A Study Of Broadcasting Over Structured Overlay

Speaker: Shashikantha

A u t h o rs : S a i f u l K h a n , A b d u l l a h G a n i , S . R av i ra j a , a n d S h a s h i ka nt h a

COMSNETS 2015, January 6-10, Bangaluru, India.

Background: P2P

• Millions of clients : centralized server becomeslow.

• Single point of failure.

• Expensive to maintain.

COMSNETS 2015, January 6-10, Bangaluru, India.

Background: P2P

• Millions of clients : centralized server becomeslow.

• Single point of failure.

• Expensive to maintain.

COMSNETS 2015, January 6-10, Bangaluru, India.

Solution:Eliminate Central Server.

P2P Architectures

P2P

Centralized Napster, etc.

HybridBit-torrent,

etc.

Decentralized

Structured

Chord

Pastry

Kademlia

D1HT etc.

Unstructured Gnutella etc.

COMSNETS 2015, January 6-10, Bangaluru, India.

Motivation

Structured overlay•Completely decentralized architecture.

• Implemented using Distributed Hash Table (DHT).

Challenges•Poor Routing efficiency.

•High maintenance Bandwidth overhead.

•Doesn’t support Complex searching.

COMSNETS 2015, January 6-10, Bangaluru, India.

Related Work

• Broadcast over Content Addressable Network(CAN) [Ratnasamy et al. 2001].

• Broadcast over Pastry [Castro et al. 2003].

• Broadcast over Chord [El-Ansary et al. 2003].

• Partition based broadcast Algorithm [Huang etal. 2009].

•Efficient broadcast algorithm[L. Wei, et al.2007].

COMSNETS 2015, January 6-10, Bangaluru, India.

Simulation Framework: Oversim

The 3-tier simulation framework implemented in OverSim simulator

COMSNETS 2015, January 6-10, Bangaluru, India.

Routing Efficiency

(a) Chord (b) Pastry

Routing efficiency vs. mean life-time of node

COMSNETS 2015, January 6-10, Bangaluru, India.

Cont.

(c) Kademlia (d) D1HT

Routing efficiency vs. mean life-time of node

COMSNETS 2015, January 6-10, Bangaluru, India.

Maintenance Bandwidth Overhead

Bandwidth overhead vs. mean life-time of node

COMSNETS 2015, January 6-10, Bangaluru, India.

(a) Chord (b) Pastry

Cont.

COMSNETS 2015, January 6-10, Bangaluru, India.

(c) Kademlia (d) D1HT

Bandwidth overhead vs. mean life-time of node

Summary : Empirical Study

• O(1) hop overlay has better lookup performance.

• Increase in routing table size: improved lookupperformance.

• Opportunistic maintenance: reduces bandwidthoverhead.

COMSNETS 2015, January 6-10, Bangaluru, India.

Proposed Algorithm

Algorithm

Opportunistic Maintenance

Event Detection and Routing

Algorithm(EDRA)

COMSNETS 2015, January 6-10, Bangaluru, India.

Step 1

• Messages are assigned with a unique time to live(TTL) value: 0 to k − 1.

• Messages are broadcasted to its successors in thedegree of b following

COMSNETS 2015, January 6-10, Bangaluru, India.

TTL=0 TTL=1 TTL=k-1 Nlogbk

broadcast n, N = ∀ni∈ ℕ | ni = successor n, bi ∧ 0 ≤ i ≤ (k − 1)

Step 2

• Inactive nodes do not send any acknowledgement.

• Therefore, node failure event is generated.

n n1

Mn(x), TTL = x

COMSNETS 2015, January 6-10, Bangaluru, India.

ACK

Step 3

Mn(x)

• During this retransmission step, nodes piggyback all the available messages ready to send in a single message.

• Therefore, the bandwidth overhead improves significantly.

COMSNETS 2015, January 6-10, Bangaluru, India.

TTL=0 TTL=x-1TTL=x

Example network b = 2, total node = 16.

COMSNETS 2015, January 6-10, Bangaluru, India.

Node N0 initiates a broadcast.

COMSNETS 2015, January 6-10, Bangaluru, India.

TTL=0

TTL=1

TTL=2

TTL=3

M0(0)

M0(1)

M0(2)

M0(3)

Nodes further broadcast the received message.

COMSNETS 2015, January 6-10, Bangaluru, India.

TTL=0

TTL=1

TTL=2

TTL=3

M0(0)

M0(1)

M0(2)

M0(0)

M0(1)

M0(0)

M0(3)

M0(0)

M0(1)

M0(2)

Nodes further broadcasts the received messages.

COMSNETS 2015, January 6-10, Bangaluru, India.

TTL=0

TTL=1

TTL=2

TTL=3

M0(0)

M0(1)

M0(2)

M0(0)

M0(1)

M0(0)

M0(0)

M0(3)

M0(0)

M0(1)

M0(2)

M0(0)

M0(0)

M0(1)

Completition of the broadcasting of the messages.

COMSNETS 2015, January 6-10, Bangaluru, India.

TTL=0

TTL=1

TTL=2

TTL=3

M0(0)

M0(1)

M0(2)

M0(0)

M0(1)

M0(0)

M0(0)

M0(3)

M0(0)

M0(1)

M0(2)

M0(0)

M0(0)

M0(0)

M0(1)

Results: Proposed Algorithm

• The routing performance

• Maintenance bandwidth

COMSNETS 2015, January 6-10, Bangaluru, India.

Mean Lookup

Lookup Success Rate vs. mean life-time of node.

COMSNETS 2015, January 6-10, Bangaluru, India.

Mean Bandwidth

Mean bandwidth consumption per node vs. mean life-time of node

COMSNETS 2015, January 6-10, Bangaluru, India.

Opportunistic vs. Active maintenance

Mean bandwidth consumption vs. mean life-time of node

COMSNETS 2015, January 6-10, Bangaluru, India.

Conclusion

1. Studied the performance of structured overlaynetworks.

2. Proposed an improved algorithm.

3. Improved routing performance.

4. Reduced maintenance bandwidth overhead.

5. Future work•Study of delay.

•Evaluation of delay, hop count, etc..

COMSNETS 2015, January 6-10, Bangaluru, India.

Thank you.

COMSNETS 2015, January 6-10, Bangaluru, India.