TRILL Working Group                                         Hongjun Zhai
INTERNET-DRAFT                                                Fangwei Hu
Intended status: Proposed Standard                                   ZTE
Updates: 6325                                              Radia Perlman
                                                              Intel Labs
                                                         Donald Eastlake
Expires: September 9, 2012                                March 10, 2012

                       TRILL: The ESADI Protocol


   The IETF TRILL (TRansparent Interconnection of Lots of Links)
   protocol provides least cost pair-wise data forwarding without
   configuration in multi-hop networks with arbitrary topologies and
   safe forwarding even during periods of temporary loops. TRILL
   supports the multi-pathing of both unicast and multicast traffic.
   TRILL accomplishes this by using the IS-IS (Intermediate System to
   Intermediate System) link state routing protocol and encapsulating
   traffic using a header that includes a hop count.

   The ESADI (End System Address Distribution Information) protocol is a
   VLAN (Virtual Local Area Network) scoped way that RBridge can
   communicate end station addresses to each other.  An RBridge
   announcing VLAN-x connectivity (normally a VLAN-x forwarder) and
   running the TRILL ESADI protocol can receive remote address
   information and/or transmit local address information for VLAN-x to
   other such RBridges.  This document updates RFC 6325, particularly
   the documentation of the ESADI protocol.

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

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   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............................................4
      1.1 Content and Precedence.................................5
      1.2 Terminology............................................5

      2. ESADI Protocol Overview.................................6

      3. ESADI Control State.....................................8
      3.1 ESADI DRB..............................................8
      3.2 ESADI RBridge Instance States..........................8
      3.3 ESADI DRB election events..............................9
      3.4 Timers.................................................9
      3.5 ESADI Neighbor List...................................10
      3.6 State Table and Diagram...............................11

      4. ESADI PDU processing...................................13
      4.1 Sending of ESASI PDUs.................................13
      4.2 Receipt of ESADI PDUs.................................14

      5. ESADI LSP Contents.....................................16
      5.1 ESADI Participation Data..............................16
      5.2 ESADI MAC Address sub-TLV.............................17

      6. IANA Considerations....................................18
      7. Security Considerations................................18
      8. References.............................................19
      8.1 Normative references..................................19
      8.2 Informative References................................20

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1. Introduction

   The IETF TRILL (TRansparent Interconnection of Lots of Links)
   protocol [RFC6325] provides least cost pair-wise data forwarding
   without configuration in multi-hop networks with arbitrary
   topologies, safe forwarding even during periods of temporary loops,
   and support for multi-pathing of both unicast and multicast traffic.
   TRILL accomplishes this by using the IS-IS (Intermediate System to
   Intermediate System) [IS-IS] [RFC1195] [RFC6326] link state routing
   protocol and encapsulating traffic using a header that includes a hop
   count.  The design supports VLANs (Virtual Local Area Networks) and
   optimization of the distribution of multi-destination frames based on
   VLANs and IP derived multicast groups.  Devices that implement TRILL
   are called RBridges (Routing Bridges) or TRILL switches.

   There are five ways an RBridge can learn end station addresses as
   described in Section 4.8 of [RFC6325].  The ESADI (End Station
   Address Distribution Information) protocol is an optional VLAN scoped
   way RBridges can communicate end station addresses with each other.
   An RBridge that is announcing connectivity to VLAN-x (normally a
   VLAN-x appointed forwarder) MAY use the (ESADI) protocol to announce
   the end station address of some or all of its attached VLAN-x end
   nodes to other RBridges that are running ESADI for VLAN-x.

