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Versions: (draft-li-isis-mrt) 00 01 02 03

Network Working Group                                              Z. Li
Internet-Draft                                                     N. Wu
Intended status: Standards Track                                 Q. Zhao
Expires: January 1, 2018                             Huawei Technologies
                                                                A. Atlas
                                                               C. Bowers
                                                        Juniper Networks
                                                             J. Tantsura
                                                              Individual
                                                           June 30, 2017


   Intermediate System to Intermediate System (IS-IS) Extensions for
                    Maximally Redundant Trees (MRT)
                         draft-ietf-isis-mrt-03

Abstract

   This document describes extensions to IS-IS to support the
   distributed computation of Maximally Redundant Trees (MRT).  Example
   uses of MRT include IP/LDP Fast-Reroute and global protection or
   live-live for multicast traffic.  The extensions indicate what MRT
   profile(s) each router supports.  Different MRT profiles can be
   defined to support different uses and to allow transition of
   capabilities.  An extension is introduced to flood MRT-Ineligible
   links, due to administrative policy.  This document also defines the
   Controlled Convergence sub-TLV, which is useful for MRT FRR as well
   as other applications.

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 http://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 January 1, 2018.






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Copyright Notice

   Copyright (c) 2017 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
   (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
   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Overview of IS-IS Signalling Extensions for MRT . . . . . . .   4
     4.1.  Supporting MRT Profiles . . . . . . . . . . . . . . . . .   4
     4.2.  Selecting the GADAG Root  . . . . . . . . . . . . . . . .   4
     4.3.  Advertising MRT-Ineligible Links for MRT  . . . . . . . .   5
     4.4.  Triggering an MRT Computation . . . . . . . . . . . . . .   5
   5.  MRT Capability Advertisement  . . . . . . . . . . . . . . . .   5
     5.1.  MRT Profile sub-TLV in the IS-IS Router CAPABILITY TLV  .   6
       5.1.1.  A note on the M-bit in OSPF . . . . . . . . . . . . .   7
     5.2.  MRT-Ineligible Link sub-TLV in the Extended IS
           Reachability TLV  . . . . . . . . . . . . . . . . . . . .   7
     5.3.  A Note on Multi-Topology Routing  . . . . . . . . . . . .   8
   6.  Controlled Convergence sub-TLV in IS-IS Router CAPABILITY TLV   8
   7.  Handling MRT Extensions . . . . . . . . . . . . . . . . . . .  10
     7.1.  Advertising MRT extensions  . . . . . . . . . . . . . . .  10
     7.2.  Processing MRT extensions . . . . . . . . . . . . . . . .  10
   8.  Backward Compatibility  . . . . . . . . . . . . . . . . . . .  10
   9.  Implementation Status . . . . . . . . . . . . . . . . . . . .  11
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  11
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
     12.1.  MRT Profile and Controlled Convergence sub-TLVs  . . . .  11
     12.2.  MRT-Ineligible Link sub-TLV  . . . . . . . . . . . . . .  11
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     13.2.  Infomative References  . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13





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1.  Introduction

   The IS-IS protocol is specified in [ISO10589], with extensions for
   supporting IPv4 and IPv6 specified in [RFC1195] and [RFC5308].  Each
   Intermediate System (IS) (router) advertises one or more IS-IS Link
   State Protocol Data Units (LSPs) with routing information.  Each LSP
   is composed of a fixed header and a number of tuples, each consisting
   of a Type, a Length, and a Value.  Such tuples are commonly known as
   TLVs, and are a good way of encoding information in a flexible and
   extensible format.

   [RFC7812] gives a complete solution for IP/LDP fast-reroute using
   Maximally Redundant Trees (MRT) to provide alternates.  This document
   describes signalling extensions for supporting MRT-FRR in an IS-IS
   routing domain.

2.  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].

3.  Terminology

   Redundant Trees (RT): A pair of trees where the path from any node X
   to the root R along the first tree is node-disjoint with the path
   from the same node X to the root R along the second tree.  These can
   be computed in 2-connected graphs.

