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Versions: 00 01 02

Network Working Group                                          C. Franke
Internet-Draft                                              D. Lamparter
Intended status: Standards Track                                  NetDEF
Expires: October 19, 2016                                       C. Hopps
                                                        Deutsche Telekom
                                                          April 17, 2016


                  IS-IS Point-to-Multipoint operation
                      draft-lamparter-isis-p2mp-02

Abstract

   This document describes a new mode operation for IS-IS.  In addition
   to the existing LAN and point-to-point modes of operation, a point-
   to-multipoint mode is defined.  This mode is useful for operation
   both on networks with more than two routers where multicast is
   expensive in comparison to unicast, as well on networks where
   creating a LAN pseudonode cannot adequately reflect metrics.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 19, 2016.

Copyright Notice

   Copyright (c) 2016 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
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   (http://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
   to this document.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Point-To-Multipoint Pseudocircuits  . . . . . . . . . . . . .   3
     2.1.  Pseudocircuit behaviour . . . . . . . . . . . . . . . . .   3
       2.1.1.  Representation in LSPs  . . . . . . . . . . . . . . .   3
       2.1.2.  Forwarding  . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Neighbor IS discovery . . . . . . . . . . . . . . . . . .   3
       2.2.1.  Manual configuration  . . . . . . . . . . . . . . . .   4
       2.2.2.  Lower layer autodiscovery . . . . . . . . . . . . . .   4
       2.2.3.  Multicast autodiscovery . . . . . . . . . . . . . . .   4
     2.3.  Adjacency formation . . . . . . . . . . . . . . . . . . .   5
     2.4.  Pseudocircuit teardown  . . . . . . . . . . . . . . . . .   5
   3.  Configuration model . . . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Change Log  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Appendix A.  Misconfiguration With P2P over LAN . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The core functionality of the protocol outlined in this document
   consists of an additional Subnetwork dependent function per Section 8
   of ISO/IEC 10589:2002 [IS-IS].  In that regard, the next section can
   be understood as new section "8.5 Point-to-multipoint networks".

   The outlined protocol is remotely similar to the derelict section
   "8.3 ISO 8208 subnetworks" [X.25] in that multiple point-to-point
   adjacencies are established on an interface.

   Point-to-multipoint operation of IS-IS is thus not a new idea; in
   fact section 6.2 already mentions "multipoint links."  This document
   re-enables the concept.









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2.  Point-To-Multipoint Pseudocircuits

   In place of ISO 8473 call management [CLNS] establishing sessions,
   this document establishes pairwise "pseudocircuits" between two IS on
   a common medium.  Multiple such pseudocircuits can normally exist on
   one P2MP (Point-To-Multipoint) interface.

   Each pseudocircuit operates, aside from subnetwork attachment
   procedures, exactly as a P2P (Point-to-Point) link.

   It should be noted that while the Multicast autodiscovery mechanism
   requires broadcast capability, no other part of the protocol does.
   The P2MP interface type can be used on non-transitive and/or non-
   broadcast interfaces.

2.1.  Pseudocircuit behaviour

   An implementation maintains a set of pseudocircuits per P2MP
   interface.  Each pseudocircuit is uniquely identified by the local
   interface and peer's SNPA address.

   Each participating system MUST use a consistent SNPA address per
   local interface.  A change in SNPA address results in all neighbors
   treating the interface as distinct from the previous one.  A system
   MAY support multiple SNPA addresses per interface by treating them as
   distinct interfaces.

   Unnumbered media are not supported by this protocol.  Each
   participant on a link MUST have an unique SNPA address on that link.

2.1.1.  Representation in LSPs

   Pseudocircuits are represented in LSPs as a regular P2P circuit would
   be.  As a result, their treatment in SPF calculations is also
   identical to P2P circuits.

2.1.2.  Forwarding

   In scenarios where pseudocircuits do not form a full mesh of all
   participants on a medium, the best path for a packet may be through
   the same interface as the one it was received on.

   Systems implementing this specification MUST therefore support
   forwarding packets on the same interface that they were received on.
   This applies only to interfaces configured for P2MP operation.

2.2.  Neighbor IS discovery




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   The discovery machinery produces as output a "candidate neighbor
   list," which is a list of possible neighbor's SNPAs and is maintained
   per P2MP interface.  Adding and removing entries to the candidate
   neighbor list results in pseudocircuit creation and deletion.

   A neighbors presence on the candidate list may be supported by
   multiple sources.  These sources are described in the following
   sections

   The IS-IS implementation SHOULD provide user configuration to disable
   or filter individual sources.

2.2.1.  Manual configuration

   A list of neighbor IS MAY be configured by the user, providing
   possible neighbor's SNPAs on an interface.

