Decentralized Resource Management for a Distributed Continuous Media Server

1
Decentralized Resource Management for a
Distributed Continuous Media Server

• Cyrus Shahabi and Farnoush Banaei-Kashani

Presented by Leung Chi Kit
2
Outline

• Introduction
• Objectives
• Mechanism
• Performance Evaluation
• Conclusion

3
Introduction

• Many Multimedia applications
• Clients are geographically dispersed
• One large Centralized Continuous Media Server
  (CCMS) result in inefficient resource allocations
• Proposed Distributed Continuous Media Server
  (DCMS)

4
DCMS Architecture

• Pure Hierarchy
• One and only one root
• Every node (except root) has one and only one
  parent node
• Redundant Hierarchy (RedHi)
• At least two roots
• Every node (except root) has at least two parent
  nodes

5
DCMS Architecture
6
Objectives

• The resource management include two orthogonal
  issues
• Object Placement
• Object Delivery
• This paper focus on object delivery
• Objective design a object delivery scheme that
  are scalable, robust, low start-up latency and
  low resource management overhead

7
Mechanism

• Assumption of the object placement scheme
• All media objects are located at the root(s)
• When a object transfer to a client, the object is
  cached at all intermediate nodes based on the
  Least Recently Used caching policy.

8
Mechanism

• Tasks in object delivery scheme
• Object location
• Path selection
• Resource reservation
• This paper collapse the three tasks into a single
  delivery mechanism in order to minimize start-up
  latency and management overhead

9
Mechanism

• Each node only stores the metadata relevant to
  the local resources (available bandwidth of the
  node and the adjacent links, the object stored in
  the node)
• Full decentralization results in optimal
  scalability and robustness

10
Mechanism

• Mechanism
• Head-end receives a request from a client
• The head-end generate a query packet and
  propagates it to the network.

11
Mechanism

• Several propagation policies

12
Mechanism

• Each instance of query packet incrementally
  evaluate the cost of the paths.
• The node with the object replica will send a
  response packet (cost of the path) back along the
  same path
• When more than one response packet received, the
  node compare the responses. It select the path
  with the lowest cost.

13
Mechanism

• Each node wait for at most two times the maximum
  RTT between it and the root for the response. It
  send back the response to the querier after time
  out occur
• After the best path was found, the head-end send
  a start packet along the best path and the object
  server start streaming the object to the client.

14
Mechanism

• Cost Function
• P N U L

15
Mechanism

• Path selection
• Choose the path with the shortest path_length
• If the path_length of two paths are the same,
  choose the path with more path_freeBW

16
Resource Reservation

• Pessimistic
• To pre-reserve all resources that might possibly
  be required for the selected path (performed
  during query propagation)
• To release the extra resources only after the
  path is actually selected
• Resource are over-reserved

17
Resource Reservation

• Optimistic
• To start reserving the required resources after
  path selection is finalized
• The resources required for the selected path
  might have been pre-allocated to other concurrent
  requests

18
Resource Reservation

• Early Release Pessimistic (ERP)
• Extra resources are released as soon as they are
  disqualified from being in the best path
• Early Reserve Optimistic (ERO)
• Resources are reserved early during response
  processing

19
Performance Evaluation
20
Performance Evaluation
21
Performance Evaluation
Comparative evaluation of the optional techniques
Cost function
Reservation policies
22
Performance Evaluation
23
Performance Evaluation
With link failures
24
Performance Evaluation

• Latency and Communication Overhead

Worst case communication overhead
35KB/successfully request
25
Conclusion

• The decentralized resource management guarantees
  scalability, robustness, low start-up latency and
  low resource management overhead
• Best propagation Inclusive
• Best cost evaluation path_freeBWaverage
• Best reservation techniques Early Reserve
  Optimistic (ERO)
• Start-up latency and communication overhead are
  negligible