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Versions: 00 01 02 draft-ietf-isis-mrt

Network Working Group                                              Z. Li
Internet-Draft                                                     N. Wu
Intended status: Standards Track                                 Q. Zhao
Expires: July 20, 2015                               Huawei Technologies
                                                                A. Atlas
                                                               C. Bowers
                                                        Juniper Networks
                                                             J. Tantsura
                                                                Ericsson
                                                        January 16, 2015


   Intermediate System to Intermediate System (IS-IS) Extensions for
                    Maximally Redundant Trees (MRT)
                          draft-li-isis-mrt-02

Abstract

   This document describes necessary extensions to IS-IS to support the
   distributed computation of Maximally Redundant Trees (MRT).  Some
   example uses of the MRTs 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.

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 July 20, 2015.








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Copyright Notice

   Copyright (c) 2015 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.  Using MRT with Multi-Topology IGP Routing . . . . . . . . . .   4
   5.  Overview of IS-IS Signaling Extensions for MRT  . . . . . . .   5
     5.1.  Supporting MRT Profiles . . . . . . . . . . . . . . . . .   6
     5.2.  Electing GADAG Root . . . . . . . . . . . . . . . . . . .   6
     5.3.  Advertising MRT-Ineligible Links for MRT  . . . . . . . .   7
     5.4.  Triggering an MRT Computation . . . . . . . . . . . . . .   7
   6.  MRT Capability Advertisement  . . . . . . . . . . . . . . . .   7
     6.1.  Advertising MRT Capability in IS-IS LSP . . . . . . . . .   7
     6.2.  MRT Profile sub-TLV in IS-IS Router CAPABILITY TLV  . . .   8
     6.3.  MRT-Ineligible Links sub-TLV in IS-IS Router CAPABILITY
           TLV . . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  Controlled Convergence sub-TLV in IS-IS Router CAPABILITY TLV  10
   8.  Handling MRT Capability Sending and Receiving . . . . . . . .  11
     8.1.  Advertising MRT extension . . . . . . . . . . . . . . . .  12
     8.2.  Parsing MRT extension . . . . . . . . . . . . . . . . . .  12
   9.  Backwards Compatibility . . . . . . . . . . . . . . . . . . .  12
   10. Implementation Status . . . . . . . . . . . . . . . . . . . .  13
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  13
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     13.2.  Infomative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14








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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.

   [I-D.ietf-rtgwg-mrt-frr-architecture] gives a complete solution for
   IP/LDP fast-reroute using Maximally Redundant Trees (MRT) to provide
   alternates.  This document describes the necessary signaling
   extensions for supporting MRT-FRR used in 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.  Using MRT with Multi-Topology IGP Routing

   Both IS-IS and OSPF have support for multi-topology routing (see
   [RFC5120] for ISIS and [RFC4915] for OSPF.)  In addition to the
   standard topology (identified by MT-ID=0), these extensions allow the
   IGP to identify particular links and nodes as participating in
   additional topologies (identified by MT-ID!=0).  A given link can
   belong to several topologies and be assigned different metrics in
   each topology.  The IGP runs an independent SPF computation for each
   topology, finding independent shortest paths to prefixes in each
   topology.

   It is straightforward to extend the MRT computations to multi-
   topology IGP routing.  For each IGP topology identified by an IGP MT-
   ID, we need to identify the node and links belonging to an MRT Island
   for that IGP MT-ID.  This process creates a graph for the MRT Island
   for that specific IGP MT-ID, which can then be used to compute the
   transit next-hops and alternate next-hops for MRT-Red and MRT-Blue
   for that specific IGP MT-ID.

   We expect that initial implementation and deployments of MRT will be
   primarily concerned with computing MRT-Red and Blue trees for the
   standard topology (IGP MT-ID=0).  However, we have chosen to specify
   the IS-IS MRT extensions to accommodate the computation of MRT-Red
   and MRT-Blue in a multi-topology IS-IS environment.  This comes at
   the expense of 2-6 octets per TLV for MT-ID values, but it will allow
   for standards-based multi-topology aware MRT implementations for ISIS
   without any future standards work.

