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rfc:rfc7176

Internet Engineering Task Force (IETF) D. Eastlake 3rd Request for Comments: 7176 Huawei Obsoletes: 6326 T. Senevirathne Category: Standards Track Cisco ISSN: 2070-1721 A. Ghanwani

                                                                  Dell
                                                               D. Dutt
                                                      Cumulus Networks
                                                           A. Banerjee
                                                      Insieme Networks
                                                              May 2014
 Transparent Interconnection of Lots of Links (TRILL) Use of IS-IS

Abstract

 The IETF Transparent Interconnection of Lots of Links (TRILL)
 protocol provides optimal pair-wise data frame forwarding without
 configuration in multi-hop networks with arbitrary topology and link
 technology; it also provides support for multipathing of both unicast
 and multicast traffic.  This document specifies the data formats and
 code points for the IS-IS extensions to support TRILL.  These data
 formats and code points may also be used by technologies other than
 TRILL.  This document obsoletes RFC 6326.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7176.

Eastlake, et al. Standards Track [Page 1] RFC 7176 TRILL Use of IS-IS May 2014

Copyright Notice

 Copyright (c) 2014 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
    1.1. Conventions Used in This Document ..........................4
 2. TLV and Sub-TLV Extensions to IS-IS for TRILL ...................4
    2.1. Group Address TLV ..........................................5
         2.1.1. Group MAC Address Sub-TLV ...........................5
         2.1.2. Group IPv4 Address Sub-TLV ..........................7
         2.1.3. Group IPv6 Address Sub-TLV ..........................8
         2.1.4. Group Labeled MAC Address Sub-TLV ...................9
         2.1.5. Group Labeled IPv4 Address Sub-TLV .................10
         2.1.6. Group Labeled IPv6 Address Sub-TLV .................11
    2.2. Multi-Topology-Aware Port Capability Sub-TLVs .............12
         2.2.1. Special VLANs and Flags Sub-TLV ....................12
         2.2.2. Enabled-VLANs Sub-TLV ..............................13
         2.2.3. Appointed Forwarders Sub-TLV .......................14
         2.2.4. Port TRILL Version Sub-TLV .........................15
         2.2.5. VLANs Appointed Sub-TLV ............................17
    2.3. Sub-TLVs of the Router Capability and MT-Capability TLVs ..17
         2.3.1. TRILL Version Sub-TLV ..............................18
         2.3.2. Nickname Sub-TLV ...................................19
         2.3.3. Trees Sub-TLV ......................................20
         2.3.4. Tree Identifiers Sub-TLV ...........................20
         2.3.5. Trees Used Identifiers Sub-TLV .....................21
         2.3.6. Interested VLANs and Spanning Tree Roots Sub-TLV ...22
         2.3.7. VLAN Group Sub-TLV .................................24
         2.3.8. Interested Labels and Spanning Tree Roots Sub-TLV ..25
         2.3.9. RBridge Channel Protocols Sub-TLV ..................27
         2.3.10. Affinity Sub-TLV ..................................29
         2.3.11. Label Group Sub-TLV ...............................30
    2.4. MTU Sub-TLV for Extended Reachability and MT-ISN TLVs .....31
    2.5. TRILL Neighbor TLV ........................................31
 3. MTU PDUs .......................................................33

Eastlake, et al. Standards Track [Page 2] RFC 7176 TRILL Use of IS-IS May 2014

 4. Use of Existing PDUs and TLVs ..................................35
    4.1. TRILL IIH PDUs ............................................35
    4.2. Area Address ..............................................35
    4.3. Protocols Supported .......................................35
    4.4. Link State PDUs (LSPs) ....................................35
    4.5. Originating LSP Buffer Size ...............................36
 5. IANA Considerations ............................................36
    5.1. TLVs ......................................................36
    5.2. Sub-TLVs ..................................................36
    5.3. PDUs ......................................................38
    5.4. Reserved and Capability Bits ..............................38
    5.5. TRILL Neighbor Record Flags ...............................39
 6. Security Considerations ........................................39
 7. Changes from RFC 6326 ..........................................39
 8. References .....................................................41
    8.1. Normative References ......................................41
    8.2. Informative References ....................................43
 9. Acknowledgements ...............................................44

1. Introduction

 The IETF Transparent Interconnection of Lots of Links (TRILL)
 protocol [RFC6325] [RFC7177] provides transparent forwarding in
 multi-hop networks with arbitrary topology and link technologies
 using a header with a hop count and link-state routing.  TRILL
 provides optimal pair-wise forwarding without configuration, safe
 forwarding even during periods of temporary loops, and support for
 multipathing of both unicast and multicast traffic.  Intermediate
 Systems (ISs) implementing TRILL are called Routing Bridges
 (RBridges) or TRILL Switches.
 This document, in conjunction with [RFC6165], specifies the data
 formats and code points for the IS-IS [ISO-10589] [RFC1195]
 extensions to support TRILL.  These data formats and code points may
 also be used by technologies other than TRILL.
 This document obsoletes [RFC6326], which generally corresponded to
 the base TRILL protocol [RFC6325].  There has been substantial
 development of TRILL since the publication of those documents.  The
 main changes from [RFC6326] are summarized below, and a full list is
 given in Section 7.
 1.  Added multicast group announcements by IPv4 and IPv6 address.
 2.  Added facilities for announcing capabilities supported.
 3.  Added a tree affinity sub-TLV whereby ISs can request
     distribution tree association.

Eastlake, et al. Standards Track [Page 3] RFC 7176 TRILL Use of IS-IS May 2014

 4.  Added multi-topology support.
 5.  Added control-plane support for TRILL Data frame fine-grained
     labels.  This support is independent of the data-plane
     representation.
 6.  Fixed the verified erratum [Err2869] in [RFC6326].
 Changes herein to TLVs and sub-TLVs specified in [RFC6326] are
 backward compatible.

1.1. Conventions Used in This Document

 The terminology and acronyms defined in [RFC6325] are used herein
 with the same meaning.
 Additional acronyms and phrases used in this document are:
    BVL - Bit Vector Length
    BVO - Bit Vector Offset
    IIH - IS-IS Hello
    IS - Intermediate System.  For this document, all relevant
    intermediate systems are RBridges [RFC6325].
    MAC - Media Access Control
    MT - Multi-Topology
    NLPID - Network Layer Protocol Identifier
    SNPA - Subnetwork Point of Attachment (MAC Address)
 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].

2. TLV and Sub-TLV Extensions to IS-IS for TRILL

 This section, in conjunction with [RFC6165], specifies the data
 formats and code points for the TLVs and sub-TLVs for IS-IS to
 support the IETF TRILL protocol.  Information as to the number of
 occurrences allowed, such as for a TLV in a PDU or set of PDUs or for
 a sub-TLV in a TLV, is summarized in Section 5.

Eastlake, et al. Standards Track [Page 4] RFC 7176 TRILL Use of IS-IS May 2014

2.1. Group Address TLV

 The Group Address (GADDR) TLV, IS-IS TLV type 142, is carried in an
 LSP PDU and carries sub-TLVs that in turn advertise multicast group
 listeners.  The sub-TLVs that advertise listeners are specified
 below.  The sub-TLVs under GADDR constitute a new series of sub-TLV
 types (see Section 5.2).
 GADDR has the following format:
 +-+-+-+-+-+-+-+-+
 |Type=GADDR-TLV |                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
 |      sub-TLVs...
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-...
 o  Type: TLV type, set to GADDR-TLV 142.
 o  Length: variable depending on the sub-TLVs carried.
 o  sub-TLVs: The Group Address TLV value consists of sub-TLVs
    formatted as described in [RFC5305].

2.1.1. Group MAC Address Sub-TLV

 The Group MAC Address (GMAC-ADDR) sub-TLV is sub-TLV type number 1
 within the GADDR TLV.  In TRILL, it is used to advertise multicast
 listeners by MAC address as specified in Section 4.5.5 of [RFC6325].
 It has the following format:

Eastlake, et al. Standards Track [Page 5] RFC 7176 TRILL Use of IS-IS May 2014

 +-+-+-+-+-+-+-+-+
 |Type=GMAC-ADDR |                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  RESV |     Topology-ID       |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  RESV |     VLAN ID           |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |Num Group Recs |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   GROUP RECORDS (1)                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   GROUP RECORDS (2)                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   .................                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   GROUP RECORDS (N)                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 where each group record is of the following form with k=6:
 +-+-+-+-+-+-+-+-+
 | Num of Sources|                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Group Address         (k bytes)             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Source 1 Address      (k bytes)             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Source 2 Address      (k bytes)             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                    .....                                      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Source M Address      (k bytes)             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 o  Type: GADDR sub-TLV type, set to 1 (GMAC-ADDR).
 o  Length: 5 + m + k*n = 5 + m + 6*n, where m is the number of group
    records and n is the sum of the number of group and source
    addresses.
 o  RESV: Reserved.  4-bit fields that MUST be sent as zero and
    ignored on receipt.
 o  Topology-ID: This field carries a topology ID [RFC5120] or zero if
    topologies are not in use.

Eastlake, et al. Standards Track [Page 6] RFC 7176 TRILL Use of IS-IS May 2014

 o  VLAN ID: This carries the 12-bit VLAN identifier for all
    subsequent MAC addresses in this sub-TLV, or the value zero if no
    VLAN is specified.
 o  Num Group Recs: A 1-byte unsigned integer that is the number of
    group records in this sub-TLV.
 o  GROUP RECORDS: Each group record carries the number of sources.
    If this field is zero, it indicates a listener for (*,G), that is,
    a listener not restricted by source.  It then has a 6-byte
    (48-bit) multicast MAC address followed by 6-byte source MAC
    addresses.  If the sources do not fit in a single sub-TLV, the
    same group address may be repeated with different source addresses
    in another sub-TLV of another instance of the Group Address TLV.
 The GMAC-ADDR sub-TLV is carried only within a GADDR TLV.