   By default, RBridges with connected end stations learn addresses from
   the data plane when ingressing and egressing native frames. The ESADI
   protocol's potential advantages over data plane learning include the

   1. Security advantages: The ESADI protocol can be used to announce
      end stations with an authenticated enrollment (for example
      enrollment authenticated by cryptographically based EAP
      (Extensible Authentication Protocol [RFC3748]) methods via
      [802.1X]).  In addition, the ESADI protocol supports cryptographic
      authentication of its message payloads for more secure

   2. Fast update advantages: ESADI protocol provides a fast update of
      end nodes MAC (Media Access Control) addresses.  If an end station
      is unplugged from one RBridge and plugged into another, frames
      addressed to that older RBridge can be black holed.  They can be
      sent just to the older RBridge that the end station was connected
      to until cached address information at some remote RBridge times
      out, possibly for tens of seconds [RFC6325].

   MAC address reachability information and some ESADI parameters are
   carried in ESADI frames rather than in the core TRILL IS-IS protocol.
   As described below, ESADI is, for each VLAN, a virtual logical
   topology overlay in the TRILL topology. An advantage of using ESADI
   is that the end station attachment information is not flooded to all

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   RBridges through the core IS-IS instance but only to participating
   RBridges advertising ESADI support for the VLAN in which those end
   stations occur.

1.1 Content and Precedence

   This document clarifies and updates the description of the ESADI
   protocol in the TRILL basic specification, especially the ESADI DRB
   (Designated RBridge) election procedure, ESADI instance state
   specification, and ESADI parameter announcement.

   Section 2 is the ESADI protocol overview. Section 3 specifics ESADI
   control state: the DRB principles, ESADI instance state and DRB
   election are specified.  Section 4 discusses the processing of ESADI
   PDUs. Section 5 describes two ESADI sub-TLVs: the one with ESADI
   participation information and the MAC Address sub-TLV.

   This document updates [RFC6325] and prevails over [RFC6325] in the
   case of conflicts.

1.2 Terminology

   This document uses the acronyms defined in [RFC6325] and the
   following phrase:

   LSP number zero - A Link State PDU with fragment number equal to

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

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2. ESADI Protocol Overview

   ESADI is a VLAN scoped way that RBridges can announce and learn end
   station addresses rapidly and securely.  An RBridge that is
   announcing itself as connected to one or more VLANs (usually because
   it is an Appointed Forwarder) and participates in the ESADI protocol
   is called an ESADI RBridge.

   ESADI is a separate protocol from the core IS-IS instance implemented
   by all RBridges in a campus.  There is a separate ESADI instance for
   each VLAN. In essence, for each VLAN, there is an instance of the IS-
   IS reliable flooding mechanism in which ESADI RBridges may choose to
   participate. (These are not the instances being specified in
   [MultiInstance].) It is an implementation decision how independent
   the implementations of multiple ESADI instances at an RBridge are.
   For example, the ESADI link state could be in a single database with
   a field in each record indicating the VLAN to which it applies or
   could be a separate database per VLAN. But the update processes
   operate separately for each ESADI instance.

   After the TRILL header, ESADI frames have an inner Ethernet header
   with the Inner.MacDA of "All-Egress-RBridges" (formerly called "All-
   ESADI-RBridges"), an Inner.VLAN tag specifying the VLAN of interest,
   and the "L2-IS-IS" Ethertype followed by the ESADI payload as shown
   in Figure 1.  For more detail see Section 4.2.5 in the TRILL base
   protocol specification [RFC6325].

   TRILL ESADI frame Structure

                       |          Link Header           |
                       |       TRILL Data Header        |
                       |     Inner Ethernet Header      |
                       |         ESADI Payload          |
                       |          Link Trailer          |

                                 Figure 1

   All transit RBridges forward ESADI frames as if they were ordinary
   multicast TRILL Data frames.  Because of this forwarding, it appears
   to the ESADI protocol at an RBridge that it is directly connected by
   a multi-access virtual link to all other RBridges in the campus
   running ESADI for that VLAN. Thus no "routing" computation or
   decisions ever have to be made by ESADI. A participating RBridge
   merely transmits the ESADI frames it originates on this virtual link

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   as described in [RFC6325] for any multicast frame. RBridges that do
   not implement the ESADI protocol, do not have it enabled, or are not
   announcing connectivity for the Inner.VLAN of an ESADI frame do not
   decapsulate or locally process any TRILL ESADI frames they receive.
   Thus the ESADI frames are transparently tunneled through transit

   TRILL ESADI frame payloads are structured like IS-IS PDU, except as
   indicated below, but are always TRILL encapsulated on the wire as if
   they were TRILL Data frames.

