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Reverse Metric TLV draft-amante-isis-reverse-metric -01

Reverse Metric TLV draft-amante-isis-reverse-metric -01. Authors: Shane Amante Tony Li Naiming Shen Mikael Abrahamsson. Proposed Status: Standards Track. Background.

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Reverse Metric TLV draft-amante-isis-reverse-metric -01

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  1. Reverse Metric TLVdraft-amante-isis-reverse-metric-01 Authors: Shane Amante Tony Li NaimingShen MikaelAbrahamsson Proposed Status: Standards Track

  2. Background • Operational reqm’t to gracefully bi-directionally remove both p2p links and multi-access LAN’s from the ISIS topology, except as a link of last-resort • DO NOT need or want to isolate the entire router with IS-IS overload-bit – potentially affecting Tbps of ‘innocent’ traffic • Login to CLI of both (p2p) or all (LAN) devices and increase the existing IS-IS metric(s) to temporarily remove it from the topology • Service Providers don’t, can’t and/or won’t use NMS to ‘automate’ this draft-amante-isis-reverse-metric-00

  3. Current Link/LAN Isolation Procedures P2P Link Multi-access LAN • Current procedure to isolate link/LAN: • login to each router, • correctly identify specific link on both routers • Change existing, configured metric high to extremely high value • IS-IS domain should now consider Link/LAN as “link/LAN of last resort” • To un-isolate link/LAN: • (Re-)login to each router, • Correctly identify specific link/LAN • Change metric back to originally configured value R1 R2 R1 R2 R3 R4 R5 R6 draft-amante-isis-reverse-metric-00

  4. Challenges with link/LAN isolation • Correctly identify the corresponding link on two or, more routers, each with hundreds of interfaces apiece @ 3AM in the morning … • Need to temporarily change the existing, configured IS-IS metric on an interface (need to “remember” what it was to properly reset it afterward). • Cannot bidirectionally isolate a single adjacency on a multi-access LAN. draft-amante-isis-reverse-metric-00

  5. Solution: Reverse Metric TLV • Reverse Metric is wholly separate from, but added to, existing configured default metric on local device and remote neighbor • Login to a single node and temporarily assert an additive high metric in both: • Our own IS Reachbility or Ext. IS Reachability TLV’s • A Reverse Metric TLV in IIH’s xmit’ed toward your neighbor, on p2p link, or toward DIS on multi-access LAN • Router receiving Reverse Metric TLV adds to his/her own existing ‘default metric’ in Pseudonode LSP, IS Reachability or Ext. IS Reachability TLV draft-amante-isis-reverse-metric-00

  6. Proposed Link/LAN Isolation Procedures R1 New LSP P2P Link R2 New LSP Multi-access LAN R1 New LSP • Read draft or see slides online for specific proposed link/LAN procedures R1 R2 R1 R2 R3 R4 R5 R6 IIH PDU’s with Reverse Metric TLV draft-amante-isis-reverse-metric-00

  7. Current Status • LAN’s: This draft has similar concerns with persistent forwarding loops if nodes do not accumulate non-zero metric in Pseudonode LSP, as already discussed for draft-shen-isis-oper-enhance • Addressed large # of comments on mailing list in -00  -01 version • Questions? Comments? • Interest in advancing this draft, in the future? draft-amante-isis-reverse-metric-00

  8. Backup Material(Detailed Procedures)

  9. Proposed p2p Link Isolation Procedures R1 Procedures: R2 Procedures: When R2 receives Reverse Metric TLV In no particular order: Add “metric value” in Reverse Metric TLV to own IS Reachability or Ext. IS Reachability TLV’s of link on which Reverse Metric TLV is recv’d Flood new LSP’s Recalculate SPF Tree • login to one router, (R1) • correctly identify specific link • Apply new, additive IS-IS metric with extremely high value to link – leave existing, configured metric “as is”. • In no particular order: • Update own IS Reachability, Ext. IS Reachability TLV • Flood new LSP’s • Recalculate SPF Tree • Add Reverse Metric TLV to IIH PDU’s toward neighbor(s) – R1  R2 draft-amante-isis-reverse-metric-00

  10. Proposed p2p Link Un-Isolation Procedures R1 Procedures: R2 Procedures: When R2 stops receiving Reverse Metric TLV In no particular order: Remove additive “metric value” (from Reverse Metric TLV) in own IS Reachability or Ext. IS Reachability TLV’s of link on which Reverse Metric TLV was formerly recv’d Flood new LSP’s Recalculate SPF Tree • login to one router, (R1) • correctly identify specific link • Remove additive IS-IS metric with extremely high value to link – leave existing, configured metric “as is”. • In no particular order: • Update own IS Reachability, Ext. IS Reachability TLV • Flood new LSP’s • Recalculate SPF Tree • Stop sending Reverse Metric TLV in IIH PDU’s toward neighbor(s) – R1  R2 draft-amante-isis-reverse-metric-00

  11. Proposed multi-access LAN Isolation Procedures R4 (Non-DIS) Procedures: R1 (DIS) Procedures: When R1 receives Reverse Metric TLV: Update Pseudonode LSP with non-zero metric – add “metric value” in Reverse Metric TLV – to either R4 (W=0) or all nodes on LAN (W=1) Flood new Pseudonode LSP Recalculate SPF Tree • login to one router, (R4) • correctly identify specific link • Apply new, additive IS-IS metric with extremely high value to link – leave existing, configured metric “as is”. • On R4 (non-DIS), in no particular order: • Update own IS Reachability, Ext. IS Reachability TLV • Flood new LSP’s • Recalculate SPF Tree • Add Reverse Metric TLV to IIH PDU’s toward DIS – R4  R1 Other non-DIS nodes on same LAN, (R3, R5, R6), ignore Reverse Metric TLV from R4; however, each will receive Updated Psuedonode LSP from DIS And recalculate their SPF for other Node(s) attached to the LAN. draft-amante-isis-reverse-metric-00

  12. Proposed multi-access LAN Un-Isolation Procedures R4 (Non-DIS) Procedures: R1 (DIS) Procedures: When R1 stops receiving Reverse Metric TLV: Update Pseudonode LSP back to original, zero metric based on previous assertion in the Reverse Metric TLV from R4, i.e.: just R4 (W=1) or Whole LAN (W=0) Flood new Pseudonode LSP Recalculate SPF Tree • login to one router, (R4) • correctly identify specific link • Remove additive IS-IS metric with extremely high value to link – leave existing, configured metric “as is”. • On R4 (non-DIS), in no particular order: • Update own IS Reachability, Ext. IS Reachability TLV • Flood new LSP’s • Recalculate SPF Tree • Stop sending Reverse Metric TLV to IIH PDU’s toward DIS – R4  R1 Other non-DIS nodes on same LAN, (R3, R5, R6), receive new Psuedonode LSP from DIS and recalculate their SPF for other node(s) attached to the LAN. draft-amante-isis-reverse-metric-00

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