Networkaware P2P file sharing over the wireless mobile networks

1
Network-aware P2P file sharing over the wireless
mobile networks

• Chung-Ming Huang, Member, IEEE, Tz-Heng Hsu, and
  Ming-Fa Hsu
• IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS,
  VOL. 25, NO. 1, JANUARY 2007?????

2
Outline

• Introduction
• Network-aware P2P File Sharing Architecture
• P2P Network Construction
• Resource Discovery Scheme
• Performance Analysis
• Conclusion

3
Introduction

• Two concerns that affect resource discovery and
  retrieval for P2P file sharing applications in
  wireless mobile networks are
• Peers movements in wireless mobile networks
• Peers join and leave in a P2P file sharing
  network.

4
Introduction

• A mobile P2P file sharing system needs to address
  the above issues.
• A network-aware discovery scheme for mobile hosts
  to find new resource providing peers that share
  files in their currently resident wireless
  network.
• A resource discover control policy for mobile
  hosts to obtain fresh status of peers, i.e.,
  peers join and leave, in a mobile P2P file
  sharing network.

5
Introduction

• A novel network-aware P2P file sharing
  architecture that has
• A mobility-aware file discovery control (MAFDC)
  scheme for
• Obtaining fresh status of participant peers
• Reducing the number of messages used to discover
  peers in the mobile wireless networks
  environment,
• A resource provider selection algorithm for
• Selecting a new resource provider when mobile
  peers encounter broken connections in wireless
  mobile networks.

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Network-aware P2P File Sharing Architecture

• A peer u is an ordinary host that can join and
  leave a P2P file sharing network freely at any
  time.
• The peer can search, publish, and retrieve files
  in the mobile P2P file sharing network.
• A super-peer is a selected node that provides
  functions for peers to locate a specific file.

7
Network-aware P2P File Sharing Architecture
8
Network-aware P2P File Sharing Architecture

• A new super-peer is created when the first
  peer joins a network-aware cluster Cl.
• The super-peer maintains indexes of the
  shared files and indexes of peers location
  information in its network-aware cluster Cl.
• When a requesting mobile peer u sends a lookup
  request to its own network cluster super-peer
  , the super-peer checks whether the desired
  file Ai is available or not.

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Network-aware P2P File Sharing Architecture

• If the super-peer finds the desired file Ai, it
  sends a response message to the requesting mobile
  peer u.
• If no such file can be found in the network-aware
  cluster Cl, the super-peer forwards the
  lookup request to its nearby network-aware
  clusters for finding the desired file Ai.

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Network-aware P2P File Sharing Architecture

• Each lookup request has a Time To Live (TTL)
  field which is decremented by one at each queried
  cluster.
• When the value of TTL reaches zero, the lookup
  request is stop forwarding.
• Each lookup request has a 32 byte identifier to
  uniquely identify it on the proposed P2P network.
  

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Network-aware P2P File Sharing Architecture

• When a lookup request is passed through a
  super-peer
• The super-peer records the identifier of the
  lookup request.
• If a super-peer receives a lookup request with
  the same identifier which it has received before.
• The lookup request is ignored and is not
  forwarded.
• By checking the identifiers of lookup requests,
  the proposed P2P network can
• Prevent loops and indefinite propagation in whole
  network.

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P2P Network Construction

• In the network construction phase, a bootstrap
  peer directs new peers joining the network to the
  appropriate clusters.
• To find the corresponding cluster of a peer, the
  bootstrap peer maintains a cluster routing table.
  
• Each entry in the cluster routing table
  represents a network-aware cluster for peers to
  join and leave.

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P2P Network Construction

• Attributes in the cluster routing table are
  cluster identify number, the primary and backup
  network-aware cluster domains for that cluster,
  and a timer.

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P2P Network Construction

• At the very beginning (no peer exists yet), the
  cluster routing table is empty.
• When the first peer joins, the bootstrap peer
  determines its network-aware cluster using the
  BGP routing tables in nearby routers.
• If another peer joins with the same network-aware
  cluster, the most powerful of the two will become
  the super-peer of the network-aware cluster.

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P2P Network Construction

• To join the proposed network-aware P2P file
  sharing network, a peer u contacts one of the
  bootstrap peers x.
• The bootstrap peer x identifies the most suitable
  network-aware cluster Cl of the joining peer u
  and replies with a short message.
• The message contains the address of the
  super-peer of the network-aware cluster Cl
  and its backup peer of the cluster Cl.

