Overlay Neighborhoods for Distributed Publish/Subscribe Systems
description
Transcript of Overlay Neighborhoods for Distributed Publish/Subscribe Systems
![Page 1: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/1.jpg)
Overlay Neighborhoods for Distributed Publish/Subscribe Systems
Reza Sherafat KazemzadehSupervisor: Dr. Hans-Arno Jacobsen
SGS PhD Thesis DefenseUniversity of TorontoSeptember 5, 2012
![Page 2: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/2.jpg)
2
Content-Based Pub/Sub
Pub/Sub
S
SS SS
S
S
PPublish PP
P
SS
Subscribers
PPP
Publishers
![Page 3: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/3.jpg)
3
Thesis Contributions
List of publications:[ACM Surveys] Dependable publish/subscribe systems (being submitted)[Middleware’12] Opportunistic Multi-Path Publication Forwarding in Pub/Sub Overlays[ICDCS’12] Publiy+: A Peer-Assisted Pub/Sub Service for Timely Dissemination of Bulk Content[SRDS’11] Partition-Tolerant Distributed Publish/Subscribe Systems[SRDS’09] Reliable and Highly Available Distributed Publish/Subscribe Service[ACM Transactions on Parallel and Distributed Systems] Reliable Message Delivery in Distributed Publish/Subscribe Systems Using Overlay Neighborhoods (being submitted)[Middleware Demos/Posters’12] Introducing Publiy (being submitted)
Dependability
Reliability
Ordered delivery
Fault-tolerance
![Page 4: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/4.jpg)
4
Thesis Contributions
Dependability
Reliability
Ordered delivery
Fault-tolerance
Multipath forwarding
Adaptive overlay mesh
Dynamic forwarding strategies
Efficient data structure
List of publications:[ACM Surveys] Dependable publish/subscribe systems (being submitted)[Middleware’12] Opportunistic Multi-Path Publication Forwarding in Pub/Sub Overlays[ICDCS’12] Publiy+: A Peer-Assisted Pub/Sub Service for Timely Dissemination of Bulk Content[SRDS’11] Partition-Tolerant Distributed Publish/Subscribe Systems[SRDS’09] Reliable and Highly Available Distributed Publish/Subscribe Service[ACM Transactions on Parallel and Distributed Systems] Reliable Message Delivery in Distributed Publish/Subscribe Systems Using Overlay Neighborhoods (being submitted)[Middleware Demos/Posters’12] Introducing Publiy (being submitted)
![Page 5: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/5.jpg)
5
Thesis Contributions
Dependability
Reliability
Ordered delivery
Fault-tolerance
Multipath forwarding
Adaptive overlay mesh
Dynamic forwarding strategies
Efficient data structures
Content Dissemination
Bulk content dissemination
Peer-assisted hybrid architecture
Dissemination strategies
List of publications:[ACM Surveys] Dependable publish/subscribe systems (being submitted)[Middleware’12] Opportunistic Multi-Path Publication Forwarding in Pub/Sub Overlays[ICDCS’12] Publiy+: A Peer-Assisted Pub/Sub Service for Timely Dissemination of Bulk Content[SRDS’11] Partition-Tolerant Distributed Publish/Subscribe Systems[SRDS’09] Reliable and Highly Available Distributed Publish/Subscribe Service[ACM Transactions on Parallel and Distributed Systems] Reliable Message Delivery in Distributed Publish/Subscribe Systems Using Overlay Neighborhoods (being submitted)[Middleware Demos/Posters’12] Introducing Publiy (being submitted)
![Page 6: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/6.jpg)
6
Overlay Neighborhoods
Thesis Contributions
Dependability
Reliability
Ordered delivery
Fault-tolerance
Multipath forwarding
Adaptive overlay mesh
Dynamic forwarding strategies
Efficient data structures
Content Dissemination
Bulk content dissemination
Peer-assisted hybrid architecture
Dissemination strategies
List of publications:[ACM Surveys] Dependable publish/subscribe systems (being submitted)[Middleware’12] Opportunistic Multi-Path Publication Forwarding in Pub/Sub Overlays[ICDCS’12] Publiy+: A Peer-Assisted Pub/Sub Service for Timely Dissemination of Bulk Content[SRDS’11] Partition-Tolerant Distributed Publish/Subscribe Systems[SRDS’09] Reliable and Highly Available Distributed Publish/Subscribe Service[ACM Transactions on Parallel and Distributed Systems] Reliable Message Delivery in Distributed Publish/Subscribe Systems Using Overlay Neighborhoods (being submitted)[Middleware Demos/Posters’12] Introducing Publiy (being submitted)
