1. Resource Management – a Solution for Providing QoS over IP Tudor Dumitraş, Frances Jen-Fung Ning and Humayun Latif

2. Outline Motivation QoS solutions –Int-Serv –Diff-Serv Darwin –Darwin mechanisms –Xena Globus –Components –Operation Comparison Q&A

3. Motivation IP was not originally designed for QoS –Datagram oriented, variable-length packets –Best-effort service: make better use of bandwidth –Cannot give any QoS guarantees (bandwidth, jitter, latency) –Streaming multimedia needs QoS –Need a circuit switched – like paradigm

4. QoS Solutions: Int-Serv Reserves resources for every flow at every router hop Uses the Resource Reservation Protocol (RSVP) for signaling Needs to maintain soft states at every router along the path Requires a lot of signaling: scalability is a key concern

5. QoS Solutions: Diff-Serv (1) Light-weight alternative to Int-Serv Consistent policies will be applied inside each trusted domain Traffic is classified at edge routers Uses the ToS field from IP headers to indicate the class of service Diff-Serv framework

6. QoS Solutions: Diff-Serv (2) Bandwidth brokers –Establish relationships of limited trust with their peers in adjacent domains –Allocate traffic within the domain –Maintain a policy database –Configure leaf routers Diff-Serv with bandwidth broker

7. Darwin A CMU Project Resource Management mechanisms that support deployment of customizable, value- added services in a network. Supports application oriented QoS via: –Application oriented service brokers –Delegates – to customize runtime management –Hierarchical scheduling –Signaling protocol

8. Darwin Mechanisms… Resource Brokers: –Perform global resource allocation. –App. Specifies QoS value metric –Use domain knowledge for optimizations –Coordinate allocations for interdependent resources –Darwin : Xena Delegates: –Enable service specific dynamic behavior in network. –Runtime adaptation at switching points in interior network (as opposed to flow endpoints). –Darwin : Java code segments executing on routers.

9. Darwin Mechanisms Hierarchical Scheduling –Resource, contention exists at many levels; physical ~ among service providers; provider level ~ lower level providers; application level ~ individual flows –Hierarchical scheduler allows all entities to specify independent sharing policies and ensures they are met. –Darwin : HFSC (Fair Service Curve) Signaling Protocol: –Provides interface between resource broker’s abstract network view and low level network resources. –Allocates “real” resources e.g. bandwidth, buffers, cycles, memory. –Hides network heterogeneity details from Xena. –Darwin : Beagle

10. Applications (1) submit requests to Xena (2) Xena identifies resources needed & passes request to Beagle (3) Beagle allocates resources (4) For each resource, Beagle interacts with local resource manager. Resource Manager modifies local state: classifier and scheduler to guarantee appropriate service Beagle can set up delegates Darwin at work

11. Xena – A closer look Resource Discovery : Locating resources that can potentially be used Optimization: Satisfy requirement while min. cost and max. quality Apps request resources in varying degrees of abstraction –Abstract: Service of class S needed –Specific: Place this node at network address X App. can even specify flow semantic content (e.g. Motion JPEG with specific frame rate) Allows Xena to insert semantic preserving transformations e.g. transcoders at two ends of network segment Xena optimization criteria: application-specified objective function that maps candidate solutions to numeric value Allows application to customize definition of service quality

12. Globus Architecture for Reservation and Allocation (GARA) Provides End to End QoS guarantees in network applications Enables construction of application-level reservation libraries that applications use to assemble resource collections guided by application QoS requirements and resource administration policies. Supports: Dynamic Discovery and Immediate Reservation of Heterogeneous Resources that are Independently Administered and Controlled

13. GARA Components Generic Resource Object Information Service Co-Reservation Agent Co-Allocation Agent Global Resource Allocation Manager Local Resource Managers Physical Resources

14. GARA – Reservation vs. Allocations GARA Introduces Generic Resource Object to address heterogeneous physical resources in a generalized way Reservation made via “Create Object” request Create Object returns Reservation Handle to application. No “allocation” made at this point. Allocation made later by passing resource handle to co-allocation agent. Advantage of separating reservation VS allocation ~ enables advance reservations of resources when a resource is in high demand.

15. GARA – Operation Application passes request with description of service to Co- reservation agent CR-Agent maps QoS requirements to resources by queries to Information Service and app. Specific knowledge. CR-Agent creates reservation by directing request to Globus Resource Allocation Manager (GRAM). GRAM authenticates request, creates reservation and returns handle. Handle used to allocate resources later.

16. GARA Example Candidate resources for Data Analysis Application include multiple cached copies of data set Right: Physical location of resources Left: Search tree constructed by the co-reservation agent. “R”s represent reservations

17. Comparison – Reservation Requests & Resource Allocations Darwin + Very flexible in QoS metric specification + Avoids duplication of effort & expertise in areas where there are specialized SPs + Allows customized mgt that supports tasks that require detailed network knowledge while others require domain- specific knowledge - Only supports immediate reservations ~ not optimal in timing of resource allocation Globus + Advance reservation possibility - guarantees resource availability for high contention resources -Not a very flexible way to specify app. QoS level.

18. Conclusion Neither really better/worse than other Darwin: –More flexible for specifying degree of abstraction in resource requirement of different types of services Globus: –Provides advance reservations –Doesn’t leave decision making to resource mgrs in network architecture.

19. Questions