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Versions: (draft-eastlake-trill-rbridge-fine-labeling) 00 01 02 03 04 05 06 07 RFC 7172

TRILL Working Group                                      Donald Eastlake
INTERNET-DRAFT                                              Mingui Zhang
Intended status: Proposed Standard                                Huawei
Updates: 6325, 6327                                       Puneet Agarwal
                                                           Radia Perlman
                                                              Intel Labs
                                                             Dinesh Dutt
                                                        Cumulus Networks
Expires: June 11, 2013                                 December 12, 2012

                      TRILL: Fine-Grained Labeling


   The IETF has standardized TRILL (TRansparent Interconnection of Lots
   of Links), a protocol for least cost transparent frame routing in
   multi-hop networks with arbitrary topologies and link technologies,
   using link-state routing with a hop count. The TRILL base protocol
   standard supports labeling of TRILL data with up to 4K IDs. However,
   there are applications that require more fine-grained labeling of
   data. This document updates RFC 6325 and RFC 6327 by specifying
   optional extensions to the TRILL base protocol to safely accomplish

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
   http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft
   Shadow Directories can be accessed at

D. Eastlake, et al                                              [Page 1]

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Table of Contents

      1. Introduction............................................3
      1.1 Terminology............................................3
      1.2 Contributors...........................................4

      2. Fine-Grained Labeling...................................5
      2.1 Goals..................................................5
      2.2 Base Protocol TRILL Data Labeling......................6
      2.3 Fine-Grained Labeling (FGL)............................7
      2.4 VL, Limited FGL, and Full FGL TRILL Switches...........8

      3. VL versus FGL Label Differences........................10

      4. FGL TRILL Interaction with VL TRILL....................11
      4.1 FGL and VL Mixed Campus Topology......................11
      4.2 FGL and VL Mixed Campus Characteristics...............12
      4.3 FGL and VL Mixed Links................................12

      5. FGL Details............................................14
      5.1 Ingress Processing....................................14
      5.2 Transit Processing....................................15
      5.2.1 Unicast Transit Processing..........................15
      5.2.2 Multi-Destination Transit Processing................15
      5.3 Egress Processing.....................................16
      5.4 Appointed Forwarders and the DRB......................16
      5.5 Address Learning......................................17
      5.6 ESADI Extensions......................................17

      6. IS-IS Extensions.......................................18
      7. Comparison to Goals....................................19

      8. Allocation Considerations..............................20
      8.1 IEEE Allocation Considerations........................20
      8.2 IANA Considerations...................................20

      9. Security Considerations................................21
      Normative References......................................23
      Informative References....................................23
      Appendix A: Serial Unicast................................24
      Appendix Z: Change History................................25

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1. Introduction

   The IETF has standardized the TRILL (TRansparent Interconnection of
   Lots of Links) protocol [RFC6325] that provides a solution for least
   cost transparent routing in multi-hop networks with arbitrary
   topologies and link technologies, using [IS-IS] [RFC6165]
   [RFC6326bis] link-state routing with a hop count. TRILL switches are
   sometimes called RBridges (Routing Bridges).

   The TRILL base protocol standard supports labeling of TRILL data with
   up to 4K IDs. However, there are applications that require more fine-
   grained labeling of data for configurable isolation based on
   different tenants, service instances, or the like. This document
   updates [RFC6325] and [RFC6327] by specifying optional extensions to
   the TRILL base protocol to safely accomplish this. TRILL switches
   that support fine-grained labeling as specified herein have
   capabilities that are supersets of those specified in [RFC6325].

   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.

      DEI - Drop Eligibility Indicator [802.1Q].

      Edge TRILL switch - A TRILL switch announcing VLAN or Fien Grained
            Lab el interest in its LSP.

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

      FGL TRILL switch - A TRILL switch that support both FGL and VL.
            See also "Limited FGL TRILL" and "Full FGL TRILL".

      Full FGL TRILL - Capabilities that support FGL and VL ingress,
            transit, and egress.

      Limited FGL TRILL - Capabilities that support VL ingress, transit,
            and egress but only FGL transit, not FGL ingress and egress.

      TRILL Switch - Alternative name for an RBridge.

      VL - VLAN Labeling or VLAN Labeled or VLAN Label.

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      VL TRILL switch - A TRILL switch that supports VL but does not
            support any FGL capabilities.

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

1.2 Contributors

   Thanks for the contributions of the following:

      Tissa Senevirathne

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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 data
   label from a set consisting of significantly more than 4K labels, (b)
   TRILL switch (RBridge) ports can be labeled with a set of such data
   labels, and (c) an FGL TRILL Data frame cannot be egressed through a
   TRILL switch port unless its fine-grained label (FGL) matches one of
   the data labels of the port.