![Page 7: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/7.jpg)
7
Publications:
[SRDS’11] Partition-Tolerant Distributed Publish/Subscribe Systems
[SRDS’09] Reliable and Highly Available Distributed Publish/Subscribe Service
[ACM Transactions on Parallel and Distributed Systems] Reliable Message Delivery in Distributed Publish/Subscribe Systems Using Overlay Neighborhoods (being submitted)
[ACM Surveys] Dependable publish/subscribe systems (being submitted)
[Middleware Demos/Posters’12] Introducing Publiy (being submitted)
DEPENDABILITY IN PUB/SUB SYSTEMSPart I
![Page 8: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/8.jpg)
8
Dependable pub/sub systems
Challenges of Dependabilityin Content-based Pub/Sub Systems
The “end-to-end principle” is not applicable in a pub/sub system– Loose-coupling between publishers and subscribers (endpoints)– End-point cannot distinguish message loss from filtered
messages: This is especially true in content-based systems supporting flexible publication filtering
PS Pub/Sub
Middleware
✓✗✓✗?
Loss cannot be differentiated
from filtered pubs
Filtered out(not matching sub)
![Page 9: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/9.jpg)
9
Dependable pub/sub systems
Overlay Neighborhoods
Primary network: An initial spanning tree– Brokers maintain
neighborhood knowledge– Allows brokers to transform
overlay in a controlled manner
d-Neighborhood knowledge(d is a config. parameter):– Knowledge of other brokers
within distance d– Knowledge of forwarding paths
within neighborhood
3-neighborhood
2-neighborhood
1-neighborhood
![Page 10: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/10.jpg)
10
Dependable pub/sub systems
queue
Publication Forwarding Algorithm1. Received pubs are placed on a
FIFO msg queue and kept until processing is complete
2. All known subscriptions having interest in p are identified after matching
3. Forwarding path of the publication within downstream neighborhoods are identified
4. Publication is sent to closest available brokers towards matching subscribers
p
d-neighborhood
S
S
S
upst
ream
dow
nstr
eam
![Page 11: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/11.jpg)
11
Dependable pub/sub systems
S
S
S
When There are Failures
• Broker reconnects the overlay by creating new links to neighbors of the failed brokers
• Publications in message queue are re-transmitted bypassing failed neighbors
• Multiple concurrent failed neighbors (up to d-1) are bypassed similarly
P
![Page 12: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/12.jpg)
12
Dependable pub/sub systems
Impact of Mass Failures on ThroughputExperiment setup:• 500 brokers (failures injected at random brokers)• Measurement interval of 2 mins (aggregate publish rate changes depending number of
failures)
Expected # of deliveries w/o
failures
![Page 13: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/13.jpg)
13
Dependable pub/sub systems
Impact of Mass Failures on ThroughputExperiment setup:• 500 brokers (failures injected at random brokers)• Measurement interval of 2 mins (aggregate publish rate changes depending number of
failures)
Actual deliveries
with failures
Expected # of deliveries w/o
failures
![Page 14: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/14.jpg)
14
Dependable pub/sub systems
Impact of Mass Failures on ThroughputExperiment setup:• 500 brokers (failures injected at random brokers)• Measurement interval of 2 mins (aggregate publish rate changes depending number of
failures)
Actual deliveries
with failures
Expected # of deliveries w/o
failures
![Page 15: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/15.jpg)
15
Dependable pub/sub systems
Impact of Mass Failures on ThroughputExperiment setup:• 500 brokers (failures injected at random brokers)• Measurement interval of 2 mins (aggregate publish rate changes depending number of
failures)
Actual deliveries
with failures
Expected # of deliveries w/o
failures
![Page 16: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/16.jpg)
16
Dependable pub/sub systems