2.2.2.  Lower layer autodiscovery

   Lower protocol layers (VPLS, IEEE 802.11) may be able to provide a
   list of attached neighbors.  This list MAY be fed into the candidate
   neighbor list.

2.2.3.  Multicast autodiscovery

   For broadcast capable networks, this document defines an
   autodiscovery mechanism based on multicasting Hello packets.  This
   mechanism MAY be disabled by the user, but MUST be implemented for
   all lower layer link types with (limited or full) broadcast
   capability.

   A multicast autodiscovery packet is defined as a P2P IIH which is
   multicast over the LAN media as defined in [RFC5309].  Additionally
   it must include a Three-Way Adjacency TLV as defined in [RFC5303]
   indicating the circuit is in the DOWN state (i.e., 1 octet of value
   indicating the DOWN state).  Receiving such a Hello places the
   sending IS on the candidate list for as long as the PDU's holdtime
   indicates.

   A system MAY implement a receive-only passive multicast autodiscovery
   mode where it adds candidates (forms pseudocircuits) on receiving
   autodiscovery PDU, but does not send such PDUs itself.

   If either passive or full multicast autodiscovery is enabled,
   receiving a unicast autodiscovery PDU also adds the neighbor to the
   candidate list.





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2.3.  Adjacency formation

   Since there may be no underlying protocol layer partitioning the link
   into actual P2P circuits in this case, additional handling is
   required on bringing up the individual pseudocircuit adjacencies.

   To prevent different pseudocircuits from "bleeding" into each other,
   implementations of this protocol MUST enable [RFC5303] on all P2MP
   pseudocircuits, with changes as follows:

   o  Received IIH PDUs on P2MP pseudocircuits without the Point-to-
      Point Three-Way Adjacency option MUST be discarded.

2.4.  Pseudocircuit teardown

   Pseudocircuits are destroyed when their P2P state machine has
   transitioned into "Down" state and they are no longer supported as a
   candidate by any discovery mechanism.

   As long as a pseudocircuit is present, its P2P state machine will, as
   expected for P2P circuits, trigger transmission of further Hello
   PDUs, even when it is in Down state.

3.  Configuration model

   TODO: YANG model

4.  Security Considerations

   TODO.

5.  Privacy Considerations

   TODO.

6.  Acknowledgements

   Acknowledge Les Ginsberg for pointing out that P2P Hellos rather than
   LAN hellos could and should be used.

7.  Change Log

   April 2016 [-02]:  (no changes/keepalive)

   October 2015 [-01]:  Moved from new P2MP Hello PDU to using existing
      P2P PDU.

   July 2015 [-00]:  Initial Version



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8.  References

8.1.  Normative References

   [IS-IS]    ISO/IEC, "Intermediate System to Intermediate System
              Intra-Domain Routing Exchange Protocol for use in
              Conjunction with the Protocol for Providing the
              Connectionless-mode Network Service (ISO 8473)", ISO/IEC
              10589:2002, Second Edition, 2002.

   [RFC5303]  Katz, D., Saluja, R., and D. Eastlake, "Three-Way
              Handshake for IS-IS Point-to-Point Adjacencies", RFC 5303,
              October 2008.

   [RFC5309]  Shen, N., Ed. and A. Zinin, Ed., "Point-to-Point Operation
              over LAN in Link State Routing Protocols", RFC 5309, DOI
              10.17487/RFC5309, October 2008,
              <http://www.rfc-editor.org/info/rfc5309>.

8.2.  Informative References

   [CLNS]     ISO/IEC, "Protocol for providing the connectionless-mode
              network service: Protocol specification", ISO/IEC
              8473-1:1998, 1998.

   [RFC7176]  Eastlake, D., Senevirathne, T., Ghanwani, A., Dutt, D.,
              and A. Banerjee, "Transparent Interconnection of Lots of
              Links (TRILL) Use of IS-IS", RFC 7176, May 2014.

   [RFC7356]  Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding
              Scope Link State PDUs (LSPs)", RFC 7356, September 2014.

   [X.25]     ISO/IEC, "X.25 Packet Layer Protocol for Data Terminal
              Equipment", ISO/IEC 8208:2000, 2000.

Appendix A.  Misconfiguration With P2P over LAN

   TODO.

Authors' Addresses

   Christian Franke
   NetDEF
   Leipzig
   DE

   Email: chris@opensourcerouting.org




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   David Lamparter
   NetDEF
   Leipzig  04229
   Germany

   Email: david@opensourcerouting.org


   Christian E. Hopps
   Deutsche Telekom

   Email: chopps@chopps.org






































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