   Using MRT in a multi-topology IGP environment does have one
   complication which should be discussed.  Forwarding LDP traffic over
   MRT paths in the standard IGP topology requires the use of labels
   bound to topology-scoped FECs to identify traffic on MRT-Red and Blue
   trees.  This is described in Section 6 of
   [I-D.ietf-rtgwg-mrt-frr-architecture].  To facilitate this, an MRT
   profile specifies IANA-assigned MRT-Red and MRT-Blue LDP MT-ID
   values, which are then used by LDP to advertise labels for the MRT-
   Red and Blue forwarding topologies.  Note that the MRT-Red and MRT-
   Blue LDP MT-ID values assigned by IANA for a given MRT profile



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   correspond to the MRT-Red and Blue forwarding trees associated with
   the standard IGP topology with IGP MT-ID=0.  For example, suppose
   that a future MRT profile X is assigned (hypothetical) MRT-Red and
   MRT-Blue LDP MT-ID values of 2001 and 2002.  Then labels for shortest
   path forwarding trees associated with the standard IGP topology will
   be advertised using FECs with MT-ID=0, while the labels for the MRT-
   Red and Blue forwarding trees for profile X will be advertised using
   FECS with MT-ID=2001 and 2002, respectively.  In the absence of
   multi-topology IGP routing, all MT-IDs used by LDP for MRT are
   assigned by IANA, so there are no potential conflicts in LDP MT-ID
   usage.

   When MRT is used together with multi-topology IGP routing, additional
   LDP MT-IDs need to be specified for carrying traffic on the MRT-Red
   and Blue forwarding trees associated with the additional IGP routing
   topologies.  Building on the previous example, suppose that a network
   is configured with an additional IGP routing topology using MT-ID=20,
   in addition to the standard topology with MT-ID=0.  The router
   advertises support for MRT with respect to MT-ID=20 with profile X,
   as well as support for MRT with respect to MT-ID=0 with profile X.
   The MRT-Red and Blue LDP MT-IDs for MT-ID=0 with profile X are still
   inherited from profile X, as in the previous example.  In order to
   use LDP to create the MRT-Red and Blue forwarding trees for the IGP
   topology with MT-ID=20, the router could, for example, advertise MRT-
   Red and MRT-Blue LDP MT-ID values of 21 and 22 for IGP MT-ID=20 and
   profile X.  This overrides the (hypothetical) IANA-assigned values
   MRT-Red and MRT-Blue LDP MT-ID values for profile X, but maintains
   all other properties of profile X.  Care must be taken to avoid
   advertising LDP MT-ID values that conflict with implicitly advertised
   IANA-assigned values LDP MT-ID.

   The semantics of the IS-IS MRT extensions in this document are
   designed to handle the most common case (MRT in the absence of multi-
   topology IGP routing) in a simple manner.  Setting the IGP MT-ID
   field as well as the MRT-Blue and MRT-Red LDP MT-ID fields to 0 in
   the TLV and sub-TLVs in this document results in the desired behavior
   for the standard IGP topology.

5.  Overview of IS-IS Signaling Extensions for MRT

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





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5.1.  Supporting MRT Profiles

   The contents and requirements of an MRT profile has been defined in
   [I-D.ietf-rtgwg-mrt-frr-architecture].  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 advertiser MUST conform to the profile it claimed
   completely, especially the MT-IDs, the algorithm and the
   corresponding forwarding mechanism.  This advertisement MUST have
   level scope.  One router MAY support multiple MRT profiles and it
   MUST advertise these profiles in corresponding IS-IS level.  The MT-
   IDs used in one supported MRT Profile MUST NOT overlap with those MT-
   IDs used in a different supported MRT Profile.

   The default MRT Profile is defined in
   [I-D.ietf-rtgwg-mrt-frr-architecture].  Its behavior is intended to
   support IP/LDP unicast and multicast Fast-Reroute.  MRT-Capable
   routers SHOULD support the default MRT profile.

5.2.  Electing GADAG Root

   As per [I-D.ietf-rtgwg-mrt-frr-algorithm], a GADAG root MUST be
   selected for one MRT Island.  An unique GADAG root in common-sense
   among MRT Island routers is a necessity to do MRT computation.  Since
   the selection of the GADAG root can affect the alternates and the
   traffic through it, the selection rules give network operator a knob
   to control the alternates and the traffic inside the MRT Island.
   Relevant discussion for the relationship between GADAG root role and
   MRT Island alternates is out of the scope of this document.

   Each MRT-Capable router MUST advertise its priority for GADAG root
   selection.  One router can only have one priority in the same 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.




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   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.

5.3.  Advertising MRT-Ineligible Links for MRT

   For certain administrative or management reason, some links may not
   be involved into 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.

5.4.  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.

6.  MRT Capability Advertisement

   MRT-Capable router MUST identify its MRT capabilities through IS-IS
   Link State Packet(LSP) in level scope.

6.1.  Advertising MRT Capability in IS-IS LSP

   One new M-bit is introduced into TLV 229 to identify router is MRT-
   Capable.  Structure of TLV 229 is stated in [RFC5120] as pictured
   below:

   TYPE: 229

   LENGTH: total length of the value field, it SHOULD be 2 times the
   number of MT components.