   Section 2.1 lists FGL goals.  Section 2.2 briefly outlines the more
   coarse TRILL base protocol standard [RFC6325] data labeling.  Section
   2.3 outlines FGL for TRILL Data frames. And Section 2.4 compares VL,
   Limited FGL, and Full FGL TRILL switches.

2.1 Goals

   There are several goals that would be desirable for FGL 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 labeling supported by
      [RFC6325] provides for only ( 2**12 - 2 ) valid identifiers or
      labels. A substantially larger number is required.

   2. Silicon

      Fine-grained labeling (FGL) should, to the extent practical, use
      existing features, processing, and fields that are already
      supported in many fast path silicon implementations that support
      the TRILL base protocol. To the extent that such silicon does not
      support Full FGL TRILL, it would be desirable to support Limited
      FGL TRILL (see Section 2.4).

   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 if RBridges not implementing the
      FGL features and performing at least the transit forwarding
      function can usefully process TRILL Data frames that incorporate

D. Eastlake, et al                                              [Page 5]

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   4. Alternate Priority

      It would be desirable for an ingress TRILL Switch 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.
      This enables traffic from attached non-TRILL networks to be
      handled with different priority while transiting a TRILL network
      if desired.

2.2 Base Protocol TRILL Data Labeling

   This section provides a brief review of the [RFC6325] TRILL Data
   frame internal VL Labeling and changes the description of the TRILL
   Header by moving its end point. This descriptive change does not
   involve any change in the bits on the wire or in the behavior of
   existing [RFC6325] VL RBridges.

   VL TRILL Data frames have the structure shown below:

               | Link Header (depends on link technology)  |
               | (if link is an Ethernet link the link     |
               |  header may include an Outer.VLAN tag)    |
               | TRILL Header                              |
               | +---------------------------------------+ |
               | |    Initial Fields and Options         | |
               | +---------------------------------------+ |
               | |         Inner.MacDA         | (6 bytes) |
               | +-----------------------------+           |
               | |         Inner.MacSA         | (6 bytes) |
               | +-----------------------+-----+           |
               | | Ethertype 0x8100      |       (2 bytes) |
               | +-----------------------+                 |
               | | Inner.VLAN Label      |       (2 bytes) |
               | +-----------------------+                 |
               |               Native Payload              |
               | Link Trailer (depends on link technology) |

                       Figure 1. TRILL Data with VL

   In the base protocol as specified in [RFC6325] the 0x8100 value is
   always present and is followed by the Inner.VLAN field which includes
   the 12-bit VL.

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2.3 Fine-Grained Labeling (FGL)

   FGL expands the variety of data labels available under the TRILL
   protocol to include a fine-grained label (FGL) with a 12-bit high
   order part and a 12-bit low order part. In this document, FGLs are
   usually denoted as "(X.Y)" where X is the high order part and Y is
   the low order part of the FGL.

   FGL TRILL Data frames have the structure shown below.

               | Link Header (depends on link technology)  |
               | (if link is an Ethernet link the link     |
               |  header may include an Outer.VLAN tag)    |
               | TRILL Header                              |
               | +---------------------------------------+ |
               | |    Initial Fields and Options         | |
               | +---------------------------------------+ |
               | |         Inner.MacDA         | (6 bytes) |
               | +-----------------------------+           |
               | |         Inner.MacSA         | (6 bytes) |
               | +-----------------------+-----+           |
               | | Ethertype 0x893B      |       (2 bytes) |
               | +-----------------------+                 |
               | | Inner.Label High Part |       (2 bytes) |
               | +-----------------------+                 |
               | | Ethertype 0x893B      |       (2 bytes) |
               | +-----------------------+                 |
               | | Inner.Label Low Part  |       (2 bytes) |
               | +-----------------------+                 |
               |               Native Payload              |
               | Link Trailer (depends on link technology) |

                       Figure 2. TRILL Data with FGL

   For FGL frames, the inner MAC address fields are followed by the FGL
   information using 0x893B.

   The two bytes following each 0x893B have, in their low order 12 bits,
   fine-grained label information. The upper 4 bits of those two bytes
   are used for a 3-bit priority field and one drop eligibility
   indicator (DEI) bit.

   The priority field of the Inner.Label High Part is the priority used
   for frame transport across the TRILL campus from ingress to egress.
   The label bits in the Inner.Label High Part are the high order part

D. Eastlake, et al                                              [Page 7]

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   of the FGL and those bits in the Inner.Label Low Part are the low
   order part of the FGL.

