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?