2.1.2. Group IPv4 Address Sub-TLV

 The Group IPv4 Address (GIP-ADDR) sub-TLV is IS-IS sub-TLV type 2
 within the GADDR TLV.  It has the same format as the Group MAC
 Address sub-TLV described in Section 2.1.1 except that k=4.  The
 fields are as follows:
 o  Type: sub-TLV type, set to 2 (GIP-ADDR).
 o  Length: 5 + m + k*n = 5 + m + 4*n, where m is the number of group
    records and n is the sum of the number of group and source
    addresses.
 o  Topology-ID: This field carries a topology ID [RFC5120] or zero if
    topologies are not in use.
 o  RESV: Must be sent as zero on transmission and is ignored on
    receipt.
 o  VLAN ID: This carries a 12-bit VLAN identifier that is valid for
    all subsequent addresses in this sub-TLV, or the value zero if no
    VLAN is specified.
 o  Num Group Recs: A 1-byte unsigned integer that is the number of
    group records in this sub-TLV.

Eastlake, et al. Standards Track [Page 7] RFC 7176 TRILL Use of IS-IS May 2014

 o  GROUP RECORDS: Each group record carries the number of sources.
    If this field is zero, it indicates a listener for (*,G), that is,
    a listener not restricted by source.  It then has a 4-byte
    (32-bit) IPv4 Group Address followed by 4-byte source IPv4
    addresses.  If the number of sources do not fit in a single sub-
    TLV, it is permitted to have the same group address repeated with
    different source addresses in another sub-TLV of another instance
    of the Group Address TLV.
 The GIP-ADDR sub-TLV is carried only within a GADDR TLV.

2.1.3. Group IPv6 Address Sub-TLV

 The Group IPv6 Address (GIPV6-ADDR) sub-TLV is IS-IS sub-TLV type 3
 within the GADDR TLV.  It has the same format as the Group MAC
 Address sub-TLV described in Section 2.1.1 except that k=16.  The
 fields are as follows:
 o  Type: sub-TLV type, set to 3 (GIPV6-ADDR).
 o  Length: 5 + m + k*n = 5 + m + 16*n, where m is the number of group
    records and n is the sum of the number of group and source
    addresses.
 o  Topology-Id: This field carries a topology ID [RFC5120] or zero if
    topologies are not in use.
 o  RESV: Must be sent as zero on transmission and is ignored on
    receipt.
 o  VLAN ID: This carries a 12-bit VLAN identifier that is valid for
    all subsequent addresses in this sub-TLV, or the value zero if no
    VLAN is specified.
 o  Num Group Recs: A 1-byte unsigned integer that is the number of
    group records in this sub-TLV.
 o  GROUP RECORDS: Each group record carries the number of sources.
    If this field is zero, it indicates a listener for (*,G), that is,
    a listener not restricted by source.  It then has a 16-byte
    (128-bit) IPv6 Group Address followed by 16-byte source IPv6
    addresses.  If the number of sources do not fit in a single sub-
    TLV, it is permitted to have the same group address repeated with
    different source addresses in another sub-TLV of another instance
    of the Group Address TLV.
 The GIPV6-ADDR sub-TLV is carried only within a GADDR TLV.

Eastlake, et al. Standards Track [Page 8] RFC 7176 TRILL Use of IS-IS May 2014

2.1.4. Group Labeled MAC Address Sub-TLV

 The GMAC-ADDR sub-TLV of the Group Address (GADDR) TLV specified in
 Section 2.1.1 provides for a VLAN ID.  The Group Labeled MAC Address
 sub-TLV, below, extends this to a fine-grained label.
 +-+-+-+-+-+-+-+-+
 |Type=GLMAC-ADDR|                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  RESV |     Topology-ID       |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |        Fine-Grained Label                     | (3 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |Num Group Recs |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   GROUP RECORDS (1)                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   GROUP RECORDS (2)                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   .................                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   GROUP RECORDS (N)                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 where each group record is of the following form with k=6:
 +-+-+-+-+-+-+-+-+
 | Num of Sources|                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Group Address         (k bytes)             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Source 1 Address      (k bytes)             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Source 2 Address      (k bytes)             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                    .....                                      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   Source M Address      (k bytes)             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 o  Type: GADDR sub-TLV type, set to 4 (GLMAC-ADDR).
 o  Length: 6 + m + k*n = 6 + m + 6*n, where m is the number of group
    records and n is the sum of the number of group and source
    addresses.

Eastlake, et al. Standards Track [Page 9] RFC 7176 TRILL Use of IS-IS May 2014

 o  RESV: Reserved.  4-bit field that MUST be sent as zero and ignored
    on receipt.
 o  Topology-ID: This field carries a topology ID [RFC5120] or zero if
    topologies are not in use.
 o  Label: This carries the fine-grained label [RFC7172] identifier
    for all subsequent MAC addresses in this sub-TLV, or the value
    zero if no label is specified.
 o  Num Group Recs: A 1-byte unsigned integer that is the number of
    group records in this sub-TLV.
 o  GROUP RECORDS: Each group record carries the number of sources.
    If this field is zero, it indicates a listener for (*,G), that is,
    a listener not restricted by source.  It then has a 6-byte
    (48-bit) multicast address followed by 6-byte source MAC
    addresses.  If the sources do not fit in a single sub-TLV, the
    same group address may be repeated with different source addresses
    in another sub-TLV of another instance of the Group Address TLV.
 The GLMAC-ADDR sub-TLV is carried only within a GADDR TLV.

2.1.5. Group Labeled IPv4 Address Sub-TLV

 The Group Labeled IPv4 Address (GLIP-ADDR) sub-TLV is IS-IS sub-TLV
 type 5 within the GADDR TLV.  It has the same format as the Group
 Labeled MAC Address sub-TLV described in Section 2.1.4 except that
 k=4.  The fields are as follows:
 o  Type: sub-TLV type, set to 5 (GLIP-ADDR).
 o  Length: 6 + m + k*n = 6 + m + 4*n, where m is the number of group
    records and n is the sum of the number of group and source
    addresses.
 o  Topology-ID: This field carries a topology ID [RFC5120] or zero if
    topologies are not in use.
 o  RESV: Must be sent as zero on transmission and is ignored on
    receipt.
 o  Label: This carries the fine-grained label [RFC7172] identifier
    for all subsequent IPv4 addresses in this sub-TLV, or the value
    zero if no label is specified.
 o  Num Group Recs: A 1-byte unsigned integer that is the number of
    group records in this sub-TLV.

Eastlake, et al. Standards Track [Page 10] RFC 7176 TRILL Use of IS-IS May 2014

 o  GROUP RECORDS: Each group record carries the number of sources.
    If this field is zero, it indicates a listener for (*,G), that is,
    a listener not restricted by source.  It then has a 4-byte
    (32-bit) IPv4 Group Address followed by 4-byte source IPv4
    addresses.  If the number of sources do not fit in a single sub-
    TLV, it is permitted to have the same group address repeated with
    different source addresses in another sub-TLV of another instance
    of the Group Address TLV.
 The GLIP-ADDR sub-TLV is carried only within a GADDR TLV.

2.1.6. Group Labeled IPv6 Address Sub-TLV

 The Group Labeled IPv6 Address (GLIPV6-ADDR) sub-TLV is IS-IS sub-TLV
 type 6 within the GADDR TLV.  It has the same format as the Group
 Labeled MAC Address sub-TLV described in Section 2.1.4 except that
 k=16.  The fields are as follows:
 o  Type: sub-TLV type, set to 6 (GLIPV6-ADDR).
 o  Length: 6 + m + k*n = 6 + m + 16*n, where m is the number of group
    records and n is the sum of the number of group and source
    addresses.
 o  Topology-Id: This field carries a topology ID [RFC5120] or zero if
    topologies are not in use.
 o  RESV: Must be sent as zero on transmission and is ignored on
    receipt.
 o  Label: This carries the fine-grained label [RFC7172] identifier
    for all subsequent IPv6 addresses in this sub-TLV, or the value
    zero if no label is specified.
 o  Num Group Recs: A 1-byte unsigned integer that is the number of
    group records in this sub-TLV.
 o  GROUP RECORDS: Each group record carries the number of sources.
    If this field is zero, it indicates a listener for (*,G), that is,
    a listener not restricted by source.  It then has a 16-byte
    (128-bit) IPv6 Group Address followed by 16-byte source IPv6
    addresses.  If the number of sources do not fit in a single sub-
    TLV, it is permitted to have the same group address repeated with
    different source addresses in another sub-TLV of another instance
    of the Group Address TLV.
 The GLIPV6-ADDR sub-TLV is carried only within a GADDR TLV.

Eastlake, et al. Standards Track [Page 11] RFC 7176 TRILL Use of IS-IS May 2014

2.2. Multi-Topology-Aware Port Capability Sub-TLVs

 TRILL makes use of the Multi-Topology-Aware Port Capability TLV (MT-
 Port-Cap-TLV) as specified in [RFC6165].  The following subsections
 specify the sub-TLVs transported by the MT-Port-Cap-TLV for TRILL.

2.2.1. Special VLANs and Flags Sub-TLV

 In TRILL, a Special VLANs and Flags (VLAN-FLAGS) sub-TLV is carried
 in every IIH PDU.  It has the following format:
 +--+--+--+--+--+--+--+--+
 |    Type               |                         (1 byte)
 +--+--+--+--+--+--+--+--+
 |    Length             |                         (1 byte)
 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 |    Port ID                                    | (2 bytes)
 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 |    Sender Nickname                            | (2 bytes)
 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 |AF|AC|VM|BY|     Outer.VLAN                    | (2 bytes)
 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 |TR|R |R |R |     Designated-VLAN               | (2 bytes)
 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 o  Type: sub-TLV type, set to MT-Port-Cap-TLV VLAN-FLAGS sub-TLV 1.
 o  Length: 8.
 o  Port ID: An ID for the port on which the enclosing TRILL IIH PDU
    is being sent as specified in [RFC6325], Section 4.4.2.
 o  Sender Nickname: If the sending IS is holding any nicknames as
    discussed in [RFC6325], Section 3.7, one MUST be included here.
    Otherwise, the field is set to zero.  This field is to support
    intelligent end stations that determine the egress IS (RBridge)
    for unicast data through a directory service or the like and that
    need a nickname for their first hop to insert as the ingress
    nickname to correctly format a TRILL Data frame (see [RFC6325],
    Section 4.6.2, point 8).  It is also referenced in connection with
    the VLANs Appointed Sub-TLV (see Section 2.2.5) and can be used as
    the egress on one-hop RBridge Channel messages [RFC7178], for
    example, those use for BFD over TRILL [RFC7175].
 o  Outer.VLAN: A copy of the 12-bit outer VLAN ID of the TRILL IIH
    frame containing this sub-TLV, as specified in [RFC6325], Section
    4.4.5.