   The appropriate FGL value for an ingressed or locally originated
   native frame is determined by the ingress TRILL switch port as
   specified in Section 5.1.

2.4 VL, Limited FGL, and Full FGL TRILL Switches

   For a number of reasons, as listed below, it is desirable for FGL
   TRILL switches to be able to handle both VL and FGL TRILL Data

      o  Continued support of VL frames makes interoperation between VL
         and FGL RBridges easier as discussed in Sections 4.1 and 4.2.

      o  Due to the way TRILL works, it may be desirable to have a
         maintenance VLAN or FGL [OAMframework] in which all TRILL
         switches in the campus indicate interest. It will be simpler to
         use the same type of label for all TRILL switche for this
         purpose. That implies using VL if there might be any VL TRILL
         switches in the campus.

      o  If a campus is being upgraded from VL FGL TRILL switches, it
         avoids a requirement to immediately reconfigure all ports with
         FGL configuration.

   The table below summarizes the differences in the capabilities of VL
   TRILL switches, Limited FGL TRILL switches, and Full FGL TRILL
   switches. As discussed in Section 4, VL TRILL switches conformant to
   [RFC6325] should discard an FGL TRILL Data frame as malformed. FGL
   features are optional and VL TRILL switches are still a conformant
   implementation of the TRILL protocol.

          TRILL Data  ||  VL TRILL Switch |    FGL TRILL Switch   |
          Frame Type  ||                  |  Limited  |   Full    |
                      ||   ingress        |  ingress  |  ingress  |
           VL         ||   transit        |  transit  |  transit  |
                      ||   egress         |  egress   |  egress   |
                      ||                  |           |  ingress  |
           FGL        ||   discard        |  transit  |  transit  |
                      ||                  |           |  egress   |

              Figure 3. TRILL Switch Capabilities Comparison

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   The primary reason to specify and permit Limited FGL TRILL switches
   in a campus is that they might be upgraded VL TRILL switches not
   capable of efficiently performing FGL ingress or egress but capable
   of safely transiting FGL frames.

D. Eastlake, et al                                              [Page 9]

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3. VL versus FGL Label Differences

   There are differences between the semantics across a TRILL campus for
   TRILL Data frames that are VL data labeled and those that are FGL
   data labeled.

   With VL, data label IDs have the same meaning throughout the campus
   and are from the same label space as the C-VLAN IDs used on Ethernet
   links to end stations.

   With FGL TRILL switches, many things remain the same because an FGL
   can appear only as the Inner.Label inside a TRILL Data frame. As
   such, only a TRILL-aware device will see a fine-grained label.  The
   Outer.VLAN that may appear on native frames and that may appear on
   TRILL Data frames if those TRILL Data frames are on an Ethernet link
   can only be a C-VLAN tag. Thus ports of FGL TRILL switches, up
   through the usual VLAN and priority processing, act as they do for VL
   TRILL switches: TRILL switch ports provide a C-VLAN ID for an
   incoming frame and accept a C-VLAN ID for a frame being queued for
   output. Appointed Forwarders [RFC6439] on a link are still appointed
   for a C-VLAN. The Designated VLAN for an Ethernet link is still a C-

   The larger FGL data label space is a different space from the VL data
   label space. For ports configured for FGL, the C-VLAN on an ingressed
   native frame is mapped to the FGL data label space with a potentially
   different mapping for each port. A similar FGL to C-VLAN mapping
   occurs per port on egress. Thus, for ports configured for FGL, the
   native frame C-VLAN on one link corresponding to an FGL can be
   different from the native frame C-VLAN corresponding to that same FGL
   on a different link elsewhere in the campus or even a different link
   attached to the same TRILL switch. The FGL label space is flat and
   does not hierarchically encode any particular number of native frame
   C-VLAN bits or the like. FGLs appear only inside TRILL Data frames
   after the inner MAC addresses.

   As shown in Section 2.4, FGL TRILL switches have capabilities that
   are a superset of those for VL TRILL switches. FGL TRILL switch ports
   can be configured for FGL or VL with VL being the default. As with a
   base protocol [RFC6325] TRILL switch, an unconfigured FGL TRILL
   switch port reports an untagged frame it receives as being in VLAN 1.

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4. FGL TRILL Interaction with VL TRILL

   This section discusses various ramifications of attempting to mix FGL
   and VL TRILL switches in a campus. Section 4.1 discusses what
   behaviors are needed to render such mixed campuses safe while Section
   4.2 discusses some resulting network characteristics. Section 4.3
   gives further details of link local mixed campus behavior.