   The ESADI instance for VLAN-x at an RBridge RB1 acquires a neighbor
   when it first receives ESADI-LSP number zero from that neighbor and
   that neighbor is an existing RBridge in the core IS-IS instance link
   state database that is data and IS-IS reachable from RB1 (see Section
   2 of [ClearCorrect]). When an RBridge RB2 becomes IS-IS or data
   unreachable from RB1 or the entry for RB1 is purged from the core IS-
   IS link state database, it is lost as a neighbor and also purged from
   any ESADI instances. Because of these mechanisms, there are no
   "Hellos" or MTU probes sent in ESADI.

   The information distributed with the ESADI protocol is a list of
   local end station MAC addresses known to the originating RBridge and,
   for each such address, a one octet unsigned "confidence" rating in
   the range 0-254 (see Section 5.2). It is entirely up to the
   originating RBridge which locally connected MAC addresses it wishes
   to advertise via ESADI. It MAY advertise all, some, or none of such
   addresses it has. Future uses of ESADI may use it to distribute
   additional types of information.

   TRILL ESADI LSPs MUST NOT contain a VLAN ID in their payload. The
   VLAN ID to which the ESADI data applies is the Inner.VLAN of the
   TRILL Data frame enclosing the ESADI payload. If a VLAN ID could
   occur within the payload, it might conflict with the Inner.VLAN and
   could conflict with any future VLAN mapping scheme that may be
   adopted [VLANmapping]. If a VLAN ID field in an ESADI frame payload
   does include a VLAN ID, its contents is ignored.

   (In the future, TRILL may be extended to provide more fine-grained
   labeling of data and ports [FineGrained]. If so, it is expected that
   ESADI will be extended by allowing such fine-grained labeling of
   ESADI frames, as an alternative to the currently allowed Inner.VLAN
   labeling. As with the current ESADI specification, it would generally
   be prohibited for such fine-grained labeling information to appear
   inside such extended ESADI frames.)

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3. ESADI Control State

   This Section discusses ESADI control state in terms of DRB,
   neighbors, and instance states.


   It is necessary to elect one ESADI RBridge for each VLAN scoped
   virtual link where ESADI is being used.  The ESADI DRB is responsible
   for Link State Database synchronization with other RBridges by
   issuing ESADI-CSNP PDUs periodically and responding to PSNPs on the
   virtual link. Since there is no ESADI routing, an ESADI DRB need not
   create a pseudo node for the virtual link.

3.2 ESADI RBridge Instance States

   There are four states for the ESADI instance at each RBridge for each
   VLAN: Down, Initial, Not-DRB and DRB.  The state descriptions are as

   Down: This is a virtual state for convenience in creating state
         diagrams and tables.  It indicates that the ESADI instance is
         operationally down.

   Initial: This state indicates that an ESADI instance is up but does
         not know of any ESADI neighbors (i.e., the only entry in its
         neighbor list is itself). Once ESADI enters this state, it
         should start the Holding Timer, and multicast self-originated
         number zero LSPs on the virtual link. If a valid ESADI neighbor
         is found by receiving an ESADI-LSP number zero, the ESADI
         instance will leave this state and enter into "Not-DRB" state.
         In the Initial state, the Holding Timer will be recycled if the
         timer is expired.

   Not-DRB: This state indicates that the ESADI instance has found at
         least one valid ESADI neighbor and is not DRB yet. If there is
         no Holding Timer running, the timer will be started. If an
         ESADI-LSP or an ESADI-CSNP PDU is received from a higher
         priority ESADI RBridge, the Holding Timer will be recycled. If
         the Holding Timer expires, the ESADI instance will enter into
         "DRB" state.