Impact of Mass Failures on ThroughputExperiment setup:• 500 brokers (failures injected at random brokers)• Measurement interval of 2 mins (aggregate publish rate changes depending number of
failures)
Expected # of deliveries w/o
failures
Actual deliveries
with failures
Low deliveries with d=1
![Page 17: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/17.jpg)
17
Dependable pub/sub systems
Impact of Mass Failures on ThroughputExperiment setup:• 500 brokers (failures injected at random brokers)• Measurement interval of 2 mins (aggregate publish rate changes depending number of
failures)
Low deliveries with d=1
![Page 18: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/18.jpg)
18
Dependable pub/sub systems
Impact of Mass Failures on ThroughputExperiment setup:• 500 brokers (failures injected at random brokers)• Measurement interval of 2 mins (aggregate publish rate changes depending number of
failures)
Low deliveries with d=1
![Page 19: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/19.jpg)
19
Publications:
[Middleware’12] Opportunistic Multi-Path Publication Forwarding in Pub/Sub Overlays
OPPORTUNISTIC MULTI-PATHPUBLICATION FORWARDING
Part II
![Page 20: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/20.jpg)
20
Multi-path publication forwarding
– Forwarding paths in the overlay are constructed in“fixed end-to-end” manner (no/little path diversity)
– This results in a high number of “pure forwarding” brokers
– Low yield (ratio of msgs delivered over msgs sent is small) Low efficiency
Problems in Existing Pub/Sub Systems
B CA D E PS✗ ✗ ✓✗✓
![Page 21: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/21.jpg)
21
Multi-path publication forwarding
Monitor neighborhood
traffic
Selectively create additional soft links
Different Pub. Forwarding Strategies
Multi-Path Forwarding in a Nutshell
Actively utilize neighborhoods
A Soft links
![Page 22: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/22.jpg)
• Conventional systems:Strategy 0Total msgs: 6
• Forwarding strategy 1Total msgs: 5
• Forwarding strategy 2Total msgs: 3
Different Forwarding Strategies
A B C
* *
*
p * *
*
A B C
* *
*
p * *
*
A B C
* *
*
p * *
*
![Page 23: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/23.jpg)
23
Multi-path publication forwarding
Maximum System ThroughputExperiment setup:• 250 brokers• Publish rate of 72,000 msgs/min
S2 outperforms S0 by 90%
S1 outperforms S0 by 60%
![Page 24: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/24.jpg)
24
Publications:
[ICDCS’12] Publiy+: A Peer-Assisted Publish/Subscribe Service for Timely Dissemination of Bulk Content
BULK CONTENT DISSEMINATION INPUB/SUB SYSTEMS
Part III
![Page 25: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/25.jpg)
25
Bulk content dissemination
Applications Scenarios InvolvingBulk Content Dissemination
Fast replication of content:(video clips, pics)• Scalability• Reactive delivery• Selective delivery
Distributionof software
updates
P2P filesharing
File synch.
Replicationwithin CDN
Socialnetworks
![Page 26: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/26.jpg)
Bulk content dissemination
Control layer
brokers
Data layer
subscribers
A case for a peer-assisted design
Control layer (for metadata)• P/S broker overlay• Distributed repository
maintaining users’subscriptions
Data layer (for actual data)• Form peer swarm• Exchange blocks
of data
Subs
crib
e
Subs
crib
e
Subs
crib
e
Subs
crib
e Subs
crib
e
Hybrid Architecture
![Page 27: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/27.jpg)
27
Bulk content dissemination
Scalability w.r.t. Number of SubscribersNetwork setup:• 300 and 1000 clients• 1 source publishing 100 MB of content
![Page 28: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/28.jpg)
28
Conclusion• We introduced the notion of overlay neighborhoods in
distributed pub/sub systems– Neighborhoods expose brokers’ knowledge of nearby neighbors and
the publication forwarding paths that crosses these neighborhoods
• We used neighborhood in different ways– Passive use of neighborhoods for ensuring reliable and ordered
delivery– Active use of neighborhoods for multipath publication forwarding– Bulk content dissemination
![Page 29: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/29.jpg)
29
Thanks for your attention!
