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

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

3. IDR WGIETF Dublin, July, 2008Slide 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?

4. IDR WGIETF Dublin, July, 2008Slide 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(10 10 ) 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

5. IDR WGIETF Dublin, July, 2008Slide 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

6. IDR WGIETF Dublin, July, 2008Slide 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

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

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

9. IDR WGIETF Dublin, July, 2008Slide 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?

10. IDR WGIETF Dublin, July, 2008Slide 10 Issue: EID assignment Provider A 10.0.0.0/8 Provider B 11.0.0.0/8 R1R2 PI EID-prefix 240.1.0.0/16 10.0.0.1 11.0.0.1 ISP allocates 1 locator address per physical attachment point (follows network topology) RIR allocates EID-prefixes (follows org/geo hierarchy) Site Legend: EIDs -> Green Locators -> Red

11. IDR WGIETF Dublin, July, 2008Slide 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?

12. IDR WGIETF Dublin, July, 2008Slide 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

13. IDR WGIETF Dublin, July, 2008Slide 13 Large-site ETR policy example (placeholder slide for now)

14. IDR WGIETF Dublin, July, 2008Slide 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

15. IDR WGIETF Dublin, July, 2008Slide 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?