wdiff rfc8401.original rfc8401.txt


Internet Engineering Task Force (IETF)                  L. Ginsberg, Ed.
Internet-Draft
Request for Comments: 8401                                 Cisco Systems
Intended status:
Category: Standards Track                                  A. Przygienda
Expires: October 1, 2018
ISSN: 2070-1721                                         Juniper Networks
                                                               S. Aldrin
                                                                  Google
                                                                J. Zhang
                                                  Juniper Networks, Inc.
                                                          March 30,
                                                               June 2018

                         BIER support

        Bit Index Explicit Replication (BIER) Support via ISIS
                   draft-ietf-bier-isis-extensions-11 IS-IS

Abstract

   This document defines ISIS IS-IS extensions to support multicast
   forwarding using the Bit Index Explicit Replication (BIER)
   architecture.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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 an Internet Standards Track document.

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

   Internet-Drafts are draft documents valid the IETF community.  It has
   received public review and has been approved for a maximum publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of six months RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained 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 1, 2018.
   https://www.rfc-editor.org/info/rfc8401.

Copyright Notice

   Copyright (c) 2018 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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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   4.  Concepts  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  BIER Domains and Sub-Domains SubDomains . . . . . . . . . . . . . .   5 .   4
     4.2.  Advertising BIER Information  . . . . . . . . . . . . . .   5
   5.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Multi Topology  Multi-Topology and Sub-Domain Subdomain  . . . . . . . . . . . . . .   5
     5.2.  BFR-id Advertisements . . . . . . . . . . . . . . . . . .   6
     5.3.  Logging Misconfiguration  . . . . . . . . . . . . . . . .   6
     5.4.  Flooding Reduction  . . . . . . . . . . . . . . . . . . .   6
   6.  Packet Formats  . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  BIER Info sub-TLV Sub-TLV . . . . . . . . . . . . . . . . . . . .   7   6
     6.2.  BIER MPLS Encapsulation sub-sub-TLV Sub-sub-TLV . . . . . . . . . . .   8   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   9   8
   8.  Acknowledgements  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   9.
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . .  10
     9.1.  Normative References . . . . . . . . . .  11
   Acknowledgements  . . . . . . . .  10
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   Bit Index Explicit Replication (BIER) [RFC8279] defines an
   architecture where all intended multicast receivers are encoded as a
   bitmask in the Multicast multicast packet header within different
   encapsulations such as described in [RFC8296].  A router that
   receives such a packet will forward the packet based on the Bit Position bit
   position in the packet header towards the receiver(s), receiver(s) following a
   precomputed tree for each of the bits in the packet.  Each receiver
   is represented by a unique bit in the bitmask.

   This document presents necessary extensions to the currently deployed
   ISIS
   IS-IS for IP [RFC1195] protocol to support distribution of information
   necessary for operation of BIER domains and sub-domains. subdomains.  This
   document defines a new TLV to be advertised by every router
   participating in BIER signaling.

   This document defines support for MPLS encapsulation as specified in
   [RFC8296].  Support for other encapsulation types is outside and the
   scope of this document.  The use of
   multiple encapsulation types is are outside the scope of this document.

2.  Terminology

   Some of the terminology specified in [RFC8279] is replicated here and
   extended by necessary definitions:

   BIER:  Bit Index Explicit Replication (The Replication.  The overall architecture of
      forwarding multicast using a Bit Position). bit position.

   BIER-OL:  BIER Overlay Signaling.  (The  The method for the BFIR to learn
      about BFER's). BFERs.

   BFR:  Bit Forwarding Router (A Router.  A router that participates in Bit Index
      Multipoint Forwarding). Forwarding.  A BFR is identified by a unique BFR-
      prefix BFR-prefix
      in a BIER domain.

   BFIR:  Bit Forwarding Ingress Router (The Router.  The ingress border router that
      inserts the BM BitString into the packet). packet.  Each BFIR must have a
      valid BFR-
      id BFR-id assigned.

