Flood Reflectors
draft-przygienda-flood-reflector-00

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Network Working Group                                      A. Przygienda
Internet-Draft                                                   Juniper
Intended status: Standards Track                                  Y. Lee
Expires: March 12, 2020                                        A. Sharma
                                                                 Comcast
                                                                R. White
                                                                 Juniper
                                                       September 9, 2019

                            Flood Reflectors
                  draft-przygienda-flood-reflector-00

Abstract

   This document provides specification of an optional ISIS extension
   that allows to create l2 flood reflector topologies independent of
   resulting forwarding within L1 areas when they are used as 'transit'
   to guarantee L2 connectivity between L2 "islands".

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 RFC 2119 [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 March 12, 2020.

Copyright Notice

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

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Internet-Draft      draft-przygienda-flood-reflector      September 2019

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Description . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Further Details . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Flood Reflection TLV  . . . . . . . . . . . . . . . . . . . .   7
   4.  Non-Forwarding Adjacency Sub-TLV  . . . . . . . . . . . . . .   7
   5.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  Adjacency Forming Procedures  . . . . . . . . . . . . . . . .   9
   7.  Special Considerations  . . . . . . . . . . . . . . . . . . .   9
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     11.1.  Informative References . . . . . . . . . . . . . . . . .  10
     11.2.  Normative References . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Description

   Due to the inherent properties of link-state protocols the number of
   IS-IS routers within a flooding domain is limited by processing and
   flooding overhead on each node.  While that number can be maximized
   by well written implementations and techniques such as exponential
   back-offs, IS-IS will still reach a saturation point where no further
   routers can be added to a single flooding domain.  In certain
   deployment scenarios of L2 backbones, this limit presents an
   obstacle.

   While the standard solution to increase the scale of an IS-IS
   deployement is to break it up into multiple L1 flooding domains and a
   single L2 backbone, and alternative way is to think about "multiple"
   L2 flooding domains connected via L1 flooding domains.  In such a
   solution, the L2 flooding domains are connected by "L1/L2 lanes"
   through the L1 areas to form a single L2 backbone again.  However, in
   the simplest implementation, this requires the inclusion of most, or
   all, of the transit L1 routers as L1/L2 to allow traffic to flow
   along optimal paths through such transit areas and with that

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