![Page 30: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/30.jpg)
30
BONUS SLIDES IF NEEDED!EXTRAS
![Page 31: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/31.jpg)
31
OVERLAY NEIGHBORHOODS
![Page 32: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/32.jpg)
32
London
Toronto
Trader 1
Content-Based Publish/Subscribe
Pub/Sub
S
SS SS
S
S
PPublish PP
P
sub = [STOCK=IBM]
sub= [CHANGE>-8%]
NY
Trader 2Stock quote dissemination
application
![Page 33: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/33.jpg)
33
Overlay neighborhoods
System ArchitectureTree dissemination networks: One path from source to destination• Pros:
– Simple, loop-free– Preserves publication order
(difficult for non-tree content-based P/S)• Cons:
– Trees are highly susceptible to failures
Primary tree: Initial spanning tree that is formedas brokers join the system
– Maintain neighborhood knowledge– Allows brokers to reconfigure overlay
after failures on the fly
∆-Neighborhood knowledge: ∆ is configuration parameterensures handling ∆-1 concurrent failures (worst case)
– Knowledge of other brokers within distance ∆ Join algorithm
– Knowledge of routing paths within neighborhood Subscription propagation algorithm
3-neighborhood
2-neighborhood
1-neighborhood
![Page 34: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/34.jpg)
34
Dependable pub/sub systems
Overlay Disconnections
When there are d or more concurrent failures– Publication delivery may be interrupted– No publication loss
B BB B B
Remain connected
Subtree Subtree
B CA D E
Failed chain of d brokers
DisconnectedSubtrees are Disconnected
![Page 35: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/35.jpg)
35
Dependable pub/sub systems
Experimental Evaluation
Studied various aspects of system’s operation:– Impact of failures/recoveries on delivery delay– Impact of failures on other brokers– Size of d-neighborhoods– Likelihood of disconnections– Impact of disconnections on system throughput
Discussed next
![Page 36: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/36.jpg)
36
Dependable pub/sub systems
Publication Forwarding in Absence of Overlay Fragments
• Forwarding only uses subscriptions accepted brokers.
• Steps in forwarding of publication p:– Identify anchor of accepted subscriptions that match p– Determine active connections towards matching subscriptions’ anchors– Send p on those active connections and wait for confirmations– If there are local matching subscribers, deliver to them– If no downstream matching subscriber exists, issue confirmation towards P– Once confirmations arrive, discard p and send a conf towards p
Publications
ABCDEP SSubscriptions
☑
p
☑ ☑ ☑ ☑ ☑ ☑
CE
p p p p p
Deliver to localsubscribers
confconfconfconfconfconf
p
![Page 37: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/37.jpg)
37
Dependable pub/sub systems
Publication Forwarding in Presence of Overlay Partitions
Key forwarding invariant to ensure reliability: we ensure that no stream of publications are delivered to a subscriber after being forwarded by brokers that have not accepted its subscription.
• Case1: Sub s has been accepted with no pid. It is safe to bypass intermediate brokers
conf
conf
conf
Publications
ABCDEP S
Subscriptionsp
C BD☑ ☑ ☑ ☑ ☑ ☑ ☑
p p
Deliver to localsubscribersconf
p
![Page 38: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/38.jpg)
38
Dependable pub/sub systems
Publication Forwarding (cont’d)• Case2: Sub s has been accepted with some pid.
– Case 2a: Publisher’s local broker has accepted s and we ensure all intermediate forwarding brokers have also done so:
It is safe to deliver publications from sources beyond the partition.
conf
conf
conf
Publications
ABCDEP S
Subscriptionsp
C BD☑ ☑ ☑ ☑ ☑*
p p
conf
p
![Page 39: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/39.jpg)
39
Dependable pub/sub systems
Publication Forwarding (cont’d)• Case2: Sub s has been accepted with some pid.
– Case 2a: Publisher’s local broker has accepted s and we ensure all intermediate forwarding brokers have also done so:
It is safe to deliver publications from sources beyond the partition.
conf
conf
conf
Publications
ABCDEP S
Subscriptionsp
C BD☑ ☑ ☑ ☑ ☑*
p p
Depending on when this link has been establishedeither recovery or subscription propagation ensure
C accepts s prior to receiving p
conf
p
![Page 40: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/40.jpg)
40
Dependable pub/sub systems
Publication Forwarding (cont’d)• Case2: Subscription s is accepted with some pid tags.
– Case 2b: Publisher’s broker has not accepted s:
It is unsafe to deliver publications from this publisher (invariant).
Publications
ABCDEP S
Subscriptionsp
☑ ☑*
p p*
s was acceptedat S with the same pid tag
p p
p
Tag with pid
![Page 41: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/41.jpg)
41
Dependable pub/sub systems
Overlay Fragments• When primary tree is setup, brokers communicate with their immediate neighbors in the
primary tree through FIFO links.