   BFER:  Bit Forwarding Egress Router.  A router that participates in
      Bit Index Forwarding as a leaf.  Each BFER must be a BFR.  Each
      BFER must have a valid BFR-id assigned.

   BFT:  Bit Forwarding Tree used to reach all BFERs in a domain.

   BIER sub-domain: subdomain:  A further distinction within a BIER domain
      identified by its unique sub-domain subdomain identifier.  A BIER sub-domain subdomain
      can support multiple BitString Lengths.

   BFR-id:  An optional, unique identifier for a BFR within a BIER sub-
      domain.
      subdomain.

   Invalid BFR-id:  Unassigned BFR-id.  The special value 0 is reserved
      for this purpose.

   BAR

   BAR:  BIER Algorithm.  Used to calculate underlay next hops.

   IPA

   IPA:  IGP Algorithm.  May be used to modify, enhance enhance, or replace the
      calculation of underlay paths as defined by the BAR value

   SPF  Shortest Path First routing calculation based on IGP link metric defined by the BAR value.

   SPF:  Shortest Path First routing calculation based on the IGP link
      metric.

2.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  IANA Considerations

   This document adds the following new sub-TLV entry to the registry of Sub-
   TLVs "Sub-TLVs for TLVs 135,
   235, 236, and 237. 237" registry.

   Value: 32 (suggested - to be assigned by IANA)

   Name: BIER Info

   This document also introduces a new registry for sub-sub-TLVs for the
   BIER Info sub-TLV added above. sub-TLV.  The registration policy is Expert Review as
   defined in [RFC8126].  This registry is part of  The "Sub-sub-TLVs for BIER Info Sub-TLV" has
   been created within the "IS-IS TLV Codepoints" registry.  The name of the registry is "sub-sub-TLVs
   for BIER Info sub-TLV".  The defined values are:
   value is as follows:

     Type    Name
     ----    ----
     1       BIER MPLS Encapsulation

   IANA is requested to set up a registry called has created the "BIER Algorithm
   Registry" under category Algorithms" registry within the "Bit Index
   Explicit Replication". Replication (BIER)" registry.  The registration policies
   [RFC8126] for this registry are:

      "Standards Action" for values 0-127

      "Specification Required" for values 128-240 128-239

      "Experimental Use" for values 240-254" 240-254

   The initial values in the BIER Algorithm Registry "BIER Algorithms" registry are:

      0: No BIER specific BIER-specific algorithm is used

      1-254: Unassigned

      255: Reserved

4.  Concepts

4.1.  BIER Domains and Sub-Domains SubDomains

   An ISIS signalled IS-IS-signalled BIER domain is aligned with the scope of
   distribution of BFR-prefixes that identify the BFRs within ISIS.
   ISIS acts in IS-IS.  In
   such a case case, IS-IS acts as the supporting BIER underlay.

   Within such a domain, the extensions defined in this document
   advertise BIER information for one or more BIER sub-domains. subdomains.  Each
   sub-domain
   subdomain is uniquely identified by a subdomain-id (SD).  Each
   subdomain is associated with a single ISIS IS-IS topology (MT) [RFC5120],
   which may be any of the topologies supported by ISIS. IS-IS.  Local
   configuration controls which <MT,SD> pairs are supported by a router.
   The mapping of sub-domains subdomains to topologies MUST be consistent within the
   IS-IS flooding domain used to advertise BIER information.

   Each BIER sub-domain subdomain has as its unique attributes the encapsulation
   used and the type of tree it is using uses to forward BIER frames (currently
   always SPF).  Additionally, per supported bitstring BitString length in the sub-domain,
   subdomain, each router will advertise the necessary label ranges to
   support it.