   DRB: In this state, the ESADI instance multicasts the ESADI-CSNP PDUs
         periodically to keep Link State Database synchronization with

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         its neighbors on virtual link, and responds to ESADI-PSNP PDUs
         with ESADI-LSPs. If an ESADI PDU (i.e., ESADI-LSP, ESADI-CSNP
         and ESADI-PSNP) is received from a neighbor with a higher
         priority than its own, the ESADI instance will move to the
         "Not-DRB" state.

3.3 ESADI DRB election events

   The following events can change the ESADI state. These are all events
   for a particular RBridge's ESADI VLAN-x instance.

   E1 ESADI instance is operationally up;

   E2 Finding the first ESADI neighbor;

   E3 Holding Timer expired;

   E4 Receiving an ESADI PDU from an ESADI neighbor with higher

   E5 Losing the last ESADI neighbor;

   E6 ESADI instance goes operationally down;

   (Receiving an ESADI PDU from an ESADI neighbor with lower priority
   has no effect on the ESADI instance state.)

   Priority is determined by the priority field in the ESADI
   participation data (see Section 5.1), with the System ID as a tie
   breaker, both considered as unsigned integers with the larger
   quantity indicating higher priority.

3.4 Timers

   There are two timers for ESADI DRB election: one the Holding Timer,
   the other the Waiting Timer. The Holding Timer is a cyclic timer, and
   is used in connection with ESADI-CSNP PDUs. If this timer expires,
   the local ESADI instance will start multicasting its own ESADI-CSNP
   PDUs and, if it was in the Non-DRB state, it decides that the DRB is
   being non-responsive and moves to the DRB state.

   The Waiting Timer is a non-cyclic timer. This timer is started by the
   change of neighbor's DRB status and killed by its expiration.  It is
   used to alleviate the PDU storm stirred by Link State Database

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   synchronization in the case of current DRB being preempted by a new
   ESADI neighbor with higher priority. If this timer expires, the new
   DRB is confirmed and its ESADI parameters, such as intervals of
   holding timer and waiting timer, are accepted to overwrite the local

3.5 ESADI Neighbor List

   In order to be able to access key information about ESADI neighbors
   easily, an ESADI neighbor list is maintained for each ESADI VLAN-x
   instance. Each entry in this list represents an ESADI neighbor for

   For each neighbor, there will be a number zero LSP from that neighbor
   in the ESADI instance link state.  A list entry is created when such
   a number zero LSP is first received on the ESADI virtual link from
   some RBridge that exists in the core IS-IS instance link state
   database and is both data and IS-IS reachable (see Section 2 of
   [ClearCorrect]). A neighbor entry for an RBridge is deleted when that
   RBridge becomes data or IS-IS unreachable or if it is purged from the
   core IS-IS instance link state database. For each neighbor, the
   parameters of System-ID/nickname, priority, holding timer interval,
   waiting timer interval and the DRB flag, are stored in its respective
   entry in this list.

   The DRB flag indicates whether a neighbor is regarded as DRB or not.
   If this flag is 1, the associated neighbor is considered as DRB,
   otherwise, not DRB. At any moment, there is no more than one entry
   that is flagged as DRB in this list. The DRB status of a neighbor can
   be changed by the receipt of ESADI-CSNP PDUs coupled with the
   priorities of the originators of the PDUs, together with the priority
   of the local ESADI instance (see Section 4.2 for more details). When
   the DRB flag of one entry, such as the entry of the local ESADI
   instance, is changed in this list, the Waiting Timer will be started
   if it is not running.  When the timer is expired, the neighbor, whose
   DRB flag is 1, will be confirmed as real DRB, and its ESADI-CSNP PDUs
   will be used to accomplish Link State Database synchronization with
   other ESADI RBridges.

   If the ESADI instance is in "Initial" state, there is only one entry
   existing in this list, where the parameters of the local ESADI VLAN-x
   instance is saved. If a new entry is added to this list and the entry
   is the second one, an E2 event will occur, which drives the state of
   this ESADI instance into "Not-DRB" from "Initial".  When there are
   only two entries in this list, if the second entry is removed from
   this list, an E5 event is originated, which draws this ESADI instance
   back to "Initial" state from "Not-DRB" or "DRB".

