TRILL Working Group                                      Donald Eastlake
INTERNET-DRAFT                                              Mingui Zhang
Intended status: Proposed Standard                                Huawei
Updates: 6325                                             Puneet Agarwal
                                                             Dinesh Dutt
                                                           Radia Perlman
                                                              Intel Labs
Expires: April 27, 2012                                 October 28, 2011

                    RBridges: Fine-Grained Labeling


   The IETF has standardized RBridges (Routing Bridges), devices that
   implement the TRILL (TRansparent Interconnection of Lots of Links)
   protocol, a standard for least cost transparent frame routing in
   multi-hop networks with arbitrary topologies, using link-state
   routing and encapsulation with a hop count.

   The TRILL base protocol standard supports up to 4K VLAN IDs (Virtual
   Local Area Network IDentifiers). However, there are applications that
   require more fine-grained labeling of data and end stations. This
   document updates RFC 6325 by specifying extensions to the TRILL
   protocol to accomplish this.

Status of This Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Distribution of this document is unlimited. Comments should be sent
   to the TRILL working group mailing list.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-

   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."

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at

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Table of Contents

      1. Introduction............................................3
      1.1 Terminology............................................3

      2. Fine-Grained Labeling...................................4
      2.1 Requirements...........................................4
      2.2 Existing TRILL VLAN Labeling...........................5
      2.3 Fine-Grained Labeling (FGL)............................6

      3. Campus Wide VL versus FGL Semantic Differences..........8
      4. Coexistence with VL RBridges............................9

      5. Fine-Grained Labeling Details..........................10
      5.1 Ingress Processing....................................10
      5.2 Transit Processing....................................10
      5.2.1 Unicast Transit Processing..........................11
      5.2.2 Multi-Destination Transit Processing................11
      5.3 Egress Processing.....................................12
      5.4 Appointed Forwarders and the DRB......................13
      5.5 Address Learning......................................13

      6. IS-IS Extensions.......................................14
      7. Comparison to Requirements.............................15

      8. Allocation Considerations..............................16
      8.1 IEEE Allocation Considerations........................16
      8.2 IANA Considerations...................................16
      9. Security Considerations................................17
      10. Acknowledgements......................................17
      11. Normative References..................................18
      12. Informative References................................18

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1. Introduction

   The IETF has standardized RBridges (Routing Bridges), devices that
   implement the TRILL (TRansparent Interconnection of Lots of Links)
   protocol [RFC6325]. RBridges provide a solution for least cost
   transparent frame routing in multi-hop networks with arbitrary
   topologies, using [IS-IS] [RFC6326bis] link-state routing and
   encapsulation with a hop count addressing the problems outlined in

   The TRILL base protocol standard supports labeling with up to 4K VLAN
   IDs (Virtual Local Area Network IDentifiers). However, there are
   applications that require more fine-grained labeling of data and end
   stations. This document updates [RFC6325] by specifying extensions to
   the TRILL protocol to accomplish this.

   Familiarity with [RFC6325] and [RFC6326bis] is assumed in this

1.1 Terminology

   The terminology and acronyms of [RFC6325] are used in this document
   with the additions listed below.

      VL - VLAN Labeling or VLAN Labeled or VLAN Label

      VL RBridge - An RBridge that support VL and does not support FGL

      FGL - Fine-Grained Labeling or Fine-Grained Labeled or Fine-
            Grained Label

      FGL RBridge - An RBridge that support both FGL and VL

      Edge RBridge - An RBridge announcing VL or FGL connectivity in its
            link state

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

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2. Fine-Grained Labeling

   The essence of Fine-Grained Labeling (FGL) is that (a) when TRILL
   Data frames are ingressed or created they may incorporate a label
   from a set of significantly more than 4K labels, (b) RBridge ports
   can be labeled with a set of such labels, and (c) an FGL TRILL Data
   frame cannot be egressed through an RBridge port unless its FGL
   matches one of the labels of the port.

   Section 2.1 lists fine-grained labeling requirements.  Section 2.2
   briefly outlines TRILL Data VLAN Labeling (VL) in the TRILL base
   protocol standard [RFC6325]. And Section 2.3 then outlines a method
   of Fine-Grained Labeling (FGL) of TRILL Data frames.

2.1 Requirements

   There are several requirements that should be met by FGL in TRILL.
   They are briefly described in the list below in approximate order by
   priority with the most important first.