• Overlay fragments: Broker crash or link failures creates “fragments” and some neighbor brokers “on the fragment” become unreachable from neighboring brokers
• Active connections: At each point they try to maintain a connection to its closest neighbor in the primary tree.– Only active connections are used by brokers
ABCDEF SP D
pid1=<C, {D}>
Fragment detectorBrokers on the fragmentBrokers beyond
the fragmentBrokers onthe fragment
Active connection to E
?
x
![Page 42: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/42.jpg)
42
Dependable pub/sub systems
Overlay Fragments – 2 Adjacent Failures
• What if there are more failures, particularly adjacent failures?
• If ∆ is large enough the same process can be used for larger fragments.
ABCDEF SP D
pid1=<C, {D}>
Brokers beyondthe fragment
Brokers onthe fragment
E
+ pid2=<C, {D, E}>
Active connection to F
![Page 43: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/43.jpg)
43
Dependable pub/sub systems
Overlay Fragments - ∆ Adjacent Failures
• Worst case scenario: ∆-neighborhood knowledge is not sufficient to reconnect the overlay.
• Brokers “on” and “beyond” the fragment are unreachable.
No new active connection
ABCDEF SP D
pid1=<C, {D}>
Brokers beyondthe fragment
Brokers onthe fragment
E
pid2=<C, {D, E}>
F
+ pid3=<C, {D, E, F}>
![Page 44: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/44.jpg)
44
Dependable pub/sub systems
FragmentsBrokers are connected to closest reachable neighbors & aware of nearby fragment identifiers.
• How does this affect end-to-end connectivity? For any pair of brokers, a fragment on the primary path between them is:
– An “island” if end-to-end brokers are reachable through a sequence of active connections
– A “barrier” if end-toe-end brokers are unreachable through some sequence of active connections
ABCDEF SP DEF
ABCDEF SP D
sourcedestination
destination source
![Page 45: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/45.jpg)
45
Dependable pub/sub systems
Store-and-Forward
• A copy is first preserved on disk
• Intermediate hops send an ACK to previous hop after preserving
• ACKed copies can be dismissed from disk
• Upon failures, unacknowledged copies survive failure and are re-transmitted after recovery– This ensures reliable delivery but may cause delays while the machine is down
P P PPFromhere
Tohere
ackackack
![Page 46: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/46.jpg)
46
Dependable pub/sub systems
Mesh-Based Overlay Networks [Snoeren, et al., SOSP 2001]
• Use a mesh network to concurrently forward msgs on disjoint paths
• Upon failures, the msg is delivered using alternative routes
• Pros: Minimal impact on delivery delay
• Cons: Imposes additional traffic & possibility of duplicate delivery
PPPP
Fromhere
Tohere
![Page 47: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/47.jpg)
47
Dependable pub/sub systems
Replica-based Approach [Bhola , et al., DSN 2002]
• Replicas are grouped into virtual nodes• Replicas have identical routing information
PhysicalMachines
Virtual node
![Page 48: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/48.jpg)
48
Dependable pub/sub systems
Replica-based Approach[Bhola , et al., DSN 2002]
• Replicas are grouped into virtual nodes• Replicas have identical routing information
• We compare against this approach
PP
PP
P
P
Virtual node
![Page 49: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/49.jpg)
Multi-path publication forwarding
Problems with a Single Overlay Tree
• Tree provides no routing diversity
• Overloaded root– All traffic goes through a
single broker
• Under utilization: Not all availablecapacity is effectively used
Tree: Single path connectivitynot suitable for diverse
forwarding patterns
?
