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Clean Slate Design for the Internet Designing a Predictable Backbone Network with Valiant Load Balancing NSF 100 x 100 Clean.

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Presentation on theme: "Clean Slate Design for the Internet Designing a Predictable Backbone Network with Valiant Load Balancing NSF 100 x 100 Clean."— Presentation transcript:

1 Clean Slate Design for the Internet Designing a Predictable Backbone Network with Valiant Load Balancing NSF 100 x 100 Clean Slate Program Nick McKeown Stanford University All the hard stuff was done by: Rui Zhang-Shen

2 Backbone network design using VLB Backbone network

3 Backbone network design using VLB US Backbone Networks: Observations  ~50 nodes interconnected by long-haul optical links  Increasingly rich mesh topology –Built over mesh of WDM or TDM circuits and switches –Reduce hop count and delay –Fault tolerance –Load balancing  Low utilization—links over-provisioned –Uncertainty in traffic matrix the network is designed for –Headroom for future growth –Prepare to take over when links or routers fail –Minimize congestion and delay variation

4 Backbone network design using VLB Traffic Matrices From To Traffic matrix is hard to predict Regional Node i riri Back- bone r i is easier to predict and has to be predicted anyway riri

5 Backbone network design using VLB What fraction of traffic matrices can they support? Abilene Verio AT&T Sprint 80% utilization: 0.026% 67% utilization: 0.66% 80% utilization: % 67% utilization: 1.1% 80% utilization: % 67% utilization: 0.09% 80% utilization: % 67% utilization: 0.026% Verio, AT&T, and Sprint topologies courtesy of RocketFuel

6 Backbone network design using VLB Desired Characteristics  Dependable –Continues to operate when traffic patterns change in the short and long term –Continues to operate under failure –Recovers quickly  Efficient –And at no extra cost

7 Backbone network design using VLB Why is this hard? N … 4 r r r r r r r r r r r

8 Backbone network design using VLB Why is this hard? N … 4 r r r r r r r r r r r Nr

9 Backbone network design using VLB Our Approach  The operator already estimates r i –Requires only local knowledge of users and market estimates  Use Valiant Load Balancing (VLB) –Supports all traffic matrices  History –L. G. Valiant, G. Brebner, Parallel communication Statistical delay guarantee –C.-S. Chang, etc.; I. Keslassy etc., Switch scheduling Throughput guarantee Optimality

10 Backbone network design using VLB Valiant Load-Balancing N … 4 r r r r r r

11 Backbone network design using VLB Valiant Load-Balancing N … 4 r r r r 2r/N r r 24 In practice : The mesh could be a mesh of lambdas or TDM circuits Send on direct path, and only spread when network is congested.

12 Backbone network design using VLB Aside: Routers based on VLB Can you build a router switched backplane based on VLB? Appealing possibilities 100% throughput for any arrival pattern No per-packet arbitration and scheduling Passive switch fabric consumes almost zero power Linecards x 40 MEMS Switch Rack < 100W “Scaling Routers using Optics” Sigcomm 2003

13 Backbone network design using VLB Failures  Node failures –Takes away corresponding links and traffic –Still a full mesh network  Links failures –Asymmetric network –Many scenarios N … 4

14 Backbone network design using VLB Fault Tolerance  Load balance traffic over available paths  To tolerate any k link or router failures, sufficient to increase the capacity each link by  Example: A 50 node network requires 11% more capacity to withstand any 5 failures.

15 Backbone network design using VLB Heterogeneous Network N … 4 r1r1 r4r4 r3r3 riri rNrN r2r2 R =  i r i Homogeneous: c = 2r/N c ij  r i r j c ij = 2r i r j /R Gravity Configuration

16 Backbone network design using VLB Heterogeneous Network  As before, the total capacity we need with VLB is twice what we’d need if we knew the traffic matrix (and it was static).  With oblivious routing we need an extra capacity.

17 Backbone network design using VLB Is VLB efficient?  Not knowing the traffic matrix means we need a total capacity 2-times larger than if we did.  But we never know the traffic matrix, and it changes. So the cost is surprisingly small.  Anecdotally, a network that can support all traffic matrices and behaves predictably on failure requires less capacity than existing networks.

18 Backbone network design using VLB Interconnecting Backbones  Peering parameters: –R p is maximum peering traffic –q i ¸0 for peering nodes, q i =0 for non-peering nodes,  i q i =1  Peering link capacity: R p q i N … N 3 4 … RpRp q2q2 q3q3 q4q4

19 Backbone network design using VLB Within a VLB Network  Assume peering condition is fixed –Given: R p ; q i –Variables: p i  Spread traffic over the peering links

20 Backbone network design using VLB Spread over peering links c ij = r i p j + r j p i + min(r i,R p )(max(p j,q j )-p j ) + min(r j,R p )(max(p i,q i )-p i )  If R p > r i, optimal solution: p i = q i ; c ij = r i q j + r j q i  Efficient use of peering links  Supports all traffic matrices as before N … N 3 4 … 111

21 Backbone network design using VLB Other questions  Delay-sensitive applications –How much does it matter? –It may matter for interactive voice, video, gaming –Dealing with it: “Express paths”,Adaptive load-balancing


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