RVS-Seminar Overlay Multicast Quality of Service and Content Addressable Network (CAN)

Transcription

1 RVS-Seminar Overlay Multicast Quality of Service and Content Addressable Network (CAN) Luca Bettosini Universität Bern

2 Outline > Goals / Motivation ( CAN ) > Content Addressable Network > CAN Multicast Implementation > CAN New Multicast split-driven approach > CAN Evaluation > Overlay QoS Framework Implementation > Overlay QoS Framework Evaluation > Conclusion, Outlook > Questions 2

3 Goals / Motivation > Multicast Is one of the most efficient methods to distribute data Not widely spread ( ALM ) > Application Layer Multicast Enables Multicast usage in networks without native Multicast support Based upon Peer-to-Peer (P2P) networks (ex. Nice, Pastry, Chord, CAN) > Quality of Service for Overlay Multicast Establish QoS guarantees for existing ALMs Two different approaches Protocol specific approach ( independent Layered Approach (protocol 3

4 ( CAN ) Content Addressable Network > Distributed Hash Table system > Scalable, fault-tolerant and self-organizing > Architectural design: multidimensional coordinate space on a multi-torus > The coordinate space is dynamically partitioned among all the peers > A CAN peer: Knows his coordinate space Maintains a routing table with neighbour information y-axis x-axis 2-d CanKeySpace 4

5 CAN Routing / Joining CAN routing CAN join: Node C is joining y-axis y-axis x-axis 2-d CanKeySpace Peer D's neighbor set = {E F H G} x-axis 2-d CanKeySpace New neighbor set of D: {C E F H} Neighbor set of C: {E D G H} 5

6 CAN Leave CAN Leave ex. 1: Node C wants to leave CAN Leave ex. 2: Node C wants to leave y-axis y-axis x-axis 2-d CanKeySpace Possible TakeOver Nodes:{D G} x-axis 2-d CanKeySpace Possible TakeOver Nodes:{ } Possible temporary Take- Over Nodes { D A S T I G Y X} 6

7 Multicast on CAN > Original CAN based Multicast: Flooding The member of a group form a group-specific CAN Multicast is achieved by flooding the information over that CAN > Improvements: Flood-cache suppress algorithm Directed Flooding Boundary limits Multicast specific CAN using Flood-cache suppress algorithm: X floods a Multicast message to the network y-axis x-axis 2-d CanKeySpace 7

8 CAN Split-driven Multicast > Problem: Duplicates Directed Flooding not specified with temporary Keyspaces > Solution: Split-driven Multicast Joining node's parent is the node who splits its Keyspace Neighbors of the joining node checks if they are still a neighbor of their previous parent, else new parent is the new joining node y-axis x-axis 2-d CanKeySpace 8

9 CAN Evaluation Fan-Out > Measurements based on 3 matrices and 3 seeds p. number of node > Average Fan-Out ~2.5 9

10 CAN Evaluation - Hops to Root > Average is slowly increasing 10

11 CAN Evaluation Node to Root RTT > Average is slowly increasing 11

12 CAN Evaluation Average Duplicates per Multicast Message > On average every 5 th message is a duplicate, using improvements 12

13 CAN Evaluation Node to Root QoS > On average the QoS-requirements are ~18 % fulfilled 13

14 Overlay Framework > Overlay Framework enables QoS within a CAN Network > Design: Establish a separate CAN network for every QoS class Create gateway links between the separate CAN networks 14

15 Overlay Framework - Implementation > Independent of the underlying P2P network > Intercepts packets from P2P network > Bootstrap has the overview of all gateway nodes > Top down approach: Upper Gateway node handles leave in the lower QoS-Class 15

16 Framework Evaluation QoS To Root > 100 % QoS Requirements fulfilled 16

17 Framework Evaluation Fan-Out > Average Fan-Out ~1.9 17

18 Framework Evaluation - Hops to Root > Average ~ 16 > Needs to be improved 18

19 Framework Evaluation Node to Root RTT > Average ~ 0.65s 19

20 Conclusion, Outlook > CAN is a scalable P2P network > Overlay Framework supports QoS > Implement the split driven Multicast in CAN > Evaluate the Overlay Framework with different P2P networks (CAN, NICE, Chord, Scribe/Pastry) > Evaluate Overlay Framework and P2P with a dynamic environment (soft-qos) > Implement a hop optimization between gateways for the Overlay Framework 20

21 Questions 21