   1. Fine-Grained

      Some networks have a large number of entities that need
      configurable isolation, whether those entities are independent
      customers, applications, or branches of a single endeavor or some
      combination of these or other entities. The VLAN labeling
      supported by [RFC6325] provides for only ( 2**12 - 2 ) valid
      identifiers or labels. A substantially larger number is required.

   2. Silicon Considerations

      Fine-grained labeling (FGL) should, to the extent practical, use
      existing features, processing, and fields that are already
      supported in at least some of the existing TRILL fast path silicon

   3. Base RBridge Compatibility

      To support some incremental conversion scenarios, it is desirable
      that not all RBridges in a campus using FGL be required to be FGL
      aware. That is, it is desirable that RBridges not implementing the
      FGL feature and performing at least the transit forwarding
      function can usefully process TRILL Data frames that incorporate

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   4. Alternate Priority

      It would be desirable for an ingress RBridge to be able to assign
      a different priority to an FGL TRILL Data frame for its ingress-
      to-egress propagation from the priority of the original native
      frame. The original priority should be restored on egress.

2.2 Existing TRILL VLAN Labeling

   This section provides a brief review of existing TRILL Data frame
   VLAN Labeling (VL) and changes the description of VL from that
   appearing in [RFC6325] by moving the end of the TRILL Header. This
   description change does not involve any change in the bits on the
   wire or in the behavior of existing [RFC6325] RBridges.

   Currently TRILL Data frames have the VL structure shown below:

               | Link Header (Depends on Link Technology)  |
               | TRILL Header                              |
               | +---------------------------------------+ |
               | | Initial Fields and Options, FGLflag=0 | |
               | +---------------------------------------+ |
               | |         Inner.MacDA         | (6 bytes) |
               | +-----------------------------+           |
               | |         Inner.MacSA         | (6 bytes) |
               | +-----------------------------+           |
               | |C-VLAN EtherType (0x8100)|     (2 bytes) |
               | +-------------------------+               |
               | | Inner.VLAN Label        |     (2 bytes) |
               | +-------------------------+               |
               |               Native Payload              |
               | Link Trailer (Depends on Link Technology) |

   The FGLflag bit is the formerly reserved TRILL Header bit immediately
   adjacent to the V field that [RFC6325] specifies as always set to
   zero and ignored on receipt.

   The C-VLAN EtherType is always present and is followed by the
   Inner.VLAN field including the 12-bit VLAN ID field.

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2.3 Fine-Grained Labeling (FGL)

   FGL expands the 12-bit VLAN label available under the TRILL base
   protocol standard to a 24-bit fine-grained label. In this document,
   FGLs are usually denoted as "(X.Y)" where X is the high order 12 bits
   and Y is the low order 12 bits of the FGL. The FGL information
   appears in the TRILL Header as shown below.

               | Link Header (Depends on Link Technology)  |
               | TRILL Header                              |
               | +---------------------------------------+ |
               | | Initial Fields and Options, FGLflag=1 | |
               | +---------------------------------------+ |
               | |         Inner.MacDA         | (6 bytes) |
               | +-----------------------------+           |
               | |         Inner.MacSA         | (6 bytes) |
               | +-----------------------------+           |
               | |C-VLAN EtherType (0x8100)|     (2 bytes) |
               | +-------------------------+               |
               | | Inner.Label First Part  |     (2 bytes) |
               | +-------------------------+               |
               | |EX-TAG EtherType (0xTBD) |     (2 bytes) |
               | +-------------------------+               |
               | | Inner.Label Second Part |     (2 bytes) |
               | +-------------------------+               |
               |               Native Payload              |
               | Link Trailer (Depends on Link Technology) |

   The FGLflag bit is the formerly reserved TRILL Header bit immediately
   adjacent to the V field that [RFC6325] specifies as always set to
   zero and ignored on receipt. This document updates [RFC6325] by
   providing that that bit is set to one if and only if the TRILL Data
   frame is FGL.

   The fixed format area of the TRILL Header with the Inner.Label and
   EtherType fields 0x8100 and 0xTBD is mandatory for FGL frames. It is
   designed to be backward compatibility with [RFC6325] conformant
   RBridges although such RBridges will only be aware of the most
   significant 12-bits of the FGL.

   The two byte following the EX-TAG EtherType have, in their low order
   12 bits, a low order extension to the VLAN ID in the preceding VLAN
   tag and together they constitute the fine-grained label. The upper 4
   bits of those two bytes are used for a 3-bit priority field and one
   unused bit.