4.2.  Advertising BIER Information

   BIER information advertisements are associated with a new sub-TLV in
   the extended reachability TLVs.  BIER information is always
   associated with a host prefix prefix, which MUST be a node address for the
   advertising node.  If this is not the case case, the advertisement MUST be
   ignored.  Therefore  Therefore, the following restrictions apply:

   o  Prefix length MUST be 32 for an IPv4 prefix or 128 for an IPv6
      prefix
      prefix.

   o  When the Prefix Attributes Flags sub-TLV [RFC7794] is present present, the
      N flag MUST be set and the R flag MUST NOT be set.  [RFC7794]

   o  BIER sub-TLVs MUST be included when a prefix reachability
      advertisement is leaked between levels.

5.  Procedures

5.1.  Multi Topology  Multi-Topology and Sub-Domain Subdomain

   A given sub-domain subdomain is supported within one and only one topology.  All
   routers in the flooding scope of the BIER sub-TLVs MUST advertise the
   same sub-domain subdomain within the same multi-topology.  A router receiving an
   <MT,SD> advertisement which that does not match the locally configured pair
   MUST report a misconfiguration of the received <MT,SD> pair.  All
   received BIER advertisements associated with the conflicting <MT,SD>
   pair MUST be ignored.  Note that in the presence of such a misconfiguration
   misconfiguration, this will lead to partitioning of the sub-
   domian. subdomain.

   Example:

   The following combination of advertisements are valid: <0,0> <0,1> <0,1>,
   and <2,2>.

   The following combination of advertisements are invalid: <0,0> <0,1> <0,1>,
   and <2,0>.  Advertisements associated with <0,0> and <2,0> must be
   ignored.

5.2.  BFR-id Advertisements

   If a BFER/BFIR is configured with a BFR-id BFR-id, then it advertises this
   value in its BIER advertisements.  If no BFR-id is configured configured, then
   the value "Invalid BFR-id" is advertised.  A valid BFR-id MUST be
   unique within the flooding scope of the BIER advertisements.  All
   BFERs/BFIRs MUST detect advertisement of duplicate valid BFR-IDs for
   a given <MT, SD>. <MT,SD>.  When such duplication is detected detected, all of the
   routers advertising duplicates MUST be treated as if they did not
   advertise a valid BFR-id.  This implies they cannot act as BFER or
   BFIR in that <MT,SD>.

5.3.  Logging Misconfiguration

   Whenever an advertisement is received which that violates any of the
   constraints defined in this document document, the receiving router MUST
   support logging this occurrence.  Logging SHOULD be dampened to avoid
   excessive output.

5.4.  Flooding Reduction

   It is expected that changes in the BIER domain information which that is
   advertised by IS-IS occur infrequently.  If this expectation is not
   met for an extended period of time (more than a few seconds of
   burstiness)
   burstiness), changes will increase the number of Link State PDU (LSP)
   updates and negatively impact performance in the network.
   Implementations SHOULD protect against this possibility e.g., by by, for
   example, dampening updates if they occur over an extended period of
   time.

6.  Packet Formats

   All ISIS IS-IS BIER information is carried within the TLVs 235, 237
   [RFC5120] or TLVs 237,
   [RFC5120], 135 [RFC5305], or TLV 236 [RFC5308].

6.1.  BIER Info sub-TLV Sub-TLV

   This sub-TLV carries the information for the BIER sub-domains subdomains that the
   router participates in as a BFR.  This sub-TLV MAY appear multiple
   times in a given prefix-reachability TLV - -- once for each sub-domain subdomain
   supported in the associated topology.

   The sub-TLV advertises a single <MT,SD> combination followed by
   optional sub-sub-TLVs as described in the following sections.

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Type       |   Length      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   BAR         |    IPA        | subdomain-id  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     BFR-id                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  sub-sub-TLVs (variable)                                      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:  as  As indicated in the IANA section.

   Length:  variable

   BAR  Variable

   BAR:  BIER Algorithm.  Specifies a BIER specific BIER-specific algorithm used to
      calculate underlay paths to reach BFERs.  Values are allocated
      from the BIER Algorithm Registry. "BIER Algorithms" registry. 1 octet

   IPA octet.

