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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 - PowerPoint PPT Presentation
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IDR WG, IETF Dublin, August, 2008
Vince Fuller (for the LISP crew)
LISP+ALT Mapping SystemLISP+ALT Mapping System
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 22
AgendaAgenda
• Mapping system design needs
• Ideas we considered• Brief summary of LISP+ALT• Open issues
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 33
Mapping system: what and Mapping system: what and whywhy
• 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?
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 44
Scaling constraintsScaling 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
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 55
Tough questions/issuesTough 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
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 66
LISP+ALT: What and HowLISP+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
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 77
LISP+ALT in actionLISP+ALT in action
Legend:
EIDs
Locators
ALT connection
Physical link
Data Packet
Map-Request
Map-Reply
ETR
ETR
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
ALT-rtr
ALT-rtr
ALT-rtr
ALT-rtr
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
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 88
LISP+ALT in actionLISP+ALT in action
Legend:
EIDs
Locators
ALT connection
Physical link
Data Packet
Map-Request
Map-Reply
ETR
ETR
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 -> 240.1.1.1EID-prefix
240.0.0.0/24
240.0.0.1 -> 240.1.1.1
11.0.0.1 -> 1.1.1.1
ALT-rtr
ALT-rtr
ALT-rtr
ALT-rtr
ALT-rtr
ALT-rtr
12.0.0.1
11.0.0.1
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 99
Issue: Data-Triggered Issue: Data-Triggered MappingsMappings
• 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?
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 1010
Issue: EID assignmentIssue: EID assignment
Provider A10.0.0.0/8
Provider B11.0.0.0/8
R1 R2
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)
SiteLegend:
EIDs -> Green
Locators -> Red
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 1111
Issue: mapping system Issue: mapping system securitysecurity
• 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?
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 1212
Issue: large-site ETR Issue: large-site ETR policypolicy
• 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
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 1313
Large-site ETR policy Large-site ETR policy exampleexample
• (placeholder slide for now)
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 1414
Issue: “low-opex” xTRIssue: “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
IDR WGIDR WG IETF Dublin, July, 2008IETF Dublin, July, 2008 Slide Slide 1515
Other issues to Other issues to considerconsider
• Who runs the ALT network?– What’s the business model?– Should it be rooted at/run by the RIRs?
– Should it be free?
• Others?