1. Reverse Metric TLV draft-amante-isis-reverse-metric-01 draft-amante-isis-reverse-metric Authors: Shane Amante Tony Li Naiming Shen Mikael Abrahamsson 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 2draft-amante-isis-reverse-metric-00

3. Current Link/LAN Isolation Procedures 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 P2P LinkMulti-access LAN 3draft-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-004

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-005

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

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-enhancedraft-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-007

8. Backup Material (Detailed Procedures)

9. Proposed p2p Link Isolation Procedures R1 Procedures: 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 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 draft-amante-isis-reverse-metric-009

10. Proposed p2p Link Un-Isolation Procedures R1 Procedures: 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 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 draft-amante-isis-reverse-metric-0010

11. Proposed multi-access LAN Isolation Procedures R4 (Non-DIS) Procedures: 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 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 draft-amante-isis-reverse-metric-0011 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. 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.

12. Proposed multi-access LAN Un-Isolation Procedures R4 (Non-DIS) Procedures: 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 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 draft-amante-isis-reverse-metric-0012 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. 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.