   Maximally Redundant Trees (MRT): A pair of trees where the path from
   any node X to the root R along the first tree and the path from the
   same node X to the root R along the second tree share the minimum
   number of nodes and the minimum number of links.  Each such shared
   node is a cut-vertex.  Any shared links are cut-links.  Any RT is an
   MRT but many MRTs are not RTs.

   MRT Island: From the computing router, the set of routers that
   support a particular MRT profile and are connected via MRT- eligible
   links.

   GADAG: Generalized Almost Directed Acyclic Graph - a graph which is
   the combination of the ADAGs of all blocks.  Transforming a network
   graph into a GADAG is part of the MRT algorithm.

   MRT-Red: MRT-Red is used to describe one of the two MRTs; it is used
   to describe the associated forwarding topology and MT-ID.
   Specifically, MRT-Red is the decreasing MRT where links in the GADAG




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   are taken in the direction from a higher topologically ordered node
   to a lower one.

   MRT-Blue: MRT-Blue is used to describe one of the two MRTs; it is
   used to describe the associated forwarding topology and MT-ID.
   Specifically, MRT-Blue is the increasing MRT where links in the GADAG
   are taken in the direction from a lower topologically ordered node to
   a higher one.

4.  Overview of IS-IS Signalling Extensions for MRT

   As stated in [RFC7811], it is necessary for each MRT-Capable router
   to compute MRT next hops in a consistent fashion.  This is achieved
   by using the same MRT profile and selecting a common and unique GADAG
   root in the MRT Island which is connected by MRT-Eligible links.
   Each of these issues will be discussed in the following sections
   separately.

4.1.  Supporting MRT Profiles

   The contents and requirements of an MRT profile has been defined in
   [RFC7812].  The parameters and behavioral rules contained in an MRT
   profile define one router's MRT capabilities.  Based on common
   capabilities, one unified MRT Island is built.

   The MRT-Capable router MUST advertise its corresponding MRT profiles
   by IS-IS protocol extension within IS-IS routing domain.  The
   capabilities of the advertiser MUST completely conform to the profile
   it claimed, including the MT-IDs, the algorithm and the corresponding
   forwarding mechanism.  This advertisement MUST have level scope.  A
   given router MAY support multiple MRT profiles.  If so, it MUST
   advertise each of these profiles in the corresponding IS-IS level.

   The default MRT Profile is defined in [RFC7812].  Its behavior is
   intended to support IP/LDP unicast and multicast Fast-Reroute.  MRT-
   Capable routers SHOULD support the default MRT profile.

4.2.  Selecting the GADAG Root

   As per [RFC7811], a GADAG root MUST be selected for one MRT Island.
   An unique GADAG root in common among MRT Island routers is a
   necessity to do MRT computation.  Since the selection of the GADAG
   root can affect the quality of paths for traffic sent over MRT Red
   and Blue trees, the GADAG Root Selection Priority and the GADAG Root
   Selection Policy gives a network operator the ability to influence
   the selection of the GADAG root.





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   Each MRT-Capable router MUST advertise its priority for GADAG root
   selection.  A router can only have one priority in a given MRT
   Island.  It can have multiple priorities for different MRT Islands it
   supports.  Routers that are marked as overloaded([RFC3787]) are not
   qualified as candidate for root selection.

   The GADAG Root Selection Policy (defined as part of an MRT profile)
   may make use of the GADAG Root Selection Priority value advertised in
   the MRT Profile in the IS-IS Router CAPABILITY TLV.  For example, the
   GADAG Root Selection Policy for the default MRT profile is the
   following: Among the routers in the MRT Island and with the highest
   priority advertised, an implementation MUST pick the router with the
   highest Router ID to be the GADAG root.

   When the current root is out of service or new router with higher
   priority joined into the MRT Island, the GADAG root MUST be re-
   selected.  A new MRT computation will be triggered because of such a
   topology change.

4.3.  Advertising MRT-Ineligible Links for MRT

   For administrative or management reasons, it may be desirable to
   exclude some links from the MRT computation.  In this scenario, MRT-
   Capable router MUST claim those MRT-Ineligible links are out of MRT
   Island scope.  If such claim splits current MRT Island then MRT
   computation has to be done inside the modified MRT Island which the
   computing router belongs to.