4.1 FGL and VL Mixed Campus Topology

   It is not possible for VL TRILL switches to safely handle FGL frames
   even if the VL TRILL switch is only acting in the transit capacity.
   This is because VL frames are required to have 0x8100 at the
   beginning of the data label where FGL frames have 0x893B.  VL-only
   TRILL switches conformant to [RFC6325] should discard frames with
   this new value after the inner MAC addresses. If they do not discard
   such frames, they will be confused and could egress them into the
   wrong VLAN (see Section 9 below) or re-order them due to miscomputing
   flows for ECMP. Such difficulties are avoided by stopping TRILL data
   communication between VL and FGL TRILL switches as specified below.

   FGL TRILL switches will report their FGL capability in LSPs.  TRILL
   IS-IS communication is not affected by the blocking of TRILL data
   connectivity between VL and RFL Trill switches. So the link state
   data base will include the entire TRILL campus regardless of the
   presence of a mixture of VL and FGL TRILL switches.  Thus FGL TRILL
   switches (and any management system with access to the link state
   database) will be able to detect the existence of TRILL switches in
   the campus that do not support FGL.

   If both VL and FGL TRILL switches are present on a link then,
   although all other aspects of the adjacency machinery work as normal
   [RFC6327], any FGL TRILL switches on the link will not create a
   pseudo node for the link if they are DRB and will excommunicate the
   link by not announcing any adjacencies on the link. As a result,
   although adjacencies between two or more VL TRILL switch ports on
   such a link could become part of the campus topology and pass VL
   TRILL Data frames, no adjacency from an FGL TRILL switch port to a VL
   TRILL switch port or to a pseudo node will be reported on such a
   mixed FGL/VL link. Since an adjacency must be reported up by both
   ends before it becomes part of the campus topology, even though a VL
   TRILL switch might report an adjacency to an FGL TRILL switch, no
   TRILL Data can flow between an FGL and a VL TRILL switch port.

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4.2 FGL and VL Mixed Campus Characteristics

   The provisions described in Section 4.1 to block TRILL data
   communication between VL and FGL TRILL switches, although implemented
   only by FGL TRILL switches, have relatively symmetric effects.

   A campus of mostly FGL TRILL switches with a few isolated VL TRILL
   switches scattered throughout will work well in terms of connectivity
   for end stations attached to those FGL switches except that they will
   be unable to communicate with any end stations for which a VL switch
   is appointed forwarder. The VL TRILL switches will be isolated and
   will only be able to route TRILL Data to the extent they happen to be
   contiguously connected to other VL TRILL switches. Distribution trees
   computed by the FGL switches will not include any VL switches (see
   Section 2.1 of [ClearCorrect]). A campus of mostly VL TRILL switches
   with a few isolated FGL TRILL switches scattered throughout will also
   work reasonably well as described immediately above with all
   occurrences of "FGL" and "VL" swapped. However, a campus so badly
   misconfigured that it consists of an intermingled general mixture of
   VL and FGL TRILL switches is likely to offer abysmal data service.

   The are possible future extensions to TRILL that would eliminate the
   requirement to block TRILL Data traffic between FGL and VL TRILL
   switches improving backwards compatibility.  For example, with
   support for multiple topologies [MultiTopo], it would be possible to
   put all TRILL switches into one topology on which VL frames were sent
   and all FGL TRILL switches into a second topology on which FGL frames
   were sent. Assuming that the FGL TRILL switches are fully connected,
   everything would work fine including data traffic between VL ports in
   the same VLAN regardless of whether those VL ports were on VL or FGL
   TRILL switches

4.3 FGL and VL Mixed Links

   The usual DRB election operates on a link with mixed FGL and VL
   ports. If an FGL TRILL switch port is DRB, it MUST handle all native
   traffic or appoint only other FGL TRILL switch ports as Appointed
   Forwarder for one or more VLANs, so that all end stations will get
   service to the FGL campus. If a VL TRILL switch port is DRB, it will
   not understand that FGL TRILL switch ports are different. To the
   extent that a VL DRB handles native frames or appoints other VL TRILL
   switch ports on a link to handle native frames for one or more VLANs,
   the end stations sending and receiving those native frames will be
   isolated from the FGL campus and will receive only service from the
   VL campus to the extent the VL campus has connectivity. When a VL DRB
   happens to appoint an FGL port as Appointed Forwarder for one or more
   VLANs, the end stations sending and receiving native frames in those
   VLANs will get service to the FGL campus. This corner case behavior

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   is considered acceptable because it is assumed that the campus is
   intended to be VL or FGL and TRILL switches of the other type are
   infrequent misconfigurations.

