LISP BOF, IETF Dublin, July, 2008 Vince Fuller (for the LISP crew) LISP+ALT Mapping System

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

LISP BOFIETF Dublin, July, 2008Slide 3 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

LISP BOFIETF Dublin, July, 2008Slide 4 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?

LISP BOFIETF Dublin, July, 2008Slide 5 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

LISP BOFIETF Dublin, July, 2008Slide 6 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

LISP BOFIETF Dublin, July, 2008Slide 7 LISP+ALT: What, How, Why Hybrid push/pull approach –ALT pushes aggregates - find ETRs for EID –ITR uses LISP to find RLOCs for specific EID Hierarchical EID assignment (geo?) –Aggregation of EID prefixes Tunnel-based overlay network BGP used to advertise EIDs on overlay –Use existing technology (and not DNS) Option for data-triggered Map-Replies

LISP BOFIETF Dublin, July, 2008Slide 8 Legend: EIDs -> Green Locators -> Red GRE Tunnel Low Opex Physical link Data Packet Map-Request Map-Reply ETR ITR EID-prefix /24 LAT > > EID-prefix / > > > ALT-rtr ? > > ? > > ? < /24 < /24 < /16 ? LISP+ALT in action

LISP BOFIETF Dublin, July, 2008Slide 9 Issue: Data-Triggered Mappings ITR may forward data for “un-mapped” EID into ALT, attached to a Map-Request LISP Map-Reply returned from ETR to ITR, uses “native” path, installed in ITR cache ETR delivers attached data to end host Subsequent traffic uses cached RLOCs Scaling/complexity/performance issues Is this (Data Probes) a good idea?

LISP BOFIETF Dublin, July, 2008Slide 10 Issue: EID assignment Provider A /8 Provider B /8 R1R2 PI EID-prefix / 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

LISP BOFIETF Dublin, July, 2008Slide 11 Separate EID/RLOC topologies ID/LOC separation avoids this dilemma EIDs uses organization/geo hierarchy RLOCs follow network topology Reduce global routing state through RLOC aggregation EID prefixes are not generally visible in global routing system “Addressing can follow topology or topology can follow addressing – choose one” –Y.R.

LISP BOFIETF Dublin, July, 2008Slide 12 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?

LISP BOFIETF Dublin, July, 2008Slide 13 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

LISP BOFIETF Dublin, July, 2008Slide 14 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)

LISP BOFIETF Dublin, July, 2008Slide 15 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

LISP BOFIETF Dublin, July, 2008Slide 16 Other issues to consider 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? Others?

LISP BOFIETF Dublin, July, 2008Slide 17 Questions/Comments? Thanks! Contact us: Information: OpenLISP: