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1 Algorithms for computing Maximally Redundant Trees for IP/LDP Fast-Reroute draft-enyedi-rtgwg-mrt-frr-algorithm-01 Alia Atlas (Juniper Networks) Gabor.

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Presentation on theme: "1 Algorithms for computing Maximally Redundant Trees for IP/LDP Fast-Reroute draft-enyedi-rtgwg-mrt-frr-algorithm-01 Alia Atlas (Juniper Networks) Gabor."— Presentation transcript:

1 1 Algorithms for computing Maximally Redundant Trees for IP/LDP Fast-Reroute draft-enyedi-rtgwg-mrt-frr-algorithm-01 Alia Atlas (Juniper Networks) Gabor Enyedi, Andras Csaszar (Ericsson) IETF 83, Paris, France

2 2 Agenda Briefly about the algorithm Problem Avoid using a node Non-2-connected networks

3 3 Agenda Briefly about the algorithm Problem Avoid using a node Non-2-connected networks

4 4 ADAG and partial order Root A B C E H S G D

5 5 ADAG and partial order Root A B C E H S G D Almost DAG (ADAG) A< { "@context": "http://schema.org", "@type": "ImageObject", "contentUrl": "http://images.slideplayer.com/4294693/14/slides/slide_4.jpg", "name": "5 ADAG and partial order Root A B C E H S G D Almost DAG (ADAG) A<

6 6 ADAG and partial order S< { "@context": "http://schema.org", "@type": "ImageObject", "contentUrl": "http://images.slideplayer.com/4294693/14/slides/slide_5.jpg", "name": "6 ADAG and partial order S<

7 7 ADAG and partial order S>>A –Blue path: increasing [S,Root] and [Root, A] –Red path: decreasing [A, S] Root A B C E H S G D

8 8 ADAG and partial order S and C are not ordered –Blue path: [S, E] and [C, E] –Red path: [A, S] and [A, C] Root A B C E H S G D

9 9 Agenda Briefly about the algorithm Problem Avoid using a node Non-2-connected networks

10 10 Three trees We have tree trees –SPT –Two MRTs There is no connection between SPT and MRTs Impossible to find a redundant pair for SPT Example: S C BA D Dest Shortest path No redundant pair for that!

11 11 Agenda Briefly about the algorithm Problem Avoid using a node Non-2-connected networks

12 12 Total order Partial order can compare any X only with S –We need to compare any two nodes Make a total order as well –If A< { "@context": "http://schema.org", "@type": "ImageObject", "contentUrl": "http://images.slideplayer.com/4294693/14/slides/slide_11.jpg", "name": "12 Total order Partial order can compare any X only with S –We need to compare any two nodes Make a total order as well –If A<

13 13 A possible total order Numbers are written next to nodes Root A B C E H S G D

14 14 Possible cases If dst>>src, failed node F Root A B C E H S G D If S< { "@context": "http://schema.org", "@type": "ImageObject", "contentUrl": "http://images.slideplayer.com/4294693/14/slides/slide_13.jpg", "name": "14 Possible cases If dst>>src, failed node F Root A B C E H S G D If S<>src, failed node F Root A B C E H S G D If S<

15 15 Possible cases If dst< { "@context": "http://schema.org", "@type": "ImageObject", "contentUrl": "http://images.slideplayer.com/4294693/14/slides/slide_14.jpg", "name": "15 Possible cases If dst<

16 16 Possible cases If dst and src are not ordered –There are four sub-paths Root A B C E H S G D If F>>src, it may be on the first part of the RED path If F<dest, it may be on the second part of the RED path F and src are not ordered, and F { "@context": "http://schema.org", "@type": "ImageObject", "contentUrl": "http://images.slideplayer.com/4294693/14/slides/slide_15.jpg", "name": "16 Possible cases If dst and src are not ordered –There are four sub-paths Root A B C E H S G D 0 1 5 3 6 8 2 4 7 If F>>src, it may be on the first part of the RED path If F<dest, it may be on the second part of the RED path F and src are not ordered, and F>src, it may be on the first part of the RED path If F<dest, it may be on the second part of the RED path F and src are not ordered, and F

17 17 Agenda Briefly about the algorithm Problem Avoid using a node Non-2-connected networks

18 18 Non-2-connected problem In this case we don’t have a single order –Neither a partial order –Nor a total order Convert the GADAG into an ADAG! A B X C D Non-root blockLocal root block

19 19 Non-2-connected problem In this case we don’t have a single order –Neither a partial order –Nor a total order Convert the GADAG into an ADAG! A B X1 C D Non-root block X2 Local root block

20 20 Thank you!


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