1 ietf- 56 – te wg- san francisco inter-as mpls traffic engineering...

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IETF- 56 – TE WG- SAN FRANCISCO

Inter-AS MPLS Traffic Engineering

draft-vasseur-inter-AS-TE-00.txt

Jean-Philippe Vasseur – Cisco Systems Raymond Zhang - Infonet

draft-vasseur-inter-AS-TE-00.txt IETF-56 San Francisco

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Inter-AS MPLS Traffic Engineering requirements draft: draft-zhang-mpls-interas-te-req-02.txt (TE WG)

Inter-AS MPLS Traffic Engineering (solution draft):

draft-vasseur-inter-AS-te-00.txt (WG to be decided once inter-AS reqs draft adopted as a WG doc)

Scenario 1: per-AS TE LSP Path computation

Scenario 2: distributed path computation server


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Scenario 1: per-AS TE LSP Path Computation

AS1

ASBR2

ASBR4

ASBR1

AS2ASBR3 BA

ASBR5

AS2

ASBR6

ASBR8ASBR7

TE LSP defined as a set of loose hops:

Pref1: A-ASBR1(L)-ASBR2(L)-ASBR7(L)-ASBR8(L)-B(L)

Pref2: A-ASBR3(L)-ASBR4(L)-ASBR7(L)-ASBR8(L)-B(L)

…

ERO expand (partial path computation)

ERO expand (partial path computation)

Semi-dynamic path computation – HE crankback in case of Call admission failure

Option for ASBR discovery

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Scenario 1: additional drafts ….

Inter-AS TE LSP reoptimization (MUST in the requirement draft)

draft-vasseur-mpls-loose-path-reopt-01.txt proposes a set of mechanisms allowing:

A TE LSP Head-End LSR to trigger on every LSR (whose next hop is a loose hop) the re evaluation of the current path in order to detect a potential more optimal path (performed via signalling)

An LSR whose next hop is a loose-hop to signal, upon request or not, to the TE LSP head-end whether or not a better (lower cost) path exists

If and only if at least a better path exist in an area/AS, the HE LSR triggers a non disruptive TE Reroute (Make before break).

ASBR Node protection (with MPLS TE Fast Reroute “facility backup” (MUST in the requirements draft)

draft-vasseur-mpls-nodeid-subobject-00.txt proposes to specify an additional flag of the RRO IPv4/IPv6 sub-object used for the backup tunnel selection for inter-AS TE LSP protected by MPLS TE Fast Reroute (“Facility backup”) in case of ASBR node failure

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AS1

ASBR2

ASBR4

ASBR1

AS3ASBR3 BA

ASBR5

AS2

ASBR6

ASBR8ASBR7

A selects a PCS (static configuration or dynamic discovery (IGP Extensions))

* * *

PCC-PCS sig request (draft-vasseur-mpls-computation-rsvp-03.txt)

ASBR1 build a virtual SPT (the shortest path is built using a backward recursive computation)

Shortest path satisfying the constraint from any ASBR in AS3 – Path1: ERO1, c1 Path2: ERO2, c2

Virtual SPT

The resulting shortest path is provided to ASBR1

Virtual SPT

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SummaryScenario 1: per-AS TE LSP Path computation

- No impact on RSVP/IGP scalability,

- Semi-dynamic,

- Small set of protocol extensions required,

- No optimal end to end path

- Diverse path computation not always possible (Path protection, load balancing)

- Call set up failure,

- Support of end to end reoptimization (timer/event driven)

- Support of FRR Bypass for ASBR protection



- No impact on RSVP/IGP scalability,

- Dynamic,

- Implementation more complex,

- Optimal end to end path

- Diverse path computation always possible (Path protection, load balancing)

- No call set up failure

- Support of end to end reoptimization

- Support of FRR Bypass for ASBR protection

- TE LSP local protection recommended

Both scenario 1 and 2 are compliant with the set of requirements defined in draft-zhang-mpls-interas-te-req-02.txt

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Conclusion

• Next step: start discussion …

1 ietf- 56 – te wg- san francisco inter-as mpls traffic engineering...

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