Unutilizedbandwidth capacity
Overloaded root
![Page 50: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/50.jpg)
Multi-path publication forwarding
Related Work – Structured Topologies
• A topology is an interconnection between brokers: – Topology relatively stable: long-term connections– Most commonly a global/per-publisher spanning tree
• Topology adaptation change topology based on:– Traffic patterns [1,2] – optimize a cost function– Maintain acyclic property by adding + removing links
• Advantages:– Fixed topology enables high-throughput connections– Routes may be improved from a “course-grained” system-wide perspective
• Disadvantages:– Routes may never be optimal for individual broker pairs– Introduces pure forwarding brokers– Diversity of routing is not accounted for
[1] Virgillito, A., Beraldi, R., Baldoni, R.: On event routing in content-based publish/subscribe through dynamic networks. In: FTDCS. (2003)[2] Virgillito, A., Beraldi, R., Baldoni, R.: On event routing in content-based publish/subscribe through dynamic networks. In: FTDCS. (2003)
Re-configur
e
Tree A
Tree A’
![Page 51: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/51.jpg)
Multi-path publication forwarding
Related Work – Unstructured Topologies
• No fixed topology exists: – Short-term links are created based on
message destination– [3] uses dissemination trees computed
at the publishers’ brokers
• Advantages:– Routes may be optimal– Zero pure forwarding brokers
• Disadvantages:– Link maintenance is difficult and on-demand– Global knowledge is required and no support
for subscription covering/merging– Scalability problems
[3] Cao, F., Singh, J.: MEDYM: Match-early and dynamic multicast for content-based publish-subscribe service networks. ICDCSW (2005)
![Page 52: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/52.jpg)
52
Multi-path publication forwarding
Publication Forwarding StrategiesStrategy S1
• Publication is sent on intersection of primary paths towards matching subscribers
• Some pure forwarding brokers are bypassed
• Broker incurs no extra outgoing load
Strategy S2
• Publication is sent on as far as possible directly towards matching subscribers
• As many pure forwarding brokers as possible are bypassed
• Broker incurs high outgoing load
A B C
X
D
Y
Z
p X Y
Z
A B C
X
D
Y
Z
p X Y
Z
Local matching subscribers
Bypassed pure forwarder
Bypassed pure forwarder
![Page 53: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/53.jpg)
Master vs. Working Routing Data Structures
• Overlay views captured by brokers’ d-neighborhoods are relatively static Master Overlay Map (MOM)
• Brokers link connectivity change dynamically, brokers need an efficient way to compute forwarding paths over the changing set of links Working Overlay Map (WOM) via Edge retraction
• MOM only contains brokers with a direct link - it acts as a quick cache
Master Overlay Map
Working Overlay Map
construct
![Page 54: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/54.jpg)
54
Multi-path publication forwarding
Experimental Evaluation
Experimental setup– Various overlays
• Primary network size: 120, 250, 500 brokers• Fanout parameter: 3 and 10
– Datasets with sparse or dense matching distributions• Synthetic datasets based on Zipf distribution• Real world datasets constructed from Social Networking
user traces• Synthetic datasets with covering
![Page 55: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/55.jpg)
55
Multi-path publication forwarding
Overlay Reconfiguration
![Page 56: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/56.jpg)
56
Multi-path publication forwarding
Connectivity in the Overlay MeshExperiment setup:• 120 and 250 brokers• Fanout of 10
1000
100
100
10
1
Pair-
wise
for
war
ding
pat
hs
![Page 57: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/57.jpg)
57
Multi-path publication forwarding
Impact of Broker Fanout on Subscription CoveringExperiment setup:• 500 brokers• Fanout of 5-25
![Page 58: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/58.jpg)
58
Multi-path publication forwarding
Impact of Broker Fanout on Subscription CoveringExperiment setup:• 500 brokers• Fanout of 5-25
![Page 59: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/59.jpg)
59
Multi-path publication forwarding
Impact of Broker Fanout on Subscription CoveringExperiment setup:• 500 brokers• Fanout of 5-25
![Page 60: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/60.jpg)
60
Multi-path publication forwarding
Impact of Broker Fanout on Subscription CoveringExperiment setup:• 500 brokers• Fanout of 5-25
![Page 61: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/61.jpg)
61
