[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]

Versions: (draft-dunbar-trill-scheme-for-directory-assist) 00 01 02

INTERNET-DRAFT                                           Donald Eastlake
Intended status: Proposed Standard                          Linda Dunbar
                                                                  Huawei
                                                           Radia Perlman
                                                                     EMC
                                                          Igor Gashinsky
                                                                   Yahoo
                                                               Yizhou Li
                                                                  Huawei
Expires: November 20, 2015                                  May 21, 2015


                TRILL: Edge Directory Assist Mechanisms
         <draft-ietf-trill-directory-assist-mechanisms-02.txt>



Abstract
   This document describes mechanisms for providing directory service to
   TRILL (Transparent Interconnection of Lots of Links) edge switches.
   The directory information provided can be used in reducing multi-
   destination traffic, particularly ARP/ND and unknown unicast
   flooding. It can also be used to detect traffic with forged source
   addresses.



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-
   Drafts.

   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
   http://www.ietf.org/shadow.html.






D. Eastlake, et al                                              [Page 1]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


Table of Contents

      1. Introduction............................................3
      1.1 Uses of Directory Information..........................3
      1.2 Terminology............................................4

      2. Push Model Directory Assistance Mechanisms..............6
      2.1 Requesting Push Service................................6
      2.2 Push Directory Servers.................................6
      2.3 Push Directory Server State Machine....................7
      2.3.1 Push Directory States................................8
      2.3.2 Push Directory Events and Conditions.................9
      2.3.3 State Transition Diagram and Table..................10
      2.4 Additional Push Details...............................12
      2.5 Primary to Secondary Server Push Service..............13

      3. Pull Model Directory Assistance Mechanisms.............14
      3.1 Pull Directory Message Common Format..................15
      3.2 Pull Directory Query and Response Messages............16
      3.2.1 Pull Directory Query Message Format.................16
      3.2.2 Pull Directory Responses............................19
      3.2.2.1 Pull Directory Response Message Format............19
      3.2.2.2 Pull Directory Forwarding.........................21
      3.3 Cache Consistency.....................................22
      3.3.1. Update Message Format..............................25
      3.3.2 Acknowledge Message Format..........................26
      3.4 Pull Directory Hosted on an End Station...............26
      3.5 Pull Directory Message Errors.........................28
      3.5.1 Error Codes.........................................29
      3.5.2 Sub-Errors Under Error Codes 1 and 3................29
      3.5.3 Sub-Errors Under Error Codes 128 and 131............29
      3.6 Additional Pull Details...............................30
      3.7 The No Data Flag......................................30

      4. Directory Use Strategies and Push-Pull Hybrids.........32
      5. Security Considerations................................34

      6. IANA Considerations....................................35
      6.1 ESADI-Parameter Data Extensions.......................35
      6.2 RBridge Channel Protocol Number.......................36
      6.3 The Pull Directory (PUL) and No Data (NOD) Bits.......36
      6.4 TRILL Pull Directory QTYPEs...........................36
      6.5 Pull Directory Error Code Registries..................37

      Normative References......................................38
      Informational References..................................39
      Acknowledgments...........................................40
      Authors' Addresses........................................41




D. Eastlake, et al                                              [Page 2]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


1. Introduction

   [RFC7067] gives a problem statement and high level design for using
   directory servers to assist TRILL [RFC6325] edge nodes in reducing
   multi-destination ARP/ND [ARPreduction], reducing unknown unicast
   flooding traffic, and improving security against address spoofing
   within a TRILL campus.  Because multi-destination traffic becomes an
   increasing burden as a network scales up in number of nodes, reducing
   ARP/ND and unknown unicast flooding improves TRILL network
   scalability. This document describes specific mechanisms for
   directory servers to assist TRILL edge nodes. These mechanisms are
   optional to implement.

   The information held by the Directory(s) is address mapping and
   reachability information.  Most commonly, what MAC address [RFC7042]
   corresponds to an IP address within a Data Label (VLAN or FGL (Fine
   Grained Label [RFC7172])) and the egress TRILL switch (RBridge), and
   optionally what specific TRILL switch port, from which that MAC
   address is reachable. But it could be what IP address corresponds to
   a MAC address or possibly other address mappings or reachability.

   In the data center environment, it is common for orchestration
   software to know and control where all the IP addresses, MAC
   addresses, and VLANs/tenants are in a data center. Thus such
   orchestration software can be appropriate for providing the directory
   function or for supplying the Directory(s) with directory
   information.

   Directory services can be offered in a Push or Pull Mode [RFC7067].
   Push Mode, in which a directory server pushes information to TRILL
   switches indicating interest, is specified in Section 2. Pull Mode,
   in which a TRILL switch queries a server for the information it
   wants, is specified in Section 3. More detail on modes of operation,
   including hybrid Push/Pull, are provided in Section 4.

   The mechanism used to initially populate directory data in primary
   servers is beyond the scope of this document. A primary server can
   use the Push Directory service to provide directory data to secondary
   servers as described in Section 2.5.



1.1 Uses of Directory Information

   A TRILL switch can consult Directory information whenever it wants,
   by (1) searching through information that has been retained after
   being pushed to it or pulled by it or (2) by requesting information
   from a Pull Directory. However, the following are expected to be the
   most common circumstances leading to directory information use. All
   of these are cases of ingressing (or originating) a native frame.


D. Eastlake, et al                                              [Page 3]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


   1. ARP requests and replies [RFC826] are normally broadcast. But a
      directory assisted edge TRILL switches could intercept ARP
      messages and reply if the TRILL switch has the relevant
      information.

   2. IPv6 ND (Neighbor Discovery [RFC4861]) requests and replies are
      normally multicast.  Except in the case of Secure ND [RFC3971]
      where possession of the right keying material might be required,
      directory assisted edge TRILL switches could intercept ND messages
      and reply if the TRILL switch has the relevant information.

   3. Unknown destination MAC addresses. An edge TRILL switch ingressing
      a native frame necessarily has to determine if it knows the egress
      RBridge from which the destination MAC address of the frame (in
      the frame's VLAN or FGL) is reachable. It might learn that
      information from the directory or could query the directory if it
      does not know. Furthermore, if the edge TRILL switch has complete
      directory information, it can detect a forged source MAC address
      in the native frame and discard the frame in that case.

   4. RARP [RFC903] is similar to ARP as above.



1.2 Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

   The terminology and acronyms of [RFC6325] are used herein along with
   the following:

   CSNP Time: Complete Sequence Number PDU Time. See ESDADI [RFC7357]
         and Section 6.1 below.

   Data Label: VLAN or FGL.

   FGL:  Fine Grained Label [RFC7172].

   Host: Application running on a physical server or a virtual machine.
         A host must have a MAC address and usually has at least one IP
         address.

   IP:   Internet Protocol. In this document, IP includes both IPv4 and
         IPv6.

   MacDA: Destination MAC address.

   PDSS: Push Directory Server Status. See Sections 2 and 6.1 below.


D. Eastlake, et al                                              [Page 4]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


   PUL:  Pull Directory flag bit. See Sections 3 and 6.3 below.

   primary server: A Directory server that obtains the information it is
         serving up by a reliable mechanism outside the scope of this
         document designed to assure the freshness of that information.
         (See secondary server.)