4.4.  Triggering an MRT Computation

   A MRT Computation can be triggered through topology changes or MRT
   capability changes of any router in the MRT Island.  It is always
   triggered for a given MRT Profile in the corresponding level.  First,
   the associated MRT Island is determined.  Then, the GADAG Root is
   selected.  Finally, the actual MRT algorithm is run to compute the
   transit MRT-Red and MRT-Blue topologies.  Additionally, the router
   MAY choose to compute MRT-FRR alternates or make other use of the MRT
   computation results.

   Prefixes can be attached and detached and have their associated MRT-
   Red and MRT-Blue next-hops computed without requiring a new MRT
   computation.

5.  MRT Capability Advertisement

   An MRT-Capable router MUST identify its MRT capabilities through IS-
   IS Link State Packets(LSPs) in level scope.




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5.1.  MRT Profile sub-TLV in the IS-IS Router CAPABILITY TLV

   A new MRT Profile sub-TLV is introduced into the IS-IS Router
   CAPABILITY TLV (TLV #242 defined in [RFC4971]) to advertise MRT
   capabilities.  Since MRT has per level scope, the S-bit and D-bit of
   IS-IS Router CAPABILITY TLV MUST be set to zero.  The structure of
   the MRT Profile sub-TLV is shown below:

   TYPE: TBA-MRT-ISIS-1 (To Be Allocated by IANA)

   LENGTH: 4

   VALUE:

   MT-ID (2 octets with 4 bits reserved)

   MRT Profile ID (1 octet)

   GADAG Root Selection Priority (1 octet)

                                              Number of octets
   +-------------------------------+
   |R |R |R |R |        MT-ID      |                 2
   +-------------------------------+
   | MRT Profile ID                |                 1
   +-------------------------------+
   | GADAG Root Selection Priority |                 1
   +-------------------------------+


   MT-ID is a 12-bit field containing the multi-topology ID.  As
   discussed in Section 5.3, this document specifies that the MT-ID
   field MUST be set to zero.

   The MRT Profile ID represents the MRT profile this router supports.

   The GADAG Root Selection Priority is the priority for selection as
   GADAG root.  A router advertising the MRT Profile sub-TLV MUST
   specify a GADAG Root Selection Priority.  The range of this priority
   is [0, 255].  The RECOMMENDED default value of the GADAG Root
   Selection Priority is 128.  The GADAG Root Selection Policy defined
   as part of a given MRT profile determines how the GADAG Root
   Selection Priority value is used.

   This sub-TLV can occur multiple times if a router supports multiple
   MRT profiles.  This can happen during a network transition.  Or it
   can be used to support different uses of MRT within the same network
   which may perform better with different profiles.



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   A given router SHOULD NOT advertise multiple MRT Profile sub-TLVs
   with the same MRT profile ID.  If a router receives multiple MRT
   Profile sub-TLVs with the same MRT profile ID from the same
   originator, it MUST use one with the lowest value of GADAG Root
   Selection Priority.

5.1.1.  A note on the M-bit in OSPF

   [I-D.ietf-ospf-mrt] defines MRT signalling extensions for OSPF.  In
   addition to the OSPF version of MRT Profile sub-TLV (which is carried
   in the OSPF Router Information LSA), it also defines the M-bit (which
   is carried in the OSPF Router-LSA.)  As discussed in
   [I-D.ietf-ospf-mrt], the M-bit in the Router-LSA ensures that all
   routers in the area have up-to-date information if a router is
   downgraded to a software version that does not support MRT and the
   Router Information LSA.

   The problematic scenario that requires the M-bit in the OSPF Router-
   LSA does not occur in IS-IS.  The presence or absence of an IS-IS
   Router CAPABILITY TLV containing a given MRT Profile sub-TLV in the
   IS-IS Link State PDU provides enough information for all routers to
   determine which remote routers support MRT, even after a software
   version downgrade of remote routers.  Therefore, this document does
   not define a corresponding M-bit for IS-IS.