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P2P Network Construction

• The joining peer u sends a join request to the
  super-peer of the network-aware cluster Cl.
• The super-peer of the network-aware cluster
  Cl returns a list of the other super-peers that
  are participants of the network-aware P2P
  network.
• Then, the joining peer u establishes a connection
  with the super-peer .

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P2P Network Construction

• Over the connection time, the joining peer u
  sends information about its owned files Ai,
  ...,Am and its computing capacities to its
  super-peer .
• The computing capacities are specified in terms
  of three resources bandwidth, CPU, and storage.
• The super-peer updates its index with the new
  peer u and its data.

18
P2P Network Construction

• A joining peer u may be promoted to a super-peer
  if it owns more resources than the current
  super-peer .
• After the joining process is finished, the
  promotion process starts from bottom up.
• The super-peer that is responsible for the
  new peer u compares the new peers resources
  versus its own and each of the backup
  super-peers resources.

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P2P Network Construction

• Although all resources (bandwidth, CPU, and
  storage) can be used in the comparison
• We use the most important one offered outbound
  bandwidth.
• Fast CPUs and large disks are abundant nowadays.
• A threshold is used in the comparison to prevent
  frequent change of super-peers.

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P2P Network Construction

• If the new peer becomes the primary super-peer
• It gets the index from the replaced super-peer
• Informs
• The bootstrap peers
• All backup super-peers
• Peers in the network-aware cluster.
• Two different cases that need to be considered
  are as follows
• Regular peer leave
• Super-peer leave

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P2P Network Construction

• When a regular peer u leaves the network-aware
  P2P file sharing network
• It sends a leave message to its super-peer ,
  which updates the index to reflect the peers
  leave.
• Before leaving, a super-peer
• Selects a new primary super-peer from the backup
  list
• Informs it
• Updates its indexes
• Sends a leave message
• To the bootstrap peer x
• To the active peers in the network cluster.

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P2P Network Construction

• The leave message contains the IP address of the
  new super-peer.
• The new super-peer establishes a control
  connection with its bootstrap peer.
• The active peers
• Close the connection with the old super-peer
• Open new ones with the new super-peer.

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Resource Discovery Scheme - Mobility-Aware File
Discovery Control Scheme

• A mobile peer that requests files can send
  messages periodically to discover peers and
  select a new and better one for file retrieval.
• Waste network bandwidth if each requesting mobile
  peer sends a lot of messages periodically to
  discover peers that share files.
• We propose a novel file discovery control scheme
  named mobility-aware file discovery control
  (MAFDC) scheme.

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Resource Discovery Scheme - Mobility-Aware File
Discovery Control Scheme

• The MAFDC scheme can
• Find new resource providing peers quickly when a
  new coming file is shared.
• Reduce the number of messages that are used to
  discover new resource providing peers.
• In the MAFDC scheme, there are two kinds of query
  modes for mobile peers to discover new resource
  providing peers
• Publish-subscribe query mode
• Continuous query mode

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Resource Discovery Scheme - Mobility-Aware File
Discovery Control Scheme Publish-Subscribe
Query Mode

• In the MAFDC scheme, when they join the proposed
  P2P file sharing network mobile peers
• Connect with super-peers
• Publish shared file lists to the super-peers.
• In the publish-subscribe query mode
• A requesting mobile peer can register interests
  (queries) to super-peers by sending subscription
  messages.

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Resource Discovery Scheme - Mobility-Aware File
Discovery Control Scheme Publish-Subscribe
Query Mode

• A subscribe-driven discovery control (SDC)
  algorithm is proposed to
• Reduce the number of messages that are used to
  discover resource providing peers in the
  publish-subscribe query mode.
• When a requesting mobile peer u wants to submit
  an interest of file query q
• Peer u connects to a nearby network-aware
  super-peer .

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Resource Discovery Scheme - Mobility-Aware File
Discovery Control Scheme Publish-Subscribe
Query Mode

• Then peer u sends a SubscribeFileQuery(id, q, ql)
  message to super-peer .
• id is a unique identifier of peer u
• ql is the query life time of query q.
• A subscribed query entry which has not been
  matched for more than ql seconds will be deleted.
• When super-peer receives query message q
• It inserts the query q in its local query table
  for comparing the incoming shared file lists.