   RBridge: An alternative name for a TRILL switch.

   secondary server: A Directory server that obtains the information it
         is serving up from one or more primary servers.

   TRILL: Transparent Interconnection of Lots of Links or Tunneled
         Routing in the Link Layer.

   TRILL switch: A device that implements the TRILL protocol.




































D. Eastlake, et al                                              [Page 5]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


2. Push Model Directory Assistance Mechanisms

   In the Push Model [RFC7067], one or more Push Directory servers
   reside at TRILL switches and push down the address mapping
   information for the various addresses associated with end station
   interfaces and the TRILL switches from which those interfaces are
   reachable [IA]. This service is scoped by Data Label (VLAN or FGL
   [RFC7172]).  A Push Directory also advertises whether or not it
   believes it has pushed complete mapping information for a Data Label.
   It might be pushing only a subset of the mapping and/or reachability
   information for a Data Label. The Push Model uses the ESADI [RFC7357]
   protocol as its distribution mechanism.

   With the Push Model, if complete address mapping information for a
   Data Label is being pushed, a TRILL switch (RBridge) which has that
   complete information and is ingressing a native frame can simply drop
   the frame if the destination unicast MAC address can't be found in
   the mapping information available, instead of flooding the frame
   (ingressing it as an unknown MAC destination TRILL Data frame). But
   this will result in lost traffic if ingress TRILL switch's directory
   information is incomplete.



2.1 Requesting Push Service

   In the Push Model, it is necessary to have a way for a TRILL switch
   to subscribe to information from the directory server(s).  TRILL
   switches simply use the ESADI [RFC7357] protocol mechanism to
   announce, in their core IS-IS LSPs, the Data Labels for which they
   are participating in ESADI by using the Interested VLANs and/or
   Interested Labels sub-TLVs [RFC7176]. This will cause them to be
   pushed the Directory information for all such Data Labels that are
   being served by the one or more Push Directory servers.



2.2 Push Directory Servers

   Push Directory servers advertise their availability to push the
   mapping information for a particular Data Label to each other and to
   ESADI participants for that Data Label through ESADI by setting the
   PDSS (Push Directory Server Status) in their ESADI Parameter APPsub-
   TLV for that ESADI instance (see [RFC7357] and Section 6.1) to a non-
   zero value.  Each Push Directory server MUST participate in ESADI for
   the Data Labels for which it will push mappings and set the PDSS
   field in its ESADI-Parameters APPsub-TLV for that Data Label.

   For robustness, it is useful to have multiple Push Directory Servers
   for each Data Label. Each Push Directory server is configured with a


D. Eastlake, et al                                              [Page 6]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


   number N in the range 1 to 8, which defaults to 2, for each Data
   Label for which it can push directory information.  If the Push
   Directories for a Data Label are configured consistently with the
   same N and at least N servers are available, then N copies of the
   directory that will be pushed.

   Each Push Directory server also has an 8-bit priority to be Active
   (see Section 6.1 of this document). This priority is treated as an
   unsigned integer where larger magnitude means higher priority and is
   in its ESADI Parameter APPsub-TLV. means higher priority.

   For each Data Label it can serve, each Push Directory server checks
   to see if there are enough higher priority servers to push the
   desired number of copies. It does this by ordering, by priority, the
   Push Directory servers that it can see in the ESADI link state
   database for that Data Label that are data reachable [rfc7180bis] and
   determines its own position in that order. If a Push Directory server
   is configured to believe that N copies of the mappings for a Data
   Label should be pushed and finds that it is number K in the priority
   ordering (where number 1 is highest priority and number K is lowest),
   then if K is less than or equal to N the Push Directory server is
   Active. If K is greater than N it is Stand-By. Active and Stand-By
   behavior are specified below.

   For a Push Directory to reside on an end station, one or more TRILL
   switches locally connected to that end station must proxy for the
   Push Directory server and advertise themselves as Push Directory
   servers. It appears to the rest of the TRILL campus that these TRILL
   switches (that are proxying for the end station) are the Push
   Directory server(s). The protocol between such a Push Directory end
   station and the one or more proxying TRILL switches acting as Push
   Directory servers is beyond the scope of this document.



2.3 Push Directory Server State Machine

   The subsections below describe the states, events, and corresponding
   actions for Push Directory servers.

   The meaning of the value of the PDSS field in a Push Directory's
   ESADI Parameter APPsub-TLV is summarized in the table below.

      PDSS    Meaning
      ----   ----------
        0     Not a Push Directory Server
        1     Push Directory Server in Stand-By Mode
        2     Push Directory Server in Active Mode but not complete
        3     Push Directory Server in Active Mode that has pushed
                 complete data


D. Eastlake, et al                                              [Page 7]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


2.3.1 Push Directory States

   A Push Directory Server is in one of seven states, as listed below,
   for each Data Label it can serve. The name of each state is followed
   by a symbol that starts and ends with an angel bracket and
   representing the state. The value that the Push Directory Server
   advertises in PDSS is determined by the state.  In addition, it has
   an internal State-Transition-Time variable for each Data Label it
   serves which is set at each state transition and which enables it to
   determine how long it has been in its current state for that Data
   Label.

   Down <S1>:  A completely shut down virtual state defined for
      convenience in specifying state diagrams. A Push Directory Server
      in this state does not advertise any Push Directory data. It may
      be participating in ESDADI [RFC7357] with the PDSS field zero in
      its ESADI-Parameters or might be not participating in ESADI at
      all. (All states other than the Down state are considered to be Up
      states and imply a non-zero PDSS field.)

   Stand-By <S2>:  No Push Directory data is advertised. Any outstanding
      EASDI-LSP fragments containing directory data are updated to
      remove that data and if the result is an empty fragment (contains
      nothing except possibly an Authentication TLV), the fragment is
      purged.  The Push Directory participates in ESDADI [RFC7357] and
      advertises its ESADI fragment zero that includes an ESADI-
      Parameters APPsub-TLV with the PDSS field set to 1.

   Active <S3>:  The PDSS field in the ESADI-Parameters is set to 2. If
      a Push Directory server is Active, it advertises its directory
      data and any changes through ESADI [RFC7357] in its ESADI-LSPs
      using the Interface Addresses [IA] APPsub-TLV and updates that
      information as it changes.

   Active Completing <S4>:  Same behavior as the Active state except
      that it responds differently to events. The purpose of this state
      is to be sure there has been enough time for directory information
      to propagate to subscribing edge TRILL switches before the
      Directory Server advertises that the information is complete.

   Active Complete <S5>:  The same behavior as Active except that the
      PDSS field in the ESADI-Parameters APPsub-TLV is set to 3 and the
      server responds differently to events.

   Going Stand-By <S6>:  The same behavior as Active except that it
      responds differently to events. The purpose of this state is to be
      sure that the information that the directory is no longer complete
      has enough time to propagate to edge TRILL switches before the
      Directory Server stop advertising updates to the information.



D. Eastlake, et al                                              [Page 8]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


   Active Uncompleting <S7>: The same behavior as Active except that it
      responds differently to events. The purpose of this state is to be
      sure that the information that the directory is no longer complete
      has enough time to propagate to edge TRILL switches before the
      Directory Server might stop advertising updates to the
      information. (See note below.)