Eastlake, et al. Standards Track [Page 12] RFC 7176 TRILL Use of IS-IS May 2014

 o  Designated-VLAN: The 12-bit ID of the Designated VLAN for the
    link, as specified in [RFC6325], Section 4.2.4.2.
 o  AF, AC, VM, BY, and TR: These flag bits have the following
    meanings when set to one, as specified in the listed section of
    [RFC6325]:
         RFC 6325
    Bit  Section   Meaning if bit is one
    --------------------------------------
    AF   4.4.2     Originating IS believes it is Appointed
                   Forwarder for the VLAN and port on which the
                   containing IIH PDU was sent.
    AC   4.9.1     Originating port configured as an access port
                   (TRILL traffic disabled).
    VM   4.4.5     VLAN mapping detected on this link.
    BY   4.4.2     Bypass pseudonode.
    TR   4.9.1     Originating port configured as a trunk port
                   (end-station service disabled).
 o  R: Reserved bit.  MUST be sent as zero and ignored on receipt.

2.2.2. Enabled-VLANs Sub-TLV

 The optional Enabled-VLANs sub-TLV specifies the VLANs enabled at the
 port of the originating IS on which the containing Hello was sent, as
 specified in [RFC6325], Section 4.4.2.  It has the following format:
 +-+-+-+-+-+-+-+-+
 |     Type      |                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | RESV  |  Start VLAN ID        |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | VLAN bit-map....
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 o  Type: sub-TLV type, set to MT-Port-Cap-TLV Enabled-VLANs sub-TLV
    2.
 o  Length: Variable, minimum 3.

Eastlake, et al. Standards Track [Page 13] RFC 7176 TRILL Use of IS-IS May 2014

 o  RESV: 4 reserved bits that MUST be sent as zero and ignored on
    receipt.
 o  Start VLAN ID: The 12-bit VLAN ID that is represented by the high-
    order bit of the first byte of the VLAN bit-map.
 o  VLAN bit-map: The highest-order bit indicates the VLAN equal to
    the start VLAN ID, the next highest bit indicates the VLAN equal
    to start VLAN ID + 1, continuing to the end of the VLAN bit-map
    field.
 If this sub-TLV occurs more than once in a Hello, the set of enabled
 VLANs is the union of the sets of VLANs indicated by each of the
 Enabled-VLAN sub-TLVs in the Hello.

2.2.3. Appointed Forwarders Sub-TLV

 The Designated RBridge (DRB) on a link uses the Appointed Forwarders
 sub-TLV to inform other ISs on the link that they are the designated
 VLAN-x forwarder for one or more ranges of VLAN IDs as specified in
 [RFC6439].  It has the following format:
 +-+-+-+-+-+-+-+-+
 |     Type      |                          (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                          (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   Appointment Information (1)         |  (6 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   Appointment Information (2)         |  (6 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   .................                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   Appointment Information (N)         |  (6 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 where each appointment is of the form:
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |       Appointee Nickname              |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | RESV  |        Start.VLAN             |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | RESV  |        End.VLAN               |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Eastlake, et al. Standards Track [Page 14] RFC 7176 TRILL Use of IS-IS May 2014

 o  Type: sub-TLV type, set to MT-Port-Cap-TLV AppointedFwrdrs sub-TLV
    3.
 o  Length: 6*n bytes, where there are n appointments.
 o  Appointee Nickname: The nickname of the IS being appointed a
    forwarder.
 o  RESV: 4 bits that MUST be sent as zero and ignored on receipt.
 o  Start.VLAN, End.VLAN: This VLAN ID range is inclusive.  Setting
    both Start.VLAN and VLAN.end to the same value indicates a range
    of one VLAN ID.  If Start.VLAN is not equal to VLAN.end and
    Start.VLAN is 0x000, the sub-TLV is interpreted as if Start.VLAN
    was 0x001.  If Start.VLAN is not equal to VLAN.end and VLAN.end is
    0xFFF, the sub-TLV is interpreted as if VLAN.end was 0xFFE.  If
    VLAN.end is less than Start.VLAN, the sub-TLV is ignored.  If both
    Start.VLAN and VLAN.end are 0x000 or both are 0xFFF, the sub-TLV
    is ignored.  The values 0x000 or 0xFFF are not valid VLAN IDs, and
    a port cannot be enabled for them.
 An IS's nickname may occur as Appointed Forwarder for multiple VLAN
 ranges by occurrences of this sub-TLV within the same or different MT
 Port Capability TLVs within an IIH PDU.  See [RFC6439].

2.2.4. Port TRILL Version Sub-TLV

 The Port TRILL Version (PORT-TRILL-VER) sub-TLV indicates the maximum
 version of the TRILL standard supported and the support of optional
 hop-by-hop capabilities.  By implication, lower versions are also
 supported.  If this sub-TLV is missing from an IIH, it is assumed
 that the originating IS only supports the base version (version zero)
 of the protocol [RFC6325] and supports no optional capabilities
 indicated by this sub-TLV.
 +-+-+-+-+-+-+-+-+
 | Type          |              (1 byte)
 +-+-+-+-+-+-+-+-+
 | Length        |              (1 byte)
 +-+-+-+-+-+-+-+-+
 | Max-version   |              (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
 | Capabilities and Header Flags Supported |  (4 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+
  0                   1                 3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7   0 1

Eastlake, et al. Standards Track [Page 15] RFC 7176 TRILL Use of IS-IS May 2014

 o  Type: MT-Port-Cap-TLV sub-TLV type, set to 7 (PORT-TRILL-VER).
 o  Length: 5.
 o  Max-version: A one-byte unsigned integer set to the maximum
    version supported.
 o  Capabilities and Header Flags Supported: A bit vector of 32 bits
    numbered 0 through 31 in network order.  Bits 3 through 13
    indicate that the corresponding TRILL Header hop-by-hop extended
    flags [RFC7179] are supported.  Bits 0 through 2 and 14 to 31 are
    reserved to indicate support of optional capabilities.  A one bit
    indicates that the flag or capability is supported by the sending
    IS.  Bits in this field MUST be set to zero except as permitted
    for a capability being advertised or if a hop-by-hop extended
    header flag is supported.
 This sub-TLV, if present, MUST occur in an MT-Port-Cap-TLV in a TRILL
 IIH.  If there is more than one occurrence, the minimum of the
 supported versions is assumed to be correct and a capability or
 header flag is assumed to be supported only if indicated by all
 occurrences.  The flags and capabilities for which support can be
 indicated in this sub-TLV are disjoint from those in the TRILL-VER
 sub-TLV (Section 2.3.1) so they cannot conflict.  The flags and
 capabilities indicated in this sub-TLV relate to hop-by-hop
 processing that can differ between the ports of an IS (RBridge) and
 thus must be advertised in IIHs.  For example, a capability requiring
 cryptographic hardware assist might be supported on some ports and
 not others.  However, the TRILL version is the same as that in the
 PORT-TRILL-VER sub-TLV.  An IS, if it is adjacent to the sending IS
 of TRILL version sub-TLV(s), uses the TRILL version it received in
 PORT-TRILL-VER sub-TLV(s) in preference to that received in TRILL-VER
 sub-TLV(s).

Eastlake, et al. Standards Track [Page 16] RFC 7176 TRILL Use of IS-IS May 2014

2.2.5. VLANs Appointed Sub-TLV

 The optional VLANs Appointed sub-TLV specifies, for the port of the
 originating IS on which the containing Hello was sent, the VLANs for
 which it is Appointed Forwarder.  This sub-TLV has the following
 format:
 +-+-+-+-+-+-+-+-+
 |     Type      |                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | RESV  |  Start VLAN ID        |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | VLAN bit-map....
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 o  Type: sub-TLV type, set to MT-Port-Cap-TLV VLANS-Appointed sub-TLV
    8.
 o  Length: Variable, minimum 3.
 o  RESV: 4 reserved bits that MUST be sent as zero and ignored on
    receipt.
 o  Start VLAN ID: The 12-bit VLAN ID that is represented by the high-
    order bit of the first byte of the VLAN bit-map.
 o  VLAN bit-map: The highest-order bit indicates the VLAN equal to
    the start VLAN ID, the next highest bit indicates the VLAN equal
    to start VLAN ID + 1, continuing to the end of the VLAN bit-map
    field.
 If this sub-TLV occurs more than once in a Hello, the originating IS
 is declaring that it believes itself to be Appointed Forwarder on the
 port on which the enclosing IIH was sent for the union of the sets of
 VLANs indicated by each of the VLANs-Appointed sub-TLVs in the Hello.

2.3. Sub-TLVs of the Router Capability and MT-Capability TLVs

 The Router Capability TLV is specified in [RFC4971] and the MT-
 Capability TLV in [RFC6329].  All of the following sub-sections
 specify sub-TLVs that can be carried in the Router Capability TLV
 (#242) and the MT-Capability TLV (#144) with the same sub-TLV number
 for both TLVs.  These TLVs are in turn carried only by LSPs.

