Improving Network Agility with Seamless BGP Reconfigurations

Transcription

1 Improving Network Agility with Seamless BGP Reconfigurations Corneliu Claudiu Prodescu School of Engineering and Sciences Jacobs University Bremen Campus Ring 1, Bremen, Germany Monday 18 th March, 2013

2 Presentation Outline Introduction Issue Outline Proposed Solution Conclusions

3 Internet Routing Internet divided into Autonomous Systems (AS) Each AS administers a set of routing prefixes e.g /12 Reachability information propagates via BGP

4 BGP Border Gateway Protocol Figure: BGP inside and between Autonomous Systems source: networkeducator.com

5 BGP BGP Process runs on each router TCP port 179 Routers connect and advertise routes to each other All routers need to be connected

6 BGP Figure: Full-mesh BGP topology source: cisco.com Each router holds state for each peer BGP session Not practical due to O(n 2 ) connections

7 BGP Figure: BGP topology with Route-Reflectors source: cisco.com Routers divided into clients and route-reflectors Route reflectors connected in full-mesh Clients only connect to one (or few) route-reflectors

8 BGP Configuration Types of BGP Configuration Changes Route additions Route removals BGP Topology Changes Live Requirements SLAs discourage down-time router promotion, decommissioning Full-restart with new configurations provides little control and can overload routers

9 BGP Reconfiguration Anomalies Routing Oscillations Forwarding Anomalies Dissemination Anomalies no convergence suboptimal forwarding loss of prefix visibility

10 Seamless Reconfiguration Seamless Reconfiguration Given C i - initial configuration C f - desired final configuration Reconfiguration from C i to C f is seamless iff, at any step C j : C j is anomaly-free C j is not subject to traffic shifts

11 Reconfiguration Example Figure: Routing oscillations during reconfiguration source: INAwSBR Best practices suggest configuring bottom-up After e 2 reconfiguration, (e 2, r 3 ) is removed, generating cyclic route preference (CRP) among r 1, r 2, r 3. This is resolved in the final configuration by rr 1

12 Reconfiguration Issues Reconfigurations are fairly frequent (in 1 year approximately 6k session additions, 1.5k session removals, 100 policy modifications, etc) Current reconfiguration practices do not provide guarantees Algorithmic solutions are not always feasible Finding CRP-free reconfiguration is NP-hard

13 Proposed Solution Main idea Run 2 control planes in parallel isolated, no route leakage Configure one control plane with the final configuration Switch control planes

14 Proposed Solution Requirements Each router needs to have multiple, isolated BGP routing processes Independent propagation of all routes to all routing processes Packet tagging (explicit or implicit) Proxy at ingress / egress points Figure: BGP Reconfiguration Proxy source: INAwSBR

15 Proposed Solution Benefits Seamless reconfiguration is guaranteed Reconfiguration is easier to run, roll-back

16 Evaluation Simulation Geant (pan-european research network) reconfiguration simulation FM to RR transition 0% packets were lost, compared to 30% using the best-practice approach

17 Evaluation Feasibility Full stack software upgrades are required Double BGP load required during reconfiguration carrier-grade routers are able to sustain this Changes to infrastructure are required proxies at egress points

18 Conclusions

19 Conclusions BGP configuration is hard reconfiguration even harder

20 Conclusions BGP configuration is hard Reconfigurations are regular reconfiguration even harder

21 Conclusions BGP configuration is hard reconfiguration even harder Reconfigurations are regular Seamless BGP reconfiguration possible

22 Conclusions BGP configuration is hard reconfiguration even harder Reconfigurations are regular Seamless BGP reconfiguration possible Simulations show promising results

23 Thank you Questions?