Introduction to LISP+ALT

1. Introduction to LISP+ALT Cisco Global Routing Summit, August, 2008 Vince Fuller (for the LISP crew) http://www.vaf.net/prezos/lisp-grs.ppt

2. Agenda • What is the problem? • What is LISP? • Why Locator/ID Separation? • Data Plane Operation • Finding Mappings – LISP+ALT • Open Issues Cisco Global Routing Summit, August, 2008

3. Problem Statement • There are reasons to believe that current trends in the growth of routing and addressing state on the global Internet may cause difficulty in the long term • The Internet needs an easier, more scalable mechanism for multi-homing with traffic engineering Cisco Global Routing Summit, August, 2008

4. Problem Statement • An Internet-wide replacement of IPv4 with ipv6 represents a one-in-a-generation opportunity to either continue current trends or to deploy something truly innovative and sustainable • As currently specified, routing and addressing with ipv6 is not significantly different than with IPv4 – it shares many of the same properties and scaling characteristics • More at: www.vaf.net/prezos/rrg-prague.pdf Cisco Global Routing Summit, August, 2008

5. Scaling of Internet Routing State Cisco Global Routing Summit, August, 2008

6. What is ID/Loc Separation? • Instead of IP addresses, two numbering spaces: • Endpoint Identifiers (EIDs): hierarchically assigned to sites along administrative lines (like DNS hostnames) • Do not change on devices that remain associated with the site; think “PI” but not routable • Routing Locators (RLOCs): assigned according to network topology, like “PA” address assignments • Locators are aggregated/abstracted at topological boundaries to keep routing state scalable • When site’s connection to network topology changes, so do the locators – aggregation is preserved Cisco Global Routing Summit, August, 2008

7. Lower OpEx for Sites and Providers Improve site multi-homing Improve provider traffic engineering Reduce size of core routing tables End Site Benefit Easier Transition to ipv6 (maybe) Change provider without address change BGP R1 R2 What Features do I get? Provider A 10.0.0.0/8 Provider B 11.0.0.0/8 Site with PI Addresses Cisco Global Routing Summit, August, 2008

8. What is LISP? • Locator/ID Separation Protocol • Ground rules for LISP • Network-based solution • No changes to hosts whatsoever • No new addressing changes to site devices • Very few configuration file changes • Imperative to be incrementally deployable • Address family agnostic Cisco Global Routing Summit, August, 2008

9. New Network Elements • Ingress Tunnel Router (ITR) • Finds EID to RLOC mapping • Encapsulates to Locators at source site • Egress Tunnel Router (ETR) • Owns EID to RLOC mapping • Decapsulates at destination site Cisco Global Routing Summit, August, 2008

10. S D 11.0.0.1 -> 12.0.0.2 11.0.0.1 -> 12.0.0.2 EID-prefix: 2.0.0.0/8 Locator-set: 12.0.0.2, priority: 1, weight: 50 (D1) 13.0.0.2, priority: 1, weight: 50 (D2) Mapping Entry 1.0.0.1 -> 2.0.0.2 1.0.0.1 -> 2.0.0.2 1.0.0.1 -> 2.0.0.2 1.0.0.1 -> 2.0.0.2 S1 S2 D1 D2 Policy controlled by destination site Packet Forwarding PI EID-prefix 1.0.0.0/8 PI EID-prefix 2.0.0.0/8 ETR ITR Provider A 10.0.0.0/8 Provider X 12.0.0.0/8 12.0.0.2 10.0.0.1 ITR ETR 11.0.0.1 13.0.0.2 Provider B 11.0.0.0/8 Provider Y 13.0.0.0/8 DNS entry: D.abc.com A2.0.0.2 Legend: EIDs Locators Cisco Global Routing Summit, August, 2008

11. When the ITR has no Mapping • ITR needs to obtain from ETR • ITR sends Map Request (or Data Probe) • ETR returns Map Reply • But how do the ITR and ETR hook up? • Using the mapping system, of course Cisco Global Routing Summit, August, 2008

12. 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? Cisco Global Routing Summit, August, 2008

13. 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 • Dampen locator reachability status and locator-set changes • Each mapping system design does it differently Cisco Global Routing Summit, August, 2008

14. 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 Cisco Global Routing Summit, August, 2008

15. Ideas Considered • DNS – considered, many issues • DHTs – considered, research pending • CONS – new protocol, hybrid push+pull • Push EID-prefixes at top levels of hierarchy • Pull mappings from lower levels of hierarchy • ALT – GRE/BGP based, current focus • EMACS – like ALT, but multicast-based • NERD – pure Push design Cisco Global Routing Summit, August, 2008