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   The priority field of the initial C-VLAN is the priority used for
   frame transport from ingress to egress.

   The appropriate FGL value for an ingressed native frame is determined
   by the input RBridge port as specified in Section 4.1.  Ports of
   RBridges supporting FGL also have capabilities to transmit frames
   being forwarded or egressed as untagged or Outer.VLAN tagged as
   specified in Section 4.3.

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3. Campus Wide VL versus FGL Semantic Differences

   There are significant differences between the semantics across a
   campus for VLAN labels (VLs) and fine-grained labels (FGLs).

   With VL, VLAN label IDs have the same meaning throughout the campus.
   In addition, the TRILL Header label in the Inner.VLAN is from the
   same label space as the VLAN IDs used on Ethernet links in the

   With TRILL FGL, many things remain the same. Ports of FGL RBridges
   act as they do for VL RBridges: Ethernet links still have C-VLAN
   labeling on them and RBridge ports provide a VLAN ID for an incoming
   frame and accept a VLAN ID for a frame being queued for output.
   Appointed Forwarders [RFCaf] on a link are still appointed for a C-
   VLAN. The Designated VLAN for a link is a C-VLAN. However, the 24-bit
   FGL label space is a different flat space from the 12-bit C-VLAN
   space. For ports configured for FGL, the C-VLAN on an ingressed
   native frame is mapped to the FGL space with a potentially different
   mapping for each port. A similar FGL to C-VLAN mapping occurs on
   egress. Thus, for ports configured for FGL, the C-VLAN corresponding
   to an FGL on one link can be different from the C-VLAN corresponding
   to that same FGL on a different link elsewhere in the campus or even
   a different link attached to the same RBridge. The FGL label space is
   flat and does not hierarchically encode any particular number of C-
   VLAN bits or the like.

   FGL RBridge ports can be configured for FGL or VL with VL being the
   default. As with a base protocol [RFC6325] RBridge, by default an FGL
   RBridge port reports an untagged frame it receives as being in VLAN

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4. Coexistence with VL RBridges

   VLAN Labeling (VL) RBridges will operate properly as transit
   RBridges.  Transit RBridges look at the Inner.VLAN ID field only for
   the filtering of multi-destination frames.  If an RBridge does not
   perform filtering, or filters on only some of the fields in the
   packet, the only consequence is that multi-destination frames will
   use more bandwidth than necessary. VL RBridges would only look at the
   high order 12 bits of the FGL, which are in the position where a VL
   RBridge would expect to find a VLAN ID. Thus they will not be able to
   prune as effectively as transit FGL RBridges could because they will
   ignore the lower 12 bits of the FGL.

   It would be more serious if a VL edge RBridge, RB1, unaware of FGL,
   forwarded an FGL frame with FGL (X.Y) onto a link through an RB1 port
   configured as VL VLAN-X. RB1 would strip the TRILL Header only
   through the Inner.Label First Part, which it thinks is an Inner.VLAN
   Label, and forward the packet with the Inner.Label Second Part and
   preceding 0xTBD field still present. This might cause other problems
   on the link. It would also be problematic if a malicious end station
   could forge an apparent FGL label (X.Y) frame by including extra
   fields in native frames ingressed by a VL edge RBridge. Therefore, it
   is highly desirable for all the edge RBridges to be FGL RBridges.

   FGL RBridges will report the FGL capability in LSPs, so FGL RBridges
   (and any management system with access to the link state database)
   will be able to detect the existence of VL edge RBridges.

   It might be useful, in a particular campus with mixed VL and FGL
   RBridges, to have some end station VLANs accessible via VL edge
   RBridges.  This is supported by reserving some number of VLANs (say
   the first k), to be VL-addressable.  These VLANs will be specified
   with a single Inner.VLAN label, whether or not the edge RBridges
   attached to these VLANs are FGL-capable.  When VL-specifiable VLANs
   are used in a FGL campus, and where there are VL edge RBridges
   advertising connectivity to those VLANs, the upper 12 bits in an FGL
   MUST NOT be equal to the value of any VL-specifiable VLAN.

   If this rule is violated, the network misconfiguration is detected by
   the FGL RBridges that will then refuse in ingress to or egress from
   label (X.Y) while VLAN X connectivity is being advertised by a VL
   edge RBridge.