   For links configured as point-to-point, if the TRILL switches at each
   end are both VL or both FGL, a bi-directional adjacency can be formed
   and reported as usual. If one is VL and one is FGL but the point-to-
   point link is otherwise correctly configured, the VL TRILL switch
   will report an adjacency but the FGL one will not. As a result, the
   link will not become part of the topology and TRILL Data cannot flow
   over the link, excommunicating the switches from each other for data.

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5. FGL Details

   This section specifies ingress, transit, egress, and other processing
   details with regard to FGL TRILL switches. A transit or egress FGL
   TRILL switch determines that a TRILL Data frame is FGL by detecting
   that the Inner.MacSA is followed by 0x893B.

5.1 Ingress Processing

   It MUST be possible to configure the ports of a Full FGL TRILL switch
   to ingress native frames as FGL. Any ports not so configured performs
   the previously specified [RFC6325] VL ingress processing on native
   frames resulting in a VL TRILL Data frame. (There is no change in
   Appointed Forwarder logic (see Section 5.4).)

   Thus Full FGL TRILL switches MUST support configurable per port
   mapping from the C-VLAN of a native frame, as reported by the ingress
   port, to an FGL. FGL TRILL switches MAY support other methods to
   determine the FGL of an incoming native frame, such as based on the
   protocol of the native frame or local knowledge.

   The FGL ingress process MUST copy the priority and DEI associated
   with an ingressed native frame to the upper 4 bits of the Inner.Label
   Low Order part. It SHOULD also associate a possibly different mapped
   priority and DEI with an ingressed frame but a TRILL switch might not
   be able to do so because of implementation limitations. The mapped
   priority is placed in the Inner.Label High Part. If such mapping is
   not supported then the original priority and DEI MUST be placed in
   the Inner.Label High Part.

   An FGL ingress TRILL switch MAY serially TRILL unicast a multi-
   destination TRILL Data frame to the relevant egress TRILL switches by
   using a known unicast TRILL Header (M=0) and SHOULD unicast such a
   multi-destination TRILL Data frame if there is only one relevant
   egress FGL TRILL switch. For FGL TRILL switches, this permits serial
   unicast of multi-destination frames by the ingress as an alternative
   to the use of a distribution tree. The relevant egress TRILL switches
   are determined by starting with those announcing interest in the
   frame's (X.Y) label. That set SHOULD be further filtered based on
   multicast listener and multicast router LSP announcements if the
   native frame was a multicast frame.

   Using a TRILL unicast header for a multi-destination frame when it
   has only one actual destination RBridge can improve traffic spreading
   and decrease latency as discussed in Appendix A. How to decide
   whether to use a distribution tree or serial unicast for a multi-
   destination TRILL Data frame that has more than one destination TRILL
   switch is beyond the scope of this document.

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5.2 Transit Processing

   Any FGL TRILL switch, Limited or Full, MUST be capable of TRILL Data
   frame transit processing. Such 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 very little change in TRILL Data frame unicast transit
   processing. A transit TRILL switch forwards any unicast TRILL Data
   frame to the next hop towards the egress TRILL switch as specified in
   the TRILL Header. All transit TRILL switches, whether VL or FGL, MUST
   take the priority and DEI used to forward a frame from the Inner.VLAN
   label or the FGL Inner.Label High Part. These bits are in the same
   place in the frame.

   An FGL TRILL switch, including a Limited FGL TRILL switch that might
   have limited knowledge of FGL formats, MUST properly distinguish
   flows if it provides ECMP for FGL frame.

5.2.2 Multi-Destination Transit Processing

   Multi-destination TRILL Data frames are forwarded on a distribution
   tree selected by the ingress TRILL switch except that an FGL ingress
   TRILL switch may TRILL unicast such a frame to all relevant egress
   TRILL switches as described in Section 5.1.  The distribution trees
   do not distinguish between FGL and VL multi-destination frames
   except, possibly, in pruning behavior. All distribution trees are
   calculated as provided for in the TRILL base protocol standard
   [RFC6325] as updated by [ClearCorrect]. There is no change in the
   Reverse Path Forwarding Check.

   An FGL TRILL switch, say RB1, having an FGL multi-destination frame
   for label (X.Y) to forward on a distribution tree, SHOULD prune that
   tree based on whether there are any edge TRILL switches on a tree
   branch that are advertising connectivity to label (X.Y). In addition,
   RB1 SHOULD prune multicast frames based on reported multicast
   listener and multicast router attachment in (X.Y).

