors learned with these
experiments would be useful for the ALTO WG.
6.2.1. Hierarchical architecture for ALTO servers
In our experiments, we present the possibility of traffic control
among multi-ISPs and multi-P2P applications using ALTO mechanism. On
the other hand, we found several problems in ISP operations to adapt
the mechanism. One is the granularity of network information. Among
inter-ISP area, it is relatively easy to treat information for public
purpose using BGP full route. On the other hand, among intra-ISP
area, it may be difficult to disclose private information of each
ISP. [11] propose some modification for 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 and moreover it is difficult to exchange the
fine-grained information between ISPs. Considering this situation,
the authors use only coarse-grained information to control backbone
traffic in the experiments this year, though demand of controlling
traffic within an ISP using fine-grained information will arise in
the near future. Therefore it led us that introducing hierarchical
structure into ALTO is necessary to cope with both situations.
Actually, the authors plan to adapt a hierarchical control mechanism
in the next steps, which include the following two steps.
o In the first step, coarse-grained information about whole the
network is used to select ISPs.
o Next, fine-grained information within the ISP is used to select a
peer.
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6.2.2. Measurement mechanism
In the experiments, there were two difficulties as follows:
o Evaluating effect of introducing a hint server was difficult,
since P2P applications had their own measurement mechanisms.
o How to treat priority orders of peers suggested by a hint server
could not be predetermined for P2P applications.
From these experiences, the authors consider that clarifying
requirements about measurement mechanisms for P2P applications are
necessary also in ALTO.
7. Security Considerations
This document does not propose any kind of protocol, practice or
standard.
8. IANA Considerations
No need to describe any request regarding number assignment.
9. Acknowledgments
Thanks to strong support by MIC (Ministry of Internal Affairs and
Communications of Japanese government), the council was established.
These experiments were performed under cooperation among P2P Network
Experiment Council members, and DREAMBOAT co.,ltd., Bitmedia Inc.,
Utagoe. Inc. and Toyama IX have especially supported analyses of the
experiments. The authors appreciate Tohru Asami, Hiroshi Esaki and
Tatsuya Yamshita for their constructive comments.
10. Informative References
[1] "On the Quality of Triangle Inequality Violation Aware Routing
Overlay Architecture", INFOCOM 2009: 2761-2765.
[2] "QRON: QoS-aware routing in overlay networks", IEEE JOURNAL ON
SELECTED AREAS IN COMMUNICATIONS, VOL. 22, NO. 1, JANUARY 2004.
[3] "Winny on Wikipedia", <http://en.wikipedia.org/wiki/Winny>.
[4] "Share on Wikipedia",
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<http://en.wikipedia.org/wiki/Share_(P2P)>.
[5] Taniwaki, "Broadband Competition Policy in Japan", 2008,
<http://www.smartireland.jp/en/forum/may-2009/>.
[6] Utagoe Inc., "UGLive technology introduction",
http://www.utagoe.com/en/technology/grid/live/index.html,
March, 2011.
[7] TVBank, "Live Delivery using `BB Broadcast'Achieving 96% Saving
in Traffic!", http:.wwww.tv-bank.com/jp/20081031.html, 2008 (in
Japanese).
[8] Cho, Fukuda, Esaki, and Kato, "The Impact and Implications of
the Growth in Residential User-to-User Traffic", SIGCOMM2006,
pp207-218, Pisa, Italy, September 2006.
[9] Open P4P, "P4P Field Tests: Yale-Pando-Verizon",
http://www.openp4p.net/front/, 2009.
[10] "RFC5632: Comcast's ISP Experiences in a Proactive Network
Provider Participation for P2P (P4P) Technical Trial",
September 2009.
[11] "ALTO H12,draft-kiesel-alto-h12-02 (work in progress)", March
2010.
Authors' Addresses
Satoshi Kamei
NTT Communications Corporation
Granpark Tower 17F, 3-4-1 Shibaura
Minato-ku, Tokyo 108-8118
JP
Phone: +81-50-3812-4697
Email: skame@nttv6.jp
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Tsuyoshi Momose
Cisco Systems G.K.
9-7-1 Akasaka
Minato-ku, Tokyo 107-6227
JP
Phone: +81-3-6738-5154
Email: tmomose@cisco.com
Takeshi Inoue
NTT Communications
3-4-1, Shibaura
Minato-ku, Tokyo 108-8118
JP
Phone: +81-3-6733-7177
Email: inoue@jp.ntt.net
Tomohiro Nishitani
NTT Communications
1-1-6, Uchisaiwaicho
Chiyodaku, Tokyo 100-8019
JP
Phone: +81-50-3812-4742
Email: tomohiro.nishitani@ntt.com
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