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3.6 State Table and Diagram

   The table below shows the transitions between the RBridge ESADI
   instance states defined above based on the events defined above:

   TRILL ESADI State Table

             | Event |  Down   | Initial | Not-DRB |  DRB    |
             |  E1   | Initial |  N/A    |  N/A    |  N/A    |
             |  E2   |   N/A   | Not-DRB |  N/A    |  N/A    |
             |  E3   |   N/A   | Initial |  DRB    |  N/A    |
             |  E4   |   N/A   | Initial | Not-DRB | Not-DRB |
             |  E5   |   N/A   |  N/A    | Initial | Initial |
             |  E6   |   Down  |  Down   |  Down   |  Down   |

                                 Figure 2

   N/A indicates that the event to the left is Not Applicable in the
   state at the top of the column.

   The first state is "Down". Once an RBridge ESADI instance is
   operationally up, it enters into "Initial" state. On transition into
   the Initial state, an ESADI instance starts its Holding Timer and
   multicasts its self-originated number zero LSP on the virtual link.
   When the first valid ESADI neighbor is found on the virtual link, the
   ESADI instance enters "Not-DRB" state, otherwise the ESADI instance
   remains in "Initial" state. While in Initial state, whenever the
   timer expires it recycles the Holding Timer and multicasts its ESADI-
   LSP number zero. And if the neighbor's priority is higher than its
   own, the Holding Timer will be recycled before the ESADI instance
   enters the "Not-DRB" state.

   In both the "Non-DRB" and "DRB" states, the ESADI RBridge multicasts
   all its self-originated LSP fragments.

   In the "Not-DRB" state, if any ESADI PDUs are received from ESADI
   neighbors with higher priorities, the Holding Timer will be recycled.
   Otherwise, if the timer expires without hearing from a higher
   priority neighbor, the ESADI instance will enter "DRB" state. If the
   DRB receives an ESADI PDU from a higher priority neighbor, the ESADI
   instance will move to "Not-DRB" state. As DRB, an ESADI instance will
   multicast ESADI-CSNP PDUs to all neighbors on the virtual link
   periodically, and respond to the ESADI-PSNP PDUs with ESADI-LSP PDUs
   by multicasting them.

   Below is the same information as in the state table above presented
   as a diagram.

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   TRILL ESADI state diagram

              |       Down       |<--------+
              +------------------+         |
                |        |     ^           |
                |E1      | E6  |           |
                V        +-----+           |
              +------------------+   E6    |
        +---->|      Initial     |---------|
        |     +------------------+         |
        |      |   ^   |       ^           |
        |      |E2 |E5 |E3,E4  |           |
        |      V   |   +-------+           |
        |     +------------------+   E6    |
        |     |     Not-DRB      |---------|
        |     +------------------+         |
        |      |   ^   |       ^           |
        |      |E3 |E4 | E4    |           |
        |      V   |   +-------+           |
        | E5  +------------------+   E6    |
        +-----|       DRB        |---------+

                             Figure 3

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4. ESADI PDU processing

   VLAN-x ESADI neighbors are usually not connected directly by a
   physical link, but are always logically connected by a virtual link.
   There could be hundreds of ESADI RBridges on the virtual link.  There
   are only LSP, CSNP and PSNP PDUs used in ESADI. In particular, there
   are no Hello or MTU PDUs because ESADI does not build a topology and
   does not do any routing.

   In IS-IS, multicasting is normally on a local link and no effort is
   made to optimize to unicast because under the original conditions
   when IS-IS was designed (commonly a piece of multi-access Ethernet
   cable), any frame made the entire link busy for that frame time. But
   in ESADI what appears to be a simple multi-access link is actually a
   multi-hop distribution tree that may or may not be pruned. Thus,
   transmitting a multicast frame on such a tree imposes a substantially
   greater load than transmitting a unicast frame. This load may be
   justified if there are likely to be multiple listeners but may not be
   justified if there is only one recipient of interest. For this
   reason, under some circumstances, ESADI PDUs MAY be TRILL unicast.