         Note: It might appear that a Push Directory could transition
         directly from Active Complete to Active, since Active state
         continues to advertise updates, eliminating the need for the
         Active Uncompleting transition state. But consider the case of
         the Push Directory being configured to be incomplete and then
         the Stand-By Condition (see Section 2.3.2) occurring
         immediately thereafter. If the first of these two events caused
         the server to transition directly to the Active state then,
         when the Stand-By Condition occurred, it would immediately
         transition to Stand-By and stop advertising updates even though
         there might not have been enough time for knowledge of its
         incompleteness to have propagated to all edge TRILL switches.

   The following table summarizes PDSS value for each state:

       State                     PDSS
      ----------                ------
      Down <S1>                   0
      Stand-By <S2>               1
      Active <S3>                 2
      Active Completing <S4>      2
      Active Complete <S5>        3
      Going Stand-By <S6>         2
      Active Uncompleting <S7>    2



2.3.2 Push Directory Events and Conditions

   Three auxiliary conditions referenced later in this section are
   defined as follows for convenience:

   The Activate Condition: In order to have the desired number of Push
      Directory servers pushing data, this Push Directory server should
      be active. This is determined by the server finding that it is
      priority K among the data reachable Push Directory servers (where
      highest priority is 1), it is configured that there should be N
      copies pushed, and K is less than or equal to N. For example, the
      Push Directory server is configured that 2 copies should be pushed
      and finds that it is priority 1 or 2 among the Push Directory
      servers it can see.

   The Stand-By Condition: In order to have the desired number of Push


D. Eastlake, et al                                              [Page 9]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


      Directory servers pushing data, this Push Directory server should
      be stand-by (not active). This is determined by the server finding
      that it is priority K among the data reachable data reachable Push
      Directory servers (where highest priority is 1), it is configured
      that there should be N copies pushed, and K is greater than N. For
      example, the Push Directory server is configured that 2 copies
      should be pushed and finds that it is priority 3 or lower priority
      (higher number) among the Push directory servers it can see.

   The Time Condition: The Push Directory server has been in its current
      state for a configurable amount of time that defaults to twice its
      CSNP time (see Section 6.1).)

   The events and conditions listed below cause state transitions in
   Push Directory servers.

   1. Push Directory server was Down but is now Up.

   2. The Push Directory server or the TRILL switch on which it resides
      is being shut down.

   3. The Activate Condition is met and the server is not configured to
      believe it has complete data.

   4. The Stand-By Condition is met.

   5. The Activate Condition is met and the server is configured to
      believe it has complete data.

   6. The server is configured to believe it does not have complete
      data.

   7. The Time Condition is met.



2.3.3 State Transition Diagram and Table

   The state transition table is as follows:

   State|Down|Stand-By|Active|  Active  | Active | Going  |   Active
   -----+    |        |      |Completing|Complete|Stand-By|Uncompleting
   Event|<S1>|  <S2>  | <S3> |   <S4>   |  <S5>  |  <S6>  |    <S7>
   -----+----+--------+------+----------+--------+---------+------------
     1  |<S2>|  <S2>  | <S3> |   <S4>   |  <S5>  |  <S6>  |    <S7>
     2  |<S1>|  <S1>  | <S2> |   <S2>   |  <S6>  |  <S6>  |    <S7>
     3  |<S1>|  <S3>  | <S3> |   <S3>   |  <S7>  |  <S3>  |    <S7>
     4  |<S1>|  <S2>  | <S2> |   <S2>   |  <S6>  |  <S6>  |    <S6>
     5  |<S1>|  <S4>  | <S4> |   <S4>   |  <S5>  |  <S5>  |    <S5>
     6  |<S1>|  <S2>  | <S3> |   <S3>   |  <S7>  |  <S6>  |    <S7>


D. Eastlake, et al                                             [Page 10]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


     7  |<S1>|  <S2>  | <S3> |   <S5>   |  <S5>  |  <S2>  |    <S3>

   The above state table is equivalent to the following transition
   diagram:

     +-----------+
     | Down <S1> |<---------+
     +-----------+          |
       |1  ^   | 3,4,5,6,7  |
       |   |   +------------+
       V   |2
     +---------------+
     | Stand-By <S2> |<------------------------------------------+
     +---------------+    ^   ^            ^                     |
       |5   |3  |1,4,6,7  |   |            |                     |
       |    |   +---------+   |            |                     |
       |    V                 |2,4         |                     |
       |  +---------------------+          |                     |
       |  | Active <S3>         |<---------|-----------------+   |
       |  +---------------------+     ^    |                 |   |
       |   |5  ^    |1,3,6,7  ^       |    |                 |   |
       |   |   |    |         |       |    |                 |   |
       |   |   |    +---------+       |    |                 |   |
       |   |   |                      |    |                 |   |
       V   V   |3,6                   |    |                 |   |
     +------------------------+       |    |                 |   |
     | Active Completing <S4> |------------+                 |   |
     +------------------------+ 2,4   |                      |   |
       |7  |1,5    ^                  |                      |   |
       |   |       |                  |                      |   |
       |   +-------+                  |                      |   |
       |                              |                      |   |
       |          +--------------------------------------+   |   |
       |          |                   |                  |   |   |
       V          V                   |7                 |5  |3  |7
     +---------------+ 3,6    +----------------+ 4    +----------------+
     |    Active     |------->|     Active     |----->|     Going      |
     |   Complete    |        |  Uncompleting  |      |    Stand-By    |
     |     <S5>      |<-------|      <S7>      |      |      <S6>      |
     +---------------+      5 +----------------+      +----------------+
       |1,5,7  ^   |2,4         |1,2,3,6     ^          ^   |1,2,4,6 ^
       |       |   |            |            |          |   |        |
       +-------+   |            +------------+          |   +--------+
                   |                                    |
                   +------------------------------------+

                    Figure 2. Push Server State Diagram





D. Eastlake, et al                                             [Page 11]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


2.4 Additional Push Details

   Push Directory mappings can be distinguished for other data
   distributed through ESADI because mappings are distributed only with
   the Interface Addresses APPsub-TLV [IA] and are flagged in that
   APPsub-TLV as being Push Directory data.

   TRILL switches, whether or not they are a Push Directory server, MAY
   continue to advertise any locally learned MAC attachment information
   in ESADI [RFC7357] using the Reachable MAC Addresses TLV [RFC6165].
   However, if a Data Label is being served by complete Push Directory
   servers, advertising such locally learned MAC attachment generally
   SHOULD NOT be done as it would not add anything and would just waste
   bandwidth and ESADI link state space. An exception might be when a
   TRILL switch learns local MAC connectivity and that information
   appears to be missing from the directory mapping.

   Because a Push Directory server needs to advertise interest in one or
   more Data Labels even though it might not want to receive multi-
   destination data in those Data Labels, the No Data (NOD) flag bit is
   provided as discussed in Section 3.7.

   When a Push Directory server is no longer data reachable
   [rfc7180bis], TRILL switches MUST ignore any Push Directory data from
   that server because it is no longer being updated and may be stale.

