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CRIO: Scaling IP Routing with the Core Router-Integrated Overlay

CRIO: Scaling IP Routing with the Core Router-Integrated Overlay. Xinyang (Joy) Zhang Paul Francis Jia Wang Kaoru Yoshida. Internet Architecture Board Routing Workshop (Oct 2006).

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CRIO: Scaling IP Routing with the Core Router-Integrated Overlay

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  1. CRIO:Scaling IP Routing with the Core Router-Integrated Overlay Xinyang (Joy) Zhang Paul Francis Jia Wang Kaoru Yoshida

  2. Internet Architecture BoardRouting Workshop (Oct 2006) • It was clear at the workshop, and probably clearly evident elsewhere, that if there is a highest ranked “problem” in the routing space then it would be that of scaling the routing system • It appears that unbounded continued growth of the routing and forwarding system in the Internet appears to trigger off some real limitations relating to hardware design and switching centre infrastructure ---- Geoff Huston

  3. 200K Active BGP entries (FIB) 0 89 06 Date Why is Scaling a Problem? • A glimpse of current routing system: • Static table size • Global IPv4 : ~ 200K entries • VPN: ~800K entries • And more routes are coming: IPV6, traffic-engineered, etc. • Routing Dynamics • BGP update churns • Persistent instabilities • Long convergence time (due to damping and MRAI timer) • Looking into the future: • Can we support a routing table twice (or 10 times) the size of today? • Can we rely on the hardware advances to alleviate the scaling pressure? • This talk is about the static • characteristics of the scaling • Validity of CRIO approach

  4. CRIO’s Approach to Scaling • Tunneling • Revisit old idea (by Deering) • Decouples addressing from topology • Virtual Prefix • Novel approach • Greatly shrink forwarding table

  5. CRIO Tunneling: an Illustration Prefix TE Source Mapping Adv. 24.1.1.0/24 TE=PE2 PE2 ---- BGP Prefix TE Source 24.1.1.0/24 PE2 Mapping 24.1.1.0/24 ---- BGP/OSPF 24.1.1.0/24 PE3 Mapping Provider Networks PE1 PE2 24.1.1.1 PE2 24.1.1.1 PE3 24.1.1.1 Routing Adv. 24.1.1.0/24 NH=CE2 CE1 CE2 Customer Site C2 24.1.1.0/24 Customer Site C1

  6. CRIO Tunneling: Benefits • Separate Mapping from Routing • BGP only computes routes to TE prefixes • On the order of one thousand entries • Stable ISP provisioned prefixes • Mappings are easy to distribute • A mapping entry is the same no matter where it appears • Support multi-homing without burdening the routing system

  7. What about router’s forwarding table? • CRIO tunneling can not shrink forwarding information • Forwarding table is expected to get larger • Since CRIO supports for fine-grained multi-homing • Benefits for having small forwarding tables • Smaller memory requirement on routers’ line cards • Faster transfer for forwarding table updates

  8. CRIO Virtual Prefix: an Illustration • A virtual prefix is a super-prefix that spans a large portion of the address space • Routers that advertise a given virtual prefix must hold the mappings for every prefix within the virtual prefix Prefix TE Source Routing Adv. 24.0.0.0/8 PE2 ---- BGP 24.1.1.0/24 PE2 Mapping 24.2.2.0/24 PE4 Mapping PE3 24.1.1.1 PE2 PE2 24.1.1.1 24.1.1.0/24 24.1.1.1 PE1 Customer Site CE2 Prefix TE Source PE2 ---- BGP PE3 ---- BGP 24.0.0.0/8 ---- BGP 24.1.1.0/24 PE2 Mapping 24.2.2.0/24 PE4 Mapping

  9. CRIO Virtual Prefix: Trade-off • Virtual prefixes provide a tuning knob for the router • trade-off forwarding table size for path length • Per-prefix basis • It’s a good trade-off to make • Few prefixes handle most traffic (power law) • Routers could shed most of their prefixes with very little overall increase in traffic volume • Save routers from handling large amount of mapping updates • Virtual Prefix is particularly suitable for VPNs

  10. CRIO Evaluation: Static Analysis • Evaluate the static performance of CRIO by simulation • Quantify table size vs. path length tradeoff • Simulated both Global Internet and VPN • Based on actual Internet topology & ISP traffic matrices • Simulation tool: C-BGP

  11. CRIO Evaluation: Data Collection • Global Internet • Topology: • POP-level from RocketFuel • 23 Tier-1 ISP, 1219 POPs, 4159 inter-POP links • Mappings: • Derived <prefix, TE> mappings from RocketFuel raw traces • Internet Traffic Matrices: • Prefix-level, across all POP in our topology • Use Netflow records from Tier-1 ISP backbone • VPN • Same data is collected for VPN from a large VPN provider and one of its national-sized customers

  12. PE2 CRIO Evaluation: Forwarding Table Content • Direct Entries • Virtual Prefix Entries • “Extra” Path-Shrinking Entries Routing Adv. 24.0.0.0/8 Prefix TE Source PE2 ---- BGP PE3 24.1.1.0/24 PE2 Mapping 24.1.1.0/24 PE1 Customer Site CE2 Prefix TE Source Prefix TE Source PE2 ---- BGP 24.1.1.0/24 ---- BGP PE3 ---- BGP 24.0.0.0/8 ---- BGP 24.1.1.0/24 PE2 Mapping

  13. Prefix TE Source Prefix TE Source PE2 ---- BGP PE2 ---- BGP 24.1.1.0/24 PE2 Mapping 24.1.1.0/24 PE2 Mapping PE3 PE2 PE4 Prefix TE Source Prefix TE Source Prefix TE Source 24.1.1.0/24 ---- BGP PE3 ---- BGP PE4 ---- BGP 24.0.0.0/8 ---- BGP 24.0.0.0/8 ---- BGP CRIO Evaluation: Virtual Prefix Placement Policy • Inter-ISP (Random) • Intra-ISP • Intra-ISP shortest customer path Routing Adv. 24.0.0.0/8 Routing Adv. 24.0.0.0/8 Provider 2 Provider 1 PE1 24.1.1.0/24 Customer Site CE2

  14. Path-length vs. Table-size Trade-off Virtual Prefix does increase the path length Average path length converges quickly as the # path-shrinking entries increases Reduce FIB size by 3-5 times with very little path length penalty CRIO Global Internet Simulation Results Increase the percentage of shortest path traffic by increasing # of Path-Shrinking Entries 99% Traffic uses shortest path

  15. CRIO VPN Simulation Results (One Customer) • Hub-Spoke nature of VPN traffic exploits the tradeoff better • Reduce table size by 10-20 times with very little path length penalty Cumulative Distribution of PE Routers PE Routers In Hub Sites

  16. Conclusions • CRIO is a new routing architecture, aimed to provide • Scalable and stable core routing • Reduce BGP RIB by two order of magnitude • FIB size reduction • Reduce FIB by one order of magnitude for global Internet, 10-20x for VPN

  17. Future Work • Design and implement the mapping distribution infrastructure • Study the dynamics aspect of CRIO • Study the security aspect of CRIO • Explore the use of CRIO to provide traffic engineering for multi-homed site • Address (??) new management challenges

  18. Thank you!

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