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5. Fine-Grained Labeling Details

   This section specifies ingress, transit, egress, and other processing
   of TRILL Data frames with regard to Fine-Grained Labels (FLGs). A
   transit or egress FGL RBridge detects FGL TRILL Data frames by
   noticing that the FGLflag in the TRILL Header is set.

5.1 Ingress Processing

   An FGL RBridge may be configured, on one or more ports, to FGL
   ingress native frames. There is no change in VL ingress processing,
   which is the default unless a port has been configured for FGL, and
   no change in Appointed Forwarder logic (see Section 5.4).

   FGL RBridges MUST support configurable per port mapping from the C-
   VLAN ID associated with a native frame to a 24-bit fine-grained
   label. FGL RBridges MAY support other methods to determine the FGL ID
   of an incoming native frame, such as based on the protocol of the
   native frame. If the resulting label (X.Y) is such that VLAN X
   connectivity is being advertised by a VL edge RBridge in the campus,
   the ingressed frame MUST be dropped.

   The FGL ingress process MUST place the priority associated with an
   ingressed native frame in upper 3 bits of the second Inner.Label
   part. It SHOULD also associate a possibly different mapped priority
   with an ingressed frame. The mapped priority is placed in the
   Inner.Label First Part. If such mapping is not supported then the
   original priority is also placed in the Inner.Label First Part.

   An FGL ingress RBridge MAY serially TRILL unicast a multi-destination
   TRILL Data frame to the relevant egress RBridges, if those egress
   RBridges are all FGL RBridges, after encapsulating it as a TRILL
   known unicast data frame (M=0) and SHOULD so unicast such a multi-
   destination TRILL Data frame if there is only one relevant egress FGL
   RBridge. The relevant egress RBridges are determined by starting with
   those announcing connectivity to the frame's (X.Y) label. That set
   SHOULD be further filtered based on multicast listener and router
   connectivity if the native frame was a multicast frame.

   Use of S-tags is beyond the scope of this document but is an obvious

5.2 Transit Processing

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   TRILL Data frame transit processing is fairly straightforward as
   described in Section 5.2.1 for known unicast TRILL Data frames and in
   Section 5.2.2 for multi-destination TRILL Data frames.

5.2.1 Unicast Transit Processing

   There is almost no change in TRILL Data frame unicast transit
   processing. A transit RBridge forwards any unicast TRILL Data frame
   to the next hop towards the egress RBridge as specified in the TRILL
   Header. Just as transit RBridges conformant to the TRILL base
   protocol standard [RFC6325] do not examine the Inner.VLAN of unicast
   TRILL Data frames, transit FGL RBridges do not examine the 24-bit FGL
   of unicast TRILL Data frames.

   All transit RBridges, whether VL or FGL, MUST take the priority used
   to forward a frame from the Inner.VLAN label or the FGL Inner.Label
   First Part. These bits are in the same relative position for VL and
   FGL frames so VL RBridges will do this automatically even though they
   do not fully understand FGL frames.

5.2.2 Multi-Destination Transit Processing

   All multi-destination TRILL Data frames are forwarded on a
   distribution tree selected by the ingress RBridge. The distribution
   trees for FGL and VL multi-destination frames are the same and are
   calculated as provided for in the TRILL base protocol standard
   [RFC6325]. There is no change in the Reverse Path Forwarding Check.

   An FGL RBridge, say RB1, having an FGL multi-destination frame for
   label (X.Y) to forward on a distribution tree, SHOULD prune based on
   whether there are any edge RBridges on the tree branch that are
   connected to label (X.Y). In addition, RB1 SHOULD prune multicast
   frames based on reported multicast listener and multicast router
   attachment in (X.Y). Finally, a transit FGL RBridge MAY drop any
   multi-destination frame for label (X.Y) if some VL RBridge is
   advertising connectivity to VLAN X. "MAY" is chosen in this case to
   minimize the checking burden on transit RBridges.

   To ensure that a transit VL RBridge does not falsely filter traffic
   for FGL label (X.Y), an FGL edge RBridge attached to FGL label (X.Y)
   MUST report connection to VLAN X, as if X were a VLAN label, in
   addition to reporting connectivity to label (X.Y).  Because of this,
   VL transit RBridges can safely apply pruning to all TRILL Data
   frames, both VL and FGL, based on the reported VLAN-X connectivity of
   all downstream RBridges.