   The nature of dynamic distributed asynchronous systems is such that
   it is impossible for a TRILL switch receiving Push Directory
   information to be absolutely certain that it has complete
   information.  However, it can obtain a reasonable assurance of
   complete information by requiring two conditions to be met:
      1. The PDSS field is 3 in the ESADI zero fragment from the server
         for the relevant Data Label.
      2. In so far as it can tell, it has had continuous data
         connectivity to the server for a configurable amount of time
         that defaults to twice the server's CSNP time.
   Condition 2 is necessary because a client TRILL switch might be just
   coming up and receive an EASDI LSP meeting the requirement in
   condition 1 above but have not yet received all of the ESADI LSP
   fragment from the Push Directory server.

   There may be conflicts between mapping information from different
   Push Directory servers or conflicts between locally learned
   information and information received from a Push Directory server. In
   case of such conflicts, information with a higher confidence value
   [RFC6325] is preferred over information with a lower confidence. In
   case of equal confidence, Push Directory information is preferred to
   locally learned information and if information from Push Directory
   servers conflicts, the information from the higher priority Push
   Directory server is preferred.


D. Eastlake, et al                                             [Page 12]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


2.5 Primary to Secondary Server Push Service

   A secondary Push or Pull Directory server is one that obtains its
   data from a primary directory server. Other techniques MAY be used
   but, by default, this data transfer occurs through the primary server
   acting as a Push Directory server for the Data Labels involved while
   the secondary directory server takes the pushed data it receives from
   the highest priority Push Directory server and re-originates it. Such
   a secondary server may be a Push Directory server or a Pull Directory
   server or both for any particular Data Label. Because the data from a
   secondary server will necessarily be at least a little less fresh
   than that from a primary server, it is RECOMMENDED that the re-
   originated secondary server data be given a confidence level of one
   less than that of the data as received from the primary (or unchanged
   if it is alreayd of minimum confidence).





































D. Eastlake, et al                                             [Page 13]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


3. Pull Model Directory Assistance Mechanisms

   In the Pull Model [RFC7067], a TRILL switch (RBridge) pulls directory
   information from an appropriate Directory Server when needed.

   Pull Directory servers for a particular Data Label X are found by
   looking in the core TRILL IS-IS link state database for data
   reachable [rfc7180bis] TRILL switches that advertise themselves by
   having the Pull Directory flag (PUL) on in their Interested VLANs or
   Interested Labels sub-TLV (see Section 6.3)) for that Data Label. If
   multiple such TRILL switches indicate that they are Pull Directory
   Servers for a particular Data Label, pull requests can be sent to any
   one or more of them but it is RECOMMENDED that pull requests be
   preferentially sent to the server or servers that are lowest cost
   from the requesting TRILL switch.

   Pull Directory requests are sent by enclosing them in an RBridge
   Channel [RFC7178] message using the Pull Directory channel protocol
   number (see Section 6.2).  Responses are returned in an RBridge
   Channel message using the same channel protocol number. See Section
   3.2 for Query and Response Message formats. For cache consistency or
   notification purposes, Pull Directory servers, under certain
   conditions, MUST send unsolicited Update Messages to client TRILL
   switches they believe may be holding old data and those clients can
   acknowledge such updates, as described in Section 3.3. All these
   messages have a common header as described in Section 3.1. Errors
   returns can be sent for queries or updates as described in Section
   3.5.

   The requests to Pull Directory Servers are typically derived from
   ingressed ARP [RFC826], ND [RFC4861], or RARP [RFC903] messages, or
   data frames with unknown unicast destination MAC addresses,
   intercepted by an ingress TRILL switch as described in Section 1.1.

   Pull Directory responses include an amount of time for which the
   response should be considered valid. This includes negative responses
   that indicate no data is available. It is RECOMMENDED that both
   positive responses with data and negative responses can be cached and
   used to locally handle ARP, ND, RARP, unknown destination MAC frames,
   or the like, until the responses expire.  If information previously
   pulled is about to expire, a TRILL switch MAY try to refresh it by
   issuing a new pull request but, to avoid unnecessary requests, SHOULD
   NOT do so if it has not been recently used. The validity timer of
   cached Pull Directory responses is NOT reset or extended merely
   because that cache entry is used.







D. Eastlake, et al                                             [Page 14]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


3.1 Pull Directory Message Common Format

   All Pull Directory messages are transmitted as the payload of RBridge
   Channel messages [RFC7178].  Pull Directory messages are formatted as
   described herein starting with the following common 8-byte header:

                           1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Ver  | Type  | Flags | Count |      Err      |    SubErr     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Sequence Number                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Type Specific Payload - variable length
      +-+-+- ...

      Ver: Version of the Pull Directory protocol as an unsigned
         integer.  Version zero is specified in this document.

      Type: The Pull Directory message type as follows:

            Type   Section    Name
            ----   -------   --------
               0    -         Reserved
               1    3.2.1     Query
               2    3.2.2     Response
               3    3.3.1     Update
               4    3.3.2     Acknowledge
            5-14    -         Unassigned
              15    -         Reserved

      Flags: Four flag bits whose meaning depends on the Pull Directory
         message Type. Flags whose meaning is not specified are
         reserved, MUST be sent as zero, and MUST be ignored on receipt.

      Count: Pull Directory message types specified herein have zero or
         more occurrences of a Record as part of the type specific
         payload. The Count field is the number of occurrences of that
         Record as an unsigned integer. For any Pull Directory messages
         not structured with such occurrences, this field MUST be sent
         as zero and ignored on receipt.

      Err, SubErr: The error and suberror fields are only used in
         messages that are in the nature of replies. In messages that
         are requests or updates, these fields MUST be sent as zero and
         ignored on receipt. An Err field containing the value zero
         means no error. The meaning of values in the SubErr field
         depends on the value of the Err field but in all cases, a zero
         SubErr field is allowed and provides no additional information
         beyond the value of the Err field.


D. Eastlake, et al                                             [Page 15]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


      Sequence Number: An opaque 32-bit quantity set by the TRILL switch
         sending a request or other unsolicited message and returned in
         every corresponding reply or acknowledgement. It is used to
         match up responses with the message to which they respond.

      Type Specific Payload: Format depends on the Pull Directory
         message Type.



3.2 Pull Directory Query and Response Messages

   The format of the Pull Directory Query and Response Messages is
   specified below.



3.2.1 Pull Directory Query Message Format

   A Pull Directory Query Message is sent as the Channel Protocol
   specific content of an RBridge Channel message [RFC7178] TRILL Data
   packet or as a native RBridge Channel data frame (see Section 3.4).
   The Data Label of the packet is the Data Label in which the query is
   being made. The priority of the channel message is a mapping of the
   priority of the frame being ingressed that caused the query with the
   default mapping depending, per Data Label, on the strategy (see
   Section 4) or a configured priority for generated queries. (Generated
   queries are those not the result of a mapping. For example, a query
   to refresh a cache entry.) The Channel Protocol specific data is
   formatted as a header and a sequence of zero or more QUERY Records as
   follows:

                           1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Ver  | Type  | Flags | Count |      Err      |    SubErr     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Sequence Number                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | QUERY 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
      | QUERY 2
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
      | ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
      | QUERY K
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...