Eastlake, et al. Standards Track [Page 17] RFC 7176 TRILL Use of IS-IS May 2014

2.3.1. TRILL Version Sub-TLV

 The TRILL Version (TRILL-VER) sub-TLV indicates the maximum version
 of the TRILL standard supported and the support of optional
 capabilities by the originating IS.  By implication, lower versions
 are also supported.  If this sub-TLV is missing, it is assumed that
 the originating IS only supports the base version (version zero) of
 the protocol [RFC6325], and no optional capabilities indicated by
 this sub-TLV are supported.
 +-+-+-+-+-+-+-+-+
 | Type          |              (1 byte)
 +-+-+-+-+-+-+-+-+
 | Length        |              (1 byte)
 +-+-+-+-+-+-+-+-+
 | Max-version   |              (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+
 | Capabilities and Header Flags Supported |  (4 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+
  0                   1                 3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7   0 1
 o  Type: Router Capability sub-TLV type, set to 13 (TRILL-VER).
 o  Length: 5.
 o  Max-version: A one-byte unsigned integer set to the maximum
    version supported.
 o  Capabilities and Header Flags Supported: A bit vector of 32 bits
    numbered 0 through 31 in network order.  Bits 14 through 31
    indicate that the corresponding TRILL Header extended flags
    [RFC7179] are supported.  Bits 0 through 13 are reserved to
    indicate support of optional capabilities.  A one bit indicates
    that the originating IS supports the flag or capability.  For
    example, support of multi-level TRILL IS-IS [MultiLevel].  Bits in
    this field MUST be set to zero except as permitted for a
    capability being advertised or an extended header flag supported.
 This sub-TLV, if present in a Router Capability TLV, MUST occur in
 the LSP number zero for the originating IS.  If found in a Router
 Capability TLV in other fragments, it is ignored.  If there is more
 than one occurrence in LSP number zero, the minimum of the supported
 versions is assumed to be correct, and an extended header flag or
 capability is assumed to be supported only if indicated by all
 occurrences.  The flags and capabilities for which support can be
 indicated in this sub-TLV are disjoint from those in the PORT-TRILL-
 VER sub-TLV (Section 2.2.4) so they cannot conflict.  However, the

Eastlake, et al. Standards Track [Page 18] RFC 7176 TRILL Use of IS-IS May 2014

 TRILL version is the same as that in the PORT-TRILL-VER sub-TLV, and
 an IS that is adjacent to the originating IS of TRILL-VER sub-TLV(s)
 uses the TRILL version it received in PORT-TRILL-VER sub-TLV(s) in
 preference to that received in TRILL-VER sub-TLV(s).
 For multi-topology-aware TRILL Switches, the TRILL version and
 capabilities announced for the base topology are assumed to apply to
 all topologies for which a separate TRILL version announcement does
 not occur in an MT-Capability TLV.  Such announcements for non-zero
 topologies need not occur in fragment zero.

2.3.2. Nickname Sub-TLV

 The Nickname (NICKNAME) Router Capability sub-TLV carries information
 about the nicknames of the originating IS, along with information
 about its priority to hold those nicknames and the priority for each
 nickname to be a tree root as specified in [RFC6325], Section 3.7.3.
 Multiple instances of this sub-TLV may occur.
 +-+-+-+-+-+-+-+-+
 |Type = NICKNAME|                         (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                         (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                NICKNAME RECORDS (1)                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                NICKNAME RECORDS (2)                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   .................                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                NICKNAME RECORDS (N)                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 where each nickname record is of the form:
 +-+-+-+-+-+-+-+-+
 | Nickname.Pri  |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |     Tree Root Priority        |  (2 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |           Nickname            |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 o  Type: Router Capability and MT-Capability sub-TLV type, set to 6
    (NICKNAME).
 o  Length: 5*n, where n is the number of nickname records present.

Eastlake, et al. Standards Track [Page 19] RFC 7176 TRILL Use of IS-IS May 2014

 o  Nickname.Pri: An 8-bit unsigned integer priority to hold a
    nickname as specified in Section 3.7.3 of [RFC6325].
 o  Tree Root Priority: This is an unsigned 16-bit integer priority to
    be a tree root as specified in Section 4.5 of [RFC6325].
 o  Nickname: This is an unsigned 16-bit integer as specified in
    Section 3.7 of [RFC6325].

2.3.3. Trees Sub-TLV

 Each IS providing TRILL service uses the TREES sub-TLV to announce
 three numbers related to the computation of distribution trees as
 specified in Section 4.5 of [RFC6325].  Its format is as follows:
 +-+-+-+-+-+-+-+-+
 |Type =  TREES  |                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |  Length       |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Number of trees to compute    |  (2 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Maximum trees able to compute |  (2 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Number of trees to use        |  (2 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 o  Type: Router Capability and MT-Capability sub-TLV type, set to 7
    (TREES).
 o  Length: 6.
 o  Number of trees to compute: An unsigned 16-bit integer as
    specified in Section 4.5 of [RFC6325].
 o  Maximum trees able to compute: An unsigned 16-bit integer as
    specified in Section 4.5 of [RFC6325].
 o  Number of trees to use: An unsigned 16-bit integer as specified in
    Section 4.5 of [RFC6325].

2.3.4. Tree Identifiers Sub-TLV

 The Tree Identifiers (TREE-RT-IDs) sub-TLV is an ordered list of
 nicknames.  When originated by the IS that has the highest priority
 to be a tree root, it lists the distribution trees that the other ISs
 are required to compute as specified in Section 4.5 of [RFC6325].  If

Eastlake, et al. Standards Track [Page 20] RFC 7176 TRILL Use of IS-IS May 2014

 this information is spread across multiple sub-TLVs, the starting
 tree number is used to allow the ordered lists to be correctly
 concatenated.  The sub-TLV format is as follows:
 +-+-+-+-+-+-+-+-+
 |Type=TREE-RT-IDs|               (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |Starting Tree Number         |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   Nickname (K-th root)      |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   Nickname (K+1 - th root)  |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   Nickname (...)            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 o  Type: Router Capability and MT-Capability sub-TLV type, set to 8
    (TREE-RT-IDs).
 o  Length: 2 + 2*n, where n is the number of nicknames listed.
 o  Starting Tree Number: This identifies the starting tree number of
    the nicknames that are trees for the domain.  This is set to 1 for
    the sub-TLV containing the first list.  Other Tree-Identifiers
    sub-TLVs will have the number of the starting list they contain.
    In the event the same tree identifier can be computed from two
    such sub-TLVs and they are different, then it is assumed that this
    is a transient condition that will get cleared.  During this
    transient time, such a tree SHOULD NOT be computed unless such
    computation is indicated by all relevant sub-TLVs present.
 o  Nickname: The nickname at which a distribution tree is rooted.

2.3.5. Trees Used Identifiers Sub-TLV

 This Router Capability sub-TLV has the same structure as the Tree
 Identifiers sub-TLV specified in Section 2.3.4.  The only difference
 is that its sub-TLV type is set to 9 (TREE-USE-IDs), and the trees
 listed are those that the originating IS wishes to use as specified
 in [RFC6325], Section 4.5.

Eastlake, et al. Standards Track [Page 21] RFC 7176 TRILL Use of IS-IS May 2014

2.3.6. Interested VLANs and Spanning Tree Roots Sub-TLV

 The value of this sub-TLV consists of a VLAN range and information in
 common to all of the VLANs in the range for the originating IS.  This
 information consists of flags, a variable length list of spanning
 tree root bridge IDs, and an Appointed Forwarder status lost counter,
 all as specified in the sections of [RFC6325] listed with the
 respective information items below.
 In the set of LSPs originated by an IS, the union of the VLAN ranges
 in all occurrences of this sub-TLV MUST be the set of VLANs for which
 the originating IS is Appointed Forwarder on at least one port, and
 the VLAN ranges in multiple VLANs sub-TLVs for an IS MUST NOT overlap
 unless the information provided about a VLAN is the same in every
 instance.  However, as a transient state, these conditions may be
 violated.  If a VLAN is not listed in any INT-VLAN sub-TLV for an IS,
 that IS is assumed to be uninterested in receiving traffic for that
 VLAN.  If a VLAN appears in more than one INT-VLAN sub-TLV for an IS
 with different information in the different instances, the following
 apply:
  1. If those sub-TLVs provide different nicknames, it is unspecified

which nickname takes precedence.

  1. The largest Appointed Forwarder status lost counter, using serial

number arithmetic [RFC1982], is used.

  1. The originating IS is assumed to be attached to a multicast IPv4

router for that VLAN if any of the INT-VLAN sub-TLVs assert that

    it is so connected and similarly for IPv6 multicast router
    attachment.
 -  The root bridge lists from all of the instances of the VLAN for
    the originating IS are merged.
 To minimize such occurrences, wherever possible, an implementation
 SHOULD advertise the update to an interested VLAN and Spanning Tree
 Roots sub-TLV in the same LSP fragment as the advertisement that it
 replaces.  Where this is not possible, the two affected LSP fragments
 should be flooded as an atomic action.  An IS that receives an update
 to an existing interested VLAN and Spanning Tree Roots sub-TLV can
 minimize the potential disruption associated with the update by
 employing a hold-down timer prior to processing the update so as to
 allow for the receipt of multiple LSP fragments associated with the
 same update prior to beginning processing.

Eastlake, et al. Standards Track [Page 22] RFC 7176 TRILL Use of IS-IS May 2014

 The sub-TLV layout is as follows:
 +-+-+-+-+-+-+-+-+
 |Type = INT-VLAN|                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   Nickname                    |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+
 |   Interested VLANS                            |        (4 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+
 |   Appointed Forwarder Status Lost Counter     |        (4 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+
 |         Root Bridges                                |  (6*n bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
 o  Type: Router Capability and MT-Capability sub-TLV type, set to 10
    (INT-VLAN).
 o  Length: 10 + 6*n, where n is the number of root bridge IDs.
 o  Nickname: As specified in [RFC6325], Section 4.2.4.4, this field
    may be used to associate a nickname held by the originating IS
    with the VLAN range indicated.  When not used in this way, it is
    set to zero.
 o  Interested VLANS: The Interested VLANs field is formatted as shown
    below.
      0    1    2    3     4 - 15      16 - 19     20 - 31
    +----+----+----+----+------------+----------+------------+
    | M4 | M6 |  R |  R | VLAN.start |   RESV   |  VLAN.end  |
    +----+----+----+----+------------+----------+------------+
  1. M4, M6: These bits indicate, respectively, that there is an

IPv4 or IPv6 multicast router on a link for which the

       originating IS is Appointed Forwarder for every VLAN in the
       indicated range as specified in [RFC6325], Section 4.2.4.4,
       item 5.1.
  1. R, RESV: These reserved bits MUST be sent as zero and are

ignored on receipt.

