SRIFT: Segment Routing In Fat Trees
draft-zzhang-rift-sr-01

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RIFT                                                            Z. Zhang
Internet-Draft                                          Juniper Networks
Intended status: Standards Track                             J. Tantsura
Expires: October 27, 2019                                    Apstra, Inc
                                                                D. Fedyk
                                                              Individual
                                                          April 25, 2019

                  SRIFT: Segment Routing In Fat Trees
                        draft-zzhang-rift-sr-01

Abstract

   This document specifies signaling procedures for Segment Routing
   [RFC8402] with RIFT.  Each node's loopback address, Segment Routing
   Global Block (SRGB) and Node Segment Identifier (SID), which must be
   unique within the SR domain and are typically assigned by SR
   controllers or management, are distributed southbound from the Top Of
   Fabric (TOF) nodes via the Key-Value distribution mechanism, so that
   each node can compute how to reach a node represented by the topmost
   Node SIDs .  For an ingress node to send SR traffic to another node
   via an explicit path, an SR controller signals the corresponding
   label stack to the ingress node so that the ingress node can send
   packets accordingly.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC2119.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 27, 2019.

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Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Specifications  . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Before we discuss the SR procedures for RIFT, let us first review how
   SR works with OSPF/ISIS [I-D.ietf-ospf-segment-routing-extensions]
   [I-D.ietf-isis-segment-routing-extensions].

   Each node is provisioned with a loopback address, an SRGB, and a Node
   SID.  The loopback address and Node SID are co-ordinated centrally -
   it is unique for each node across the SR network - and then
   communicated out of band to each node and stored as configuration
   information.  For example, the out of band communication could be via
   primitive pen and paper, or modern signaling from controllers.

   SRGB configuration can be local to each node and different node can
   have the same or different label blocks for flexible label
   allocation.  Typically, modern SR networks have identical SRGB on
   each node so that a Node SID corresponds to the same label on each
   node.  However that is not mandatory.  Either way, the SRGB is part
   of the node's local configuration.  In today's network it is very
   likely pushed down from some controllers.

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   Each node will then signal its SRGB, and its Node SID.  The Node SID