A Flexible Model for Resource Management in Virtual Private Networks

1. A Flexible Model for Resource Management in Virtual Private Networks Sanket Naik CS590F Fall 2000

2. What Is a Virtual Private Network? Virtual private networks (VPN) provide an encrypted connection between a user's distributed sites over a public network (e.g., the Internet). By contrast, a private network uses dedicated circuits and possibly encryption. Tom Dunigan, Network Research Group, Oak Ridge National Lab (ORNL)

3. Requirements for IP-based VPNs • Opaque packet transport • Data security • Quality of service guarantees • Tunneling mechanism A framework for IP based VPNs - RFC 2764 (informational)

4. Resource Management in VPN? • Isolation from other flows • Guaranteed bandwidth, loss and delay characteristics • Over an existing public network • Yet, same performance assurances as a private network!

5. Hose Model • Customer's interface into the network • Performance guarantee based on the "aggregate" traffic • To and from a given endpoint to the set of all other endpoints

6. Hose Model

7. Advantages for customer • Ease of specification - one rate per endpoint vis-a-vis one rate per pair of endpoints • Flexibility - traffic to multiple endpoints multiplexed on one hose • Multiplexing gain - Total of hose rates < Aggregate rate in a Private network • Characterization - Statistical variability over multiple pairs smoothed into hose • Billing - Resize hose capacities dynamically

8. Implementation Scenarios

9. Provisioned VPNs • Worst-case traffic split - provider-pipes between each pair of end-points • Resource sharing - aggregate overlapping pipes for an end-point • Explicit routing - shortest paths • VPN specific state - aggregate overlapping pipes for the VPN

10. Dynamically Resized VPNs • Disadvantage of provisioned VPNs Reserved capacity may not be used • Resized provider pipes • Resized trees • Resized trees with explicit routing • Resource aggregation across a VPN

11. Requirements for Dynamically Resized VPNs • Prediction of required capacity based on traffic measurement - technique suggested • Signaling protocols to dynamically reserve resources - future work

12. Prediction of Traffic Rate • Tmeas - measurement window • Tren - next window for which rate is renegotiated • Tsamp - regularly spaced samples • Ri - average rate over inter-sample intervals • Local maximum predictor Rren = max{Ri} • Local Gaussian predictor Rren = m + v m = mean of Ri v = variance of Ri  = Multiplier

13. Simulation Experiments • 2 sets of traces – voice and data • PSTN traffic == IP telephony traffic? • Benefits for customer • Traffic matrix does change • Statically provisioned access hose-gain • Hose resizing gain • Predictor tracks actual traffic quite closely • Dynamically resized access hose gain

14. Benefits for Provider • Statically provisioned tree gain • Dynamic resizing gains • Provider-pipes • Trees • VPNs

15. Conclusions • Pros • Most efforts in IP-based VPNs focussed on security rather than performance guarantees • Simulation results look positive • Cons • Model is incomplete - signaling primitives required • How was dynamic resizing done for simulation?

16. Questions?