   An undesirable storm of LSP PDUs could be sent to update a new
   RBridge participant in VLAN-x ESADI if it has higher priority and
   becomes DRB on the virtual link. ESADI has a feature to ameliorate

   Section 4.1 describes the sending of ESADI PDUs. Section 4.2 covers
   the receipt of ESADI PDUs.

4.1 Sending of ESASI PDUs

   When the VLAN-x ESADI instance is in "Not-DRB" or "DRB" state and a
   new neighbor is found, its self-originated LSP fragments are
   scheduled to be sent and MAY be unicast to that neighbor. The
   interval elapsed before sending the LSP(s), depends on the priority
   of the local ESADI instance.  The higher the priority, the shorter
   the interval is.

   In the case of receiving an LSP with a smaller sequence number than
   the LSP copy stored in local Link State Database, the local ESADI
   instance will also schedule to transmit the stored LSP copy and MAY
   unicast it to the sender. After the sender receives such a LSP, it
   can originate a new LSP, whose sequence number is bigger than the
   received sequence number, to refresh the LSP in all the neighbors.

   If the ESADI instance is DRB, it multicasts an ESADI-CSNP
   periodically to keep the Link State Database synchronized among its

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   neighbors on the virtual link. After receiving an ESADI-PSNP PDU, the
   DRB will transmit the LSPs requested by the PSNP on the virtual link.

   If the ESADI instance is not DRB, it will schedule multicasting only
   its self-originated LSP on the virtual link when (1) it updates an
   LSP and (2) it finds the DRB losing some LSPs or having stale LSPs,
   including the local ESADI instance's self-originated LSPs, from the
   ESADI-CSNP PDUs it receives. The higher the priority, the shorter the
   interval that it waits before sending the LSPs in case 2.

   The format of a unicast ESADI frame is the format of TRILL ESADI
   frame, in section 4.2 in [RFC6325], except that, in the TRILL header,
   the M bit is set to zero and the Egress Nickname is the nickname of
   the destination RBridge.

4.2 Receipt of ESADI PDUs

   When an ESADI PDU is received, the receiver checks for the
   originator's System ID in the receiver's core IS-IS instance link
   state database. If the System ID is not present or appears to be data
   or IS-IS unreachable, the ESADI PDU is discarded.

   After receiving a new ESADI-LSP PDU that passes the above check, the
   LSP will be installed into or replaced the older copy of this LSP in
   the local ESADI Link State Database.  If it is a number zero LSP, the
   local ESADI instance will try to find the originator of the LSP in
   its neighbor list. If the neighbor is found, any different parameters
   of this neighbor will be stored in the associated entry in the
   neighbor list. Otherwise, a new neighbor is detected, and an
   associated entry is inserted into the list to store this neighbor's
   information. If the local ESADI instance is in "Initial" state, the
   entry will be the second entry in the neighbor list, an E2 event will
   be originated, which will move this ESADI instance into "Not-DRB"
   state from "Initial".

   On receiving an ESADI-CSNP PDU from an ESADI neighbor list member,
   the PDU is used for Link State Database synchronization. If received
   from some other RBridge, it is discarded.

   If the ESADI-CSNP PDU is not discarded and the local ESADI instance
   is in "Not-DRB" or "DRB" state, it will be used to update the DRB
   flag in the entries in the neighbor list, i.e., the originator's DRB
   flag is set to 1 and other entries' DRB flag is cleared to zero. The
   above update may make the potential DRB change from one neighbor to
   another; if so, the Waiting Timer will be started if it is not
   running.  If potential DRB doesn't change from one neighbor to
   another, and the Waiting Timer is not running yet, this CSNP PDU is

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   used for Link State Database synchronization. ESADI-PSNP PDUs will be
   multicast on the virtual link to request fresh copies of lost or
   stale LSPs from DRB, if necessary.

