From Wikipedia, the free encyclopedia P2P caching
P2P caching
P2P
Peer-to-peer caching (P2P caching) is a computer net- derstand what traffic is running across their networks
work traffic management technology used by Internet and to separate it and treat it for the most efficient de-
Service Providers (ISPs) to accelerate content delivered livery. DPI products identify and pass P2P packets to the
over peer-to-peer (P2P) networks while reducing related P2P caching system so it can cache the traffic and accel-
bandwidth costs. erate it.
P2P caching is similar in principle to the content Peerapp Ltd. holds the first patent [6] for P2P caching
caching long used by ISPs to accelerate Web (HTTP) con- technology, which was filed in 2000.
tent. P2P caching temporarily stores popular content
that is flowing into an ISP’s network. If the content re-
quested by a subscriber is available from a cache, the
The P2P bandwidth problem
cache satisfies the request from its temporary storage, It is estimated that peer-to-peer traffic accounts for 50%
eliminating data transfer through expensive transit links of all Internet traffic in 2008. However, P2P traffic is ex-
and reducing network congestion. However, this ap- pected to quadruple between 2008 and 2013, reaching
proach could make ISPs vulnerable to copyright infringe- 3.3 exabytes per month– or the equivalent of 500 million
ment as significant fraction of files shared by P2P systems DVDs each month.[7] .
are illegal[1] . Increasing P2P traffic has created problems for ISPs.
P2P content responds well to caching because it has Networks can become saturated with P2P traffic, creating
high reuse patterns reflecting a Zipf’s-like distribution[2] congestion for other types of Internet use. The cost of
[3] [4] . P2P communities have different Zipf’s parame- P2P traffic is disproportionate to the amount of revenue
ters[4] which determine what fraction of files is requested ISPs make from these customers because of the flat-rate
multiple times. For example, one P2P community may re- packages of bandwidth commonly sold. To prevent P2P
quest 75% of content multiple times while another may traffic from degrading service for all subscribers, ISPs
request only 10%. typically face three choices:
Some P2P caching devices can also accelerate HTTP • Invest in additional bandwidth and equipment.
video streaming traffic from YouTube, Facebook, Unfortunately, increasing bandwidth often does not
RapidShare, MegaUpload, Google, AOL Video, MySpace solve the problem, because P2P applications
and other web video-sharing sites.[5] inherently tend to consume as much bandwidth as
available.
• Implement stricter byte caps, policies, or P2P traffic-
How P2P caching works shaping, limiting the speed of P2P traffic. The
P2P caching involves creating a cache or temporary stor- difficulty is that P2P packets are becoming harder
age space for P2P data, using specialized communications and harder to identify, especially with the
hardware, disk storage and associated software. This introduction of encryption (such as BitTorrent
cache is placed in the ISP’s network, either co-located protocol encryption). Traffic shaping can also
with the Internet transit links or placed at key aggrega- generate negative publicity and customer reactions.
tion points or at each cable head-end. • Implement a form of P2P caching.
Once a P2P cache is established, the network will Caching releases the bandwidth demand on critical Inter-
transparently redirect P2P traffic to the cache, which ei- net links and improves the experience for all users – P2P
ther serves the file directly or passes the request on to users whose file sharing is improved through using the
a remote P2P user and simultaneously caches that data cache, and non-P2P users who experience better perfor-
for the next user. To what extent the caching is beneficial mance from networks un-congested from P2P traffic.
depends on how similar the content interests of ISP’s cus- The initial adopters of P2P caching have been ISPs in
tomers. Due to relatively small number of content shared Asia, the Pacific Rim, Latin America, the Caribbean and
in P2P systems (compared to Web) and semantic, geo- the Middle East, whose subscribers are heavy users of P2P
graphic, and organization interests of users[4] sharing ra- networks and where providing the additional bandwidth
tio in P2P can be significantly higher than HTTP/Web to handle P2P data is very costly due to the expense of in-
caching[citation needed]. ternational transit links.
P2P caching typically works with a network traffic- P2P caching is expected to become an increasingly es-
mitigation technology called Deep Packet Inspection sential technology for ISPs and MSOs (multiple system
(DPI). DPI technology is used by service providers to un- operators) worldwide, particularly with the growing
1
From Wikipedia, the free encyclopedia P2P caching
popularity of P2P content among broadband subscribers • Traffic shaping
and the adoption of P2P as a content-distribution strate-
gy by mainstream content providers such as the BBC.
Sources
[1] Jacob, Assaf M.; Zoe Argento (1). "To Cache or Not
P2P caching implementations to Cache – That is the Question; P2P ‘System
• Dalesa [2] is an open source P2P web cache designed Caching’ – The Copyright Dilemma". Whittier Law
for local area networks. Any browser attached to a 31:
Review 31 421-. http://ssrn.com/abstract=1670289.
computer within the LAN can participate in P2P [2] Sripanidkulchai, K.. "The popularity of Gnutella
caching process by using Dalesa P2P application. It queries and its implications on scalability".
uses IP multicasting based protocol to perform http://www.cs.cmu.edu/~kunwadee/research/
distributed cache lookups. A peer-to-peer cache p2p/gnutella.html. Retrieved 6 January 2012.
lookup protocol based on Distributed Hash Tables [3] Klemm, A.; C. Lindemann, M. K. Vernon, and O. P.
(DHTs) is scheduled to be delivered in a forthcoming Waldhorst (2004). "Characterizing the query
release. The DHT protocol will become an alternative behavior in peer-to-peer file sharing systems". 4th
to the current IP-multicasting-based lookup protocol ACM SIGCOMM Conf. on Internet Measurement.
which was introduced in version 0.1. [4] ^ Bandara, H. M. N. Dilum; A. P. Jayasumana (June
• PeerApp UltraBand Media Caching Software [3] 2011). "Exploiting communities for enhancing
• Corelli [8] is a community-based P2P caching system lookup performance in structured P2P systems".
that operates in a decentralized way across multiple IEEE Int. Conf. on Communications (ICC ’11).
peers. This allows a caching service to be realised in doi:10.1109/icc.2011.5962882.
environments that do not possess fixed caching [5] http://www.peerapp.com/Technology/
infrastructure, e.g. a Wireless ad hoc network. VideoCaching.aspx
• Community Caching is a P2P community-interest- [6] U.S Patent Number 7,203,741 B2
aware, distributed caching solution for structured [7] Cisco. "Approaching the Zettabyte Era". Cisco.
(DHT-based) P2P systems. It alleviates the overhead http://www.cisco.com/en/US/solutions/
due to isolating P2P communities and loss of content collateral/ns341/ns525/ns537/ns705/ns827/
popularity due to aggregation of content from white_paper_c11-481374_ns827_Networking_Solutions_White_Pa
multiple communities[4] . Retrieved 6 January 2012.
[8] Gareth Tyson, Andreas Mauthe, Sebastian Kaune,
See also Mu Mu and Thomas Plagemann. Corelli: A Dynamic
Replication Service for Supporting Latency-
• Caching Dependent Content in Community Networks. [1]
• Deep packet inspection
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Categories:
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