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   To ensure that a transit VL RBridge does not falsely prune traffic
   for FGL label (X.Y) base on multicast filtering, an FGL edge RBridge
   attached to label (X.Y) MUST also report for VLAN X either (1) that
   it is attached to both IPv4 and IPv6 multicast routers or (2) its
   merged FGL label (X.Y) multicast listener and router connectivity for
   all Y.

5.3 Egress Processing

   Egress processing is generally the reverse of ingress progressing
   described in Section 5.1.

   If any VL RBridge in the campus is announcing connectivity to VLAN-X,
   an FGL RBridge MUST NOT egress a frame with FGL label (X.Y) but must
   drop such a frame.

   An FGL RBridge MUST be able to configurably convert the 24-bit fine
   grained label in an FGL TRILL Data frame it is egressing to a 12-bit
   C-VLAN ID for the resulting native frame on a per port basis. A port
   MAY be configured to strip such tagging. It is the responsibility of
   the network manager to properly configure the RBridges and ports in
   the campus to obtain the desired mappings.

   An FGL RBridge egresses FGL frames with the above tag conversion
   similarly to the egressing of VL frames, as follows:

   1. A known unicast FGL frame is egressed to the FGL port matching its
      fine-grained label and Inner.MacDA. If there is no such port, it
      is flooded out all FGL ports with its fine-grained label unless
      the RBridge has knowledge that the frames Inner.MacDA cannot be
      out that port.

   2. A multi-destination FGL frame is decapsulated and flooded out all
      ports with its fine-grained label, subject to multicast pruning.

   FGL RBridges MUST accept multi-destination encapsulated frames that
   are sent to them as TRILL unicast frames, that is, frames with a
   multicast or broadcast Inner.MacDA and the TRILL Header M bit = 0.
   They locally egress such frames, if appropriate, but MUST NOT forward
   them (other than egressing them as native frames on their local

   Use of S-tags is beyond the scope of this document but is an obvious

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5.4 Appointed Forwarders and the DRB

   There is no change in Adjacency [RFC6327] or Appointed Forwarder
   logic [RFCaf] on a link regardless of whether some or all the ports
   on the link are for FGL RBridges. However, if it is intended for
   native frames on a link in some VLAN-X to be ingressed and egressed
   with FGL, the Appointed Forwarder for VLAN-X for that link obviously
   MUST be an FGL RBridge.

   If there are FGL and VL RBridges connected to a link, it may be best
   if the priorities are configured so that the DRB is an FGL RBridge.
   However, there is no inherent difficulty in a VL DRB RBridge
   appointing an FGL RBridge connected to the link as Appointed
   Forwarder for whatever VLANs are appropriate.

5.5 Address Learning

   An FGL RBridge learns addresses on FGL ports based on the fine-
   grained label rather than VLAN ID. Addresses learned from ingressed
   native frames are logically represented by { MAC address, fine-
   grained label, port, confidence, timer } while remote addresses
   learned from egressing FGL frames are logically represented by { MAC
   address, fine grained label, remote RBridge nickname, confidence,
   timer }.

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6. IS-IS Extensions

   Extensions to the TRILL use of IS-IS are required to support the

   1. An method for an RBridge to announce itself in its LSP as
      supporting FGL.

   2. A sub-TLV analogous to Interested VLANs and Spanning Tree Roots
      sub-TLV of the Router Capabilities TLV but indicating fine-grained
      labels rather than VLANs.

   3. A sub-TLV analogous to the GMAC-ADDR sub-TLV of the Group Address
      TLV that specifies a fine-grained label rather than a VLAN.

   See [RFC6326bis] and Section 8.2.

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7. Comparison to Requirements

   Comparing TRILL fine-grained labeling (FGL), as specified in this
   document, with the requirements given in Section 2.1, we find they
   are met as follows:

   1. Fine-Grained: FGL provides approaching 2**24 labels, vastly more
      labels than the 4K VLAN IDs.

   2. Silicon Considerations: Existing TRILL fast path silicon chips
      can, almost by definition, perform base TRILL Header insertion and
      removal to support ingress and egress. In addition, it is believed
      that most such silicon chips can also perform the 12-bit VLAN ID
      and port to fine-grained label mapping and the encoding of the
      fine-grained label as specified herein, as well as the inverse
      decoding and mapping. Some existing silicon can perform only one
      of these operations on a frame in the fast path and is thus not
      suitable to implement fast path TRILL FGL processing; however,
      other existing chips are believed to be able to perform both
      operations on the same frame in the fast path and are suitable for
      FGL implementation.