   When receiving an ESADI-PSNP PDU, if the local ESADI instance is DRB
   and the Waiting Timer is not running, ESADI-LSP PDU requested by the
   ESADI-PSNP will be multicast on the virtual link. Otherwise, the
   ESADI-PSNP PDU is discarded.

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5. ESADI LSP Contents

   The only PDUs used in ESADI are the Level 1 ESADI-LSP, ESADI-CSNP,
   and ESADI-PSNP PDUs. This section specifies the format for ESADI
   participation data APPsub-TLV and gives the reference for the ESADI
   MAC Reachability TLV.

5.1 ESADI Participation Data

   The figure below presents the format of the ESADI participation data.
   This APPsub-TLV MUST be included in a TRILL GENAPP TLV in ESADI LSP
   number zero. LSP number zero MUST NOT exceed 1470 bytes in length.

         Participation Data

              |    Type       |              (1 byte)
              |    Length     |              (1 byte)
              |D|  RESV       |              (1 byte)
              | Priority      |              (1 byte)
              | Holding Time  |              (1 byte)
              | Waiting Time  |              (1 byte)
              | Reserved for expansion       (variable)

                                 Figure 4

   Type: set to TRILL APPsub-TLV type 1.

   Length: Set to 4 to 255.

   D: If the sub-TLV is originated by an ESADI instance that thinks it
      is DRB or an ESADI instance sending ESADI-CSNPs as DRB, the D
      field is set to 1, otherwise, the field is zero.

   RESV: Reserved bits. MUST be sent as zero and ignored on receipt.

   Priority: The Priority field gives the ESADI instance's priority for
      being DRB on the TRILL ESADI virtual link for the VLAN in which
      the PDU containing the Participation data was sent. It is an
      unsigned integer with larger magnitude indication higher priority.

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   Holding Time: Gives the holding time in seconds as an unsigned

   Waiting Time: Gives the waiting time in seconds as an unsigned

   Reserved for future expansion: Future versions of the ESADI
      Parameters APPsub-TLV may have additional information. A receiving
      ESADI RBridge ignores any additional data here unless it
      implements such future expansion(s).

   When an ESADI instance receives a participation data sub-TLV in which
   the D field is set to 1 and the originator of this LSP is confirmed
   DRB by the local ESADI instance as highest priority, the RBridge sets
   the local Holding Timer according to the value of holding time field,
   and sets the local Waiting Timer according to the value of waiting
   time field.

5.2 ESADI MAC Address sub-TLV

   The information in TRILL ESADI-LSP PDUs consists of one or more MAC
   Reachability (MAC-RI) TLVs as specified in [RFC6165].  These TLVs
   contain one or more unicast MAC addresses of end stations that are
   both on a port and in a VLAN for which the originating RBridge is
   appointed forwarder, along with the one octet unsigned Confidence in
   this information with a value in the range 0-254.

   To avoid conflict with the Inner.VLAN ID, the TLVs in TRILL ESADI
   PDUs, including the MAC-RI TLV, MUST NOT containing the VLAN ID. If a
   VLAN-ID is present in the MAC-RI TLV, it is ignored. The VLAN to
   which the ESADI-LSP applies is indicated only by the Inner.VLAN tag
   in the encapsulated TRILL ESADI frame.

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6. IANA Considerations

   IANA is requested to allocate an IS-IS Application Identifier under
   the Generic Information TLV (#251) for TRILL [RFCgenapp] and to
   create a subregistry in the TRILL Parameters Registry for "TRILL
   APPsub-TLVs under IS-IS TLV #251 Application Identifier #TBD".  The
   initial contents of this subregistry are as follows:

             Type   Name                Reference
            ------ --------            -----------
                0  Reserved            <this RFC>
                1  ESADI Parameters    <this RFC>
            2-254  Available           <this RFC>
              255  Reserved            <this RFC>

