should be required to disclose such
practices, and if they should be allowed
at all to discriminate among different
traffic types is the subject of an ongoing debate.
Independent of the outcome of this
debate, the tension will have to be resolved in a way that allows P2P applications to thrive while ensuring the profitability of ISPs. A promising technical
approach is to bias the peer selection
in P2P applications toward nodes connected to the same ISP or to ISPs that
peer with each other. 20 Another solution is for ISPs to change their pricing
A more fundamental tension is
that some ISPs view many of the currently deployed P2P applications as
competing with their own value-added
services. For instance, ISPs that offer
conventional telephone service may
view P2P VoIP applications as competition, and cable ISP may view P2P IPTV
applications as competing with their
own IPTV services. In either case, such
ISP’s market share in the more profitable value-added services is potentially
diminished in favor of carrying more
In the long term, however, ISPs will
likely benefit, directly and indirectly,
from the innovation and emergence of
new services that P2P systems enable.
Moreover, ISPs may find new revenue
sources by offering infrastructure support for successful services that initially developed as P2P applications.
In this article, we have sketched the
promise, technology, and challenges
of P2P systems. As a disruptive technology, P2P creates significant opportunities and challenges for the Internet, industry, and society. Arguably the most
significant promise of P2P technology
lies in its ability to significantly lower
the barrier for innovation. But the great
strength of P2P, its independence of
dedicated infrastructure and centralized control, may also be its weakness,
as it creates new challenges that must
be dealt with through technical, commercial, and legal means.
One possible outcome is that P2P
will turn out to be especially valuable
as a proving ground for new ideas and
services, in addition to keeping its role
as a platform for grassroots services
that enable free speech and the unreg-
ulated exchange of information. Ser-
vices that turn out to be popular, legal,
and commercially viable may then be
transformed into more infrastructure-
based, commercial services. Here,
ideas from P2P systems may be com-
bined with traditional, centralized ap-
proaches to build highly scalable and
1. about skype: 100 billion skype-to-skype Minutes
2. adar, e. and huberman, b.a. Free riding on gnutella.
First Monday 5, 10 (oct. 2000).
3. anderson, d.P. boinc: a system for public-resource
computing and storage. in Proceedings of the
5th IEEE/ACM International workshop on Grid
Computing (2004), 4–10.
4. bbc news. one million viewers use iPlayer. http: //
5. bittorrent (protocol). wikipedia; http://en.wikipedia.
6. blake, c. and rodrigues, r. high availability, scalable
storage, dynamic peer networks: Pick two. in
Proceedings of the 9th workshop on Hot Topics in
Operating Systems (May 2003).
7. castro, M., druschel, P., ganesh, a., rowstron, a.
and wallach, d.s. security for structured peer-to-peer overlay networks. in Proceedings of the
5th Symposium on Operating Systems Design and
Implementation (dec. 2002).
8. christin, n., weigend, a.s. and chuang, J. content
availability, pollution and poisoning in file sharing
peer-to-peer networks. in Proceedings of the 6th ACM
Conference on Electronic Commerce (June 2005).
9. clarke, i., sandberg, o., wiley, b. and hong, t.w.
Freenet: a distributed anonymous information
storage and retrieval system. in Proceedings of
the Designing Privacy Enhancing Technologies—
International workshop on Design Issues in
Anonymity and unobservability (July 2000).
10. cohen, b. incentives build robustness in bittorrent.
in Proceedings of the 1st International workshop on
Economics of P2P Systems (June 2003).
11. cox, L.P. Murray, c.d. and noble, b.d. Pastiche:
Making backup cheap and easy. in Proceedings of
the 5th Symposium on Operating Systems Design
and Implementation (dec. 2002).
12. cox, L.P. and noble, b.d. samsara: honor among
thieves in peer-to-peer storage. in Proceedings of
the 19th ACM Symposium on Operating Systems
Principles (oct. 2003).
13. decandia, g., hastorun, d., Jampani, M., Kakulapati,
g., Lakshman, a., Pilchin, a., sivasubramanian, s.,
Vosshall, P. and Vogels, w. dynamo: amazon’s highly
available key-value store. in Proceedings of the 21st
ACM Symposium on Operating Systems Principles
14. dischinger, M., Mislove, a. haeberlen, a. and
gummadi, K.P. detecting bittorrent blocking. in
Proceedings of the 8th Internet Measurement
Conference (oct. 2008).
15. douceur, J. the sybil attack. in Proceedings of
the First International workshop on Peer-to-Peer
Systems (Mar. 2002).
16. Freedman, M.J., Freudenthal, e. and Mazières, d.
democratizing content publication with coral. in
Proceedings of the 1st uSENIX Symposium on
Networked Systems Design and Implementation
17. hei, X., Liang, c., Liang, J., Liu, y. and ross, K.w.
insights into PPLive: a measurement study of a
large-scale P2P iPtV system. in Proceedings of
the 15th International world wide web Conference,
IPTV workshop (May 2006).
18. hildrum, K., Kubiatowicz, J.d., rao, s. and Zhao, b.y.
distributed object location in a dynamic network. in
Proceedings of the 14th Annual ACM Symposium on
Parallel Algorithms and Architectures (2002), 41–52.
19. huebsch, r., hellerstein, J.M., Lanham, n., Loo, b.t,
shenker, s. and stoica, i. Querying the internet
with Pier. in Proceedings of the 29th International
Conference on Very Large Data Bases (sept. 2003).
Rodrigo Rodrigues ( firstname.lastname@example.org) is a tenure-track faculty member at the Max Planck institute for
software systems (MPi-sws), where he heads the
dependable systems group.
Peter Druschel ( email@example.com) is the founding
director of the Max Planck institute for software
systems (MPi-sws), where he heads the distributed