Towards Efficient Simulation of Large Scale P2P Networks

1
Towards Efficient Simulation of Large Scale P2P
Networks

• Tobias Hoßfeld

ITG-Fachgruppe 5.2.1Cooperating and Scalable
Networks Aachen, Ericsson, J. Sachs, 04.05.2006
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Cartography of P2P Architectures

• Two control functions in P2P systems
• Resource mediationwhere are files located
• Resource access controlwho may download a file
  and when
• Mapping of P2P architectures into architectural
  space
• pure P2P
• hybrid P2P
• classic client/server
• Identification of control objectives

PureP2P
P2P Cartography
hybrid P2P
3
Peer-to-Peer Architectures
Information Seeker
Information Provider
Information Mediator
Structured P2P-Network (Chord)
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Basic Functions of P2P Networks

• join()

• leave()

new node
peer informs its neighbors and bootstrap server
node failures detected by periodical updates or
not answered requests resilience
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Basic Functions of P2P Networks (contd.)

• insert(key,data)

• retrieve(key)

peer x wants to insert (key,data) using DHTs
key hash(data)
peer x searches for key
x
and asks its neighbors
which redirect requests
y sends data to x
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Basic Function of P2P Content Distribution

• Main feature is multiple source download.
• Peers issue several download requests for the
  same file to multiple providing peers in
  parallel.
• Providing peers serve the requesting peers
  simultaneously.

providingpeer
After successfully downloading a whole chunk, it
is provided to other peers.
downloading peer 1
index server 2
index server 1
providingpeer
providingpeer
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Features of P2P Systems and Their Implications

• Usually a large number of participating peers
• Large-scale a lot of nodes and even higher
  number of resources need to be simulated
• Peers may arbitrary join or leave
• Highly dynamic a lot of user created event (due
  to churn, i.e. peers joining and leaving
  arbitrarily, as key feature of P2P systems)
• Cooperative working of peers and robust systems
• Complexity
• one event can cause a large number of events at
  other peers, i.e. system events, due to
  cooperation among peers
• additionally periodic or provisional systems
  event to cope with the self-organization of p2p
  systems

Target of Workshop Focus on large-scale P2P
networks in order to consider key characteristics
(e.g. regarding churn for 100 peers reasonable?)
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Approach For Simulating Large-Scale P2P Systems

• System state has to be stored at simulation
  machine
• requires efficient data structures (e.g. calendar
  queue)
• How to model in order to reduce the number of
  events?
• Resource mediation might not require to model
  bandwidth, only signalling delay
• Resource exchange might not require to model
  delay if large contents are exchanged requires
  modelling of bandwidth
• other performance influence factors packet loss,
  moving users,
• appropriate abstractions models for
  investigated application
• Clustering of peers to user groups...
• might allow parallel simulation of clusters

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Workshop in Würzburg

• Efficient Data Structures
• Andreas Binzenhöfer, Calendar Queue and Event
  Design Algorithms
• Jens Oberender, Modelling Resource Fragmentation
• Abstractions and Models
• Kolja Eger, Packet-based Simulation
• Gerald Kunzmann, Signaling in Voice/Video over IP
  Systems
• Daniel Schlosser, Tobias Hoßfeld, Periodic and
  Market-Based Bandwidth Allocation
• Parallel Simulation
• Ivan Dedinski, Parallel Discrete Event Simulation

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Talks Today
Hier könnte Ihr Name stehen !
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Periodic and Market-Based Bandwidth Allocation
ineDonkey Networks

• Tobias Hoßfeld, Daniel Schlosser

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Measurements of eDonkey Traffic

• Case-by-case measurements of eDonkey file-sharing
  application in public GPRS/UMTS network
• Multiple source download via GPRS

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eDonkey Data Exchange via UMTS

• UMTS upload restricts throughput

• UMTS download restricts throughput

• Max-min-fair share of available bandwidth is
  observed
• How to model the bandwidth allocation of
  fair-share P2P file-sharing applications?

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Simulation of Fair-Share Bandwidth Allocation

• Events which influence the bandwidth allocation
  are that a peer
• starts the download of a file
• finishs a download
• goes offline while downloading
• continues downloading a file after joining the
  network again
• We consider eDonkey-like file-sharing networks
• Aim Modeling of bandwidth allocation in
  fair-share networks

Events
t
Dt
Dt
Dt
Dt
Dt
Dt
Dt
Dt
Dt
Dt
Dt
Computation of allocated bandwidth
t
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Stream-based or packet-based approach?

