PeertoPeer Beyond File Sharing: Where are P2P Systems Going

1
Peer-to-Peer Beyond File SharingWhere are P2P
Systems Going?

• HotP2P 2009 Rome, May 29 2009

Renato Lo Cigno Tommaso Pecorella, Matteo
Sereno, Luca Veltri
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Thanks

• To my co-authors
• Tommaso, Matteo, Luca
• To the entire Profiles staff, who made this talk
  possible
• http//profiles.disi.unitn.it

• University of Trento Networking Group
• University of Firenze Telecommunication
  network Lab
• University of Parma Department of Information
  engineering
• University of Torino Department of Computer
  Science
• University of Catania Department of
  Informatics and Telecommunications
• University of Pavia Electric Communication
  and Remote Sensing Lab
• University of Rome II Networking Group

3
Outline

• Where we started
• Some bits of retrospective
• Where we are
• Applications
• Security
• Business
• Where are we going
• Applications
• Expectations
• Trends
• Security
• Outrageous thoughts
• Providers based P2P
• CrossLayer P2P
• P2P IPv6

4
Outline

• Where we started
• Some bits of retrospective
• Where we are
• Applications
• Security
• Business
• Where are we going
• Applications
• Expectations
• Trends
• Security
• Outrageous thoughts
• Providers based P2P
• CrossLayer P2P
• P2P IPv6

5
(Pre)History Bits

• Peer-to-Peer definitions
• A class of systems and applications that use
  distributed resources (CPU, memory, bandwidth,
  ...) to implement critical functions
• Communication paradigm where the entities/actors
  are providers and users at the same time
• Internet was indeed born following a P2P approach
• The first nodes were always client and servers at
  the same time!!

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Initial Studies

• Sharing information at the application level
• Search and Retrieval problems ? DHTs, Gossipping
  protocols, ...
• Closed communities ? Rare Contents, Finding
  Buddies, ...
• Exploiting unused (CPU) resources for distributed
  computing
• Often not exactly P2P, but voluntary donations
• Supporting privacy and anonymous communications

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Initial Studies

• P2P recognized as a possible different
  communication/distributed applications paradigm,
  contrasted to client/server
• Sharing involves much more than files
• Bandwidth, CPU, Storage, Knowledge, ...
• The key enabling factor is that resource
  composition is more than the sum of resources
• some resources do not scale (try to buy a single
  processor 100 times more powerful of your
  Pentium!)
• others are localized (local bandwidth comes for
  free, global bandwidth is very costly)

8
History Bits

• P2P exploded with file sharing
• legal problems made it infamous
• some service components were centralized
• P2P paradigms is now considered for a bunch of
  applications
• Content Distribution and Distributed Storage
• Personal Communications (Instant Messaging,
  Telephone)
• Distributed computing (grid, SETI_at_home)
• Video Distribution (Application Level Multicast)
• Gaming
• ...
• Depending on the measurement point P2P traffic
  represents between 50 and 90 of all Internet
  traffic

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Typical Example Bandwidth Sharing for Massive
File Distribution
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Cooperative Distribution Intuition
Source server 100 Mb/s Clients 10 Mb/s 1.
Antivirus update 100,000 clients File 4 MB 2.
Daily database update 1000 clients File 600 MB
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Cooperative Distribution Intuition
Source server 100 Mb/s Clients 10 Mb/s 1.
Antivirus update 100,000 clients File 4 MB 2.
Daily database update 1000 clients File 600 MB
Client/Server
Cooperative
Cooperative
1. 9h52m 2. 14h48m
1. 52s 2. 09m54s
Client/Server
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Outline

• Where we started
• Some bits of retrospective
• Where we are
• Applications
• Security
• Business
• Where are we going
• Applications
• Expectations
• Trends
• Security
• Outrageous thoughts
• Providers based P2P
• CrossLayer P2P
• P2P IPv6

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Background

• Internet has been enormously successful due to
  its resilience
• Client/server model both as transport paradigms
  and as business
• Business dominated by
• network providers
• information intermediates (Google, Yahoo, ...)
• Service providers are agonizing ... why??