5.2.  MRT-Ineligible Link sub-TLV in the Extended IS Reachability TLV

   As a matter of policy, an operator may choose to mark some links as
   ineligible for carrying MRT traffic.  For instance, policy can be
   made to prevent fast-rerouted traffic from taking those links.

   For a link to be marked as ineligible for use in the MRT calculation,
   it MUST be advertised including the MRT-Ineligible Link sub-TLV in
   the Extended IS Reachability TLV (TLV #22 defined in [RFC5305] )
   corresponding to the ineligible link.  The MRT-Ineligible Link sub-
   TLV is a zero-length sub-TLV as shown below:

   TYPE: TBA-MRT-ISIS-2 (To Be Allocated by IANA)

   LENGTH: 0

   VALUE: None

   The presence of the zero-length MRT-Ineligible Link sub-TLV in the
   Extended IS Reachability TLV indicates that the associated link MUST
   NOT be used in the MRT calculation for the default topology for all
   profiles.




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5.3.  A Note on Multi-Topology Routing

   [RFC5120] specifies how to support multi-topology routing in IS-IS.
   The current document specifies how to signal support for MRT in the
   default routing topology only.  The format of the extensions in this
   document allows the MRT Profile sub-TLV and the MRT-Ineligible Link
   sub-TLV to be scoped to topologies with non-zero MT-ID at some point
   in the future.  However, this document restricts these extensions to
   apply only to the default topology.  The MRT Profile sub-TLV is
   restricted by explicitly requiring the MT-ID field to be set to zero.
   The MRT-Ineligible Link sub-TLV is restricted by only allowing it to
   be included in the Extended IS Reachability TLV (TLV#22) which is
   scoped to the default topology, and not allowing it to appear TLV#222
   (the topology-scoped version of the Extended IS Reachability TLV).

   Lifting these restrictions is for further study.  Note that the MRT
   signalling extensions in this document can co-exist with IS-IS multi-
   topology routing, with the limitation that MRT Red and Blue
   forwarding trees can only be built for the default topology.

   The format of the Controlled Convergence sub-TLV (discussed below)
   also contains an MT-ID field, allowing a Controlled Convergence sub-
   TLV to be scoped to a particular topology.  This document does not
   place restrictions on the MT-ID field in the Controlled Convergence
   sub-TLV.  The Controlled Convergence sub-TLV has potential
   applications that are not limited to MRT, and a topology-scoped FIB
   compute/install time makes sense on its own.

6.  Controlled Convergence sub-TLV in IS-IS Router CAPABILITY TLV

   Section 12.2 of [RFC7812] describes the need to wait for a configured
   or advertised period after a network failure to insure that all
   routers are using their new shortest path trees.  Similarly, avoiding
   micro-forwarding loops during convergence [RFC5715] requires
   determining the maximum among all routers in the area of the worst-
   case route computation and FIB installation time.  More details on
   the specific reasoning and need for flooding this value are given in
   [I-D.atlas-bryant-shand-lf-timers].

   A new Controlled Convergence sub-TLV is introduced into the IS-IS
   Router CAPABILITY TLV (TLV #242 defined in [RFC4971]) to advertise
   the worst-case time for a router to compute and install all IS-IS
   routes in the level after a change to a stable network.  This
   advertisement has per level scope, so the S-bit and D-bit of IS-IS
   Router CAPABILITY TLV MUST be set to zero.  The advertisement is
   scoped by MT-ID, allowing a router supporting multi-topology routing
   to advertise a different worst-case FIB compute/install time for each
   topology.  This makes sense as the SPF computations and FIB



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   installations for each IGP topology can potentially be done
   independently of one another, and may have different worst-case
   compute and install times.

   The structure of the Controlled Convergence sub-TLV is shown below:

   TYPE: TBA-MRT-ISIS-3 (To Be Allocated by IANA)

   LENGTH: 3

   VALUE:

   MT-ID (2 octets with 4 bits reserved)

   FIB compute/install time (1 octet)

                                              Number of octets
   +-------------------------------+
   |R |R |R |R |        MT-ID      |                 2
   +-------------------------------+
   |  FIB compute/install time     |                 1
   +-------------------------------+

   MT-ID is a 12-bit field containing the multi-topology ID.