• TCP can be neglected if conditions are fulfilled
  (540 kB blocks)
• Signaling vs. data exchange RTT vs. bandwidth

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What means fair-share?

• All peers get the same bandwidth
• If a peer cannot consume completely the allocated
  bandwidth, the surplus is distributed among the
  remaining peers

3 kbps
11 kbps
13 kbps
13 kbps
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Periodic Bandwidth Allocation

• For each Dt, for each peer compute bandwidth
  allocation

Allocated bandwidth can be overbooked or
underbooked
Peer 1
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Market-Based Bandwidth Allocation

• For each event, consider affected, i.e.
  connected, peers
• All affected peers make a bid
• Strategy
• If there are no other bids, propose x not
  allocated bandwidth / peers
• If minimal bid y of all affected peers is smaller
  than x, then keep bid y and compute x
• If all bids are larger than x, then bid x on
  these connections
• Finish If lower bid of a connection is the
  minimal bid of a peer and is repeated

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Market-Based Bandwidth Allocation
Downloading network links
Uploading network links
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NL3 40kbps
3.333
15
NL4 30kbps
NL0 10kbps
10
NL1 10kbps
5
NL5 10kbps
5
NL2 80kbps
NL6 10kbps
20
10
NL7 10kbps
Initial bid x BW / peers
40
NL8 40kbps
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MBBA Example
Downloading network links
Uploading network links
20
NL3 40kbps
3.333
15
NL4 30kbps
3.333
NL0 10kbps
26.667
10
NL1 10kbps
5
NL5 10kbps
5
3.333
25
NL2 80kbps
5
NL6 10kbps
25
6.667
25
20
10
NL7 10kbps
If minimal bid y of all connected peers holds
yltx, then set bid y and compute x x BW /
peers. If all yltx, keep x.
40
NL8 40kbps
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MBBA Example
Downloading network links
Uploading network links
20
NL3 40kbps
3.333
NL4 30kbps
3.333
NL0 10kbps
26.667
10
NL1 10kbps
5
NL5 10kbps
3.333
25
NL2 80kbps
5
NL6 10kbps
25
6.667
25
10
NL7 10kbps
Finish If lower bid of a connection is the
minimal of a peer and is repeated
40
NL8 40kbps
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MBBA Example
Downloading network links
Uploading network links
NL3 40kbps
3.333
NL4 30kbps
NL0 10kbps
5
26.667
NL1 10kbps
NL5 10kbps
24.444
NL2 80kbps
NL6 10kbps
6.667
6.667
24.444
24.444
10
NL7 10kbps
Finish If lower bid of a connection is the
minimal of a peer and is repeated Minimal bid
yltx, set y and compute x
40
NL8 40kbps
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MBBA Example
Downloading network links
Uploading network links
NL3 40kbps
3.333
NL4 30kbps
NL0 10kbps
5
26.667
NL1 10kbps
NL5 10kbps
24.444
31.667
6.667
NL2 80kbps
NL6 10kbps
10
24.444
24.444
31.667
10
NL7 10kbps
Finish If lower bid of a connection is the
minimal of a peer and is repeated If all yltx,
keep x.
40
NL8 40kbps
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MBBA Example
Downloading network links
Uploading network links
NL3 40kbps
3.333
NL4 30kbps
NL0 10kbps
5
26.667
NL1 10kbps
NL5 10kbps
6.667
NL2 80kbps
NL6 10kbps
31.667
36.666
10
NL7 10kbps
Finish If lower bid of a connection is the
minimal of a peer and is repeated
40
NL8 40kbps
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MBBA Example
Downloading network links
Uploading network links
NL3 40kbps
3.333
NL4 30kbps
NL0 10kbps
5
26.667
NL1 10kbps
NL5 10kbps
6.667
NL2 80kbps
NL6 10kbps
10
NL7 10kbps
36.666
NL8 40kbps
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Comparison PBA vs. MBBA

• Exchange of small files

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Comparison PBA vs. MBBA

• Exchange of large files

MBBA computes and allocates immediately
fair-share bandwidth -gt in real systems this
requires some time PBA bandwidth overbooked or
underbooked for ?t -gt in next step bandwidth is
adapted
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Conclusion

• For P2P content distribution networks, like
  eDonkey, resource access control is crucial point
• Fair-share bandwidth allocation has to be modeled
  
• We have proposed two stream-based approaches
  which are valid in the considered scenarios
• Periodic bandwidth allocation PBA
• Market-based bandwidth allocation MBBA
• Depending on the number of events influencing the
  resource access control PBA or MBBA has to be
  preferred