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Resource Discovery Scheme - Mobility-Aware File
Discovery Control Scheme Publish-Subscribe
Query Mode

• Each query message q has a timeout value
  QueryTimeOut for preventing stale information
  stored in the query table.
• Once a new peer v joins the P2P file sharing
  network, the peer v
• connects a super-peer
• sends a message PublishFileResource(id, l)
• l is the shared file list of the new joined
  peer.
• When super-peer receives the message
• It compares shared file lists for finding the
  matching query q.

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Resource Discovery Scheme - Mobility-Aware File
Discovery Control Scheme Publish-Subscribe
Query Mode

• Once a matching query has been found from the
  shared file lists, super-peer sends a
  notification message FileNotification(id, r)
• r is a list containing resource indicators which
  point to the matching resource providing peers.
• In case of a requesting mobile node u moves from
  network C1 to a new visit network C2
• The requesting mobile node u can send a
  messageRenewQuery(id, q, ip) to the original
  super-peer .

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Resource Discovery Scheme - Mobility-Aware File
Discovery Control Scheme Publish-Subscribe
Query Mode

• The super-peer will update its query table
  with the new ip address of the mobile node u.
• Once a matching query has been found from the
  shared file lists
• Super-peer sends a notification message to
  the new ip address of the mobile node u.

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Resource Discovery Scheme - Mobility-Aware File
Discovery Control Scheme Continuous Query Mode

• In the continuous query mode, a requesting mobile
  peer u can send discovery messages for finding
  resource providing peers according to the
  connection status of the mobile peers.
• The receiver-driven discovery control (RDC)
  algorithm can be adopted to tackle this mode.
• The RDC algorithm is used to reduce the number of
  messages that are used to discover resource
  providing peers in the continuous query mode.

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Resource Discovery Scheme - Mobility-Aware File
Discovery Control Scheme Continuous Query Mode

• The RDC algorithm uses a pre-configured threshold
  RequiredTransRate
• Evaluate that a connection is usable or less
  usable for retrieving a file in wireless mobile
  networks.

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Resource Discovery Scheme - Mobility-Aware File
Discovery Control Scheme Continuous Query Mode

• Connections transmission rate gt
  RequiredTransRate
• The next time period for sending discovery
  messages will be extended in order to reduce the
  number of messages for finding resource providing
  peers.
• Connections transmission rate lt
  RequiredTransRate
• The next time period for sending discovery
  messages will be shrunk in order to find new and
  better resource providing peers as soon as
  possible.

34
Resource Discovery Scheme - Resource Provider
Selection

• In case of a resource provider v being a fixed
  node, the performance of file retrieval will be
  degraded when a requesting mobile node u roams
  among different networks.
• The requesting mobile node u can send a new query
  q to the nearby super-peer when the mobile
  node u moves from network C1 to a new visit
  network C2.

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Resource Discovery Scheme - Resource Provider
Selection

• In the proposed scheme, the super-peer will
  response a message to the requesting mobile peer
  u.
• The responded message contains a list of
  candidate resource providing peers that are
  located in current network.
• The requesting mobile peer u can select a new
  resource providing peer w according to the
  network performance metrics such as bandwidth and
  round-trip time (RTT) information.

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Resource Discovery Scheme - Resource Provider
Selection

• In case of a resource provider v being a mobile
  node, the performance of file retrieval will be
  degraded when a requesting mobile node u or
  resource providing peer v roams among different
  networks.
• The resource providing peer v can register its
  mobility information with the nearby super-peer
  when the resource providing peer
  v moves from network C2 to a new visit network
  C3.

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Resource Discovery Scheme - Resource Provider
Selection

• Meanwhile, the resource providing peer v needs to
  
• Update its information with super-peer
• Send messages to notify those peers who are
  retrieving files from it.
• When a requesting mobile peer u receives the
  notification
• Send a new query to its nearby super-peer
  for rediscovering a desired file in the currently
  visited network C2.

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Resource Discovery Scheme - Resource Provider
Selection

• The super-peer will response a message to the
  requesting mobile peer u.
• The responded message contains
• A list of candidate resource providers
• Their mobility information.