   The FIB compute/install time is the worst-case time the router may
   take to compute and install all IS-IS routes in the level after a
   change to a stable network.  The value is an unsigned integer in
   units of milliseconds.

   The FIB compute/install time value sent by a router SHOULD be an
   estimate taking into account network scale or real-time measurements,
   or both.  Advertisements SHOULD be dampened to avoid frequent
   communication of small changes in the FIB compute/install time.

   A router receiving the Controlled Convergence sub-TLV SHOULD estimate
   the network convergence time as the maximum of the FIB compute/
   install times advertised by the routers in a level for a given MT-ID,
   including itself.  In order to account for routers that do not
   advertise the Controlled Convergence sub-TLV, a router MAY use a
   locally configured minimum network convergence time as a lower bound
   on the computed network convergence time.  A router MAY use a locally
   configured maximum network convergence time as an upper bound on the
   computed network convergence time.







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7.  Handling MRT Extensions

7.1.  Advertising MRT extensions

   MRT sub-TLVs are encapsulated in the Router Capability TLV and
   advertised using the LS-PDU with level-wide scope.  MRT sub-TLVs are
   optional.  If one router does not support MRT, it MUST NOT advertise
   those sub-TLVs.

   Since the advertisement scope of the MRT sub-TLV is level-wide, the
   D-Bit and S-Bit of the Router Capability TLV MUST be set as 0 when it
   is advertised.  If other sub-TLVs in the Router Capability TLV need
   different values for those two bits, then the router MUST originate
   multiple Router Capability TLVs with different bit values.

   When MRT-related information is changed for the router or existing
   IS-IS LSP mechanisms are triggered for refreshing or updating, MRT
   sub-TLVs MUST be advertised if the router is MRT-Capable.

   Based on administrative policy, it may be desirable to exclude
   certain links from the MRT computation.  The MRT-Ineligible sub-TLV
   is used to advertise which links should be excluded.  Note that an
   interface advertised as MRT-Ineligible by a router is ineligible with
   respect to all profiles advertised by that router.

7.2.  Processing MRT extensions

   The processing associated with MRT extensions SHOULD NOT
   significantly degrade IS-IS adjacency formation and maintenance or
   the routing calculation for normal shortest path routes.

   MRT sub-TLVs SHOULD be validated like other sub-TLVs when received.
   MRT sub-TLVs SHOULD also be taken into account for checksum
   calculations and authentication.

   Links advertised as MRT-ineligible using the MRT-Ineligible sub-TLV
   MUST be excluded from the MRT computation.  The removal of individual
   links from the MRT Island can partition an MRT Island or it can
   significantly modify the construction of the GADAG and the result MRT
   Red and Blue trees.  Therefore, all routers must perform the same
   computation using the same set of links.

8.  Backward Compatibility

   The MRT Profile sub-TLV, the MRT-Ineligible Link sub-TLV, and the
   Controlled Convergence sub-TLV defined in this document are
   compatible with existing implementations of IS-IS.  Routers that do
   not support these extensions are expected to silently ignore them.



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   Router that do support these extensions have mechanisms to recognize
   routers that don't support these extensions (or are not configured to
   participate in MRT) and behave accordingly.

9.  Implementation Status

   [RFC Editor: please remove this section prior to publication.]

   Please see [RFC7812] for details on implementation status.

10.  Security Considerations

   The IS-IS extensions in this document do not introduce new security
   concerns.

11.  Acknowledgements

   The authors would like to thank Shraddha Hegde for her useful
   suggestions.

12.  IANA Considerations

12.1.  MRT Profile and Controlled Convergence sub-TLVs

   IANA is requested to allocate values for the following sub-TLVs types
   in the IS-IS Router CAPABILITY TLV defined in [RFC4971]: the MRT
   Profile sub-TLV (TBA-MRT-ISIS-1) and Controlled Convergence sub-TLV
   (TBA-MRT-ISIS-3).  The IANA registry for these sub-TLV types is
   displayed as "sub-TLVs for TLV 242" (http://www.iana.org/assignments/
   isis-tlv-codepoints/isis-tlv-codepoints.xhtml#isis-tlv-codepoints-
   242).  The new entries in this registry are shown below.