  1. VLAN.start and VLAN.end: This VLAN ID range is inclusive.

Setting both VLAN.start and VLAN.end to the same value

       indicates a range of one VLAN ID.  If VLAN.start is not equal
       to VLAN.end and VLAN.start is 0x000, the sub-TLV is interpreted
       as if VLAN.start was 0x001.  If VLAN.start is not equal to

Eastlake, et al. Standards Track [Page 23] RFC 7176 TRILL Use of IS-IS May 2014

       VLAN.end and VLAN.end is 0xFFF, the sub-TLV is interpreted as
       if VLAN.end was 0xFFE.  If VLAN.end is less than VLAN.start,
       the sub-TLV is ignored.  If both VLAN.start and VLAN.end are
       0x000 or both are 0xFFF, the sub-TLV is ignored.  The values
       0x000 or 0xFFF are not valid VLAN IDs, and a port cannot be
       enabled for them.
 o  Appointed Forwarder Status Lost Counter: This is a count of how
    many times a port that was Appointed Forwarder for the VLANs in
    the range given has lost the status of being an Appointed
    Forwarder for some port as discussed in Section 4.8.3 of
    [RFC6325].  It is initialized to zero at an IS when the zeroth LSP
    sequence number is initialized.  No special action need be taken
    at rollover; the counter just wraps around.
 o  Root Bridges: The list of zero or more spanning tree root bridge
    IDs is the set of root bridge IDs seen for all ports for which the
    IS is Appointed Forwarder for the VLANs in the specified range as
    discussed in [RFC6325], Section 4.9.3.2.  While, of course, at
    most one spanning tree root could be seen on any particular port,
    there may be multiple ports in the same VLANs connected to
    different bridged LANs with different spanning tree roots.
 An INT-VLAN sub-TLV asserts that the information provided (multicast
 router attachment, Appointed Forwarder status lost counter, and root
 bridges) is the same for all VLANs in the range specified.  If this
 is not the case, the range MUST be split into subranges meeting this
 criteria.  It is always safe to use sub-TLVs with a "range" of one
 VLAN ID, but this may be too verbose.

2.3.7. VLAN Group Sub-TLV

 The VLAN Group sub-TLV consists of two or more VLAN IDs as specified
 in [RFC6325], Section 4.8.4.  This sub-TLV indicates that shared VLAN
 learning is occurring at the originating IS between the listed VLANs.
 It is structured as follows:
 +-+-+-+-+-+-+-+-+
 |Type=VLAN-GROUP|                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | RESV  |  Primary VLAN ID      |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | RESV  |  Secondary VLAN ID    |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  more Secondary VLAN IDs ...     (2 bytes each)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Eastlake, et al. Standards Track [Page 24] RFC 7176 TRILL Use of IS-IS May 2014

 o  Type: Router Capability and MT-Capability sub-TLV type, set to 14
    (VLAN-GROUP).
 o  Length: 4 + 2*n, where n is the number of secondary VLAN ID fields
    beyond the first.  n MAY be zero.
 o  RESV: a 4-bit field that MUST be sent as zero and ignored on
    receipt.
 o  Primary VLAN ID: This identifies the primary VLAN ID.
 o  Secondary VLAN ID: This identifies a secondary VLAN in the VLAN
    Group.
 o  more Secondary VLAN IDs: zero or more byte pairs, each with the
    top 4 bits as a RESV field and the low 12 bits as a VLAN ID.

2.3.8. Interested Labels and Spanning Tree Roots Sub-TLV

 An IS that can handle fine-grained labeling [RFC7172] announces its
 fine-grained label connectivity and related information in the
 Interested Labels and Spanning Tree Roots sub-TLV (INT-LABEL).  It is
 a variation of the Interested VLANs and Spanning Tree Roots sub-TLV
 (INT-VLAN) and is structured as follows.
 +-+-+-+-+-+-+-+-+
 |Type=INT-LABEL |                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   Nickname                    |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+
 |   Interested Labels                                 |  (7 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+
 |   Appointed Forwarder Status Lost Counter           |  (4 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
 |         Root Bridges                                |  (6*n bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
 o  Type: Router Capability and MT-Capability sub-TLV type, set to 15
    (INT-LABEL).
 o  Length: 11 + 6*n, where n is the number of root bridge IDs.
 o  Nickname: This field may be used to associate a nickname held by
    the originating IS with the Interested Labels indicated.  When not
    used in this way, it is set to zero.

Eastlake, et al. Standards Track [Page 25] RFC 7176 TRILL Use of IS-IS May 2014

 o  Interested Labels: The Interested Labels field is seven bytes long
    and formatted as shown below.
      0  1  2  3  4  5  6  7
    +--+--+--+--+--+--+--+--+
    |M4|M6|BM| R| R| R| R| R|               .               .
    +--+--+--+--+--+--+--+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Label.start - 24 bits                  |
    +--+--+--+--+--+--+--+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Label.end or bit-map - 24 bits              |
    +--+--+--+--+--+--+--+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      0                          1                   2
      0  1  2  3  4  5  6  7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
  1. M4, M6: These bits indicate, respectively, that there is an

IPv4 or IPv6 multicast router on a link to which the

       originating IS is Appointed Forwarder for the VLAN
       corresponding to every label in the indicated range.
  1. BM: If the BM (bit-map) bit is zero, the last three bytes of

the Interested Labels is a Label.end label number. If the BM

       bit is one, those bytes are a bit-map as described below.
  1. R: These reserved bits MUST be sent as zero and are ignored on

receipt.

  1. Label.start and Label.end: If the BM bit is zero, this fine-

grained label [RFC7172] ID range is inclusive. These fields

       are treated as unsigned integers.  Setting them both to the
       same label ID value indicates a range of one label ID.  If
       Label.end is less than Label.start, the sub-TLV is ignored.
  1. Label.start and bit-map: If the BM bit is one, the fine-grained

labels that the IS is interested in are indicated by a 24-bit

       bit-map.  The interested labels are the Label.start number plus
       the bit number of each one bit in the bit-map.  So, if bit zero
       of the bit-map is a one, the IS is interested in the label with
       value Label.start, and if bit 23 of the bit-map is a one, the
       IS is interested in the label with value Label.start+23.
 o  Appointed Forwarder Status Lost Counter: This is a count of how
    many times a port that was Appointed Forwarder for a VLAN mapping
    to the fine-grained label in the range or bit-map given has lost
    the status of being an Appointed Forwarder as discussed in Section
    4.8.3 of [RFC6325].  It is initialized to zero at an IS when the
    zeroth LSP sequence number is initialized.  No special action need
    be taken at rollover; the counter just wraps around.

Eastlake, et al. Standards Track [Page 26] RFC 7176 TRILL Use of IS-IS May 2014

 o  Root Bridges: The list of zero or more spanning tree root bridge
    IDs is the set of root bridge IDs seen for all ports for which the
    IS is Appointed Forwarder for a VLAN mapping to the fine-grained
    label in the specified range or bit-map.  (See [RFC6325], Section
    4.9.3.2.)  While, of course, at most one spanning tree root could
    be seen on any particular port, there may be multiple relevant
    ports connected to different bridged LANs with different spanning
    tree roots.
 An INT-LABEL sub-TLV asserts that the information provided (multicast
 router attachment, Appointed Forwarder status lost counter, and root
 bridges) is the same for all labels specified.  If this is not the
 case, the sub-TLV MUST be split into subranges and/or separate bit
 maps meeting this criteria.  It is always safe to use sub-TLVs with a
 "range" of one VLAN ID, but this may be too verbose.

2.3.9. RBridge Channel Protocols Sub-TLV

 An IS announces the RBridge Channel protocols [RFC7178] it supports
 through use of this sub-TLV.
 +-+-+-+-+-+-+-+-+
 |Type=RBCHANNELS|                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...
 |   Zero or more bit vectors                            (variable)
 +-+-+-+-...
 o  Type: Router Capability and MT-Capability RBridge Channel
    Protocols sub-TLV, set to 16 (RBCHANNELS).
 o  Length: variable.
 o  Bit Vectors: Zero or more byte-aligned bit vectors where a one bit
    indicates support of a particular RBridge Channel protocol.  Each
    byte-aligned bit vector is formatted as follows:
    | 0  1  2  3  4  5  6  7| 8  9 10 11 12 13 14 15|
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |  Bit Vector Length |     Bit Vector Offset    |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |  bits
    +--+--+--...
    The Bit Vector Length (BVL) is a seven-bit unsigned integer field
    giving the number of bytes of bit vector.  The Bit Vector Offset
    (BVO) is a nine-bit unsigned integer field.

Eastlake, et al. Standards Track [Page 27] RFC 7176 TRILL Use of IS-IS May 2014

    The bits in each bit vector are numbered in network order, the
    high-order bit of the first byte of bits being bit 0 + 8*BVO, the
    low-order bit of that byte being 7 + 8*BVO, the high order bit of
    the second byte being 8 + 8*BVO, and so on for BVL bytes.  A bit
    vector of RBridge Channel protocols supported MUST NOT extend
    beyond the end of the value in the sub-TLV in which it occurs.  If
    it does, it is ignored.  If multiple byte-aligned bit vectors are
    present in one such sub-TLV, their representations are contiguous,
    the BVL field for the next starting immediately after the last
    byte of bits for the previous bit vector.  The one or more bit
    vectors present MUST exactly fill the sub-TLV value.  If there are
    one or two bytes of value left over, they are ignored; if more
    than two, an attempt is made to parse them as one or more bit
    vectors.
    If different bit vectors overlap in the protocol number space they
    refer to and they have inconsistent bit values for a channel
    protocol, support for the protocol is assumed if any of these bit
    vectors has a 1 for that protocol.
    The absence of any occurrences of this sub-TLV in the LSP for an
    IS implies that the IS does not support the RBridge Channel
    facility.  To avoid wasted space, trailing bit vector zero bytes
    SHOULD be eliminated by reducing BVL, any null bit vectors (ones
    with BVL equal to zero) eliminated, and generally the most compact
    encoding used.  For example, support for channel protocols 1 and
    32 could be encoded as
       BVL = 5
       BVO = 0
        0b01000000
        0b00000000
        0b00000000
        0b00000000
        0b10000000
    or as
       BVL = 1
       BVO = 0
        0b01000000
       BLV = 1
       BVO = 4
        0b1000000
    The first takes 7 bytes while the second takes only 6; thus, the
    second would be preferred.

Eastlake, et al. Standards Track [Page 28] RFC 7176 TRILL Use of IS-IS May 2014

 In multi-topology-aware RBridges, RBridge Channel protocols for which
 support is announced in the base topology are assumed to be supported
 in all topologies for which there is no separate announcement for
 RBridge Channel protocol support.

