Distributed Session Announcement Agents for Real-time Streaming Applications

Keio University,Graduate School of Media and Governance

Kazuhiro Mishima <three@sfc.wide.ad.jp>

This work is partly supported by

National Institute of Information and Communications Technology (NICT), Japan.

Background• Development of Multimedia contents

– Demand of increasing multimedia contents– High-quality streaming architecture

• Session Information– Contains…

• Media Locater (Streaming Source Information)• Meta-level Information (Title, Description etc…)

– Receiver MUST obtain the information about the specified multimedia content (Require some announcement method)

Requirements of Session Announcement

• Scalability– System MUST manage a large number of session

information

• Dynamicity– Streaming sessions change frequently– System MUST announce information fast

• Policy Definition– Session Information MUST be limited to specified

receivers by sender (Secret or Private contents)

Purpose of our work• Building a new Session Announcement or

Distribution Architecture as an alternative to present announcement system for the future media streaming services

Related Works• SAP (Announcement with ASM)

Pros: Broadly used on multicast environmentPros: Low latency (UDP multicast)Cons: No reliabilityCons: Scalability issue (SAP DoS/SAP Storm)Cons: No access control

• Search EnginePros: Scalability using server distributionPros: Contents information aggregationCons: Latency issue (occurred by robot crawling)Cons: Central management (no scope or user control)

System Operation Overview

Architecture• Tree-based System

– Multiple Agent– Agent Tree

• Transfer the info. through the tree structure

• DHT-based System– Multiple Agent– Each agents create the

DHT global storage– DHT Global Cloud

• All information are stored into this cloud

Tree-based system: Registration

WebUI LocalDB

Agent

Registration

Store

All information are stored into LocalDB by agent

Agent stores information andtransfer to the neighbor agents

Store

Store

Store

Store

Store

Hop-by-Hop Transfer

Tree-based system: Retrieve

WebUI LocalDB

Agent

Request

Retrieve

Search

Use only LocalDBto retrieve the information

DHT-based system: Registration

WebUI LocalDBDHT Engine

Registration

Store

Replicate

selected by DHT algorithm

selected by DHT algorithm

for local session information(if specify “Local”)

for global session information(if specify “Global”)

DHT-based system: Retrieve

WebUI LocalDBDHT Engine

Request

Search

Retrieve

Retrievefrom selected node

Search results are combined LocalDB’s and DHT’s data

Policy-aware Information Distribution• To fulfill the “Policy Definition” requirement, we propose a

new Information Distribution technique

– Tree-based system• At the Hop-by-Hop transfer time, each agent confirm the agent

has “Group Label”. If the agent has no specified “Group Label”, transferred information will discard.

– DHT-based system• Next slide…

• Using this method, secret or private information are distributed only specified agent

Policy-aware Information Distribution

• DHT-based system– Information Filtering method using the DHT’s

characteristic (Exact Match)

– DHT key:Secret! ff02:9a8c:aacd::3

<secret value><DHT key>

– DHT value:session_title ff02:9a8c:aacd::3 2001:200::13ca 2008-10-03 ...

<DHT value>

By putting the secret value on top of the DHT key, users who know the secret value, only can retrievethe information

Policy-aware Information Distribution

Implementation• gSOAP

• XMLRPC-C

• MySQL– for storing session and management data

• DHT– OpenDHT

• Algorithm: Pastry

Evaluation• Perform on PlanetLab

• Tree-based system– 51 nodes on US site

• 6 root• 45 neighbor

– All sites are statically connected

• DHT-based system– Using OpenDHT– About 200 nodes

Tree-based evaluation connection

Performance of Tree-based system

• Registration time– Message size: 800B– Min.: 2.39s– Avg.: 5.18s– Std.: 3.9

• Retrieval time– Message size: 800B– Min: 0.045s– Avg.: 0.047s– Std.: 0.001

Registration

Retrieve

Performance of DHT-based system• Registration time

– Message size: 400B– Min.: 0.55s– Avg.: 0.59s– Std.: 0.079

• Retrieval time– Message size: 800B– Min: 0.23s– Avg.: 0.33s– Std.: 0.088

Registration

Retrieve

Tree-based v.s. DHT-based• On the “Latency” view

– Tree-based: Longer registration time since hop-by-hop transfer, but very short time to retrieve

– DHT-based: Less registration and retrieval time

• On the “Scalability” view– DHT-based system’s transmitted message size is half of

the Tree-based system

• On the “Management” view– Tree-based system must maintain the tree statically by

site administrator (Very High Cost!!)

Conclusion• New Session Announcement Architecture

– Cooperation with multiple agents– Actual implementation of our agent system with

two methods of operation• Tree-based system• DHT-based system

– Performance evaluation using real network environment (on the PlanetLab)

Future works• Promote our agent system

• Agent and DHT bootstrap node address acquisition method

• Adaptive to end-user’s communication environment– Computing Resource of end-user’s machine– Authentication of end-user