   IPA:  IGP algorithm. Algorithm.  Specifies an IGP Algorithm to either modify,
      enhance
      enhance, or replace the calculation of underlay paths to reach
      BFERs as defined by the BAR value.  Values are from the IGP
      Algorithm registry. 1 octet octet.

   subdomain-id:  Unique value identifying the BIER sub-domain. subdomain. 1 octet octet.

   BFR-id:  A 2 octet 2-octet field encoding the BFR-id, as documented in
      [RFC8279].  If no BFR-id has been assigned assigned, the value of this
      field is set to "Invalid BFR-id", which is defined as illegal in
      [RFC8279] .
      [RFC8279].

   The use of non-zero values in either the BAR field or the IPA field
   is outside the scope of this document.  If an implementation does not
   support the use of non-zero values in these fields, fields but receives a
   BIER Info sub-TLV containing non-zero values in these fields, it
   SHOULD treat the advertising router as incapable of supporting BIER
   (one way of handling incapable routers is documented in section Section 6.9
   of [RFC8279] and additional methods may be defined in the future).

6.2.  BIER MPLS Encapsulation sub-sub-TLV Sub-sub-TLV

   This sub-sub-TLV carries the information for the BIER MPLS
   encapsulation including the label range for a specific bitstring BitString
   length for a certain <MT,SD>.  It is advertised within the BIER Info
   sub-TLV (Section 6.1) . 6.1).  This sub-sub-TLV MAY appear multiple times
   within a single BIER info Info sub-TLV.

   If the same Bitstring BitString length is repeated in multiple sub-sub-TLVs
   inside the same BIER Info Sub-TLV, sub-TLV, the BIER Info sub-TLV MUST be
   ignored.

   Label ranges within all BIER MPLS Encapsulation sub-sub-TLVs across
   all BIER Info sub-TLVs advertised by the same BFR MUST NOT overlap.
   If overlap is detected, the advertising router MUST be treated as if
   it did not advertise any BIER sub-TLVs.

   Label values MUST NOT match any of the reserved values defined in
   [RFC3032]
   [RFC3032].

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Type       |   Length      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Max SI      |BS Len |                    Label              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:  value  Value of 1 indicating MPLS encapsulation.

   Length:  4

   Max SI SI:  Maximum Set Identifier (section (Section 1 of [RFC8279]) used in the
      encapsulation for this BIER sub-domain subdomain for this bitstring BitString length, 1
      octet.  Each SI maps to a single label in the label range.  The
      first label is for SI=0, the second label is for SI=1, etc.  If
      the label associated with the Maximum Set Identifier exceeds the
      20 bit range
      20-bit range, the sub-sub-TLV MUST be ignored.

   Local BitString Length (BS Len):  Encoded bitstring BitString length as per
      [RFC8296]. 4 bits.

   Label:  First label of the range, 20 bits.  The labels are as defined
      in [RFC8296].

7.  Security Considerations

   Security concerns for IS-IS are addressed in [RFC5304] and [RFC5310].

   The Security Considerations section of [RFC8279] discusses the
   possibility of performing a Denial of Service Denial-of-Service (DoS) attack by setting
   too many bits in the BitString of a BIER-encapsulated packet.

   However, this sort of DoS attack cannot be initiated by modifying the
   ISIS
   IS-IS BIER advertisements specified in this document.  A BFIR decides
   which systems are to receive a BIER-encapsulated packet.  In making
   this decision, it is not influenced by the ISIS IS-IS control messages.
   When creating the encapsulation, the BFIR sets one bit in the
   encapsulation for each destination system.  The information in the
   ISIS
   IS-IS BIER advertisements is used to construct the forwarding tables
   that map each bit in the encapsulation into a set of next hops for
   the host that is identified by that bit, but it is not used by the
   BFIR to decide which bits to set.  Hence  Hence, an attack on the ISIS IS-IS
   control plane cannot be used to cause this sort of DoS attack.

