Scalable Overlay Network for Peer-to-Peer File Sharing

1. Scalable Overlay Network for Peer-to-Peer File Sharing Park, Chanmo Networked Media Lab. Kwang-Ju Institute of Science and Technology (KJIST) KOREA cmpark@netmedia.kjist.ac.kr

2. Contents • Overview • Peer-to-Peer Computing and Core Operations • Challenges in P2P File Sharing • Structured Overlay Network Support for P2P • Good and Bad • Existing Overlay Network Approaches • Initial Thoughts on Scalable Overlay Network • Conclusions

3. Peer-to-Peer Computing of the Internet2 • create and administer collaboration areas • access to the freshest data • help businesses with large-scale • computer processing needs using • idle CPU cycle and disk space • move data closer to the point • at which it is actually consumed • act as a network caching mechanism • allow computing networks to dynamically work together • using intelligent agents.

4. Core Operations of P2P • Identity Operation • Refers to the name and credentials that identify an entity • Discovery Operation • Find out peers, services, or resources • Authentication Operation • Verify identity (person or machine) • Authorization Operation • Allow the verified entity permission for specific actions and/or access • Function Operation • Application specific actions

5. Challenges in Scalable P2P File Sharing Flooding 2 4 3 1 • Flooding & Loop Path In Discovery Operation • results in many duplicated packet. • Increase the network traffics • Reducing large number of Discovery operations • A new topology such as structured overlay network should be considered Loop Loop 2 3 4 Loop Loop Loop Loop Loop 2 3 4 3

6. Structured Overlay Network Support for P2PGood and Bad • Good • may reduce duplicated packets • may remove loop in message forwarding • Bad • should maintain redundant link in overlay network • Network partitioning

7. Existing Overlay Network Approaches • AMRoute. • ScatterCast • End System Multicast • ALMI 1998 1999 2000 2001 2002 1998.8 AMRoute 2001.3 ALMI 1999.7 Scattercast 1989 IP Multicast 2001.7 End System Multicast

8. AMRoute • Goal : Robust IP Multicast in mobile ad hoc network • Concept • Dynamic logical cores • Selected by core resolution algorithm • creates the mesh of a group • creates the user-multicast tree • User-multicast trees • create a bi-directional, share tree for data distribution with group members • Low scalability • Electing a Logical core

9. ScatterCast • Goal: partitioning a heterogeneous set of session participants into disjoint data groups • Concept • SCX(ScatterCast proXy)s • organize themselves into an overlay network of unicast connections (mesh) • build data distribution tree on the top of this overlay structure (tree) • using native IP Multicast The Internet SCX Unicast Connection Client Client SCX Multicast Group Client Client Client

10. A A C C 1 1 1 1 25 25 R1 R1 R2 R2 1 1 B B D D 2 2 End System Multicast • Goal : overlay network efficiency • Concept • construct and maintain the mesh using distributed algorithm • Improving mesh quality by probing each others • construct tree based on distance vector, latency • Not scalable due to probing each nodes

11. ALMI (An Application Level Multicast Infrastructure) • Goal: support of multicast groups of small size • Concept • Node of a session are connected via a virtual multicast tree • Tree is formed as a minimum spanning tree by session controller Session Controller • handle member registration • maintain multicast tree • RRT monitoring • Parent • Virtual Multicast Tree • Child

12. From Existing Approaches • Mesh-first Topology • AMRoute, ScatterCast, End System Multicast • is suitable for multimedia multicast • Data delivery path is constructed over mesh • If no RPs • Not scalable • Not suitable for P2P File Sharing • Existing Approaches finally construct only one data delivery path • Mesh topology is proper for failure recovery • In the case of P2P File Sharing, Network efficiency is not issue • For Scalability, Tree-first can be considered as possible as can

13. Initial Thoughts on Scalable Overlay Network for Peer-to-Peer File Sharing • Challenges are reducing duplicationsand preventing loop • Node Grouping (Tree) • For reducing duplications • Flooding Messages are forced to sent to limited scoped nodes by grouping • Shift from Undetermined path to Determined path • For Loop Avoidance • Tree is constructed at first and maintained

14. Initial Thoughts on Scalable Overlay Network for Peer-to-Peer File Sharing(2) • we construct tree for grouping nodes • tree • Is a scope of message flooding • Is a shared tree • Is a data path along which all message are sent • Single Data Path within a tree • Loop avoidance • Messages are sent to parent and child nodes except of received node.

15. Initial Thoughts on Scalable Overlay Network for Peer-to-Peer File Sharing(3) • In case of Exchanging messages between trees • New connection type (such as a InterTreeConnection) is introduced to distinguish link within a tree from link between trees • These types of connections are determined when a new tree is created • New tree is created when limited number of nodes is reached • These type messages are used when a node connected to other tree sends messages.

16. Conclusion • We show Problems of Unstructured P2P • Flooding • Looping • Overview the existing Overlay Network • Our Initial Thoughts on Scalable Structured Overlay Network • Grouping into a tree for reducing duplicated messages • a shared data path for loop avoidance • Future Works • Consider proper group size and Recovery mechanism from failure • Implement our thoughts

17. Thanks!