      Ver, Sequence Number: See 3.1.



D. Eastlake, et al                                             [Page 16]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


      Type: 1 for Query. Queries received by an TRILL switch that is not
         a Pull Directory for the relevant Data Label result in an error
         response (see Section 3.5) unless inhibited by rate limiting.
         (See [RFC7178] for response if the Pull Directory RBridge
         Channel protocol is not enabled.)

      Flags, Err, and SubErr: MUST be sent as zero and ignored on
         receipt.

      Count: Number of QUERY Records present. A Query Message Count of
         zero is explicitly allowed, for the purpose of pinging a Pull
         Directory server to see if it is responding. On receipt of such
         an empty Query Message, a Response Message that also has a
         Count of zero is sent unless inhibited by rate limiting.

      QUERY: Each QUERY Record within a Pull Directory Query Message is
         formatted as follows:

             0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
           |        SIZE           |FL|  RESV  |   QTYPE   |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
         If QTYPE = 1
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
           |                      AFN                      |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
           |  Query address ...
           +--+--+--+--+--+--+--+--+--+--+--...
         If QTYPE = 2, 3, 4, or 5
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
           |  Query frame ...
           +--+--+--+--+--+--+--+--+--+--+--...

         SIZE: Size of the QUERY Record in bytes as an unsigned integer
            not including the SIZE field and following byte. A value of
            SIZE so large that the material doesn't fit in the Query
            Message indicates a malformed QUERY Record. The QUERY Record
            with the illegal SIZE value and any subsequent QUERY Records
            MUST be ignored and the entire Query Message MAY be ignored.

         FL: The FLooded flag that is ignored if QTYPE is zero. If QTYPE
            is 2 through 5 and the directory information sought is not
            found, the frame provided is flooded, otherwise it is not
            forwarded. See Section 3.2.2.2.

         RESV: A block of three reserved bits. MUST be sent as zero and
            ignored on receipt.

         QTYPE: There are several types of QUERY Records currently
            defined in two classes as follows: (1) a QUERY Record that


D. Eastlake, et al                                             [Page 17]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


            provides an explicit address and asks for all addresses for
            the interface specified by the query address and (2) a QUERY
            Record that includes a frame. The fields of each are
            specified below. Values of QTYPE are as follows:

                  QTYPE   Description
                  -----   -----------
                     0    Reserved
                     1    Address query
                     2    ARP query frame
                     3    ND query frame
                     4    RARP query frame
                     5    Unknown unicast MAC query frame
                  6-14    Unassigned
                    15    Reserved

            AFN: Address Family Number of the query address.

            Query Address: The query is asking for any other addresses,
               and the nickname of the TRILL switch from which they are
               reachable, that correspond to the same interface, within
               the data label of the query. Typically that would be
               either (1) a MAC address with the querying TRILL switch
               primarily interested in the TRILL switch by which that
               MAC address is reachable, or (2) an IP address with the
               querying TRILL switch interested in the corresponding MAC
               address and the TRILL switch by which that MAC address is
               reachable. But it could be some other address type.

            Query Frame: Where a QUERY Record is the result of an ARP,
               ND, RARP, or unknown unicast MAC destination address, the
               ingress TRILL switch MAY send the frame to a Pull
               Directory Server if the frame is small enough that the
               resulting Query Message fits into a TRILL Data packet
               within the campus MTU.

   If no response is received to a Pull Directory Query Message within a
   timeout configurable in milliseconds that defaults to 100, the Query
   Message should be re-transmitted with the same Sequence Number up to
   a configurable number of times that defaults to three. If there are
   multiple QUERY Records in a Query Message, responses can be received
   to various subsets of these QUERY Records before the timeout. In that
   case, the remaining unanswered QUERY Records should be re-sent in a
   new Query Message with a new sequence number.  If a TRILL switch is
   not capable of handling partial responses to queries with multiple
   QUERY Records, it MUST NOT sent a Request Message with more than one
   QUERY Record in it.

   See Section 3.5 for a discussion of how Query Message errors are
   handled.


D. Eastlake, et al                                             [Page 18]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


3.2.2 Pull Directory Responses

   A Pull Directory Query Message result in a Pull Directory Response
   Message as described in Section 3.2.2.1.

   In addition, if the QUERY Record QTYPE was 2, 3, 4, or 5, the frame
   included in the Query may be modified and forwarded by the Pull
   Directory server as described in Section 3.2.2.2.



3.2.2.1 Pull Directory Response Message Format

   Pull Directory Response Messages are sent as the Channel Protocol
   specific content of an RBridge Channel message [RFC7178] TRILL Data
   packet or as a native RBridge Channel data frame (see Section 3.4).
   Responses are sent with the same Data Label and priority as the Query
   Message to which they correspond except that the Response Message
   priority is limited to be not more than a configured value.  This
   priority limit is configurable per TRILL switch and defaults to
   priority 6. Pull Directory Response Messages SHOULD NOT be sent with
   priority 7 as that priority SHOULD be reserved for messages critical
   to network connectivity.

   The RBridge Channel protocol specific data format is as follows:

                           1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Ver  | Type  | Flags | Count |      Err      |    SubErr     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Sequence Number                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | RESPONSE 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
      | RESPONSE 2
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
      | ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
      | RESPONSE K
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...

      Ver, Sequence Number: As specified in Section 3.1.

      Type: 2 = Response.

      Flags: MUST be sent as zero and ignored on receipt.

      Count: Count is the number of RESPONSE Records present in the
         Response Message.


D. Eastlake, et al                                             [Page 19]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


      Err, SubErr: A two-part error code. Zero unless there was an error
         in the Query Message, for which case see Section 3.5.

      RESPONSE: Each RESPONSE record within a Pull Directory Response
         Message is formatted as follows:

           0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15
         +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
         |         SIZE          |OV|  RESV  |   Index   |
         +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
         |                   Lifetime                    |
         +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
         |                Response Data ...
         +--+--+--+--+--+--+--+--+--+--+--...

         SIZE: The size of the RESPONSE Record is an unsigned integer
            number of bytes not including the SIZE field and following
            byte. A value of SIZE so large that the material doesn't fit
            in the Query Message indicates a malformed QUERY Record. The
            QUERY Record with such an excessive SIZE value and any
            subsequent QUERY Records MUST be ignored and the entire
            Query Message MAY be ignored.

         OV: The overflow flag. Indicates, as described below, that
            there was too much Response Data to include in one Response
            Message.

         RESV: Three reserved bits that MUST be sent as zero and ignored
            on receipt.

         Index: The relative index of the QUERY Record in the Query
            Message to which this RESPONSE Record corresponds. The index
            will always be one for Query Messages containing a single
            QUERY Record. If the Index is larger than the Count was in
            the corresponding Query, that RESPONSE Record MUST be
            ignored and subsequent RESPONSE Records or the entire
            Response Message MAY be ignored.

         Lifetime: The length of time for which the response should be
            considered valid in units of 100 milliseconds except that
            the values zero and 2**16-1 are special. If zero, the
            response can only be used for the particular query from
            which it resulted and MUST NOT be cached. If 2**16-1, the
            response MAY be kept indefinitely but not after the Pull
            Directory server goes down or becomes unreachable. (The
            maximum definite time that can be expressed is a little over
            1.8 hours.)