16. Why LISP+ALT was Selected • Use existing technology where reasonable • Low memory impact on ITR • Optional data path to reduce latency • Allow infrastructure players to achieve new revenue source Cisco Global Routing Summit, August, 2008

17. LISP+ALT: What and How • Hybrid push/pull approach • ALT pushes aggregates - find ETRs for EID • ITR uses LISP to find RLOCs for specific EID • 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 Cisco Global Routing Summit, August, 2008

18. LISP-ALT Routers and the ALT • LISP+ALT routers form “Alternative Logical Topology” (ALT) • Interconnected by tunnels (GRE or …) • eBGP used for EID prefix propagation • Isomorphic topology and EID assignment • ITRs and ETRs connect at “edge” • Issue: Who runs LISP+ALT routers? • ISPs, IXCs, RIRs, Neutral parties? Cisco Global Routing Summit, August, 2008

19. Tunnel and BGP Operation • EID prefixes originated into BGP at edge • By ETRs (or by ALT router with “static route” to “low-opex” ETR) • ITR learns EID prefixes via eBGP • From ALT router (“low-opex ITR” uses “static default” to ALT router) • Map-Request forwarded into the ALT via first-hop ALT router • ALT forwards Map-Request to “owning” ETR for EID prefix • ALT routers aggregate prefixes “upward” in the alternative topology Cisco Global Routing Summit, August, 2008

20. 11.0.0.1 -> 240.1.1.1 11.0.0.1 -> 240.1.1.1 240.0.0.1 -> 240.1.1.1 240.0.0.1 -> 240.1.1.1 <- 240.1.1.0/24 < - 240.1.0.0/16 <- 240.1.2.0/24 240.0.0.1 -> 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 ? ? ? ? 1.1.1.1 -> 11.0.0.1 240.0.0.1 -> 240.1.1.1 ALT-rtr ALT-rtr ALT-rtr ALT-rtr ALT-rtr ALT-rtr LISP+ALT in action EID-prefix 240.0.0.0/24 EID-prefix 240.1.1.0/24 1.1.1.1 11.0.0.1 2.2.2.2 12.0.0.1 Legend: EIDs -> Green Locators -> Red GRE Tunnel Low Opex Physical link Data Packet Map-Request Map-Reply 3.3.3.3 LAT Cisco Global Routing Summit, August, 2008

21. Data-Triggered Mappings • ITRs have the option of forwarding data for “un-mapped” EIDs into ALT • Effectively attached to Map-Request to ETR, delivered to destination host as side-effect • LISP Map-Reply “triggered” from ETR to ITR, installed in ITR cache • Following traffic uses cached RLOCs • Just like if Map-Request/Map-Reply done • Issue: scaling/complexity/performance Cisco Global Routing Summit, August, 2008

22. ISP allocates 1 locator address per physical attachment point (follows network topology) RIR allocates EID-prefixes (follows org/geo hierarchy) R1 R2 Hierarchical 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 Cisco Global Routing Summit, August, 2008

23. 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? Cisco Global Routing Summit, August, 2008

24. Issue: Large-site ETR Policy • ALT separates ETR discovery from the ITR-ETR mapping exchange • Very coarse prefixes advertised globally • 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 Cisco Global Routing Summit, August, 2008

25. Large-site ETR policy example • (someday, this will be a pretty, animated slide that shows how LISP and ALT can achieve the same “best exit” effect as advertising more-specifics with MEDs…today is not that day, unfortunately) Cisco Global Routing Summit, August, 2008

26. 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 has “static EID-prefix route” pointing to ETR • originates EID prefix on behalf of ETR Cisco Global Routing Summit, August, 2008

27. More open ALT issues • Who runs the ALT network? • What’s the business model? • Should it be rooted at/run by the RIRs? • Different levels run by different orgs • Should it be free? • OK to renumber to get “PI” EID prefix? • Interworking/transition strategies (later) • Work in standards/ops community (later) • Others? Cisco Global Routing Summit, August, 2008

28. LISP Internet Drafts draft-farinacci-lisp-08.txt draft-fuller-lisp-alt-02.txt draft-lewis-lisp-interworking-01.txt draft-farinacci-lisp-multicast-00.txt draft-meyer-lisp-eid-block-01.txt draft-mathy-lisp-dht-00.txt draft-iannone-openlisp-implementation-01.txt draft-brim-lisp-analysis-00.txt draft-meyer-lisp-cons-04.txt draft-lear-lisp-nerd-04.txt draft-curran-lisp-emacs-00.txt Cisco Global Routing Summit, August, 2008

29. Questions/Comments? Contact us: lisp-interest@lists.civil-tongue.net Information: http://www.lisp4.net OpenLISP: http://inl.info.ucl.ac.be Thanks! Cisco Global Routing Summit, August, 2008 Slide 29