RIFT: Routing in Fat Trees
draft-ietf-rift-rift-06

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RIFT Working Group                                      The RIFT Authors
Internet-Draft                                             June 23, 2019
Intended status: Standards Track
Expires: December 25, 2019

                       RIFT: Routing in Fat Trees
                        draft-ietf-rift-rift-06

Abstract

   This document outlines a specialized, dynamic routing protocol for
   Clos and fat-tree network topologies.  The protocol (1) deals with
   fully automated construction of fat-tree topologies based on
   detection of links, (2) minimizes the amount of routing state held at
   each level, (3) automatically prunes and load balances topology
   flooding exchanges over a sufficient subset of links, (4) supports
   automatic disaggregation of prefixes on link and node failures to
   prevent black-holing and suboptimal routing, (5) allows traffic
   steering and re-routing policies, (6) allows loop-free non-ECMP
   forwarding, (7) automatically re-balances traffic towards the spines
   based on bandwidth available and finally (8) provides mechanisms to
   synchronize a limited key-value data-store that can be used after
   protocol convergence to e.g.  bootstrap higher levels of
   functionality on nodes.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on December 25, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

The RIFT Authors        Expires December 25, 2019               [Page 1]
Internet-Draft                    RIFT                         June 2019

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Table of Contents

   1.  Authors . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   7
   3.  Reference Frame . . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   7
     3.2.  Topology  . . . . . . . . . . . . . . . . . . . . . . . .  10
   4.  Requirement Considerations  . . . . . . . . . . . . . . . . .  12
   5.  RIFT: Routing in Fat Trees  . . . . . . . . . . . . . . . . .  15
     5.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .  16
       5.1.1.  Properties  . . . . . . . . . . . . . . . . . . . . .  16
       5.1.2.  Generalized Topology View . . . . . . . . . . . . . .  16
       5.1.3.  Fallen Leaf Problem . . . . . . . . . . . . . . . . .  26
       5.1.4.  Discovering Fallen Leaves . . . . . . . . . . . . . .  28
       5.1.5.  Addressing the Fallen Leaves Problem  . . . . . . . .  29
     5.2.  Specification . . . . . . . . . . . . . . . . . . . . . .  30
       5.2.1.  Transport . . . . . . . . . . . . . . . . . . . . . .  30
       5.2.2.  Link (Neighbor) Discovery (LIE Exchange)  . . . . . .  31
       5.2.3.  Topology Exchange (TIE Exchange)  . . . . . . . . . .  33
         5.2.3.1.  Topology Information Elements . . . . . . . . . .  33
         5.2.3.2.  South- and Northbound Representation  . . . . . .  33
         5.2.3.3.  Flooding  . . . . . . . . . . . . . . . . . . . .  36
         5.2.3.4.  TIE Flooding Scopes . . . . . . . . . . . . . . .  36
         5.2.3.5.  'Flood Only Node TIEs' Bit  . . . . . . . . . . .  39
         5.2.3.6.  Initial and Periodic Database Synchronization . .  40
         5.2.3.7.  Purging and Roll-Overs  . . . . . . . . . . . . .  40
         5.2.3.8.  Southbound Default Route Origination  . . . . . .  41
         5.2.3.9.  Northbound TIE Flooding Reduction . . . . . . . .  41
         5.2.3.10. Special Considerations  . . . . . . . . . . . . .  46
       5.2.4.  Reachability Computation  . . . . . . . . . . . . . .  47
         5.2.4.1.  Northbound SPF  . . . . . . . . . . . . . . . . .  47