         Response Data: There are two types of RESPONSE Records.
            -  If the Err field of the enclosing Repose message is non-


D. Eastlake, et al                                             [Page 20]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


               zero, then the Response Data in the REPONSE Record is
               null and SIZE will be zero. See Section 3.5 for
               additional information on errors.
            -  If the Err field of the enclosing Repose message is zero,
               then the Response Data is formatted as the value of an
               Interface Addresses APPsub-TLV [IA]. The maximum size of
               such contents is 255 bytes in the case when the RESPONSE
               record SIZE field is 255.

   Multiple RESPONSE Records can appear in a Response Message with the
   same Index if the answer to a QUERY Record consists of multiple
   Interface Address APPsub-TLV values. This would be necessary if, for
   example, a MAC address within a Data Label appears to be reachable by
   multiple TRILL switches. However, all RESPONSE Records to any
   particular QUERY Record MUST occur in the same Response Message. If a
   Pull Directory holds more mappings for a queried address than will
   fit into one Response Message, it selects which to include by some
   method outside the scope of this document and sets the overflow flag
   (OV) in all of the RESPONSE Records responding to that query address.

   See Section 3.5 for a discussion of how errors are handled.



3.2.2.2 Pull Directory Forwarding

   Query Messages with QTYPEs 2, 3, 4, and 5 are interpreted and handled
   as described below. In these cases, if the information sought is not
   in the directory, the provided frame is forwarded by the Pull
   Directory server as a multi-destination TRILL Data packet if the FL
   flag in the Query Message was one, otherwise the frame is not
   forwarded. If there was no error in the handling of the enclosing
   Query Message then the Pull Directory server forwards the frame
   inside that QUERY Record, after modifying it in some cases, as
   described below.

   ARP: When QTYPE is 2, an ARP [RFC826] frame is included in the QUERY
      Record. The ar$op field MUST be ares_op$REQUEST and for the
      response described in 3.2.2.1, this is treated as a query for the
      target protocol address where the AFN of that address is given by
      ar$pro.  (ARP field and value names with embedded dollar signs are
      specified in [RFC826].) If ar$op is not ares_op$REQUEST or the ARP
      is malformed or the query fails, an error is returned. Otherwise
      the ARP is modified into the appropriate ARP response that is then
      sent by the Pull Directory server as a TRILL Data packet.

   ND: When QTYPE is 3, an IPv6 Neighbor Discover (ND [RFC4861]) frame
      is included in the QUERY Record. Only Neighbor Solicitation ND
      frames (corresponding to an ARP query) are allowed. An error is
      returned for other ND frames or if the target address is not


D. Eastlake, et al                                             [Page 21]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


      found. Otherwise an ND Neighbor Advertisement response is returned
      by the Pull Directory server as a TRILL Data packet.

   RARP: When QTYPE is 4, a RARP [RFC903] frame is included in the QUERY
      Record. If the ar$op field is ares_op$REQUEST, the frame is
      handled as an ARP above. Otherwise the ar$op field MUST be
      'reverse request' and for the response described in 3.2.2.1, this
      is treated as a query for the target hardware address where the
      AFN of that address is given by ar$hrd. (See [RFC826] for RARP
      fields.) If ar$op is not one of these values or the RARP is
      malformed or the query fails, an error is returned. Otherwise the
      RARP is modified into the appropriate RARP response that is then
      unicast by the Pull Directory server as a TRILL Data packet to the
      source hardware MAC address.

   MacDA: When QTYPE is 5, indicating a fame is provided in the QUERY
      Record whose destination MAC address TRILL switch attachment is
      unknown, the only requirement is that this MAC address must be
      unicast. If it is group addressed an error is returned. For the
      response described in 3.2.2.1, it is treated as a query for the
      MacDA. If the Pull Directory contains TRILL switch attachment
      information for the MAC address in the Data Label of the Query
      Message, it forwards the frame to that switch in a unicast TRILL
      Data packet.



3.3 Cache Consistency

   Unless it sends all responses with a Lifetime of zero, a Pull
   Directory MUST take action, by sending Update Messages, to minimize
   the amount of time that a TRILL switch will continue to use stale
   information from that Pull Directory. The format of Update Messages
   and the Acknowledge Messages used to respond to Update Messages are
   given in Sections 3.3.1 and 3.3.2.

   A Pull Directory server MUST maintain one of the following three sets
   of records, in order of increasing specificity. Retaining more
   specific records, such as that given in method 3 below, minimizes
   spontaneous Update Messages sent to update pull client TRILL switch
   caches but increases the record keeping burden on the Pull Directory
   server. Retaining less specific records, such as that given in method
   1, will generally increase the volume and overhead due to spontaneous
   Update Messages and due to unnecessarily invalidating cached
   information, but will still maintain consistency and will reduce the
   record keeping burden on the Pull Directory server. In all cases,
   there may still be brief periods of time when directory information
   has changed but cached information a pull clients has not yet been
   updated or expunged.



D. Eastlake, et al                                             [Page 22]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


     1. An overall record per Data Label of when the last positive
        response data sent will expire at some requester and when the
        last negative response will expire at some requester, assuming
        those requesters cached the response.

     2. For each unit of data (IA APPsub-TLV Address Set [IA]) held by
        the server and each address about which a negative response was
        sent, when the last response sent with that positive response
        data and when the last negative response will expire at a
        requester, assuming the requester cached the response.

     3. For each unit of data held by the server (IA APPsub-TLV Address
        Set [IA]) and each address about which a negative response was
        sent, a list of TRILL switches that were sent that data as a
        positive response or sent a negative response for the address,
        and the expected time to expiration for that data or address at
        each such TRILL switch, assuming the requester cached the
        response.

   RESPONSE Records sent with a zero lifetime are considered to have
   already expired and so do not need to be tracked.

   A Pull Directory server may have a limit as to how many TRILL
   switches for which it can maintain expiry information by method 3
   above or how many data units or addresses it can maintain expiry
   information for by method 2 or the like. If such limits are exceeded,
   it MUST transition to a lower numbered method but, in all cases, MUST
   support, at a minimum, method 1.

   When data at a Pull Directory is changed, deleted, or added and there
   may be unexpired stale information at a requesting TRILL switch, the
   Pull Directory MUST send an Update Message as discussed below. The
   sending of such an Update Message MAY be delayed by a configurable
   number of milliseconds that default to 50 milliseconds to await other
   possible changes that could be included in the same Update.

     1. If method 1, the crudest method, is being followed, then when
        any Pull Directory information in a Data Label is changed or
        deleted and there are outstanding cached positive data
        response(s), an all-addresses flush positive data Update Message
        is flooded within that Data Label as an RBridge Channel Message
        with an Inner.MacDA of All-Egress-RBridges. Similarly if data is
        added and there are outstanding cached negative responses, an
        all-addresses flush negative message is similarly flooded. The
        Count field being zero in an Update Message indicates "all-
        addresses". On receiving an all-addresses flooded flush positive
        Update from a Pull Directory server it has used, indicated by
        the F and P bits being one and the Count being zero, a TRILL
        switch discards the cached data responses it has for that Data
        Label.  Similarly, on receiving an all addresses flush negative


D. Eastlake, et al                                             [Page 23]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


        Update, indicated by the F and N bits being one and the Count
        being zero, it discards all cached negative replies for that
        Data Label. A combined flush positive and negative can be
        flooded by having all of the F, P, and N bits set to one
        resulting in the discard of all positive and negative cached
        information for the Data Label.

