1. On the Use of Service Level Agreements in AssessGrid
Karim Djemame and Dominic Battré

2. Outline System Overview Scenarios Architecture Towards Dynamic SLAs
End-user
Broker
Provider
Towards Dynamic SLAs
Summary

3. System Overview Aim Risk awareness incorporated across three layers
integrate a risk-aware Service Level Agreement (SLA) model into current Grid technology
Risk awareness incorporated across three layers
Therefore an architecture designed to
Give resource providers the capability to perform risk assessments prior to making offers
Give the broker the ability to assess the reliability of providers’ risk assessments
Give the end-user the ability to choose offers based on risk alongside price and penalty.

4. Role Description RP Broker RP End-user RP Resource Providers
I offer access to resources and services through formal SLA offers
I need to find suitable resource providers to take SLA
I need to perform a specific task with associated
requirements through an SLA RP
Broker RP
End-user RP
Resource Providers

5. Architectural Overview
WS-Agreement Negotiation for SLAs
RMS: Resource Management System

6. Usage Scenarios Broker as a mediator Broker as a contractor
End-user submits SLA request to broker
Once end-user selects SLA offer
Broker’s responsibility ends
End-user interacts directly with provider
Broker as a contractor
Acts as a virtual provider
End-user agrees SLA with broker
Broker agrees SLAs with provider(s)
Useful to map workflows to resources
Direct SLA negotiation end-user – provider
End-user submits SLA request to provider
End-user can query broker’s confidence service

7. Scenario 1: User – Provider Negotiaion
Fill Template
Job description
Max. PoF
Min. Penalty
Commit
Contract
SLA Request
Get Template
SLA Offer
User requests template
User defines job to be executed, max PoF and Penalty (the letter are given from the business of the user)
RMS analyzes SLA request, and in case it accepts it, is defines a required price (depends on risk, resource requirements, …)
User can decide whether price is acceptable and commits
Contract between parties established
Create Offer
RMS: Resource Management System PoF: Probability of Failure

8. Scenario 2a: Broker = Mediator
Get Templates
Template Subscription
Broker receives templates over WS-Notification as subscription from RMS
End User asks Broker for template – most favorable situation: only one template that matches all RMS
RMS: Resource Management System

9. Scenario 2a: Broker = Mediator
SLA Request
Evaluate Reliability
SLA Offer
User submits SLA request, broker forwards it to only those RMS that might be capable of providing the resources
RMS calculate price and PoF
Broker submits offers to user
User asks Broker to assess the real risk of failure (incorporating that some providers might tend to underestimate the PoF)
RMS: Resource Management System

10. Scenario 2a: Broker = Mediator
Commit
User agrees one offer
Other offer expires
RMS: Resource Management System

11. Scenario 2b: Broker = Contractor
Broker can be a provider as well. Job submitted/negotiated with broker, who subcontracts
Very interesting for work flows
RMS: Resource Management System

12. Provider - Negotiation Manager
Open source implementation of WS-Agreement specification for negotiating SLAs between end-user, broker, and provider
Protocol more powerful and agile

13. Provider – Extending WS-Agreement
Changed the original single-round acceptance model to a two-phase acceptance model
Introduced the negotiation possibility, in other words the bargaining capability:
Flexible SLA negotiation scheme – getQuotes method
Two-phase commit negotiation protocol

14. Dynamic SLAs - Extending WS-Agreement
Anticipate violations
state for the agreement in which a warning has been issued due to the fact that one or more guarantees are likely to be violated in the near future.
Negotiation
Is part of its life-cycle
initial negotiation before the execution of the services under SLA
run-time re-negotiation: occurs in case of
a recoverable violation of a term, or
the monitoring system is anticipating a possible violation of a term (pessimistic scenario)
the monitoring system is anticipating a better QoS to be delivered

15. Re-Negotiation (pessimistic scenario)
Example: provider anticipating a possible violation of a term
- monitoring of dynamic risk
- re-negotiate the SLA instead of paying a (high) penalty fee
lower price
Provider
Customer
I can do X instead of Y for you
for Z in return?
SLA
SLA
Request to re-negotiate
Accept
Reject
Need to ensure both parties get a better deal through the new agreement

16. Re-Negotiation (optimistic scenario)
Example: user would like to increase the price to get a lower Penalty of Failure
Provider
Customer
Can you
do X for me
for Y in return?
SLA
SLA
Request to re-negotiate
SLA-Accept
SLA-Reject
Need to define specific properties in the agreement:
Re-negotiation needs an EPR

17. Re-Negotiation (optimistic scenario)
Example: provider is able to provide a better service
- increase the price
- lower Probability of Failure
Provider
Customer
I can do X for you
for Y in return?
SLA
SLA
Request to re-negotiate
Accept
Reject
Need to ensure both parties get a better deal through the new agreement

18. Summary
AssessGrid architecture provides a framework for supporting risk assessment and management throughout the Grid infrastructure
Single tasks
Workflows
Advanced risk assessment models
Provider and broker layers
Interaction between components within the architecture
Use as much as possible of WS-Agreement specification
Preliminary work on extension of WS-Agreement
Scenarios identified
Current implementation of the architecture
Currently deployed in three separate administrative domains