   While a BIER-encapsulated packet is traversing the network, a BFR
   that receives a BIER-encapsulated packet with n bits set in its
   BitString may have to replicate the packet and forward multiple
   copies.  However, a given bit will only be set in one copy of the
   packet.  That  This means that each transmitted replica of a received
   packet has fewer bits set (i.e., is targeted to fewer destinations)
   than the received packet.  This is an essential property of the BIER BIER-
   forwarding process as defined in [RFC8279].  While a failure of this
   process might cause a DoS attack (as discussed in the Security
   Considerations of [RFC8279]), such a failure cannot be caused by an
   attack on the ISIS IS-IS control plane.

   Further discussion of BIER specific BIER-specific security considerations can be
   found in [RFC8279].

8.  Acknowledgements

   The RFC is aligned with the [I-D.ietf-bier-ospf-bier-extensions]
   draft as far as the protocol mechanisms overlap.

   Many thanks for comments from (in no particular order) Hannes
   Gredler, Ijsbrand Wijnands, Peter Psenak and Chris Bowers.

   Special thanks to Eric Rosen.

9.  References

9.1.

8.1.  Normative References

   [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
              dual environments", RFC 1195, DOI 10.17487/RFC1195,
              December 1990, <https://www.rfc-editor.org/info/rfc1195>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3032]  Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
              Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
              Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
              <https://www.rfc-editor.org/info/rfc3032>.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/RFC5120, February 2008,
              <https://www.rfc-editor.org/info/rfc5120>.

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, DOI 10.17487/RFC5304, October
              2008, <https://www.rfc-editor.org/info/rfc5304>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <https://www.rfc-editor.org/info/rfc5305>.

   [RFC5308]  Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
              DOI 10.17487/RFC5308, October 2008,
              <https://www.rfc-editor.org/info/rfc5308>.

   [RFC5310]  Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
              and M. Fanto, "IS-IS Generic Cryptographic
              Authentication", RFC 5310, DOI 10.17487/RFC5310, February
              2009, <https://www.rfc-editor.org/info/rfc5310>.

   [RFC7794]  Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
              U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
              and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
              March 2016, <https://www.rfc-editor.org/info/rfc7794>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8279]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
              Explicit Replication (BIER)", RFC 8279,
              DOI 10.17487/RFC8279, November 2017,
              <https://www.rfc-editor.org/info/rfc8279>.

   [RFC8296]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
              for Bit Index Explicit Replication (BIER) in MPLS and Non-
              MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
              2018, <https://www.rfc-editor.org/info/rfc8296>.

9.2.

8.2.  Informative References

   [I-D.ietf-bier-ospf-bier-extensions]

   [OPSFv2BIER]
              Psenak, P., Kumar, N., Wijnands, I., Dolganow, A.,
              Przygienda, T., Zhang, Z., and S. Aldrin, "OSPFv2
              Extensions for BIER", draft-ietf-bier-ospf-bier-
              extensions-16 (work Work in progress), March Progress, draft-ietf-bier-
              ospf-bier-extensions-17, April 2018.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

Acknowledgements

   This RFC is aligned with "OSPFv2 Extensions for BIER" [OPSFv2BIER]
   document as far as the protocol mechanisms overlap.

   Many thanks for comments from (in no particular order) Hannes
   Gredler, Ijsbrand Wijnands, Peter Psenak, and Chris Bowers.

   Special thanks to Eric Rosen.

Authors' Addresses

   Les Ginsberg (editor)
   Cisco Systems
   510 McCarthy Blvd.
   Milpitas, CA  95035
   USA
   United States of America

   Email: ginsberg@cisco.com

   Tony Przygienda
   Juniper Networks

   Email: prz@juniper.net

   Sam Aldrin
   Google
   1600 Amphitheatre Parkway
   Mountain View, CA
   USA
   United States of America

   Email: aldrin.ietf@gmail.com
   Jeffrey (Zhaohui) Zhang
   Juniper Networks, Inc.
   10 Technology Park Drive
   Westford, MA  01886
   USA
   United States of America

   Email: zzhang@juniper.net