   Pruning is an optimization. If a transit TRILL switch does less
   pruning than it could, there may be greater link utilization than
   strictly necessary but the campus will still operate correctly. A
   transit TRILL switch MAY prune based on an arbitrary subset of the
   bits in the FGL label, for example only the High Part or only the Low
   Part of the label.

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5.3 Egress Processing

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

   A Full FGL TRILL switch MUST be able to configurably convert the FGL
   in an FGL TRILL Data frame it is egressing to a C-VLAN ID for the
   resulting native frame on a per port basis. The priority and DEI of
   the egressed native frame are taken from the Inner.Label Low Order
   Part. A port MAY be configured to strip output VLAN tagging.

   It is the responsibility of the network manager to properly configure
   the TRILL switches in the campus to obtain the desired mappings.

   An FGL TRILL switch egresses FGL frames similarly to the egressing of
   VL frames, as follows:

      1. A known unicast FGL TRILL Data frame is egressed to the FGL
         port or ports matching its FGL and Inner.MacDA. If there are no
         such ports, it is flooded out all FGL ports that have its FGL
         except any ports that for which the TRILL switch has knowledge
         that the frame's Inner.MacDA cannot be out that port.

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

   An FGL TRILL switch, including a Limited FGL TRILL switch that might
   have limited knowledge of FGL formats, MUST NOT egress an FGL frame
   with label (X.Y) to any port not configured with that label even if
   the port is configured to egress VL frames in VLAN X.

   FGL TRILL switches MUST accept multi-destination TRILL Data frames
   that are sent to them as TRILL unicast frames, that is, frames that
   may have a multicast or broadcast Inner.MacDA (or are being sent to
   an unknown unicast Inner.MacDA) and the TRILL Header M bit set to 0.
   They locally egress such frames, if appropriate, but MUST NOT forward
   them (other than egressing them as native frames on their local

5.4 Appointed Forwarders and the DRB

   There is no change in Adjacency [RFC6327] or Appointed Forwarder
   logic [RFC6439] on a link regardless of whether some or all the ports
   on the link are for FGL TRILL switches except for the refusal of FGL
   TRILL switches to report adjacencies on links with mixed VL and FGL
   TRILL switches, as described in Section 4 above.

D. Eastlake, et al                                             [Page 16]

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5.5 Address Learning

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

5.6 ESADI Extensions

   The TRILL ESADI (End Station Address Distribution Information)
   protocol is specified in [RFC6325] as optionally transmitting MAC
   address connection information through TRILL Data frames between
   participating TRILL switches over the virtual link provided by the
   TRILL multicast frame distribution mechanism. In [RFC6325], the VL to
   which an ESADI frame applies is indicated only by the Inner.VLAN
   label and no indication of that VL is allowed within the ESADI

   ESADI is extended to support FGL by providing for the indication of
   the FGL to which an ESADI frame applies only in the Inner.Label of
   that frame and no indication of that FGL is allowed within the ESADI

D. Eastlake, et al                                             [Page 17]

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6. IS-IS Extensions

   Extensions to the TRILL use of IS-IS are required to support FGL
   include the following:

      1. An method for a TRILL switch to announce itself in its LSP as
         supporting FGL (see Section 8.2).

      2. A sub-TLV analogous to Interested VLANs and Spanning Tree Roots
         sub-TLV of the Router Capabilities TLV but indicating FGLs
         rather than VLs. This is called the Interested Labels and
         Spanning Tree Roots sub-TLV in [rfc6326bis].

      3. Sub-TLVs analogous to the GMAC-ADDR sub-TLV of the Group
         Address TLV that specifies an FGL rather than a VL. These are
         called the GLMAC-ADDR, GLIP-ADDR, and GLIP6 ADDR sub-TLVs in

D. Eastlake, et al                                             [Page 18]

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7. Comparison to Goals

   Comparing TRILL FGL, as specified in this document, with the goals
   given in Section 2.1, we find as follows:

   1. Fine-Grained: FGL provides 2**24 labels, vastly more than the 4K
      VL labels provided in [RFC6325].

   2. Silicon: Existing TRILL fast path silicon chips can perform base
      TRILL Header insertion and removal to support ingress and egress.
      In addition, it is believed that most such silicon can also
      perform the native frame to FGL mapping and the encoding of the
      FGL 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 one pass through the fast path and so is
      likely to be suitable as a full speed Limited FGL TRILL switch or
      a reduced rate Full FGL TRILL switch requiring two passes for
      ingress/egress; however, other existing chips are believed to be
      able to perform both operations on the same frame in one pass
      through their fast path and are thus suitable for full rate Full
      FGL TRILL processing.

