A Novel Approach A Novel Approach for Transparent for Transparent

Bandwidth Bandwidth ConservationConservation

David Salyers, Aaron StriegelDavid Salyers, Aaron StriegelUniversity of Notre DameUniversity of Notre Dame

Department of Computer Science and Department of Computer Science and EngineeringEngineering

Supported by NSF Grant: CNS03-47392Supported by NSF Grant: CNS03-47392

2IFIP Networking 2005

IntroductionIntroduction

Internet has grown an evolvedInternet has grown an evolved Simple connectivity → sophisticated Simple connectivity → sophisticated

applicationsapplications Point-to-point naturePoint-to-point nature

Increased redundancyIncreased redundancy

Techniques to reduce redundancyTechniques to reduce redundancy Active (multicast)Active (multicast) Passive (caching)Passive (caching)

3IFIP Networking 2005

Multicast TechniquesMulticast Techniques

Current Multicast TechniquesCurrent Multicast Techniques IP MulticastIP Multicast Application Layer Multicast (ALM)Application Layer Multicast (ALM)

IssuesIssues Require global deploymentRequire global deployment Application and/or end-to-end network Application and/or end-to-end network

support required support required

4IFIP Networking 2005

Caching TechniquesCaching Techniques

Types:Types: Web/media cachingWeb/media caching Packet Caching [Santos,Wetherall Packet Caching [Santos,Wetherall

USENIX 1998]USENIX 1998] Benefits:Benefits:

Simple deploymentSimple deployment Reduces long term redundancyReduces long term redundancy

Drawbacks:Drawbacks: Cannot handle short term redundancyCannot handle short term redundancy

5IFIP Networking 2005

Our SolutionOur Solution

Dynamic “Stealth” multicastDynamic “Stealth” multicast Dynamic formation of virtual multicast Dynamic formation of virtual multicast

groupsgroups Multicast only occurs inside a domainMulticast only occurs inside a domain Uses existing multicast within domain (PIM-Uses existing multicast within domain (PIM-

SSM)SSM) Does not require global multicast Does not require global multicast

support.support. Does not require application support.Does not require application support.

6IFIP Networking 2005

Stealth Multicast: Stealth Multicast: OverviewOverview

Cloud

Server

Server

Server

Server

Stealth MCast

Client

Client

Client

Client

12

34

12

34 M

12

34

Unicast Stealth Multicast Unicast

7IFIP Networking 2005

Key PrinciplesKey Principles

External TransparencyExternal Transparency The end clients and server applications The end clients and server applications

should not be aware that stealth should not be aware that stealth multicast is operatingmulticast is operating

Limited QoS impactLimited QoS impact Stealth multicast should not Stealth multicast should not

significantly affect the QoS of the significantly affect the QoS of the application, specifically the end-to-end application, specifically the end-to-end delaydelay

8IFIP Networking 2005

Stealth Multicast Stealth Multicast OperationOperation

Virtual Group Detection Manager Virtual Group Detection Manager (VGDM)(VGDM)

Key ResponsibilitiesKey Responsibilities Signature generationSignature generation Background Traffic AnalysisBackground Traffic Analysis Managing Virtual GroupsManaging Virtual Groups

Converts to multicastConverts to multicast Creates/Updates physical treesCreates/Updates physical trees

9IFIP Networking 2005

Stealth Multicast Stealth Multicast Operation: VGDMOperation: VGDM

10IFIP Networking 2005

Virtual Group Virtual Group ManagementManagement

Only amenable packets are queued Only amenable packets are queued for possible multicast transport.for possible multicast transport. Non-amenable packets are never Non-amenable packets are never

queuedqueued Bounded QoS impact.Bounded QoS impact.

MHT – Maximum Hold TimeMHT – Maximum Hold Time TSW – Time Search WindowTSW – Time Search Window PSW – Packet Search WindowPSW – Packet Search Window

11IFIP Networking 2005

Stealth Multicast Stealth Multicast TransportTransport

PIM-SSM (Single Source Multicast)PIM-SSM (Single Source Multicast) Source = ingress pointSource = ingress point Receivers = egress pointsReceivers = egress points Note:Note:

Egress points << # of clientsEgress points << # of clients

Source driven changes (VGDM)Source driven changes (VGDM) Join/Leave operationsJoin/Leave operations Resource management/billingResource management/billing

12IFIP Networking 2005

State ManagementState Management

ProblemProblem Preservation of unique client information.Preservation of unique client information.

