Jian Pu Department of Computer Science University of Victoria December, 2002

1. A SLA Admission Controller for Reliable MPLS Networks -- Unification of Reliability and Admission Controls for Optimal Network Performance with QoS Guarantees Jian Pu Department of Computer Science University of Victoria December, 2002

2. Outline • Motivation • Background • Reliable MPLS (R-MPLS) • SLA Optimizer (SLAOpt) • Limitations of SLAOpt • The proposed R-SLAOpt • Simulations • Conclusions

3. Motivation • Improve network performance • Reduce recovery time from failure • Maintain QoS guarantees

4. Reliable MPLS (R-MPLS) • R-MPLS = MPLS + Alternate Path Routing • Routes with limited shared edges • pre-calculate alternate paths and pre-establish them • use the “path restoration” scheme for fast recovery time

5. SLA Optimizer (SLAOpt) • SLA (Service Level Agreement) • It is a contract of a session between a network service provider and a customer, providing multiple possible levels of service: flow attributes for a pair of node, delay bound, bandwidth requirement (for a certain time, at a given price). • SLA-based admission control (maximize utility) • to optimally accommodate income flows described by SLAs • to calculate K shortest paths as candidate paths • to map admission control problem to an MMKP (Multi-Choice, Multi-Dimension 0-1 Knapsack Problem), and solve it.

6. Limitations of SLAOpt • SLAOpt is static (in terms of network topology) • The initial snapshot of the network topology is used for path calculations. • The calculated paths assumed not to fail. • Node or link failures are not considered. • Hence, SLAOpt may not fit in practice.

7. Reliable SLAOpt (R-SLAOpt) • Overview • The structure • Requirements for underlying routing protocol • The proposed alternate path selection algorithm • SLA adaptation by MMKP • Resource reservation schemes • Path switching • How it works

8. Overview • R-SLAOpt = SLAOpt + R-MPLS • In practice, network topology may constantly changes. Reliability becomes one of the major concerns. • R-SLAOpt is proposed to deal with the dynamic topology changes, and tries to balance the needs on reliability and performance of admission control.

9. The structure New algorithm to calculate multiple candidate path groups, each of which has 2 or 3 paths New Source reservation schemes on alternate paths, and path switching when failures occur SLA adaptation by solving MMKP (a few changes to old SLAOpt) Extend SLA with reliability parameters: path number, desired reliability Reliable SLAOpt (R-SLAOpt)

10. Requirements for underlying routing protocol • Use QOSPF, QoS extension to OSPF, as the underlying routing protocol • All topology changes and traffic load data on each link will be correctly traced. • All failures in the network will be detected, and all nodes will be informed immediately.

11. The proposed alternate path selection algorithm • GAPA -- Grouped Alternate Path-finding Algorithm • GAPA selects appropriate path groups, each of which meets the constraints of maximum path length (Lmax). and minimum connection reliability (Rmin). • How GAPA works • step 1: prune all links that have no enough bandwidth; • step 2: calculate K shortest paths with end-to-end delay constraint (i.e. L<= Lmax); • step 3: compose all possible path groups, calculate their connection reliability R (the probability that the connection SD not failed) • step 4: the groups with R > Rmin will be selected.

12. SLA adaptation by MMKP • I-HEU is used to solve the MMKP based on multiple path groups (based multiple paths in SLAOpt). • One path group will be selected from the candidate groups as the working group, which will maximize the utility. • The shortest path in the group will be selected as the primary path. The others are used as alternatives.

13. Resource reservation schemes • Assume there are three paths P0, P1 and P2.P0is the primary path. • scheme 1: reserve required BW on all links in paths P0, P1 and P2 • conservative way  simple but may waste resource • scheme 2: a percentage p of the total required BW is reserved on the links in paths P0, P1 and P2. For P0, this parameter would be p = 1; for P1 and P2, p < 1 • aggressive way  risk but may save resource • scheme 3: reserve BW on P1 and P2 only for SLA flows. Non-SLA flows, such as FTP or email traffic, could be transmitted on these paths while they were not in use. However, SLA flows would have priority access to the resources on the alternate paths.

14. Path switching • is performed at the source s • is supported by R-MPLS • after s receives failure notification • locating the affected paths • choosing an available alternate path for each affected path. The alternate path must be in the same group with the affected path. • starting to use the new paths

15. How it works

16. Simulations • The sample network • Test sets • Reliability vs. utility trade-off • Time cost of path switching • The affected SLA caused by injected failures

17. The sample network A sample 25-node network for the simulations

18. Test sets • We randomly generated SLA batches of different sizes. • The bandwidth requirement for any given QoS level of an SLA was set to vary with the size of the SLA batch so that there was always contention for network bandwidth. • Same SLA test sets were applied to SLAOpt and R-SLAopt for all comparisons.

19. Reliability vs. utility trade-off

20. Time cost of path switching k = 3 k = 2

21. The affected SLA caused by injected failures • To simulate the real world, in each epoch following the initial adaptation, 10% of the initial batch size SLAs will be removed from the system, and new ones (12.5% of initial batch size) will be submitted. • The group size k was varied from 1 to 3 for different test runs. • Random node failures were injected into the system, at intervals of H = 5, 20 and 100 epochs.

22. Conclusions • Apply our reliability considerations (by using alternate paths) into SLA admission control problem. • Propose a new admission control model (R-SLAOpt), and develop related algorithm to calculate appropriate path groups. • Simulation results show • R-SLAOpt has quick recovery time. • Quite fewer SLAs will be affected in R-SLAOpt than that in old SLAOpt under same failure conditions.

23. References [1]. S. Khan, Quality Adaptation in a Multi-Session Adaptive Multimedia System: Model and Architecture, PhD thesis, Department of Electrical and Computer Engineering, University of Victoria, 1998 [2]. S. Khan, K. F. Li, E. G. Manning, The Utility Model for Adaptive Multimedia Systems, presented at the International Conference on Multimedia Modeling, 1997, pp. 111-126, Nov 17-20, Singapore [3]. R. K. Watson, Applying the Utility Model to IP Networks: Optimal Admission & Upgrade of Service Level Agreements, Master Thesis, Department of Electrical and Computer Engineering, University of Victoria, 2001 [4]. M M Akbar, E. G. Manning, R. K. Watson, G. C. Shoja, S. Khan, K. F. Li, Optimal Admission Controllers for Service Level Agreements in Enterprise Networks, 6th SCI Conference, Orlando, FL July 14-18, 2002 [5]. M. M. Akbar, E. G. Manning, G. C. Shoja, Admission Control and QoS adaptation in Distributed Multimedia Server System, ITCom 2001, August, 2001, Denver, USA [6]. S. Khan, K. F. Li, E. G. Manning, M. M. Akbar, Solving the Knapsack Problem for Adaptive Multimedia System, Studia Informatica, 2002 [7]. M. M. Akbar, E. G. Manning, G. C. Shoja, S. Khan, Heuristic Solutions for the Multiple-Choice Multi-Dimension Knapsack Problem, International Conference on Computational Science, May 2001, San Francisco, USA [8]. J. Pu, E. G. Manning, and G. C. Shoja , Reliable Routing in MPLS Networks, Proc. IASTED CCN 2002, Boston, USA, Nov. 2002 [9]. E. Rosen, A. Viswanathan, R. Callon, RFC3031, Multiprotocol Label Switching Architecture, Jan. 2001