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NOBEL Valladolid Meeting A2.2.1 contribution: MRDV Multipath Routing with Dynamic Variance

NOBEL Valladolid Meeting A2.2.1 contribution: MRDV Multipath Routing with Dynamic Variance. Telefónica I+D. Introduction. Objective: Efficient use of network resources Requirement: Better policies and mechanisms IP routing plays a major role Current IP routing is:

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NOBEL Valladolid Meeting A2.2.1 contribution: MRDV Multipath Routing with Dynamic Variance

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  1. NOBEL Valladolid MeetingA2.2.1 contribution: MRDVMultipath Routing with Dynamic Variance Telefónica I+D NOBEL Valladolid meeting

  2. Introduction • Objective: Efficient use of network resources • Requirement: Better policies and mechanisms • IP routing plays a major role • Current IP routing is: • ... distributed: routing decissions are taken hop by hop • ... static: independent from occupation in links • This approach has important advantages... • Simple • Highly scalable • Compatible! • ... but it also has problems: • Non-autonomous. It cannot react to sudden changes in demand autonomously. • Inefficient. Traffic concentrates on few links • Routers “see” the same costs • Little control over performance of individual flows NOBEL Valladolid meeting

  3. State of the Art in Intra-Domain IP Routing • Multipath Routing (static): • ECMP • Distributes traffic among all paths with optimal cost • It usually behaves like monopath routing • Multipath with variance • It also uses non-optimal paths • Distributes traffic among paths where: • Allowed degree of similarity  VARIANCE • Dynamic Routing • Link Cost = F(Link Load) • Approaches: • Centralized: Poor scalability • Distributed: Oscillations / Instability Cost < Costminimal · Variance Routing = F(network state) NOBEL Valladolid meeting

  4. Why using Native IP? • Advantages of native IP • SIMPLE • Great scalability • Compatibility • Many things can be easily improved NOBEL Valladolid meeting

  5. Multipath Routing with Variance Dynamic Routing Protocols +  Variance = F(first-hop occupation) Nº feasible paths = F(link occupation) MRDV Algorithm Description (I) • Objective: • Basically: • Parameters: • Variance: Associated to interfaces • Occupation: Interface is the first-hop of an optimal path • Behaviour: • Low load in first-hop  very low variance  1 route • High load in first-hop  higher variance  Several routes • Distribution of traffic (when multipath): • Cost (i.e. +BWbottleneck)  + % of traffic NOBEL Valladolid meeting

  6. B D A C MRDV Algorithm Description (II) Demand Time Routing tableSrc. A  Dst. D 50 100 Next-hop Path cost B 4 25 10 50 8 C NOBEL Valladolid meeting

  7. Demand Time B Routing tableSrc. A  Dst. D D 50 A 100 Next-hop Path cost B 4 10 50 8 C C MRDV Algorithm Description (II) 100% of demand  = 0.4 25  = 0 NOBEL Valladolid meeting

  8. Demand Time B 100% of demand Routing tableSrc. A  Dst. D  = 0.4 D 50 A 100 Next-hop Path cost B 4 25 10 50 8 C  = 0 C MRDV Algorithm Description (II) NOBEL Valladolid meeting

  9. Time B Routing tableSrc. A  Dst. D  = 0.4 D 50 A 100 Next-hop Path cost B 4 25 10 50 8 C  = 0 C MRDV Algorithm Description (II) Demand 67% of demand 33% of demand NOBEL Valladolid meeting

  10. Demand Time B 67% of demand Routing tableSrc. A  Dst. D  = 0.27 D 50 A 100 Next-hop Path cost B 4 25 10 50 8 C  = 0.13 C 33% of demand MRDV Algorithm Description (II) NOBEL Valladolid meeting

  11. Demand Time B 100% of demand Routing tableSrc. A  Dst. D  = 0.4 D 50 A 100 Next-hop Path cost B 4 25 10 50 8 C  = 0 C MRDV Algorithm Description (II) NOBEL Valladolid meeting

  12. Prevention of instability • To prevent oscillations: • Costs of links are constant • Every router “sees” a diferent network • Hysteresis cycle for variance calculation • Hysteresis cycle: • Criterion: • Many other criteria are possible Relative increments in variance must be proportional to relative increments in average load Vmax=4 Kup=2 Kdn =0.5 NOBEL Valladolid meeting

  13. Other considerations • Choice of the update interval: • Design parameter • Tradeoff: Response time vs. Accuracy in measures • Stability: > 10 sec (at least) • Shorter time-scales: Diffserv • Packet disorder must be avoided! • Same flow should take same path (if nothing else changes) • SOLUTION: Hash function • Advantage: Simple and scalable • Compatible with currently deployed IP networks • Easy deployment: • Selective • Gradual Hash = F(source IP, destination IP) NOBEL Valladolid meeting

  14. Conclusions • Intelligent and autonomous distribution of traffic: • According to nominal bandwidth • According to occupation. • Simple operation and maintenance • It allows selective or incremental deployments • Routers only need an easy software upgrade • Stable behaviour: • Decisions are taken locally in every router (non-centralized): • No oscillations • No convergence time • More robustness • Extensions to IP are not required  Fully compatible. • No additional load in network. NOBEL Valladolid meeting

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