Multi-path publication forwarding
Impact of Broker Fanout on Subscription CoveringExperiment setup:• 500 brokers• Fanout of 5-25
![Page 62: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/62.jpg)
62
Multi-path publication forwarding
Publication Hop CountExperiment setup:• 120 Brokers• Sparse publication/subscription workload• Publish rate of 1,800 msgs/sec Deliveries: 73,000 in 5 min
![Page 63: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/63.jpg)
63
Multi-path publication forwarding
Publication Hop CountExperiment setup:• 120 Brokers• Sparse publication/subscription workload• Publish rate of 1,800 msgs/sec Deliveries: 73,000 in 5 min
![Page 64: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/64.jpg)
64
Multi-path publication forwarding
Publication Hop CountExperiment setup:• 120 Brokers• Sparse publication/subscription workload• Publish rate of 1,800 msgs/sec Deliveries: 73,000 in 5 min
![Page 65: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/65.jpg)
65
Multi-path publication forwarding
Publication Hop CountExperiment setup:• 120 Brokers• Sparse publication/subscription workload• Publish rate of 1,800 msgs/sec Deliveries: 73,000 in 5 min
![Page 66: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/66.jpg)
66
Multi-path publication forwarding
Publication Hop CountExperiment setup:• 120 Brokers• Sparse publication/subscription workload• Publish rate of 1,800 msgs/sec Deliveries: 73,000 in 5 min
![Page 67: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/67.jpg)
67
Multi-path publication forwarding
Publication Hop CountSparse Matching Workload Dense Matching Workload
Multi-path forwarding is more effective in sparse workloads
![Page 68: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/68.jpg)
68
Multi-path publication forwarding
System Yield (measure of efficiency)Delivered
publicationsStrategy Number of pure
Pure ForwardersSystem Yield
73,000(Sparse Workload)
Strategy 0 91,000 44%
Strategy 1 42,000 63%
Strategy 2 29,000 71%
Delivered publications
Strategy Number of pure Pure Forwarders
System Yield
284,000(Dense Workload)
Strategy 0 195,000 59%
Strategy 1 104,000 73%
Strategy 2 69,000 80%
![Page 69: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/69.jpg)
69
Multi-path publication forwarding
Maximum System ThroughputExperiment setup:• 250 brokers• Publish rate of 72,000 msgs/min
![Page 70: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/70.jpg)
Bulk content dissemination
Data Exchange Using Network Coding
Blocks matrix(k * n)
Randomcoefficients Cused for coding
Decoding usesk linearlyindependent blocks
Segmentation Encode intodata packets DecodeSegment 3
Yi =
B1
B k
Segment 2
Yi =
Segment 1
Yi = B1
Bk
File
Segment 3
Yi =
B1
B k
Segment 2
Yi =
Segment 1
Yi = B1
Bk
FileCi Xi
Encode Transfer
![Page 71: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/71.jpg)
Bulk content dissemination
Hybrid architectureRegional dissemination Cross-Regional dissemination
Control layer
Data layer
Matchingsubscribers
PList
Control layer
Data layerPublisher
PList
Codedpackets
Matchingsubscribers
Involves routing of notificationsin control layer
Information is immediately available at broker
![Page 72: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/72.jpg)
72
Bulk content dissemination
Evaluation Results
• Experimental setup– UofT’s SciNet cluster with up to 1000 nodes– Peers have a capped uplink bandwidth
(100-200 KB/s)
• Network setup:– 5 Regions– 120, 300 or 1000 subscribers uniformly
distributed among regions
![Page 73: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/73.jpg)
73
Bulk content dissemination
Content Serving PolicyNetwork setup:• 300 clients• 1 source publishes 100 MB of content
![Page 74: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/74.jpg)
74
Bulk content dissemination
Content Serving PolicyNetwork setup:• 300 clients• 1 source publishes 100 MB of content
![Page 75: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/75.jpg)
75
Bulk content dissemination
Content Serving PolicyNetwork setup:• 300 clients• 1 source publishes 100 MB of content
![Page 76: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/76.jpg)
76
Bulk content dissemination
Content Serving PolicyNetwork setup:• 300 clients• 1 source publishes 100 MB of content
![Page 77: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/77.jpg)
77
Bulk content dissemination
Impact of Packet LossNetwork setup:• 300 clients• 1 source publishes 100 MB of content
![Page 78: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/78.jpg)
78
Bulk content dissemination
Impact of Packet LossNetwork setup:• 300 clients• 1 source publishes 100 MB of content