   3. Base RBridge Compatibility: As described in Section 3, FGL is
      compatible with base specification RBridges [RFC6325] acting as
      transit RBridges and, as described in Section 5.4, there is no
      particular problem in mixing VL and FGL RBridge on the same link.

   4. Alternate Priority: The encoding specified in Section 2.3 provides
      for a new priority in the two bytes with the high order 12 FGL
      bits and a place to preserve the original user priority, so it can
      be restored on egress, within the two bytes with the low order 12
      FGL bits.

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8. Allocation Considerations

   Allocations by the IEEE Registration Authority and IANA are listed

8.1 IEEE Allocation Considerations

   The IEEE Registration Authority has assigned EtherType TBD for EX-

8.2 IANA Considerations

   IANA is requested to allocate capability bit TBD (0 recommended) in
   the TRILL-VER sub-TLV capability bits to indicate an RBridge is FGL-

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9. Security Considerations

   See [RFC6325] for general RBridge Security Considerations.

   As with any communications system, end-to-end encryption and
   authentication should be considered for particularly sensitive data.

   Confusion between a frame with VLAN-X labeling and FGL label (X.Y) is
   a potential problem:  A TRILL Data frame with FGL label (X.Y) could
   be egressed to VLAN-X by a VL RBridge that is Appointed Forwarder for
   VLAN-X on one of its ports.  This is solved by prohibiting FGL
   RBridges from ingressing to FGL labeling (X.Y) if the RBridge campus
   is misconfigured so that a VL edge RBridge is reporting connectivity
   to VLAN-X while label (X.Y) is in use.

10. Acknowledgements

   The comments and contributions of the following are gratefully

      Anoop Ghanwani, Sujay Gupta, Jon Hudson, Vishwas Manral, Erik
      Nordmark, and Ilya Varlashkin.

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11. Normative References

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

   [802.1Q] - IEEE 802.1, "IEEE Standard for Local and metropolitan area
         networks - Virtual Bridged Local Area Networks", IEEE Std
         802.1Q-2011, May 2011.

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

   [RFC6325] - Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
         Ghanwani, "Routing Bridges (RBridges): Base Protocol
         Specification", RFC 6325, July 2011.

   [RFC6326bis] - Eastlake, D., Banerjee, A., Dutt, D., Perlman, R., and
         A. Ghanwani, "Transparent Interconnection of Lots of Links
         (TRILL) Use of IS-IS", draft-eastlake-isis-rfc6326bis-00.txt,
         work in progress.

12. Informative References

   [RFC5556] - Touch, J. and R. Perlman, "Transparent Interconnection of
         Lots of Links (TRILL): Problem and Applicability Statement",
         RFC 5556, May 2009.

   [RFC6327] - Eastlake 3rd, D., Perlman, R., Ghanwani, A., Dutt, D.,
         and V. Manral, "Routing Bridges (RBridges): Adjacency", RFC
         6327, July 2011

   [RFCaf] - Perlman, R., D. Eastlake, A. Banerjee, H. Fangwei,
         "RBridges: Appointed Forwarders", draft-ietf-trill-rbridge-af,
         work in progress.

D. Eastlake, et al                                             [Page 18]

INTERNET-DRAFT                           RBridges: Fine-Grained Labeling

Authors' Addresses

   Donald Eastlake 3rd
   Huawei Technologies
   155 Beaver Street
   Milford, MA 01757 USA

   Phone: +1-508-333-2270

   Mingui Zhang
   Huawei Technologies Co.,Ltd
   Huawei Building, No.156 Beiqing Rd.
   Z-park ,Shi-Chuang-Ke-Ji-Shi-Fan-Yuan,Hai-Dian District,
   Beijing 100095 P.R. China


   Puneet Agarwal
   Broadcom Corporation
   3151 Zanker Road
   San Jose, CA 95134 USA

   Phone: +1-949-926-5000

   Dinesh G. Dutt
   Cisco Systems
   170 Tasman Drive
   San Jose, CA 95134-1706 USA

   Phone: +1-408-527-0955

   Radia Perlman
   Intel Labs
   2200 Mission College Blvd.
   Santa Clara, CA 95054 USA

   Phone: +1-408-765-8080

D. Eastlake, et al                                             [Page 19]

INTERNET-DRAFT                           RBridges: Fine-Grained Labeling

Copyright, Disclaimer, and Additional IPR Provisions

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D. Eastlake, et al                                             [Page 20]