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The Client-Server Doom

• Dominating Paradigm
• Traditional business models
• Intuitive and well known deterministic
  technicalities
• Clear entities relationships
• But ...

• Large cost of ownership (CapEx)

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Client-Server Doom Some (failing) answers

• Push specialization and outsourcing as means of
  optimization and cost reduction
• Exploit scale-economy
• centralized solutions to reduce personnel and
  competences
• resource sharing between different applications
  and companies
• Consolidate networking and services
• Service Providers want to have networks
• Network Providers seek services to sell

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What is Pushing P2P today?

• Can the C-S model scale without limits?
• How does it react to diminishing revenues because
  services are perceived as commodities?
• How does information generation and
  consumption affect the C-S model?
• The wiki and commons models are shaking
  traditional ways of knowledge dissemination
• Do we always need a server to provide
  services?
• Why does the model of network and service
  separation does not take off?

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But Why P2P

• Cost Can offer services much cheaper especially
  CapEx is low
• Think of TV ...
• Enabler for new applications
• Can offer services that would not be possible
  otherwise (think of out-of-country TV
  broadcasting or anonymous services)
• Internet (C-S model) itself is losing its
  resilience and capacity of evolution
• Powerful end systems that are vastly
  underutilized
• Gigaflops
• 100s of Gigabyte of local disk storage
• Good network connectivity

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Available P2P applications

• File sharing,
• Voice, Video, Chat,
• Backup
• few, not much used
• Versioning
• in its infancy
• Computing
• whats beyond BOINC?
• is it really P2P??
• But also
• Anonymous networking (tor) and other applications
  that may not exist without the P2P approach

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However .... There are Open Problems

• Distributed algorithms are needed for
• Service discovery
• Overlay management (topology, join, leave, ...)
• Application level routing
• Reliability and Dependability
• QoS definition and provisioning
• Trust management, security, privacy
• Efficiency
• Mapping between the overlay and the underlying
  resources

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Objects Finding and Managing them

• Representing and Abstracting Information
• data representation
• DHT algorithms
• Protocols and Signaling
• Replicating and Consolidating Information
• Minimal duplication
• De-correlation and De-localization
• Aging information when is information
  up-to-date?
• Ownership and access who can access/modify/delete
  the information?

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Resource Management

• P2P Overlays survive only if the resources
  underneath are available
• Where are they, how to find them, how to
  guarantee their availability
• Cooperation, not Exploitation
• Game theory may not suffice in finding equilibria
  in cooperation
• Different applications have different interaction
  models
• machine-to-machine
• machine-to-human
• human-to-human

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Real-Time applications

• Typically human-to-human
• Two entirely different system models
• Share only the need of short delays ... and
  indeed not even these
• Live Streaming
• Potentially huge audience
• Low Jitter, limited delay (1s20s)
• Structured or Unstructured??
• Conferencing
• Small groups
• Definitely structured
• Very low delays (100s ms), zero jitter

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Security Privacy

• Either neglected (in current applications, not in
  research!!)
• Or centralized (skype and others)
• Or the only goal (anonymous networking)
• Security and Privacy still thought as of separate
  problems ... or even contrasting
• Different attacks possible in P2P
• Routing
• Partition
• Retrieval
• Sybil and Eclipse

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Considerations (1)
Where are we?

• P2P has very interesting characteristics
• Self-scaling Use P2P wherever the demand is
  difficult to predict and very bursty
• Very cost-efficient
• Substitution technology for applications that can
  be done using the client-server paradigm, such as
  
• file distribution, CDN, video streaming, or
  backup
• Enabler for new applications such as
• Anonymous and Privacy Aware Networking
• Reliable multicast
• Distributed network monitoring and trouble
  shooting
• IPTV

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Considerations (2)
Where are we?

