LISP+ALT Mapping System
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Transcript of LISP+ALT Mapping System
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IDR WG, IETF Dublin, August, 2008
Vince Fuller (for the LISP crew)
LISP+ALT Mapping SystemLISP+ALT Mapping System
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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
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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?
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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
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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
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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
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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
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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
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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?
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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
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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?
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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
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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)
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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
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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?