   3. Base RBridge Compatibility: As described in Section 3, FGL is not
      generally compatible with TRILL switches conformant to the base
      specification [RFC6325] although, as described in Section 4.3,
      there are possible future TRILL extensions that would enable data
      intercommunication in some topologies. In particular, an FGL-
      ignorant TRILL switch cannot be even a Limited FGL TRILL switch in
      a restricted topology because there is a risk that it would
      receive multi-destination FGL frames and egress them to the wrong
      VLAN. However, a contiguous set of VL TRILL switches can exchange
      VL frames regardless of the presence of FGL TRILL switches in the

   4. Alternate Priority: The encoding specified in Section 2.3 and the
      ingress/egress processing specified in Section 5 provide for a new
      priority and DEI in the Inner.Label High Part and a place to
      preserve the original user priority and DEI in the Low Part, so it
      can be restored on egress.

D. Eastlake, et al                                             [Page 19]

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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 0x893B for use
   as the TRILL FGL Ethertype.

8.2 IANA Considerations

   IANA is requested to allocate capability bit TBD in the TRILL-VER
   sub-TLV capability bits [RFC6326bis] to indicate a TRILL switch is
   FGL-capable (either Limited FGL or Full FGL).

D. Eastlake, et al                                             [Page 20]

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9. Security Considerations

   See [RFC6325] for general TRILL Security Considerations.

   As with any communications system, end-to-end encryption and
   authentication should be considered for sensitive data. In this case
   that would be encryption and authentication extending from a source
   end station to a destination end station.

   Confusion between a frame with VL X and FGL (X.Y) or confusion due to
   a malformed frame is a potential problem if an FGL TRILL switch did
   not properly check for the occurrence of 0x8100 or 0x893B immediately
   after the Inner.MacSA (see Sections 2.2 and 2.3) and handled the frame

   [RFC6325] requires that the Ethertype immediately after the
   Inner.MacSA be 0x8100. A VL TRILL switch that did not discard a frame
   with some other value there could cause problems. If it received a
   TRILL Data frame with FGL (X.Y) or with junk after the Inner.MacSA
   that included X where a VLAN ID would appear, then:

      1. It could egress the frame to an end station in VLAN-X. If the
         frame was a well formed FGL frame, the payload of such an
         egressed native frame would appear to begin with Ethertype
         0x893B that would likely be discarded by an end station. In any
         case, such an egress would almost certainly be a violation of
         security policy requiring the configurable separation of
         differently labeled data.

      2. If the frame was multi-destination and the TRILL switch pruned
         the distribution tree, it would incorrectly prune it on the
         basis of VLAN-X. For an FGL frame, this would probably lead to
         the multi-destination data frame not being delivered to all of
         its intended recipients.

   Possible problems with an FGL TRILL switch that received a TRILL Data
   frame with junk after the Inner.MacSA that included X where a VLAN ID
   would appear and did not check the Ethertype immediately after the
   Inner.MacSA would be that it could improperly egress the frame in
   VLAN-X, violating security policy. If the frame was multi-destination
   and was improperly forwarded, it should be discarded by properly
   implemented TRILL switches downstream in the distribution tree and
   never egressed but the propagation of the frame would still waste

   To avoid these problems all TRILL switches MUST check the Ethertype
   immediately after the Inner.MacSA and, if it is a value they do not
   know how to handle, either discard the frame or make no decisions
   based on any data after that Ethertype. In addition, care must be
   taken to avoid FGL frames being sent to or through VL TRILL switches

D. Eastlake, et al                                             [Page 21]

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   that will discard them if the VL TRILL switch is properly implemented
   or mishandle them if it is not properly implemented. This is
   accomplished, as described in Section 4, by FGL TRILL switches not
   announcing adjacency to VL TRILL switches. As a result, no TRILL data
   frames can be exchanged between VL and FGL TRILL switches and they
   will be isolated form each other for data purposes.


   The comments and suggestions of the following are gratefully

      Anoop Ghanwani, Sujay Gupta, Weiguo Hao, Jon Hudson, Phanidhar
      Koganti, Yizhou Li, Vishwas Manral, Rajeev Manur, Thomas Narten,
      Erik Nordmark, Olen Stokes, Ilya Varlashkin, and Xuxiaohu.

   The document was prepared in raw nroff. All macros used were defined
   within the source file.

D. Eastlake, et al                                             [Page 22]

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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.