     2. If method 2 is being followed, then a TRILL switch floods
        address specific positive Update Messages when data that might
        be cached by a querying TRILL switch is changed or deleted and
        floods address specific negative Update Messages when such
        information is added to. Such messages are somewhat similar to
        the method 1 flooded flush Update Messages and are also sent as
        RBridge Channel messages with an Inner.MacDA of All-Egress-
        RBridges. However the Count field will be non-zero and either
        the P or N bit, but not both, will be one. There are actually
        four possible message types that can be flooded:

        2.a If data still being cached is updated, then an Update
            Message is sent with the P flag set and the Err field zero.
            The addresses in the RESPONSE records in the unsolicited
            response are compared to the addresses about which the
            receiving TRILL switch is holding cached positive
            information from that server and, if they match, the cached
            information is updated.

        2.b If data still being cached is deleted, then an Update
            Message is sent with the P flag set and the Err field non-
            zero giving the error that would now be encountered in
            attempting to pull information for the relevant address from
            the Pull Directory server. In this non-zero Err field case,
            the RESPONSE Record(s) differ from non-zero Err Reply
            Message RESPONSE Records in that they include an interface
            address set.  Any cached positive information for the
            address is deleted and the negative response cached as per
            the lifetime given.

        2.c If data for an address about which a negative response was
            sent is added so that negative response is now incorrect, an
            Update Message is sent with the N flag set to one and the
            Err field zero. The addresses in the RESPONSE records in the
            unsolicited response are compared to the addresses about
            which the receiving TRILL switch is holding cached negative
            information from that server and, if they match, the cached
            negative information is deleted and the positive information
            provided is cached as per the lifetime given.

        2.d In the rare case where it is desired to change the lifetime
            or error associated with cached negative information, it is
            possible to send an Update Message with the N flag set to


D. Eastlake, et al                                             [Page 24]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


            one and the Err field non-zero. As in case 2.b above, the
            RESPONSE Record(s) give the relevant addresses.  Any cached
            negative information for the address is updated.

     3. If method 3 is being followed, the same sort of unsolicited
        Update Messages are sent as with method 2 above except they are
        not normally flooded but unicast only to the specific TRILL
        switches the directory server believes may be holding the cached
        positive or negative information that needs updating. However, a
        Pull Directory server MAY flood unsolicited updates under method
        3, for example if it determines that a sufficiently large
        fraction of the TRILL switches in some Data Label are requesters
        that need to be updated.

   A Pull Directory server tracking cached information with method 3
   MUST NOT clear the indication that it needs to update cached
   information at a querying TRILL switch until it has sent an Update
   Message and received a corresponding Acknowledge Message or it has
   sent a configurable number of updates at a configurable interval
   which default to 3 updates 100 milliseconds apart.

   A Pull Directory server tracking cached information with methods 2 or
   1 SHOULD NOT clear the indication that it needs to update cached
   information until it has sent an Update Message and received a
   corresponding Acknowledge Message from all of its ESADI neighbors or
   it has sent a configurable number of updates at a configurable
   interval that defaults to 3 updates 100 milliseconds apart.



3.3.1. Update Message Format

   An Update Message is formatted as a Response Message with the with
   differences described in Section 3.3 above and the following:

   o  The Type field in the message header is set to 3.

   o  The Index field in the RESPONSE Record(s) is set to zero (but the
      Count field in the Update Message header MUST still correctly
      indicate the number of RESPONSE Records present).

   Update Messages are initiated by a Pull Directory server. The
   Sequence number space used is controlled by the originating Pull
   Directory server and different from Sequence number space used in a
   Query and the corresponding Response that are controlled by the
   querying TRILL switch.

   The 4-bit Flags field of the message header for an Update Message is
   as follows:



D. Eastlake, et al                                             [Page 25]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


         +---+---+---+---+
         | F | P | N | R |
         +---+---+---+---+

   F: The Flood bit. If zero, the Update Message is unicast. If F=1, it
      is multicast to All-Egress-RBridges.

   P, N: Flags used to indicate positive or negative Update Messages.
      P=1 indicates positive. N=1 indicates negative. Both may be 1 for
      a flooded all addresses Update.

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

   For tracking methods 2 and 3 in Section 3.3.1, a particular update
   message must have either the P flag or the N flag set but not both.



3.3.2 Acknowledge Message Format

   An Acknowledge Message is sent in response to an Update to confirm
   receipt or indicate an error, unless response is inhibited by rate
   limiting. It is also formatted as a Response Message but the Type is
   set to 4.

   If there are no errors in the processing of an Update Message, the
   message is essentially echoed back with any error indication cleared
   and the Type changed to Acknowledge.

   If there was an overall or header error in an Update Message, it is
   echoed back as an Acknowledge Message with the Err and SubErr fields
   set appropriately (see Section 3.5).

   If there is a RESPONSE Record level error in an Update Message, one
   or more Acknowledge Messages may be returns as indicated in Section
   3.5.



3.4 Pull Directory Hosted on an End Station

   Optionally, a Pull Directory actually hosted on an end station MAY be
   supported. In that case, one or more TRILL switches must proxy for
   the end station and advertise themselves as Pull Directory servers.
   Such proxies must have a direct connection to the end station, that
   is a connection not involving any intermediate TRILL switches.

   When the proxy Pull Directory server TRILL switch receives a Query
   Message, it modifies the inter-RBridge Channel message received into
   a native RBridge Channel message and forwards it to the end station


D. Eastlake, et al                                             [Page 26]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


   Pull Directory server.  Later, when it receives one or more responses
   from that end station by native RBridge Channel messages, it modifies
   them into inter-RBridge Channel messages and forwards them to the
   source TRILL switch of the original Query Message. Similarly, an
   Update from the end station is forwarded to client TRILL switches and
   acknowledgements from those TRILL switches are returned to the end
   station by the proxy. Because native RBridge Channel messages have no
   TRILL Header and are addressed by MAC address, as opposed to inter-
   RBridge Channel messages that are TRILL Data packets and are
   addressed by nickname, nickname information must be added to the
   native RBridge Channel version of Pull Directory messages.

   The native Pull Directory RBridge Channel messages use the same
   Channel protocol number as do the inter-RBridge Pull Directory
   RBridge Channel messages. The native messages SHOULD be sent with an
   Outer.VLAN tag that gives the priority of each message which is the
   priority of the original inter-RBridge request packet. The Outer.VLAN
   ID used is the Designated VLAN on the link to the end station
   [RFC6325]. Since there is no TRILL Header or inner Data Label for
   native RBridge Chanel messages, that information is added to the
   header.