Destination IP/Destination PortDestination IP/Destination Port Encapsulation vs. egress storageEncapsulation vs. egress storage

Stateless (encapsulation)Stateless (encapsulation) Include after L4 (UDP) headerInclude after L4 (UDP) header Simple state coherencySimple state coherency

Stateful (egress storage)Stateful (egress storage) Unique state stored at egress pointsUnique state stored at egress points Limited packet overheadLimited packet overhead

13IFIP Networking 2005

Scalability Scalability ConsiderationsConsiderations

Queue size (memory)Queue size (memory) Needs less than 6MB of queue to Needs less than 6MB of queue to

handle 1Gbps with a MHT = 5mshandle 1Gbps with a MHT = 5ms Redundancy detectionRedundancy detection

Santos, Wetherall [USENIX 1998]Santos, Wetherall [USENIX 1998] Experimental studiesExperimental studies

Itanium 2 – RedHat Linux (user space - Itanium 2 – RedHat Linux (user space - libpcap)libpcap)

Intel IXPIntel IXP

14IFIP Networking 2005

Simulation Studies - Simulation Studies - SetupSetup

ns-2 ns-2 SimulationSimulation Random ISP domain (32 core, 16 edge nodes)Random ISP domain (32 core, 16 edge nodes) Server Farm (40 source Applications)Server Farm (40 source Applications) Average number of clients per application: 32Average number of clients per application: 32 500ms average inter-arrival time for 500ms average inter-arrival time for

join/leave eventsjoin/leave events Server Applications, UDP, exponentially Server Applications, UDP, exponentially

distributed packet rate of 50ms and size of distributed packet rate of 50ms and size of 500bytes500bytes

15IFIP Networking 2005

Types of Transport Types of Transport ComparedCompared

UnicastUnicast No multicast transmissions.No multicast transmissions.

Full StealthFull Stealth VGDM is at edge node.VGDM is at edge node.

Local StealthLocal Stealth VGDM is at server node.VGDM is at server node.

ALMALM Generic version of ALMGeneric version of ALM Ability to support 5 downstream clientsAbility to support 5 downstream clients

IP MulticastIP Multicast Ideal version of IP MulticastIdeal version of IP Multicast

16IFIP Networking 2005

Client Subscriptions: Client Subscriptions: QoS DelayQoS Delay

17IFIP Networking 2005

Client Subscriptions: Client Subscriptions: Link BWLink BW

18IFIP Networking 2005

Client Subscriptions: Client Subscriptions: Domain BWDomain BW

19IFIP Networking 2005

ConclusionsConclusions

Limited QoS (delay) impactLimited QoS (delay) impact Provides multicast benefits Provides multicast benefits

combined with ease of deployment combined with ease of deployment of cachingof caching

Key BenefitsKey Benefits No application support requiredNo application support required Simple resource management/billingSimple resource management/billing Directable economic benefitDirectable economic benefit

20IFIP Networking 2005

Current WorkCurrent Work

Stealth multicast prototypeStealth multicast prototype Wireless stealth multicastWireless stealth multicast Passive Application Layer Multicast Passive Application Layer Multicast

(PALM)(PALM)

21IFIP Networking 2005

Questions?Questions?

dsalyers@nd.edudsalyers@nd.edu

http://www.cse.nd.edu/http://www.cse.nd.edu/~dsalyers~dsalyers

22IFIP Networking 2005

Simulation Studies – Setup Simulation Studies – Setup (VGDM)(VGDM)

Maximum Maximum Groups:Groups:

5050

Maximum Hold Maximum Hold Time:Time:

5ms5ms

Time Search Time Search Width:Width:

2ms2ms

Packet Search Packet Search Width:Width:

100100

Min Group Size:Min Group Size: 22

Max Group Size:Max Group Size: 200200

State State Management:Management:

DistributedDistributed

Egress Threshold:Egress Threshold: 30%30%

Time Lock:Time Lock: 100ms100ms

23IFIP Networking 2005

Maximum Hold Time: QoS Maximum Hold Time: QoS DelayDelay

24IFIP Networking 2005

Other Issues Cont.Other Issues Cont.

Practical BenefitPractical Benefit While well suited for networks that contain a While well suited for networks that contain a

reasonable amount of redundant traffic, it is reasonable amount of redundant traffic, it is not envisioned that VGDMs are deployed at not envisioned that VGDMs are deployed at all nodes.all nodes.

Since the VGDM Since the VGDM TCPTCP

Generally TCP traffic is not amenable to Generally TCP traffic is not amenable to stealth multicast. However, we are stealth multicast. However, we are researching techniques to eliminate this researching techniques to eliminate this problem.problem.