   Value           Description                       Reference
   --------------  ------------------------------    ------------
   TBA-MRT-ISIS-1  MRT Profile sub-TLV               [This draft]
   TBA-MRT-ISIS-3  Controlled Convergence sub-TLV    [This draft]

12.2.  MRT-Ineligible Link sub-TLV

   IANA is requested to allocate a value for the following sub-TLVs type
   in the Extended IS Reachability TLV defined in [RFC5305]: MRT-
   Ineligible Link sub-TLV (TBA-MRT-ISIS-2).  The IANA registry for
   these sub-TLV types is displayed as "Sub-TLVs for TLVs 22, 23, 141,
   222, and 223" (http://www.iana.org/assignments/isis-tlv-codepoints/
   isis-tlv-codepoints.xhtml#isis-tlv-codepoints-22-23-141-222-223).
   The new entry in this registry is shown below.





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  Type            Description                 22 23 141 222 223 Ref.
  --------------  --------------------------- -- -- --- --- --- --------
  TBA-MRT-ISIS-2  MRT-Ineligible Link sub-TLV y  y   n   n   n  [This
                                                                 draft]

13.  References

13.1.  Normative References

   [RFC3787]  Parker, J., Ed., "Recommendations for Interoperable IP
              Networks using Intermediate System to Intermediate System
              (IS-IS)", RFC 3787, DOI 10.17487/RFC3787, May 2004,
              <http://www.rfc-editor.org/info/rfc3787>.

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

   [RFC7811]  Enyedi, G., Csaszar, A., Atlas, A., Bowers, C., and A.
              Gopalan, "An Algorithm for Computing IP/LDP Fast Reroute
              Using Maximally Redundant Trees (MRT-FRR)", RFC 7811,
              DOI 10.17487/RFC7811, June 2016,
              <http://www.rfc-editor.org/info/rfc7811>.

   [RFC7812]  Atlas, A., Bowers, C., and G. Enyedi, "An Architecture for
              IP/LDP Fast Reroute Using Maximally Redundant Trees (MRT-
              FRR)", RFC 7812, DOI 10.17487/RFC7812, June 2016,
              <http://www.rfc-editor.org/info/rfc7812>.

13.2.  Infomative References

   [I-D.atlas-bryant-shand-lf-timers]
              K, A. and S. Bryant, "Synchronisation of Loop Free Timer
              Values", draft-atlas-bryant-shand-lf-timers-04 (work in
              progress), February 2008.

   [I-D.ietf-ospf-mrt]
              Atlas, A., Hegde, S., Bowers, C., Tantsura, J., and Z. Li,
              "OSPF Extensions to Support Maximally Redundant Trees",
              draft-ietf-ospf-mrt-01 (work in progress), October 2015.

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







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Internet-Draft          IS-IS Extensions for MRT               June 2017


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

   [RFC4971]  Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed.,
              "Intermediate System to Intermediate System (IS-IS)
              Extensions for Advertising Router Information", RFC 4971,
              DOI 10.17487/RFC4971, July 2007,
              <http://www.rfc-editor.org/info/rfc4971>.

   [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,
              <http://www.rfc-editor.org/info/rfc5120>.

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

   [RFC5715]  Shand, M. and S. Bryant, "A Framework for Loop-Free
              Convergence", RFC 5715, DOI 10.17487/RFC5715, January
              2010, <http://www.rfc-editor.org/info/rfc5715>.

Authors' Addresses

   Zhenbin Li
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: lizhenbin@huawei.com


   Nan Wu
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: eric.wu@huawei.com








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Internet-Draft          IS-IS Extensions for MRT               June 2017


   Quintin Zhao
   Huawei Technologies
   125 Nagog Technology Park
   Acton, MA  01719
   USA


   Alia Atlas
   Juniper Networks
   10 Technology Park Drive
   Westford, MA  01886
   USA

   Email: akatlas@juniper.net


   Chris Bowers
   Juniper Networks
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089
   USA

   Email: cbowers@juniper.net


   Jeff Tantsura
   Individual
   USA

   Email: jefftant.ietf@gmail.com





















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