   TRILL APPsub-TLV Types 2 through 254 are available for allocation by
   Standard Action, as modified by [RFC4020]. For example, such APPsub-
   TLVs might be used in connection with OAM [OAMdraft]. The standards
   track RFC causing such an allocation will also include a discussion
   of security issues and of the rate of change of the information being
   advertised. TRILL APPsub-TLVs MUST NOT alter basic TRILL IS-IS
   protocol operation including the establishment of adjacencies, the
   update process, and the decision process [IS-IS] [RFC1195] [RFC6327].
   The TRILL Generic Information TLV MUST NOT be used in IS-IS instance

   The V, I, D, and S flags in the initial flags byte of a TRILL Generic
   Information TLV [RFCgenapp] are not used as TRILL operates as a Level
   1 IS-IS area and no meaning is hereby assigned to the inclusion of an
   IPv4 and/or IPv6 address via the I and V flags. Thus these flags MUST
   be zero; however, use of multi-level IS-IS is an obvious extension
   for TRILL [MultiLevel] and future IETF Standards Actions may update
   or obsolete this specification to provide for the use of any or all
   of these flags in the TRILL GENAPP TLV.

   The ESADI Parameters information, for which APPsub-TLV 1 is hereby
   assigned, is compact and slow changing (see Section 5.1).

   For Security Considerations related to ESADI and the ESADI parameters
   APPsub-TLV, see Section 7.

7. Security Considerations

   For general TRILL Security Considerations, see [RFC6325].


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8. References

   Normative and informative references for this document are below.

8.1 Normative references

   [IS-IS] - 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)", ISO/IEC 10589:2002, Second Edition, Nov

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

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

   [RFC4020] - Kompella, K. and A. Zinin, "Early IANA Allocation of
         Standards Track Code Points", BCP 100, RFC 4020, February 2005.

   [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.

   [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.

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

   [RFCgenapp] - Ginsberg, L., S. Previdi, M. Shand, "Advertising
         Generic Information in IS-IS", draft-ietf-isis-genapp-04.txt,
         in RFC Editor's queue.

   [ClearCorrect] - draft-ietf-trill-clear-correct, work in progress.

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8.2 Informative References

   [802.1X] - IEEE 802.1, "IEEE Standard for Local and metropolitan area
         networks / Port-Based Network Access Control", IEEE Std
         802.1X-2010, 5 February 2010.

   [FineGrained] - Eastlake, D., M. Zhang, P. Agarwal, D. Dutt, R.
         Perlman, "TRILL: Fine-Grained Labeling", draft-ietf-trill-fine-
         labeling, work in progress.

   [MultiInstance] - Previdi, S., L. Ginsberg, M. Shand, A. Roy, D.
         Ward, draft-ietf-isis-mi, work in progress.

   [MultiLevel] - draft-perlman-trill-rbridge-multilevel, work in

   [OAMdraft] - draft-tissa-trill-oam, work in progress.

   [RFC3748] - Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
         Levkowetz, Ed., "Extensible Authentication Protocol (EAP)", RFC
         3748, June 2004.

   [VLANmapping] - Perlman, R., D. Dutt, A. Banerjee, A. Rijhsinghani,
         and D. Eastlake, "RBridges: Campus VLAN and Priority Regions",
         draft-ietf-trill-rbridge-vlan-mapping, work in progress.

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Authors' Addresses

   Hongjun Zhai
   ZTE Corporation
   68 Zijinghua Road
   Nanjing 200012 China

   Phone: +86-25-52877345

   Fangwei Hu
   ZTE Corporation
   889 Bibo Road
   Shanghai 201203 China

   Phone: +86-21-68896273

   Radia Perlman
   Intel Labs
   2200 Mission College Blvd.
   Santa Clara, CA 95054-1549 USA

   Phone: +1-408-765-8080

   Donald Eastlake
   Huawei R&D USA
   155 Beaver Street
   Milford, MA 01757 USA

   Phone: +1-508-333-2270

H. Zhai, et al                                                 [Page 21]

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