2.3.10. Affinity Sub-TLV

 Association of an IS to a multi-destination distribution tree through
 a specific path is accomplished by using the Affinity sub-TLV.  The
 announcement of an Affinity sub-TLV by RB1 with the nickname of RB2
 as the first part of an Affinity Record in the sub-TLV value is a
 request by RB1 that all ISs in the campus connect RB2 as a child of
 RB1 when calculating any of the trees listed in that Affinity Record.
 Examples of use include [Affinity] and [Resilient].
 The structure of the Affinity sub-TLV is shown below.
 +-+-+-+-+-+-+-+-+
 | Type=AFFINITY |                (1 byte)
 +-+-+-+-+-+-+-+-+
 | Length        |                (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   AFFINITY RECORD 1                       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   AFFINITY RECORD 2                       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   ..........
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   AFFINITY RECORD N                       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 where each AFFINITY RECORD is structured as follows:
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Nickname                    |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |Affinity Flags |                (1 byte)
 +-+-+-+-+-+-+-+-+
 |Number of trees|                (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Tree-num of 1st root        |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Tree-num of 2nd root        |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |          ..........         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Tree-num of Nth root        |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Eastlake, et al. Standards Track [Page 29] RFC 7176 TRILL Use of IS-IS May 2014

 o  Type: Router Capability and MT-Capability sub-TLV type, set to 17
    (AFFINITY).
 o  Length: size of all Affinity Records included, where an Affinity
    Record listing n tree roots is 4+2*n bytes long.
 o  Nickname: 16-bit nickname of the IS whose associations to the
    multi-destination trees listed in the Affinity Record are through
    the originating IS.
 o  Affinity Flags: 8 bits reserved for future needs to provide
    additional information about the affinity being announced.  MUST
    be sent as zero and ignored on receipt.
 o  Number of trees: A one-byte unsigned integer giving the number of
    trees for which affinity is being announced by this Affinity
    Record.
 o  Tree-num of roots: The tree numbers of the distribution trees this
    Affinity Record is announcing.
 There is no need for a field giving the number of Affinity Records as
 this can be determined by processing those records.

2.3.11 Label Group Sub-TLV

 The Label Group sub-TLV consists of two or more fine-grained label
 [RFC7172] IDs.  This sub-TLV indicates that shared label MAC address
 learning is occurring at the announcing IS between the listed labels.
 It is structured as follows:
 +-+-+-+-+-+-+-+-+
 |Typ=LABEL-GROUP|                                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  Primary Label ID                             |  (3 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  Secondary Label ID                           |  (3 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  more Secondary Label IDs ...                   (3 bytes each)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 o  Type: Router Capability and MT-Capability sub-TLV type, set to 18
    (LABEL-GROUP).
 o  Length: 6 + 3*n, where n is the number of secondary VLAN ID fields
    beyond the first.  n MAY be zero.

Eastlake, et al. Standards Track [Page 30] RFC 7176 TRILL Use of IS-IS May 2014

 o  Primary Label ID: This identifies the primary Label ID.
 o  Secondary Label ID: This identifies a secondary Label ID in the
    Label Group.
 o  more Secondary Label IDs: zero or more byte triples, each with a
    Label ID.

2.4. MTU Sub-TLV for Extended Reachability and MT-ISN TLVs

 The MTU sub-TLV is used to optionally announce the MTU of a link as
 specified in [RFC6325], Section 4.2.4.4.  It occurs within the
 Extended Reachability (#22) and MT-ISN (Intermediate System
 Neighbors) (#222) TLVs.
 +-+-+-+-+-+-+-+-+
 | Type = MTU    |                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |F|  RESV       |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |               MTU             |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 o  Type: Extended Reachability and MT-ISN sub-TLV type, set to MTU
    sub-TLV 28.
 o  Length: 3.
 o  F: Failed.  This bit is a one if MTU testing failed on this link
    at the required campus-wide MTU.
 o  RESV: 7 bits that MUST be sent as zero and ignored on receipt.
 o  MTU: This field is set to the largest successfully tested MTU size
    for this link or zero if it has not been tested, as specified in
    Section 4.3.2 of [RFC6325].

2.5. TRILL Neighbor TLV

 The TRILL Neighbor TLV is used in TRILL broadcast link IIH PDUs (see
 Section 4.1 below) in place of the IS Neighbor TLV, as specified in
 Section 4.4.2.1 of [RFC6325] and in [RFC7177].  The structure of the
 TRILL Neighbor TLV is as follows:

Eastlake, et al. Standards Track [Page 31] RFC 7176 TRILL Use of IS-IS May 2014

 +-+-+-+-+-+-+-+-+
 |     Type      |                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |   Length      |                  (1 byte)
 +-+-+-+-+-+-+-+-+
 |S|L|R|  SIZE   |                  (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                Neighbor RECORDS (1)                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                Neighbor RECORDS (2)                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                   .................                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                Neighbor RECORDS (N)                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 The information present for each neighbor is as follows:
 +-+-+-+-+-+-+-+-+
 |F|O|  RESV     |                (1 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      MTU                    |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+-+
 |      SNPA (MAC Address)                           | (SIZE bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+-+-+-+
 o  Type: TLV type, set to TRILL Neighbor TLV 145.
 o  Length: 1 + (SIZE+3)*n, where n is the number of neighbor records,
    which may be zero.
 o  S: Smallest flag.  If this bit is a one, then the list of
    neighbors includes the neighbor with the smallest MAC address
    considered as an unsigned integer.
 o  L: Largest flag.  If this bit is a one, then the list of neighbors
    includes the neighbor with the largest MAC address considered as
    an unsigned integer.
 o  R, RESV: These bits are reserved and MUST be sent as zero and
    ignored on receipt.
 o  SIZE: The SNPA size as an unsigned integer in bytes except that 6
    is encoded as zero.  An actual size of zero is meaningless and
    cannot be encoded.  The meaning of the value 6 in this field is
    reserved, and TRILL Neighbor TLVs received with a SIZE of 6 are
    ignored.  The SIZE is inherent to the technology of a link and is
    fixed for all TRILL Neighbor TLVs on that link but may vary

Eastlake, et al. Standards Track [Page 32] RFC 7176 TRILL Use of IS-IS May 2014

    between different links in the campus if those links are different
    technologies, for example, 6 for EUI-48 SNPAs or 8 for EUI-64
    SNPAs [RFC7042].  (The SNPA size on the various links in a TRILL
    campus is independent of the System ID size.)
 o  F: Failed.  This bit is a one if MTU testing to this neighbor
    failed at the required campus-wide MTU (see [RFC6325], Section
    4.3.1).
 o  O: OOMF.  This bit is a one if the IS sending the enclosing TRILL
    Neighbor TLV is willing to offer the Overload Originated Multi-
    destination Frame (OOMF) service [RFC7180] to the IS whose port
    has the SNPA in the enclosing Neighbor RECORD.
 o  MTU: This field is set to the largest successfully tested MTU size
    for this neighbor or to zero if it has not been tested.
 o  SNPA (MAC Address): Subnetwork Point of Attachment of the
    neighbor.
 As specified in [RFC7177] and Section 4.4.2.1 of [RFC6325], all MAC
 addresses may fit into one TLV, in which case both the S and L flags
 would be set to one in that TLV.  If the MAC addresses don't fit into
 one TLV, the highest MAC address in a TRILL Neighbor TLV with the L
 flag zero MUST also appear as a MAC address in some other TRILL
 Neighbor TLV (possibly in a different TRILL IIH PDU).  Also, the
 lowest MAC address in a TRILL Neighbor TLV with the S flag zero MUST
 also appear in some other TRILL Neighbor TLV (possibly in a different
 TRILL IIH PDU).  If an IS believes it has no neighbors, it MUST send
 a TRILL Neighbor TLV with an empty list of neighbor RECORDS, which
 will have both the S and L bits on.

3. MTU PDUs

 The IS-IS MTU-probe and MTU-ack PDUs are used to optionally determine
 the MTU on a link between ISs as specified in Section 4.3.2 of
 [RFC6325] and in [RFC7177].
 The MTU PDUs have the IS-IS PDU common header (up through the Maximum
 Area Addresses byte) with PDU Type numbers as indicated in Section 5.
 They also have a common fixed MTU PDU header as shown below that is 8
 + 2*(ID Length) bytes long, 20 bytes in the case of the usual 6-bytes
 System IDs.

Eastlake, et al. Standards Track [Page 33] RFC 7176 TRILL Use of IS-IS May 2014

 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    PDU Length                 |  (2 bytes)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+.....+-+-+
 |    Probe ID                      (6 bytes)                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+.....+-+-+
 |    Probe Source ID               (ID Length bytes)            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+.....+-+-+
 |    Ack Source ID                 (ID Length bytes)            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+.....+-+-+
 As with other IS-IS PDUs, the PDU Length gives the length of the
 entire IS-IS packet starting with and including the IS-IS common
 header.
 The Probe ID field is an opaque 48-bit quantity set by the IS issuing
 an MTU-probe and copied by the responding IS into the corresponding
 MTU-ack.  For example, an IS creating an MTU-probe could compose this
 quantity from a port identifier and probe sequence number relative to
 that port.
 The Probe Source ID is set by an IS issuing an MTU-probe to its
 System ID and copied by the responding IS into the corresponding MTU-
 ack.  The Ack Source ID is set to zero in MTU-probe PDUs and ignored
 on receipt.  An IS issuing an MTU-ack sets the Ack Source ID field to
 its System ID.  The System ID length is usually 6 bytes but could be
 a different value as indicated by the ID Length field in the IS-IS
 PDU Header.
 The TLV area follows the MTU PDU header area.  This area MAY contain
 an Authentication TLV and MUST be padded with the Padding TLV to the
 exact size being tested.  Since the minimum size of the Padding TLV
 is 2 bytes, it would be impossible to pad to exact size if the total
 length of the required information-bearing fixed fields and TLVs
 added up to 1 byte less than the desired length.  However, the length
 of the fixed fields and substantive TLVs for MTU PDUs is expected to
 be quite small compared with their minimum length (minimum 1470-byte
 MTU on an IEEE 802.3 link, for example), so this should not be a
 problem.

