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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
draft-vasseur-inter-AS-TE-00.txt IETF-56 San Francisco
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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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Scenario 2: distributed path computation server
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
draft-vasseur-inter-AS-TE-00.txt IETF-56 San Francisco
Scenario 2: distributed path computation server
- 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 …