1. 1 GRAAP: Why do we need SLAs? Omer Rana o.f.rana@cs.cardiff.ac.uk

2. 2 OGF21, October 2007 GRAAP WG Current focus:  WS-Agreement specification  Support for negotiation being investigated Investigating:  Interoperability (and conformance) issues  Use cases Longer term:  Aspects of “dynamic” SLAs  Investigation of penalty/reward clauses

3. 3 OGF21, October 2007 What is a Service Level Agreement (SLA)? Client Provider Can you do X for me for Y in return? Yes SLA Distinguish between: Discovery of suitable provider Establishment of an SLA P2P Search, Directory Service SLA-Offer SLA-Accept SLA-Reject A relationship between a client and provider in the context of a particular capability (service) provision

4. 4 OGF21, October 2007 What is an SLA? Client Provider Can you do X for me for Y in return? No, but I can do Z for Y SLA Accept SLA-CounterOffer SLA-Offer SLA-Accept SLA-Reject

5. 5 OGF21, October 2007 What is an SLA? Client Provider Can you do X for me for Y in return? No SLA Can you do Z for me for Y in return? Negotiation Phase (Single or Multi-Round) SLA-Offer SLA-CounterOffer SLA-OfferDependency

6. 6 OGF21, October 2007 Variations Client Providers SLA Client Providers SLA Multi-provider SLA Single SLA is divided across multiple providers (e.g. workflow composition) SLA dependencies For an SLA to be valid, another SLA has to be agreed (e.g. co-allocation)

7. 7 OGF21, October 2007 Dynamically established and managed relationship between two parties Objective is “delivery of a service” by one of the parties in the context of the agreement Delivery involves:  Functional and non-functional properties of service Management of delivery:  Roles, rights and obligations of parties involved What is an SLA?

8. 8 OGF21, October 2007 Forming the Agreement Distinguish between:  Agreement itself  Mechanisms that lead to the formation of the agreement Mechanisms that lead to agreement:  Negotiation (single or multi-shot)  One-shot creation  Policy-based creation of agreements, etc.

9. 9 OGF21, October 2007 SLA Life Cycle Identify Provider  On completion of a discovery phase Define SLA  Define what is being requested Agree on SLA terms  Agree on Service Level Objectives Monitor SLA Violation  Confirm whether SLO’s are being violated Destroy SLA  Expire SLA Penalty for SLA Violation

10. 10 OGF21, October 2007 Why do we need SLAs? Provide some basis for:  Judging “Quality” of provisioning QoS can be provider or user related  If “Violations” have occurred Types of penalties  Choosing providers/clients  Capacity planning  Scheduling  Establishing trust/reputation OGF19 BoF: Difficulty in differentiating between QoS and SLAs OGF20: Dynamic SLA workshop Grid 2007 (Sept. 07): SLA Management for Grids (with CoreGrid – book from workshop will appear shortly)

11. 11 OGF21, October 2007 WS-Agreement Framework for SLA creation – interface conforming to Web Services standards Service Client/Provider does not need to be a Web Service Provides a two layered model:  Agreement layer: Web Service-based interface to create, represent and monitor agreements  Service layer: Application specific-layer of service being provided

12. 12 OGF21, October 2007 WS-Agreement Agreement Initiator may be Service Consumer or Service Provider Service Layer Agreement Layer

13. 13 OGF21, October 2007 WS-Agreement Name/ID Context Terms Composition Guarantee Terms Service Terms Agreement Information about Agreement Initiator Responder Expiration Time Information about Service Service Description Terms (generally, these are domain dependent) Information about Service Level Service Level Objectives, Qualifying Conditions for the agreement to be valid, Penalty Terms, etc

14. 14 OGF21, October 2007 WS-Agreement Terms From: Viktor Yarmolenko (U Manchester)

15. 15 OGF21, October 2007 Usage A number of projects utilizing this  Implementations vary – two key implementations currently being developed  Others utilizing part of the spec: Various European projects (CATNETs, SORMA, OntoGrid) National projects (VIOLA)

16. 16 OGF21, October 2007 CATNETS Scenario Service Consumer Resource Provider Service Provider Service Market Resource Market Complex Service Resource Service Basic Service Resource Consumer

17. 17 OGF21, October 2007 Orderbook Complex Service Container 1 (40€) Container 2 (50€) Container 3 (70€) Query Service Demand: Complex Database Query < 200 € Query Service Query Service (1) (2) (3) Basic Service Demand: (8CPUs,1GB,30GB) < 40 € Service Market Total Cost < Cost of service + Cost of resource

18. 18 OGF21, October 2007 Orderbook Basic Service 1 Buy-Order 1 (10€) Buy-Order 2 (18€) Buy-Order 3 (35€) (4CPU, 1GB, 15GB) Demand: (8CPUs,1GB,30GB) < 40 € (4CPU, 1GB, 15GB) (8CPU, 1GB, 30GB) [1,3] bundles allowed Sum = 28 € (1) (2) (3) Ranking buy-orders Build bundle Resource Market

19. 19 OGF21, October 2007 CATNETs: Metrics “Pyramid”

20. ClientApplication Service Builder Master Grid Service ServiceFactory (GT4/JavaWS) ComplexService Agent Application CATNETS Middleware Resource (GT4/WSRF/.NETWS/JWS) BasicService Agent ResourceAgent Base Platform ServiceInstance (GT4/JavaWS) 1. Request 2. Requirements 7. Service Reference 8. Invocation 3. Service negotiation 4. Resource negotiation 5. Service instantiation 6. Service Reference Catallactic Access Point WSAG WS Use of WS-Agreement CATNETS: U Bayreuth, U Karlsruhe, UPC/Barcelona, U Ancona, ITC/IRST (Trento), U Cardiff EU FP6 “Future and Emerging Technologies”

21. 21 OGF21, October 2007 Dynamic SLA Limitations of a single agreement  Modifications since agreement was in place Cost of doing re-establishment  Not fully aware of operating environment Flexibility in describing Service Level Objectives  Not sure what to ask for (not fully aware of the environment in which operating)  Too many violations

22. 22 OGF21, October 2007 Dynamic WS-Agreement Case 1: Static Agreement  Identify Service Description Terms,  Guarantee Terms, and  Service Level Objectives (SLOs) Case 2: Dynamic Agreement  Identify Service Description Terms,  Guarantee Terms: defined as ranges or as functions  Service Level Objectives: defined as ranges or as functions

23. 23 OGF21, October 2007 Conclusion WS-Agreement provides a useful basis for SLA Still restricted to “static” SLAs  Does not support negotiation mechanisms Negotiation should not be part of SLA  SLA should result as a consequence of negotiation Mechanisms for dynamic SLAs  Function-based or Category based (adaptation between categories) Dynamic SLA networks  Means to support dynamic SLA exchange networks