Eastlake, et al. Standards Track [Page 34] RFC 7176 TRILL Use of IS-IS May 2014

4. Use of Existing PDUs and TLVs

 The sub-sections below provide details of TRILL use of existing PDUs
 and TLVs.

4.1. TRILL IIH PDUs

 The TRILL IIH PDU is the variation of the IIH PDU used by the TRILL
 protocol.  Section 4.4 of the TRILL standard [RFC6325] and [RFC7177]
 specify the contents of the TRILL IIH and how its use in TRILL
 differs from Layer 3 LAN IIH PDU use.  The adjacency state machinery
 for TRILL neighbors is specified in detail in [RFC7177].
 In a TRILL IIH PDU, the IS-IS common header and the fixed PDU Header
 are the same as a Level 1 IIH PDU.
 The IS-IS Neighbor TLV (6) is not used in a TRILL IIH and is ignored
 if it appears there.  Instead, TRILL LAN IIH PDUs use the TRILL
 Neighbor TLV (see Section 2.5).

4.2. Area Address

 TRILL uses a fixed zero Area Address as specified in [RFC6325],
 Section 4.2.3.  This is encoded in a 4-byte Area Address TLV (TLV #1)
 as follows:
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   0x01, Area Address Type     |   (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   0x02, Length of Value       |   (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   0x01, Length of Address     |   (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |   0x00, zero Area Address     |   (1 byte)
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4.3. Protocols Supported

 NLPID (Network Layer Protocol ID) 0xC0 has been assigned to TRILL
 [RFC6328].  A Protocols Supported TLV (#129, [RFC1195]) including
 that value appears in TRILL IIH PDUs and LSP number zero PDUs.

4.4. Link State PDUs (LSPs)

 An LSP number zero MUST NOT be originated larger than 1470 bytes, but
 a larger LSP number zero successfully received MUST be processed and
 forwarded normally.

Eastlake, et al. Standards Track [Page 35] RFC 7176 TRILL Use of IS-IS May 2014

4.5. Originating LSP Buffer Size

 The originatingLSPBufferSize TLV (#14) MUST be in LSP number zero;
 however, if found in other LSP fragments, it is processed normally.
 Should there be more than one originatingLSPBufferSize TLV for an IS,
 the minimum size, but not less than 1470, is used.

5. IANA Considerations

 This section gives IANA considerations for the TLVs, sub-TLVs, and
 PDUs specified herein.  A number of new code points are assigned, and
 those that were assigned by [RFC6326] are included here for
 convenience.  IANA has replaced all [RFC6326] references in the IANA
 registries with references to this document.

5.1. TLVs

 This document specifies two IS-IS TLV types -- namely, the Group
 Address TLV (GADDR-TLV; type 142) and the TRILL Neighbor TLV (type
 145).  The PDUs in which these TLVs are permitted for TRILL are shown
 in the table below along with the section of this document where they
 are discussed.  The final "NUMBER" column indicates the permitted
 number of occurrences of the TLV in their PDU, or set of PDUs in the
 case of LSPs, which in these two cases is "*" indicating that the TLV
 MAY occur 0, 1, or more times.
 IANA has registered these two code points in the IANA IS-IS TLV
 registry (ignoring the "Section" and "NUMBER" columns, which are
 irrelevant to that registry).
                      Section TLV IIH LSP SNP Purge NUMBER
                      ======= === === === === ===== ======
   GADDR-TLV            2.1   142  n   y   n    n     *
   TRILL Neighbor TLV   2.5   145  y   n   n    n     *

5.2. Sub-TLVs

 This document specifies a number of sub-TLVs.  The TLVs in which
 these sub-TLVs occur are shown in the second table below along with
 the section of this document where they are discussed.  The TLVs
 within which these sub-TLVs can occur are determined by the presence
 of an "X" in the relevant column; the column headers are described in
 the first table below.  In some cases, the column header corresponds
 to two different TLVs in which the sub-TLV can occur.

Eastlake, et al. Standards Track [Page 36] RFC 7176 TRILL Use of IS-IS May 2014

   Column Head    TLV    RFC      TLV Name
   ===========   =====  ========  ==============
    Grp. Adr.     142    7176      Group Address
    MT Port       143    6165      MT-Port-Cap-TLV
    MT Cap.       242    4971      Router CAPABILITY
                  144    6329      MT-Capability
    Ext. Reach     22    5305      Extended IS Reachability
                  222    5120      MT-ISN
 The final "NUMBER" column below indicates the permitted number of
 occurrences of the sub-TLV cumulatively within all occurrences of
 their TLV(s) in those TLVs' carrying a PDU (or set of PDUs in the
 case of LSPs), as follows:
 0-1 = MAY occur zero or one times.
  1  = MUST occur exactly once.  If absent, the PDU is ignored.  If it
       occurs more than once, results are unspecified.
  *  = MAY occur 0, 1, or more times.
 The values in the "Section" and "NUMBER" columns are irrelevant to
 the IANA sub-registries.
                              sub-   Grp.  MT    MT    Ext.
   Name            Section    TLV#   Adr.  Port  Cap.  Reach  NUMBER
   =================================================================
   GMAC-ADDR        2.1.1       1     X     -     -     -      *
   GIP-ADDR         2.1.2       2     X     -     -     -      *
   GIPV6-ADDR       2.1.3       3     X     -     -     -      *
   GLMAC-ADDR       2.1.4       4     X     -     -     -      *
   GLIP-ADDR        2.1.5       5     X     -     -     -      *
   GLIPV6-ADDR      2.1.6       6     X     -     -     -      *
   VLAN-FLAGS       2.2.1       1     -     X     -     -      1
   Enabled-VLANs    2.2.2       2     -     X     -     -      *
   AppointedFwrdrs  2.2.3       3     -     X     -     -      *
   PORT-TRILL-VER   2.2.4       7     -     X     -     -     0-1
   VLANs-Appointed  2.2.5       8     -     X     -     -      *
   NICKNAME         2.3.2       6     -     -     X     -      *
   TREES            2.3.3       7     -     -     X     -     0-1
   TREE-RT-IDs      2.3.4       8     -     -     X     -      *
   TREE-USE-IDs     2.3.5       9     -     -     X     -      *
   INT-VLAN         2.3.6      10     -     -     X     -      *
   TRILL-VER        2.3.1      13     -     -     X     -     0-1
   VLAN-GROUP       2.3.7      14     -     -     X     -      *
   INT-LABEL        2.3.8      15     -     -     X     -      *
   RBCHANNELS       2.3.9      16     -     -     X     -      *

Eastlake, et al. Standards Track [Page 37] RFC 7176 TRILL Use of IS-IS May 2014

   AFFINITY         2.3.10     17     -     -     X     -      *
   LABEL-GROUP      2.3.11     18     -     -     X     -      *
   MTU              2.4        28     -     -     -     X     0-1
   =================================================================
   Name            Section    sub-   Grp.  MT    MT    Ext.   NUMBER
                              TLV#   Adr.  Port  Cap.  Reach
 IANA has entered the newly assigned sub-TLV numbers in the above
 table in the relevant existing sub-TLV registries, as determined by
 which column has an X for that sub-TLV.  For the sub-TLVs from
 NICKNAME through and including VLAN-GROUP, which previously existed
 only in the registry of sub-TLVs under TLV 242, IANA has added each
 sub-TLV with the same sub-TLV number to the existing registry for
 sub-TLVs under TLV 144.

5.3. PDUs

 The IS-IS PDUs registry remains as established in [RFC6326] except
 that the references to [RFC6326] are updated to reference this
 document.

5.4. Reserved and Capability Bits

 Any reserved bits (R), bits in reserved fields (RESV), or
 capabilities bits in the PORT-TRILL-VER and TRILL-VER sub-TLVs, which
 are specified herein as "MUST be sent as zero and ignored on receipt"
 or the like, are allocated based on IETF Review [RFC5226].
 Two sub-registries have been created within the TRILL Parameters
 Registry as follows:
    Sub-Registry Name: TRILL-VER Sub-TLV Capability Flags
    Registration Procedures: IETF Review
    Reference: (This document)
     Bit   Description                       Reference
    ===== =============                     ===========
      0    Affinity sub-TLV support.         [Affinity]
      1    FGL-safe                          [RFC7172]
     2-13  Unassigned
    14-31  Extended header flag support.     [RFC7179]

Eastlake, et al. Standards Track [Page 38] RFC 7176 TRILL Use of IS-IS May 2014

    Sub-Registry Name: PORT-TRILL-VER Sub-TLV Capability Flags
    Registration Procedures: IETF Review
    Reference: (This document)
     Bit   Description                       Reference
    ===== =============                     ===========
      0    Hello reduction support.          [RFC7180]
     1-2   Unassigned
     3-13  Hop-by-hop extended flag support. [RFC7179]
    14-31  Unassigned

5.5. TRILL Neighbor Record Flags

 A sub-registry has been created within the TRILL Parameters Registry
 as follows:
    Sub-Registry Name: TRILL Neighbor TLV NEIGHBOR RECORD Flags
    Registration Procedures: Standards Action
    Reference: (This document)
    Bit Short Name   Description            Reference
    ==============  =============          ===========================
     0   Fail       Failed MTU test        [RFC6325][RFC7176][RFC7177]
     1   OOMF       Offering OOMF service  [RFC7180]
    2-7  -          Unassigned

6. Security Considerations

 For general TRILL protocol security considerations, see the TRILL
 base protocol standard [RFC6325].
 This document raises no new security issues for IS-IS.  IS-IS
 security may be used to secure the IS-IS messages discussed here.
 See [RFC5304] and [RFC5310].  Even when IS-IS authentication is used,
 replays of Hello packets can create denial-of-service conditions; see
 [RFC6039] for details.  These issues are similar in scope to those
 discussed in Section 6.2 of [RFC6325], and the same mitigations may
 apply.

7. Changes from RFC 6326

 Non-editorial changes from [RFC6326] are summarized in the list
 below:
 1.  Added five sub-TLVs under the Group Address (GADDR) TLV covering
     VLAN-labeled IPv4 and IPv6 addresses and fine-grained-labeled
     MAC, IPv4, and IPv6 addresses (Sections 2.1.2, 2.1.3, 2.1.4,
     2.1.5, and 2.1.6).

