P2PCAST: A Multi-Cast Scheme for Streaming Data - PowerPoint PPT Presentation
1 / 18
Title: P2PCAST: A Multi-Cast Scheme for Streaming Data
1
P2PCAST A Multi-Cast Scheme for Streaming Data
- Antonio NICOLOSI
- Siddhartha ANNAPUREDDY
2
Motivation
- Want to stream data to lots of users
- Easy solution
- Pay for lots of bandwidth
- Only fat cats can afford it
- More democratic alternative
- Users donate bandwidth to help disseminate the
data
3
The Setting
- A single content provider (the source)
- Other participants are peers
- Each node has limited bandwidth
- Assume users exhibit fail-stop behavior
4
Goals
- Scale to thousands of nodes
- Participants join/leave dynamically
- Users donate as much bandwidth as they take
- Fault-tolerance
- Security
5
Design Guidelines
- Join by contacting a random node in system
- No need to give notice while leaving
- Forest of multicast trees
- Each node is internal in exactly one tree
- Trees are repaired locally upon node failures
6
Algorithm
- Forest of f trees (of arity f)
- Insertion Joining the system
- Deletion Survive node loss
7
Insertion
- Users are leaf in all trees of the forest but one
- Place new user in the next-to-last level of one
(random) tree - Each node is either complete or incomplete
- Incomplete nodes only at the next-to-last level
- Randomness ensures (almost) balanced trees
8
Insertion (contd)
- Contact a random node in the system
- The node contacted can be
- Complete
- Incomplete
- Lonely child
9
Insertion (contd)
- Complete node
- Join tree where the contact is a leaf
- Search down the other tree
- Two Subcases
- Complete/Incomplete
10
Insertion (contd)
- Incomplete node
- Adopt the contact node in one tree
- Become its child in the other tree
- Lonely Child
- Redirect to the parent (back to case above)
11
Deletion
- Ideally, undo the join process
- Not easy ? failed node can be high up in the
tree - Get as close as possible
- Push bubble down the tree
- Repair the last level easy ?
12
Deletion (contd)
- Get down to the next-to-last level
- Just exchange parent with an arbitrary child
- Finally, bubble can end up being
- Complete
- Incomplete
13
Deletion (contd)
- Complete bubble
- Drop an arbitrary child
- Ask failed nodes other parent to adopt it
- Incomplete bubble
- Drop child in the other tree
- Ask failed nodes other parent to adopt it
14
Architecture
stream
P2Pcast Protocol
registry
15
Implementation
- Random node selection simulated via centralized
registry can be replaced using any routing
overlay - For fault-tolerance, stream of data is
forward-error corrected
16
RPC Protocols
- Control Protocol
- TAKEON, SUBSTITUTE, SEARCH (Insertion)
- REPLACE, DIRECT
(Deletion) - INSPECT, UPDATE
(Misc) - Registry Protocol
- JOIN, DELETE
17
Related Work
- Scribe/SplitStream
- Assume some users have spare bandwidth
- Require users to be willing to relay data for
groups they do not belong to - Properties of the forest of multicast trees bound
to parameters of Pastry
18
Conclusions and Future Work
- Scale to thousands of nodes
- Participants join/leave dynamically
- Users donate as much bandwidth as they take
- Fault-tolerance
- Security
Recommended
CrystalGraphics Presentations