• P2P systems are now mainly scattered pieces of
  software, without coordination between them and
  without coordination with the network below
• Merging multiple applications on a single overlay
  management platform starts to be considered
• Mapping the overlay on the underlay resources is
  intriguing, but awfully difficult
• Cooperation between the network (IP) level and
  the overlay may increase performances, but both
  operators and users were against this idea ...
  until a little ago

26
Outline

• Where we started
• Some bits of retrospective
• Where we are
• Applications
• Security
• Business
• Where are we going
• Applications
• Expectations
• Trends
• Security
• Outrageous thoughts
• Providers based P2P
• CrossLayer P2P
• P2P IPv6

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Dominant applications

• Traditional file sharing (BitTorrent the like)
• Still generating the largest traffic
• Slowly loosing their forbidden appeal,
  exchanging all possible information
• Probably the only pure P2P systems so far (at
  least some of them)
• Voice Chat
• Lack of standards hamper the evolution
• Video and TV
• If not live (VoD) falls in file sharing class
• P2P-TV is exploding, with all the promises and
  concerns
• Conferencing is lagging behind (as usual)

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Network-Application Cooperation (NAC)

• Some BitTorrent dialects are already considering
  form of network awareness to improve performance
• An application which wisely uses resources is
  cheaper to run
• Operators are starting to consider P2P as a
  resource, not a foe after all if it was not for
  P2P they would not have sold large bandwidth
  access ?

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NAC What can ISP do?

• Application Level Redirection
• Application Cashing
• Introduce network peers in strategic points
• Manipulate routing
• Manipulate resource availability to force local
  overlays

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Multi-Application Platforms

• P2P is fundamentally re-inventing the
  communication level every new application
  inefficient!!!
• We need to understand P2P as a novel paradigm for
  communication/computing and provide high-level
  models that
• Enable the definition of general purpose P2P
  platforms
• Guarantee interoperability
• P2P support as a novel distributed OS

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P2P Standardization

• Should we standardize P2P?
• Signaling IETF is working (SIPpeer, ALTO, ...)
• Transport maybe is time to go beyond UDP/TCP ...
  
• Is PTP (P2P Transport Protocol) useful/needed??
• What does it mean
• Protocols only?
• APIs?
• End devices and OS that are P2P aware
• Segregating local and shared data
• Managing the resource/information sharing
  policies
• Business needs standards (or not?)

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Vulnerability Resilience

• Byzantine resistant systems are available
• Based on approximate Nash Equilibria
• Complex
• Is this what we need?
• P2P systems are resilient
• To random mistakes/failures
• To (many) external attacks
• Still they are quite unreliable
• Lets ConfCall with Skype ... and fall back to
  PSTN if it does not work ...
• Why?

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Privacy

• Little considered in general
• Sociology studies show that people are willing to
  trade privacy (when they know what it means) for
  commodity
• Little understanding of the implication of
  linkage in general
• Once more TV example
• Standard Broadcasting
• Server-Based IPTV
• P2P Options
• Server-based
• Anonymous, DHT based

34
Outline

• Where we started
• Some bits of retrospective
• Where we are
• Applications
• Security
• Business
• Where are we going
• Applications
• Expectations
• Trends
• Security
• Outrageous thoughts
• Providers based P2P
• CrossLayer P2P
• P2P IPv6

35
Providers P2P

• Server-assisted P2P is becoming a promising
  networking (and business) model at least in TV
  (but BitTorrent dialects AS-aware exists as we
  said)
• PPLive, UUsee, ...

ISP
ISP
ISP
ISP
ISP
ISP
ISP
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Providers P2P

• ISP-Assisted is a different model
• Do you trust more ISPs or Service Providers?
• Set-Top boxes can play the game

ISP
ISP
ISP
ISP
ISP
ISP
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Cross layering

• Anything farther then Application Level
  Networking??
• tor is an example of cross-layer-1 ?
• But
• Media-aware schedulers
• Network Aware Topologies
• TCP-friendly P2P
• are all examples of cross-layering

38
IPv6 P2P

• Restores end-to-end semantics (no NATs, ...)
• But
• Somebody (Cornell) is implementing IPv6 routers
  as a P2P overlay on top of IPv4!!!
• Current P2P applications are relaying on IPv4
  details
• Maybe IPv6 addresses can be used as a common
  platform for P2P addressing ... leaving IPv4
  where it is

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THE END

• Thank you!
• Questions?
• Comments?