Transcript Study of the Relationship between Peer-to

Study of the Relationship
between Peer-to-Peer Systems
and IP Multicasting
T. Oh-ishi, K. Sakai, K. Kikuma, and A. Kurokawa
NTT Network Service Systems Laboratories, NTT
Corporation
IEEE Communications Magazine, vol41(1), Jan. 2003
Presented by Ho Tsz Kin
28/01/2004
Agenda
Introduction
 Features of P2P Systems
 IP Multicasting over P2P Systems
 Routing Protocol
 Evaluation
 Conclusion

Introduction
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Peer-to-peer (P2P) systems
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Involve a number of directly connected
“peers” exchanging various types of
information among themselves
Problems of P2P systems
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Not specific application
Generate a lot of network traffic
Require the resources of every peer (e.g.
CPU, memory, and bandwidth)
Introduction
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IP multicasting
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Is mainly for live streaming services
Can solve problems of P2P systems
Applying IP multicasting to P2P systems
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Is it applicable?
Is it worth?
What is the suitable routing protocol?
What happen when part of the network does
not support IP multicasting?
Features of P2P Systems
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Current P2P systems
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Send broadcast packets or a series of
identical unicast packets to peers
Two types
Hybrid P2P
 Pure P2P
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Two phases
Features of P2P systems
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Discovery phase
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Heavier traffic in Pure P2P system
Delivery phase
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No differences between Pure and Hybrid P2P systems
All peers must have the same messages. When new
messages arrive, they should be passed on to all the
other peers
Features of P2P systems
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P2P systems essentially require a
broadcast mechanism
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Continuous unicast packets
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Need substantial CPU power and bandwidth
of peers and all of the network resources
Broadcast packets
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use a series of unicast or broadcast packets
wasting various resources
Security problem
IP multicasting
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Solution for broadcast mechanism in P2P
systems
IP multicasting over P2P
Systems
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Almost all P2P application produce heavy
traffic
Reduction of such traffic using IP
multicasting seems to be effective
IP multicasting over P2P
Systems

Comparison between live streaming and
P2P systems
Live Streaming
P2P Systems
Contents sender
Can only be streaming
servers
All peers can be senders
Opportunities to
update member list
Updating when content
receivers joins/leaves
Updating when content senders and
receivers joins/leaves
Types of traffic flow
Video streams
Few packets per event
Range of
propagation
Intra-ISP or inter-ISP
Intra-ISP or inter-ISP
Number of content
senders
Smaller than the number
of content receiver
Same as the number of content
receivers
Join/leave of
contents sender
Statically
Dynamically
Routing Protocol
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PIM
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The protocols compose multicast trees using routing tables
made by an arbitrary unicast routing protocol
Protocol Independent Multicast-Sparse Mode
(PIM-SM)
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Peers send IGMP join message
to rendezvous point (RP)
The multicast tree is originating
from the RP
When a peer sends multicast
content, the packets is
encapsulated by the closest
edge router, and sent to RP
Routing Protocol
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PIM-Source Specific Multicast (PIM-SSM)
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Source-specific protocol
The contents receiver can specify the addresses of
desired sources in the IGMP join message
When the closest edge
router receives an IGMP
join, it configures the
shortest path between
the receiver and the
sender
Sequence for joining groups
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PIM-SM
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One IGMP join/leave to RP
PIM-SSM
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Joining
• Send IGMP join to all senders
• Get all other peers to send it an IGMP join
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Leaving
• Send IGMP leave to all senders
Comparison of PIM-SM and
PIM-SSM
PIM-SM
PIM-SSM
Load
balancing
By distributing RPs
By using a unicast
routing protocol
Router
complexity
Slightly more complex
procedures
Simpler
Groupjoining
procedure
simpler
More complex
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Conclude that PIM-SM is better
for P2P systems
Evaluation
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Simulation Model
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Members exchange information across two ISPs
• ISP-A does not support IP multicasting
• ISP-B support IP multicasting
Only one router in each ISP
All peers belong to a virtual group
Evaluation
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Simulation #1
 Peers of ISP-A use unicast to all other peers
 Peers of ISP-B use unicast to peers of ISP-A and
multicast to peers of ISP-B
Simulation #2
 Peers of ISP-A use
unicast to peers of
ISP-A, and send
multicast packets to
ISP-B’s RPs
 Peers of ISP-B use
unicast to peers of
ISP-A and multicast
to peers of ISP-B
Conclusion
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Analyze features of P2P systems
Suitable routing protocol is discussed
IP multicasting is the solution for
heavy traffic generated in P2P
systems
Future Works
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Sequence for joining/leaving groups
Effect of RP’s location on traffic
characteristics
Multicast address allocation and traffic
control methods for the entire network
Discussion
Combining Peer-to-Peer and IP
Multicasting
 The simulation details are not
mentioned, e.g. traffic
characteristics, duration, application
 Benefits of using IP multicasting
over P2P systems