   [RFC6327] - Eastlake 3rd, D., Perlman, R., Ghanwani, A., Dutt, D.,
         and V. Manral, "Routing Bridges (RBridges): Adjacency", RFC
         6327, 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-ietf-isis-rfc6326bis, Work in

   [ClearCorrect] - D. Eastlake, M. Zhang, A. Ghanwani, A. Banerjee, V.
         Manral, draft-ietf-trill-clear-correct-06.txt, in RFC Editor's

Informative References

         - draft-tissa-trill-mt-encode, Work in Progress.
         - draft-eastlake-trill-rbridge-multi-topo, Work in Progress.

   [OAMframework] - draft-ietf-trill-oam-framework, Work in Progress.

   [RFC6165] - Banerjee, A. and D. Ward, "Extensions to IS-IS for
         Layer-2 Systems", RFC 6165, April 2011.

   [RFC6439] - Perlman, R., Eastlake, D., Li, Y., Banerjee, A., and F.
         Hu, "Routing Bridges (RBridges): Appointed Forwarders", RFC
         6439, November 2011.

D. Eastlake, et al                                             [Page 23]

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Appendix A: Serial Unicast

   This appendix discusses advantages and disadvantages of using serial
   unicast instead of a distribution tree for multi-destination TRILL
   Data frames. See Sections 5.1 and 5.3.

   Consider a large TRILL campus with hundreds of TRILL switches in
   which, say, 300 end stations are in some particular FGL data label.

   At one extreme, if all 300 end stations were on links attached to a
   single TRILL switch, then no other TRILL switch would be advertising
   interest in that FGL and likely a multi-destination (say broadcast)
   frame from one such end station would, even if put on a distribution
   tree, because of pruning, not get sent to any another TRILL switch.

   At the other extreme, assume the 300 end stations are attached, one
   each, to 300 different TRILL switches; in that case you are almost
   certainly better off using a distribution tree because if you tried
   to serially unicast you would probably have to output multiple copies
   through the same port port and would cause much higher link

   Now assume these 300 end stations are connected to exactly two TRILL
   switches, say 200 to one and 100 to the other. Using unicast TRILL
   Data frames between these two TRILL switches is best because the
   frames will follow least cost paths, possibly with such traffic
   spread over a number of equal cost least cost paths. On the other
   hand, if a distribution trees were used, each frame would be
   constrained to the tree used for that frame and would likely follow a
   more circuitous route, depending on where the tree's root ia, and
   only a single path would be available per tree. Thus this document
   says that unicast "SHOULD" be used if there are exactly two TRILL
   switches involved.

   It is a more complex decision whether to use a distribution tree or
   serial unicast if the end stations are connected to a number of TRILL
   switches greater than two. Which would be better would depend on many
   factors including network topology and application data patterns. How
   to make this decision in such more complex cases is beyond the scope
   of this document.

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Appendix Z: Change History

   RFC Editor Note: Please delete this appendix before publication.

   From -00 to -01:

         Update author info and make editorial changes.

   From -01 to -02

      1. Change the value after the inner MAC addresses for FGL frames
         from 0x8100 to 0x893B

      2. As a consequence of item 1 above, for safety prohibit use for
         TRILL Data of links between FGL and VL RBridges, isolating any
         VL RBridges. Make appropriate changes throughout document,
         including Security Considerations section, based on this

      3. Reference and contributor updates.

      4. Minor editorial changes.

   From -02 to -03

      1. Addition of the terms "Limited FGL" and "Full FGL".

      2. Addition of Appendix A.

      3. Clarifications:
         3.a That FGL TRILL switches also support VL ports and frames
             (Add Section 2.4, etc.).
         3.b That the FGL extensions to TRILL are optional. A VL TRILL
             switch is still a conformant implementation.
         3.c The utility of the alternate priority goal.

      4. Expand Security Considerations discussion of misparsed frames.

      5. Substantial editorial changes.

D. Eastlake, et al                                             [Page 25]

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Authors' Addresses

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

   Phone: +1-508-333-2270
   Email: d3e3e3@gmail.com

   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

   Email: zhangmingui@huawei.com

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

   Phone: +1-949-926-5000
   Email: pagarwal@broadcom.com

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

   Phone: +1-408-765-8080
   Email: Radia@alum.mit.edu

   Dinesh G. Dutt
   Cumulus Networks
   1089 West Evelyn Avenue
   Sunnyvale, CA 94086 USA

   Email: ddutt.ietf@hobbesdutt.com

D. Eastlake, et al                                             [Page 26]

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Copyright, Disclaimer, and Additional IPR Provisions

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D. Eastlake, et al                                             [Page 27]

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