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Resource Discovery Scheme - Resource Provider
Selection

• The requesting mobile peer u can select a new
  resource provider according to the mobility
  information such as
• moving speed
• network performance metrics
• Bandwidth
• round-trip time (RTT) information.
• The mobility information is an important metric
  that affect the retrieval performance
• The connection with mobile resource provider will
  be broken unpredictably

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Resource Discovery Scheme - Resource Provider
Selection

• The resource provider selection (RPS) algorithm
• Help peers to resume interrupted connection
  quickly.
• The resource provider selection (RPS) algorithm
  uses
• The roundtrip time (RTT) information
• Packet loss rate as the cost function c(u, v).
• The resource provider selection (RPS) will select
  the node that has the minimum cost as the current
  resource-providing peer.

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Performance Analysis

• 2000 wired nodes in a (10000m 10000m) grid in
  the simulated P2P model.
• The generated mobile nodes mobility patterns
• based on the random way-point mobility model.
• The mobile node is moving to its destination with
  a speed uniformly selected from (0 m/s, 2 m/s).

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Performance Analysis

• Each mobile node is configured with the 802.11b
  MAC protocol
• Transmission range 250m
• Transmission rate 2Mbits/sec
• Mobile nodes retrieve desired files using the FTP
  protocol.
• New peers join the P2P network according to the
  Poisson distribution.

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Performance Analysis

• Arrival rates of mobile nodes
• 10 nodes/sec
• Average number of mobiles nodes per cluster
• 100 nodes/cluster
• Number of shared files of each node
• 10 files/node.
• The simulation is the average over 50 independent
  simulations.

44
Performance Analysis

• Three resource discovery schemes are evaluated in
  the simulation
• Receiver-driven discovery control (RDC) scheme
• Periodical-based discovery control (PDC) scheme
• Subscribe-driven discovery control (SDC) scheme

45
Performance Analysis

• A requesting mobile peer retrieves a file from
  the peer that has the most available bandwidth
• In the RDC scheme by sending query messages
  according to the proposed RDC algorithm.
• In the PDC scheme by sending query messages
  periodically.
• In the SDC control scheme, a super-peer responses
  matched query messages to requesting mobile peers
  in the publish-subscribe mode.

46
Performance Analysis

• Figure 2 shows the influence that the movement of
  the mobile node causes.

47
Performance Analysis

• The data packet routing path may be changed and
  the data loss rate may be increased in wireless
  mobile networks.
• The performance of retrieving files in wireless
  mobile networks is unstable.

48
Performance Analysis

• It shows that the RDC method is better than the
  SDC method in a wireless mobile network.

49
Performance Analysis

• The SDC method lets a mobile peer subscribe its
  interest (query) to a super-peer.
• When new files are shared/published in the
  subscribed cluster, the super-peer sends a
  matched query message to the requesting mobile
  peer.

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Performance Analysis

• When new files are shared/published in other
  clusters, the requesting mobile peer will not be
  notified because it does not subscribe its
  interests to these clusters.
• This makes the requesting mobile peer not be able
  to select the best resource providing peers.
• Therefore, the average data throughput is not so
  good as the RDC approach in a wireless mobile
  network.

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Performance Analysis

• RDC can find resource providing peers outside the
  nearby network-aware cluster
• Because of the TTL field in the lookup request.
• If no such file can be found in the current
  network-aware cluster
• The super-peer forwards the lookup request to its
  nearby network-aware clusters.
• When the value of TTL reaches zero, the lookup
  request is stop forwarding.

52
Performance Analysis

• The average data throughput of the RDC method is
  better than that of the PDC method
• Because the requesting mobile peer can discover
  new resource providers aperiodically according to
  the network status in the RDC method.

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Performance Analysis

• If a mobile requesting peer roams to different
  networks
• Increases the number of discoveries to capture
  the fresh information of peers in the RDC
  discovery scheme.
• Therefore, a mobile requesting peer can retrieve
  the desired file from a peer quickly.

54
Conclusion

• We proposed a novel network-aware P2P file
  sharing architecture which has
• A mobility-aware file discovery control (MAFDC)
  scheme obtain
• Fresh status of participant peers
• Reduce the number of messages that are used to
  discover peers in the wireless networks
  environment.
• A resource provider selection algorithm
• Select a new resource provider for mobile peers
  experienced connection broken in wireless mobile
  networks.

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Conclusion

• As a result, the performance of file retrieval
  for mobile peers can be improved in the wireless
  mobile networks environment.