Eastlake, et al. Standards Track [Page 39] RFC 7176 TRILL Use of IS-IS May 2014

 2.  Added the PORT-TRILL-VER sub-TLV (Section 2.2.4).
 3.  Added the VLANs-Appointed sub-TLV (Section 2.2.5).
 4.  Changed the TRILL-VER sub-TLV as listed below.
     a.  Added 4 bytes of TRILL Header extended flags and capabilities
         supported information.
     b.  Required that the TRILL-VER sub-TLV appear in LSP number
         zero.
     The above changes to TRILL-VER are backward compatible because
     the [RFC6326]-conformant implementations of TRILL thus far have
     only supported version zero and not supported any optional
     capabilities or extended flags, the level of support indicated by
     the absence of the TRILL-VER sub-TLV.  Thus, if an
     [RFC6326]-conformant implementation of TRILL rejects this sub-TLV
     due to the changes specified in this document, it will, at worst,
     decide that support of version zero and no extended flags or
     capabilities is indicated, which is the best an
     [RFC6326]-conformant implementation of TRILL can do anyway.
     Similarly, a TRILL implementation that supports TRILL-VER as
     specified herein and rejects TRILL-VER sub-TLVs in an
     [RFC6326]-conformant TRILL implementation because they are not in
     LSP number zero will decide that the implementation supports only
     version zero with no extended flag or capabilities support, which
     will be correct (Section 2.3.1).
 5.  Clarified the use of invalid VLAN IDs (0x000 and 0xFFF) in the
     Appointed Forwarders sub-TLV and the Interested VLANs and
     Spanning Tree Roots sub-TLV (Sections 2.2.3 and 2.3.6).
 6.  Added the Interested Labels and Spanning Tree Roots sub-TLV to
     indicate attachment of an IS to a fine-grained label [RFC7172]
     analogous to the existing Interested VLANs and Spanning Tree
     Roots sub-TLV for VLANs (Section 2.3.8).
 7.  Added the RBridge Channel Protocols sub-TLV so ISs can announce
     the RBridge Channel protocols they support (Section 2.3.9).
 8.  Permitted specification of the length of the link SNPA field in
     TRILL Neighbor TLVs.  This change is backward compatible because
     the size of 6 bytes is specially encoded as zero, the previous
     value of the bits in the new SIZE field (Section 2.5).

Eastlake, et al. Standards Track [Page 40] RFC 7176 TRILL Use of IS-IS May 2014

 9.  Made the size of the MTU PDU Header Probe Source ID and Ack
     Source ID fields be the ID Length from the IS-IS PDU Header
     rather than the fixed value 6 (Section 3).
 10. For robustness, required that LSP number zero PDUs be originated
     as no larger than 1470 bytes but processed regardless of size
     (Section 4.4).
 11. Required that the originatingLSPBufferSize TLV, if present,
     appear in LSP number zero (Section 4.5).
 12. Created sub-registries for and specified the IANA Considerations
     policy for reserved and capability bits in the TRILL version sub-
     TLVs (Section 5.4).
 13. Added the distribution tree Affinity sub-TLV so ISs can request
     distribution tree attachments (Section 2.3.10).
 14. Added the LABEL-GROUP sub-TLV analogous to the VLAN-GROUP sub-TLV
     (Section 2.3.11).
 15. Added multi-topology to permit sub-TLVs previously only in the
     Router Capability TLV to also appear in the MT-Capability TLV and
     to permit the MTU sub-TLV previously limited to the Extended
     Reachability TLV to also appear in the MT-ISN TLV.
 16. Added a sub-registry for Neighbor TLV Neighbor RECORD flag bits
     (Section 5.5).
 17. Explicitly stated that if the number of sources in a GADDR-TLV
     sub-TLV is zero, it indicates a listener for (*,G), that is, a
     listener not restricted by source (Section 2.1).

8. References

8.1. Normative References

 [ISO-10589]
            International Organization for Standardization,
            "Intermediate System to Intermediate System intra-domain
            routeing information exchange protocol for use in
            conjunction with the protocol for providing the
            connectionless-mode network service (ISO 8473)", Second
            Edition, November 2002.
 [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
            dual environments", RFC 1195, December 1990.

Eastlake, et al. Standards Track [Page 41] RFC 7176 TRILL Use of IS-IS May 2014

 [RFC1982]  Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
            August 1996.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [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,
            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.
 [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
            IANA Considerations Section in RFCs", BCP 26, RFC 5226,
            May 2008.
 [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
            Engineering", RFC 5305, October 2008.
 [RFC6165]  Banerjee, A. and D. Ward, "Extensions to IS-IS for Layer-2
            Systems", RFC 6165, April 2011.
 [RFC6325]  Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
            Ghanwani, "Routing Bridges (RBridges): Base Protocol
            Specification", RFC 6325, July 2011.
 [RFC6328]  Eastlake 3rd, D., "IANA Considerations for Network Layer
            Protocol Identifiers", BCP 164, RFC 6328, July 2011.
 [RFC6329]  Fedyk, D., Ed., Ashwood-Smith, P., Ed., Allan, D., Bragg,
            A., and P. Unbehagen, "IS-IS Extensions Supporting IEEE
            802.1aq Shortest Path Bridging", RFC 6329, April 2012.
 [RFC6439]  Perlman, R., Eastlake, D., Li, Y., Banerjee, A., and F.
            Hu, "Routing Bridges (RBridges): Appointed Forwarders",
            RFC 6439, November 2011.
 [RFC7172]  Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R., and
            D. Dutt, "Transparent Interconnection of Lots of Links
            (TRILL): Fine-Grained Labeling", RFC 7172, May 2014.
 [RFC7177]  Eastlake 3rd, D., Perlman, R., Ghanwani, A., Yang, Y., and
            V. Manral, "Transparent Interconnection of Lots of Links
            (TRILL): Adjacency", RFC 7177, May 2014.

Eastlake, et al. Standards Track [Page 42] RFC 7176 TRILL Use of IS-IS May 2014

 [RFC7178]  Eastlake 3rd, D., Manral, V., Li, Y., Aldrin, S., and D.
            Ward, "Transparent Interconnection of Lots of Links
            (TRILL): RBridge Channel Support", RFC 7178, May 2014.
 [RFC7179]  Eastlake 3rd, D., Ghanwani, A., Manral, V., Li, Y., and C.
            Bestler, "Transparent Interconnection of Lots of Links
            (TRILL): Header Extension", RFC 7179, May 2014.
 [RFC7180]  Eastlake 3rd, D., Zhang, M., Ghanwani, A., Manral, V., and
            A.  Banerjee, "Transparent Interconnection of Lots of
            Links (TRILL): Clarifications, Corrections, and Updates",
            RFC 7180, May 2014.

8.2. Informative References

 [Err2869]  RFC Errata, Errata ID 2869, RFC 6326,
            <http://www.rfc-editor.org>.
 [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
            Authentication", RFC 5304, October 2008.
 [RFC5310]  Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
            and M. Fanto, "IS-IS Generic Cryptographic
            Authentication", RFC 5310, February 2009.
 [RFC6039]  Manral, V., Bhatia, M., Jaeggli, J., and R. White, "Issues
            with Existing Cryptographic Protection Methods for Routing
            Protocols", RFC 6039, October 2010.
 [RFC6326]  Eastlake, D., Banerjee, A., Dutt, D., Perlman, R., and A.
            Ghanwani, "Transparent Interconnection of Lots of Links
            (TRILL) Use of IS-IS", RFC 6326, July 2011.
 [RFC7042]  Eastlake 3rd, D. and J. Abley, "IANA Considerations and
            IETF Protocol and Documentation Usage for IEEE 802
            Parameters", BCP 141, RFC 7042, October 2013.
 [RFC7175]  Manral, V., Eastlake 3rd, D., Ward, D., and A. Banerjee,
            "Transparent Interconnection of Lots of Links (TRILL):
            Bidirectional Forwarding Detection (BFD) Support", RFC
            7175, May 2014.
 [Affinity] Senevirathne, T., Pathangi, J., and J. Hudson,
            "Coordinated Multicast Trees (CMT) for TRILL", Work in
            Progress, April 2014.

Eastlake, et al. Standards Track [Page 43] RFC 7176 TRILL Use of IS-IS May 2014

 [MultiLevel]
            Perlman, R., Eastlake 3rd, D., Ghanwani, A., and H. Zhai,
            "Flexible Multilevel TRILL (Transparent Interconnection of
            Lots of Links)", Work in Progress, January 2014.
 [Resilient]
            Zhang, M. Senevirathne, T., Pathangi, J., Banerjee, A.,
            and A. Ghanwani, "TRILL Resilient Distribution Trees",
            Work in Progress, December 2013.

9. Acknowledgements

 The authors gratefully acknowledge the contributions and reviews by
 the following individuals: Ross Callon, Spencer Dawkins, Adrian
 Farrel, Alexey Melnikov, Radia Perlman, Carlos Pignataro, and Joe
 Touch.
 The authors also acknowledge the contributions to [RFC6326] by the
 following individuals: Mike Shand, Stewart Bryant, Dino Farinacci,
 Les Ginsberg, Sam Hartman, Dan Romascanu, Dave Ward, and Russ White.
 In particular, thanks to Mike Shand for his detailed and helpful
 comments.

Eastlake, et al. Standards Track [Page 44] RFC 7176 TRILL Use of IS-IS May 2014

Authors' Addresses

 Donald Eastlake 3rd
 Huawei Technologies
 155 Beaver Street
 Milford, MA 01757
 USA
 Phone: +1-508-333-2270
 EMail: d3e3e3@gmail.com
 Tissa Senevirathne
 Cisco Systems
 375 East Tasman Drive,
 San Jose, CA 95134
 USA
 Phone: +1-408-853-2291
 EMail: tsenevir@cisco.com
 Anoop Ghanwani
 Dell
 5450 Great America Parkway
 Santa Clara, CA  95054
 USA
 EMail: anoop@alumni.duke.edu
 Dinesh Dutt
 Cumulus Networks
 1089 West Evelyn Avenue
 Sunnyvale, CA 94086
 USA
 EMail: ddutt.ietf@hobbesdutt.com
 Ayan Banerjee
 Insieme Networks
 210 West Tasman Drive
 San Jose, CA 95134
 USA
 EMail: ayabaner@gmail.com

Eastlake, et al. Standards Track [Page 45]

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