IS-IS Spine-Leaf
IETF 97, Seoul
Naiming Shen, Cisco
Sanjay Thyamagundalu, Cisco
Draft History
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draft-shen-isis-spine-leaf-ext-02
First presented at IETF 96 in Berlin
Removed the ‘Default Route Metric’ field
from the Spine-Leaf TLV, and changed to
using Reverse Metric in IIH PDU
Published 02 version in October 2016
Spine-Leaf Use Cases
• Spine-Leaf Setup popular in Data Center
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and Campus
Normally leaf-to-leaf traffic goes through
one of the spine nodes, for east-west
Normally leaf-to-leaf traffic goes through
one of the spine nodes, for east-west
Basically some ECMP load sharing from
leaf to spine nodes
Rich mesh of spine-leaf topology
generates LSP flooding issues
TLV in Hello PDU
• L: Leaf mode bit; R: Default Route Gateway
bit; B: Leaf-Leaf bit
• ‘Default Route metric’ is removed. Can use
IS-IS Reverse Metric from Spine to Leaf
nodes
Extension Operation (1/2)
Core Layer with IS-IS
Full IS-IS
Database
Normal ISIS Operation
S2
S1
Aggregation Layer
Only default
routes to
Spines
L1
L2
L3
Access Layer
Extension Operations (2/2)
For
point-to-point IS-IS link
Spine nodes have interconnections, include the
‘Core’ layer on top of ‘Aggregation’ layer
CSNP is not needed over the SL link
Allow Leaf-to-leaf local exchange
Leaf set ‘OL’ bit in its LSP
Spine may pass ‘Hostname’ in IIH
Spine may send different ‘Reverse Metric’ to
influence the leaf’s ECMP
Next Steps
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Review and comment and discussion
Request WG Adoption