![Page 79: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/79.jpg)
79
Bulk content dissemination
Impact of Packet LossNetwork setup:• 300 clients• 1 source publishes 100 MB of content
![Page 80: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/80.jpg)
80
Bulk content dissemination
Impact of source Fanout on dissemination timeNetwork setup:• 300 clients• 1 source publishes 100 MB of content
![Page 81: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/81.jpg)
81
Bulk content dissemination
Impact of source Fanout on dissemination timeNetwork setup:• 300 clients• 1 source publishes 100 MB of content
![Page 82: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/82.jpg)
82
Bulk content dissemination
Impact of source Fanout on dissemination timeNetwork setup:• 300 clients• 1 source publishes 100 MB of content
![Page 83: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/83.jpg)
83
Bulk content dissemination
Impact of source Fanout on dissemination timeNetwork setup:• 300 clients• 1 source publishes 100 MB of content
![Page 84: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/84.jpg)
84
Bulk content dissemination
Effectiveness of Traffic Shaping
REG 1 REG 2 REG 3 REG 4 REG 5
REG 1
REG 2
REG 3
REG 4
REG 5
Experiment setup:• 5 regions and 1000 clients (capped uplink bandwidth at 200 KB/s)• 1 sources publish 100 MB
![Page 85: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/85.jpg)
85
Bulk content dissemination
Effectiveness of Traffic Shaping
REG 1 REG 2 REG 3 REG 4 REG 5
REG 1 19.57%
REG 2
REG 3
REG 4
REG 5
Experiment setup:• 5 regions and 1000 clients (capped uplink bandwidth at 200 KB/s)• 1 sources publish 100 MB
Regional traffic
![Page 86: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/86.jpg)
86
Bulk content dissemination
Effectiveness of Traffic Shaping
REG 1 REG 2 REG 3 REG 4 REG 5
REG 1 19.57% 0.109% 0.109% 0.109% 0.108%
REG 2
REG 3
REG 4
REG 5
Experiment setup:• 5 regions and 1000 clients (capped uplink bandwidth at 200 KB/s)• 1 sources publish 100 MB
Regional traffic
Cross-regional traffic
![Page 87: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/87.jpg)
87
Bulk content dissemination
Effectiveness of Traffic Shaping
REG 1 REG 2 REG 3 REG 4 REG 5
REG 1 19.57% 0.109% 0.109% 0.109% 0.108%
REG 2 0.110% 19.57% 0.109% 0.109% 0.109%
REG 3 0.110% 0.110% 19.55% 0.108% 0.108%
REG 4 0.114% 0.114% 0.114% 19.57% 0.114%
REG 5 0.110% 0.110% 0.110% 0.111% 19.49%
Experiment setup:• 5 regions and 1000 clients (capped uplink bandwidth at 200 KB/s)• 1 sources publish 100 MB
Regional traffic
Cross-regional traffic
![Page 88: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/88.jpg)
88
Bulk content dissemination
Traffic Sharing Among Competing Contentwith Uniform Popularity
Experiment setup:• 5 regions and 1000 clients (capped uplink bandwidth at 200 KB/s)• 15 sources (3 in each region) publish 100 MB with uniform popularity
1 TB of data
![Page 89: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/89.jpg)
89
Bulk content dissemination
Traffic Sharing Among Competing Contentwith Different Popularity
Experiment setup:• 5 regions and 1000 clients (capped uplink bandwidth at 200 KB/s)• 15 sources (3 in each region) publish 100 MB • Content has 1x, 2x, and 3x popularity
Most popular
Least popular
Medium popularity
![Page 90: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/90.jpg)
90
Bulk content dissemination
Contribution of PeersContribution of the source
Avg per segment: 136% content size
Contribution of subscribers
Overall avg: 102% of download size
Network setup:• 300 clients• 1 source publishes 100 MB of content
![Page 91: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/91.jpg)
91
Bulk content dissemination
Comparison With BitTorrentExperiment setup:• 120 clients (capped uplink bandwidth at 200 KB/s)• 1 source publishes 100 MB of content
Upon release all clients start download
Within 1300 s download ends
![Page 92: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/92.jpg)
92
Bulk content dissemination
Comparison With BitTorrentExperiment setup:• 120 clients (capped uplink bandwidth at 200 KB/s)• 1 source publishes 100 MB of content
[BT]: Polling intervalof 10 minutes
[BT]: Within 1700 s downloads end
![Page 93: Overlay Neighborhoods for Distributed Publish/Subscribe Systems](https://reader035.fdocuments.in/reader035/viewer/2022062811/56816253550346895dd29cba/html5/thumbnails/93.jpg)
93
Bulk content dissemination
Comparison With BitTorrentExperiment setup:• 120 clients (capped uplink bandwidth at 200 KB/s)• 1 source publishes 100 MB of content
Polling intervalof 2 seconds
[BT]: Within 1600 s downloads end