   VALUE: one or more 2-byte MT components, structured as follows:





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                                       No. of Octets
   +--------------------------------+
   |O |A |M |R |        MT ID       |      2
   +--------------------------------+

   Bit M identifies the originator is of MRT-Capable.  The MRT-Blue and
   the MRT-Red alternates will be calculated for the MT identified by
   MT-ID.

   This M-bit MUST be set and checked in LSP fragment 0.  A MRT-Capable
   router MUST advertise this TLV with M-bit set for corresponding MT.
   For instance, if M-bit is set for MT-ID #0, MRT alternates will be
   calculated for standard topology.

   If only M-bit is advertised for MRT-Capabilities without any other
   MRT information then the router is regarded as supporting default MRT
   profile with default GADAG root selection priority.

6.2.  MRT Profile sub-TLV in IS-IS Router CAPABILITY TLV

   A new MRT Profile sub-TLV is introduced into IS-IS Router CAPABILITY
   TLV[RFC4971] to advertise MRT capabilities.  Since MRT is 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 pictured as
   below:

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

   LENGTH: 8

   VALUE:

   MT ID (2 octet with 4 bits reserved)

   Profile ID (1 octet)

   MRT-Red LDP MT-ID (2 octet)

   MRT-Blue LDP MT-ID (2 octet)












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   +--------------------------------+
   |R |R |R |R |        MT ID       |      2
   +----------------+---------------+
   |   Profile ID   |                      1
   +----------------+
   | GADAG Priority |                      1
   +----------------+---------------+
   |      MRT-Red LDP MT-ID         |      2
   +--------------------------------+
   |      MRT-Blue LDP MT-ID        |      2
   +--------------------------------+

   12-bit MT ID represents the base MT topology which MRT computation is
   based on.  Profile ID represents the MRT profile this router supports
   and GADAG Root Selection Priority is the priority for root selection.
   The range of this priority is [0, 255] with 128 as the default value.
   The GADAG Root Selection Policy defined as part of a given MRT
   profile determine how the GADAG Root Selection Priority value is
   used.

   If the MRT-Blue LDP MT-ID is 0, then the value specified in the
   associated MRT Profile is assumed.  If the MRT-Red LDP MT-ID is 0,
   then the value specified in the associated MRT profile is assumed.
   The MRT-Blue LDP MT-ID and MRT-Red LDP MT-ID MUST NOT be the reserved
   values for LDP MT-IDs ([I-D.ietf-mpls-ldp-multi-topology] ).  The
   value for MRT-Blue LDP MT-ID and MRT-Red LDP MT-ID MUST be different
   except for 0.  As stated above, the MRT-Blue LDP MT-ID and MRT-Red
   LDP MT-ID MUST NOT overlap among profiles if multiple MRT-Profile
   sub-TLVs are advertised.

   This sub-TLV can occur multiple times if this router support multiple
   MRT profiles.  This can happen during transition or to support
   multiple uses of MRT which prefer different profiles.

6.3.  MRT-Ineligible Links sub-TLV in IS-IS Router CAPABILITY TLV

   As a matter of policy, some links may not be available for the MRT
   computation, which can prevent alternates or traffic using these
   links.  For instance, policy can be made to prevent fast-rerouted
   traffic from taking those links.

   For a link to be excluded from the MRT computation, it MUST be
   advertised as sub-TLV in IS-IS Router CAPABILITY TLV which is in
   level scope with S-bit and D-bit unset.  The MRT-Ineligible Link sub-
   TLV is structured as below:

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




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   LENGTH: from 9 to 255 octets

   VALUE:

   MT ID (2 octet with 4 bits reserved)

   System ID and pseudo-node number (7 octet for each MRT-Ineligible
   Link)

                                       No. of Octets
   +--------------------------------+
   |R |R |R |R |        MT ID       |      2
   +--------------------------------+
   |System ID and pseudonode number |      7
   +--------------------------------+
   |         Default metric         |      3
   +--------------------------------+
   .                                .
   .                                .
   +--------------------------------+
   |System ID and pseudonode number |      7
   +--------------------------------+
   |         Default metric         |      3
   +--------------------------------+

   Each MRT-Ineligible Link is identified by neighbor's System ID and
   pseudo-node number and Default metric, same as IS Reachability TLV.
   This sub-TLV MAY occur multiple times if multiple links are
   ineligible.

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

   Section 12.2 of [I-D.ietf-rtgwg-mrt-frr-architecture] describes the
   need to wait for a configured or advertised period after a network
   failure to insure that all routers are using their new SPTs.
   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 [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 IGP MT-ID, allowing a router
   supporting multi-topology IGP routing to advertise a different worst-



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   case compute and install time for each IGP topology.  This make sense
   as the SPF computations for each IGP topology are independent 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 octet with 4 bits reserved)

   FIB compute/install time (1 octet)

   +--------------------------------+
   |R |R |R |R |        MT ID       |      2
   +----------------+---------------+
   |FIB comp/in time|                      1
   +----------------+

   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 in 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, 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.

