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LISP+ALT Mapping System

LISP+ALT Mapping System. IDR WG, IETF Dublin, August, 2008 Vince Fuller (for the LISP crew). Agenda. Mapping system design needs Ideas we considered Brief summary of LISP+ALT Open issues. Mapping system: what and why. Need a scalable EID to Locator mapping lookup mechanism

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LISP+ALT Mapping System

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  1. LISP+ALT Mapping System IDR WG, IETF Dublin, August, 2008 Vince Fuller (for the LISP crew)

  2. Agenda • Mapping system design needs • Ideas we considered • Brief summary of LISP+ALT • Open issues IETF Dublin, July, 2008

  3. Mapping system: what and why • Need a scalable EID to Locator mapping lookup mechanism • Network based solutions • Have query/reply latency • Can have packet loss characteristics • Or, have a full table like BGP does • How does one design a scalable Mapping Service? IETF Dublin, July, 2008

  4. Scaling constraints • Build a large distributed mapping database service • Scalability paramount to solution • How to scale: (state * rate) • If both factors large, we have a problem • state will be O(1010) hosts • Aggregate EIDs into EID-prefixes to reduce state • rate must be small • Damp locator reachability status and locator-set changes • Each mapping system design does it differently IETF Dublin, July, 2008

  5. Tough questions/issues • Where to store the mappings? • How to find the mappings? • Push model or pull model? • Full database or cache? Secondary storage? • How to secure mapping entries? • How to secure control messages? • Protecting infrastructure from attacks • Control over packet loss and latency IETF Dublin, July, 2008

  6. LISP+ALT: What and How • Hybrid push/pull approach • ALT pushes aggregates, LISP pulls specifics • Hierarchical EID prefix assignment • Aggregation of EID prefixes • Tunnel-based overlay network • BGP used to advertise EIDs on overlay • Option for data-triggered Map-Replies IETF Dublin, July, 2008

  7. LISP+ALT in action <- 240.1.1.0/24 < - 240.1.0.0/16 <- 240.1.2.0/24 240.0.0.1 -> 240.1.1.1 11.0.0.1 -> 240.1.1.1 ITR ITR ETR ETR ETR 1.1.1.1 -> 11.0.0.1 ALT-rtr ALT-rtr ALT-rtr ALT-rtr ALT-rtr ALT-rtr EID-prefix 240.0.0.0/24 EID-prefix 240.1.1.0/24 1.1.1.1 11.0.0.1 EID-prefix 240.1.2.0/24 2.2.2.2 12.0.0.1 Legend: EIDs Locators ALT connection Physical link Data Packet Map-Request Map-Reply 3.3.3.3 EID-prefix 240.2.1.0/24 IETF Dublin, July, 2008

  8. LISP+ALT in action 240.0.0.1 -> 240.1.1.1 240.0.0.1 -> 240.1.1.1 ITR ITR ETR ETR ETR 11.0.0.1 -> 1.1.1.1 240.0.0.1 -> 240.1.1.1 ALT-rtr ALT-rtr ALT-rtr ALT-rtr ALT-rtr ALT-rtr EID-prefix 240.0.0.0/24 EID-prefix 240.1.1.0/24 1.1.1.1 11.0.0.1 EID-prefix 240.1.2.0/24 2.2.2.2 12.0.0.1 Legend: EIDs Locators ALT connection Physical link Data Packet Map-Request Map-Reply 3.3.3.3 EID-prefix 240.2.1.0/24 IETF Dublin, July, 2008

  9. Issue: Data-Triggered Mappings • ITRs have the option of forwarding data for “un-mapped” EIDs into ALT • Data forwarded across ALT to ETR that originates the EID prefix • LISP Map-Reply “triggered” from ETR to ITR, uses “native” path, installed in ITR cache • Subsequent traffic uses cached RLOCs • Scaling/complexity/performance issues • Is this (Data Probes) a good idea? IETF Dublin, July, 2008

  10. ISP allocates 1 locator address per physical attachment point (follows network topology) RIR allocates EID-prefixes (follows org/geo hierarchy) R1 R2 Issue: EID assignment Provider A 10.0.0.0/8 Provider B 11.0.0.0/8 11.0.0.1 10.0.0.1 Site Legend: EIDs -> Green Locators -> Red PI EID-prefix 240.1.0.0/16 IETF Dublin, July, 2008

  11. Issue: mapping system security • ALT can use existing/proposed BGP security mechanisms (SBGP, etc.) • DOS-mitigation using well-known control plane rate-limiting techniques • Nonce in LISP protocol exchange • More needed? IETF Dublin, July, 2008

  12. Issue: large-site ETR policy • ALT separates ETR discovery from the ITR-ETR mapping exchange • very coarse prefixes globally-advertised • more-specific info exchanged where needed • Regional ETRs could return more- specific mappings for simple TE • Alternative to current practice of advertising more-specific prefixes IETF Dublin, July, 2008

  13. Large-site ETR policy example • (placeholder slide for now) IETF Dublin, July, 2008

  14. Issue: “low-opex” xTR • BGP configuration complexity is a barrier to site-multihoming • Remove xTR/CPE BGP requirement: • ITR has “static default EID-prefix route” to “first hop” ALT router • “first hop” ALT router originates EID prefix on behalf of site ETR IETF Dublin, July, 2008

  15. Other issues to consider • Who runs the ALT network? • What’s the business model? • Should it be rooted at/run by the RIRs? • Should it be free? • Others? IETF Dublin, July, 2008

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