8.  Handling MRT Capability Sending and Receiving

   The M-bit which identifies router's MRT capability MUST be advertised
   in LSP fragment 0.  Those MRT related sub-TLVs SHOULD be ignored when
   MRT Capability bit is unset.  When changes in MRT capabilities are
   received, a MRT computation SHOULD be triggered but MAY be delayed
   for a while to allow reception of all MRT-related information.



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8.1.  Advertising MRT extension

   MRT sub-TLVs are encapsulated in the Router Capability TLV and
   advertised through LSP PDU for the level-wide.  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, there MUST be an independent
   Router Capability TLV for MRT sub-TLVs.

   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.

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

8.2.  Parsing MRT extension

   MRT extension MUST NOT affect the peer setup and the routing
   calculation of the standard topology.

   MRT sub-TLVs SHOULD be validated like other sub-TLVs when received.
   MRT sub-TLVs SHOULD also be taken for the checksum calculation and
   authentication.

   If MT-ID conflict is found for MRT-Red or MRT-blue from multiple sub-
   TLVs then those associated sub-TLVs MUST be ignored.

   Links advertised in MRT-Ineligible sub-TLV MUST be precluded from MRT
   Computation.  The removal of those links may change the computing
   router's MRT Island significantly.

9.  Backwards Compatibility

   The M-bit for MRT capability, the MRT Profile sub-TLV and the MRT-
   Ineligible Link sub-TLV defined in this document SHOULD NOT introduce
   any interoperability issues.  Routers that do not support these MRT
   extensions SHOULD silently ignore them.  Alternates or traffic MUST
   NOT be affected in current IS-IS routing domain.





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10.  Implementation Status

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

   Please see [I-D.ietf-rtgwg-mrt-frr-architecture] for details on
   implementation status.

11.  Security Considerations

   This IS-IS extension is not believed to introduce new security
   concerns.

12.  IANA Considerations

   Please allocate values for the following IS-IS Router CAPABILITY TLV
   Types [RFC4971]: MRT Profile sub-TLV (TBA-MRT-ISIS-1), MRT-Ineligible
   Link sub-TLV (TBA-MRT-ISIS-2), and Controlled Convergence sub-TLV
   (TBA-MRT-ISIS-3).

13.  References

13.1.  Normative References

   [I-D.ietf-mpls-ldp-multi-topology]
              Zhao, Q., Raza, K., Zhou, C., Fang, L., Li, L., and D.
              King, "LDP Extensions for Multi Topology", draft-ietf-
              mpls-ldp-multi-topology-12 (work in progress), April 2014.

   [I-D.ietf-rtgwg-mrt-frr-algorithm]
              Enyedi, G., Csaszar, A., Atlas, A., Bowers, C., and A.
              Gopalan, "Algorithms for computing Maximally Redundant
              Trees for IP/LDP Fast-Reroute", draft-rtgwg-mrt-frr-
              algorithm-01 (work in progress), July 2014.

   [I-D.ietf-rtgwg-mrt-frr-architecture]
              Atlas, A., Kebler, R., Bowers, C., Enyedi, G., Csaszar,
              A., Tantsura, J., Konstantynowicz, M., and R. White, "An
              Architecture for IP/LDP Fast-Reroute Using Maximally
              Redundant Trees", draft-rtgwg-mrt-frr-architecture-04
              (work in progress), July 2014.

   [RFC3137]  Retana, A., Nguyen, L., White, R., Zinin, A., and D.
              McPherson, "OSPF Stub Router Advertisement", RFC 3137,
              June 2001.

   [RFC3787]  Parker, J., "Recommendations for Interoperable IP Networks
              using Intermediate System to Intermediate System (IS-IS)",
              RFC 3787, May 2004.



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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.

   [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
              dual environments", RFC 1195, December 1990.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4915]  Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
              Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", RFC
              4915, June 2007.

   [RFC4971]  Vasseur, JP., Shen, N., and R. Aggarwal, "Intermediate
              System to Intermediate System (IS-IS) Extensions for
              Advertising Router Information", RFC 4971, July 2007.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120, February 2008.

   [RFC5308]  Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, October
              2008.

   [RFC5715]  Shand, M. and S. Bryant, "A Framework for Loop-Free
              Convergence", RFC 5715, January 2010.

Authors' Addresses

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

   Email: lizhenbin@huawei.com











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

   Email: eric.wu@huawei.com


   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
   Ericsson
   300 Holger Way
   San Jose, CA  95134
   USA

   Email: jeff.tantsura@ericsson.com










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