   The native RBridge Channel message Pull Directory message protocol
   dependent data part is the same as for inter-RBridge Channel messages
   except that the 8-byte header described in Section 3.1 is expanded to
   14 or 18 bytes as follows:

                           1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Ver  | Type  | Flags | Count |      Err      |    SubErr     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Sequence Number                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Nickname  (2 bytes)         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
      |   Data Label ... (4 or 8 bytes)                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+
      | Type Specific Payload - variable length
      +-+-+- ...

      Fields not described below are as in Section 3.1.

      Nickname: The nickname of the original TRILL switch that is
         communicating with the end station Pull Directory. Usually this
         is a remote TRILL switch but it could be the TRILL switch to
         which the end station is attached. The proxy copies this from
         the ingress nickname when mapping a Query or Acknowledge
         Message to native form. It also takes this from a native
         Response or Update Message to be used as the egress of the


D. Eastlake, et al                                             [Page 27]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


         inter-RBridge form on the message unless it is a flooded Update
         in which case a distribution tree is used.

      Data Label: The Data Label that normally appears right after the
         Inner.MacSA of the an RBridge Channel Pull Directory message
         appears here in the native RBridge Channel message version.
         This might appear in a native Query Message, to be reflected in
         a Response Message, or it might appear in a native Update to be
         reflected in an Acknowledge Message.



3.5 Pull Directory Message Errors

   A non-zero Err field in the Pull Directory message header indicates
   an error message.

   If there is an error that applies to an entire Query Message or its
   header, as indicated by the range of the value of the Err field, then
   the QUERY records in the request are just echoed back in the RESPONSE
   records of the Response Message but expanded with a zero Lifetime and
   the insertion of the Index field. If there is an error that applies
   to an entire Update Message or its header, then the RESPONSE records
   in the update, if any, are echoed back in the corresponding
   Acknowledge Message.

   If errors occur at the QUERY Record level for a Query Message, they
   MUST be reported in a Response Message separate from the results of
   any successful non-erroneous QUERY Records. If multiple QUERY Records
   in a Query Message have different errors, they MUST be reported in
   separate Response Messages. If multiple QUERY Records in a Query
   Message have the same error, this error response MAY be reported in
   one or multiple Response Messages.  In an error Response Message, the
   QUERY Record or records being responded to appear, expanded by the
   Lifetime for which the server thinks the error might persist and with
   their Index inserted, as the RESPONSE record or records.

   If errors occur at the RESPONSE Record level for an Update Message,
   they MUST be reported in a Acknowledge Message separate from the
   acknowledgement of any non-erroneous RESPONSE Records. If multiple
   RESPONSE Records in an Update have different errors, they MUST be
   reported in separate Acknowledge Messages. If multiple RESPONSE
   Records in an Update Message have the same error, this error response
   MAY be reported in one or multiple Acknowledge Messages.  In an error
   Acknowledge Message, the RESPONSE Record or records being responded
   to appear, expanded by the time for which the server thinks the error
   might persist and with their Index inserted, as a RESPONSE Record or
   records.

   ERR values 1 through 126 are available for encoding Request or Update


D. Eastlake, et al                                             [Page 28]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


   Message level errors. ERR values 128 through 254 are available for
   encoding QUERY or RESPONSE Record level errors. The SubErr field is
   available for providing more detail on errors. The meaning of a
   SubErr field value depends on the value of the Err field.



3.5.1 Error Codes

       Err     Meaning
      -----    -------
          0     (no error)

          1     Unknown or reserved Query Message field value
          2     Request Message/data too short
          3     Unknown or reserved Update Message field value
          4     Update Message/data too short
      5-126     (Available for allocation by IETF Review)
        127     Reserved

        128     Unknown or reserved QUERY Record field value
        129     QUERY Record truncated
        130     Address not found
        131     Unknown or reserved RESPONSE Record field value
        132     RESPONSE Record truncated
      133-254   (Available for allocation by IETF Review)
        255     Reserved



3.5.2 Sub-Errors Under Error Codes 1 and 3

   The following sub-errors are specified under error code 1 and 3:

      SubErr   Field with Error
      ------   ----------------
          0     Unspecified
          1     Unknown Ver field value
          2     Unknown Type field value
          3     Specified Data Label not being served
      4-254     (Available for allocation by Expert Review)
        255     Reserved



3.5.3 Sub-Errors Under Error Codes 128 and 131

   The following sub-errors are specified under error code 128 and 131:




D. Eastlake, et al                                             [Page 29]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


      SubErr   Field with Error
      ------   ----------------
          0     Unspecified
          1     Unknown AFN field value
          2     Unknown or Reserved QTYPE field value
          3     Invalid or inconsistent SIZE field value
          4     Invalid frame for QTYPE 2, 3, 4, or 5
      5-254     (Available for allocation by Expert Review)
        255     Reserved




3.6 Additional Pull Details

   If a TRILL switch notices that a Pull Directory server is no longer
   data reachable [rfc7180bis], it MUST promptly discard all pull
   responses it is retaining from that server as it can no longer
   receive cache consistency update Messages from the server.

   A secondary Pull Directory server is one that obtains its data from a
   primary directory server. See discussion of primary to secondary
   directory information transfer in Section 2.5.




3.7 The No Data Flag

   In the TRILL base protocol [RFC6325] as extended for FGL [RFC7172],
   the mere presence of an Interested VLANs or Interested Labels sub-
   TLVs in the LSP of a TRILL switch indicates connection to end
   stations in the VLAN(s) or FGL(s) listed and thus a desire to receive
   multi-destination traffic in those Data Labels. But, with Push and
   Pull Directories, advertising that you are a directory server
   requires using these sub-TLVs to indicate the Data Label(s) you are
   serving. If such a directory server does not wish to received multi-
   destination TRILL Data packets for the Data Labels it lists in one of
   these sub-TLVs, it sets the "No Data" (NOD) bit to one. This means
   that data on a distribution tree may be pruned so as not to reach the
   "No Data" TRILL switch as long as there are no TRILL switches
   interested in the Data that are beyond the "No Data" TRILL switch on
   the distribution tree.  The NOD bit is backwards compatible as TRILL
   switches ignorant of it will simply not prune when they could, which
   is safe although it may cause increased link utilization.

   Example of a TRILL switch serving as a directory that might not want
   multi-destination traffic in some Data Labels would be a TRILL switch
   that does not offer end station service for any of the Data Labels
   for which it is serving as a directory and is either


D. Eastlake, et al                                             [Page 30]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


      -  a Pull Directory and/or
      -  a Push Directory for which all of the ESADI traffic will be
         handled by unicast ESDADI [RFC7357].

   A Push Directory MUST NOT set the NOD bit for a Data Label if it
   needs to communicate via multi-destination ESADI PDUs in that data
   label since such PDUs look like TRILL Data packets to transit TRILL
   switches and are likely to be incorrectly pruned if NOD was set.












































D. Eastlake, et al                                             [Page 31]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


4. Directory Use Strategies and Push-Pull Hybrids

   For some edge nodes that have a great number of Data Labels enabled,
   managing the MAC and Data Label <-> Edge RBridge mapping for hosts
   under all those Data Labels can be a challenge. This is especially
   true for Data Center gateway nodes, which need to communicate with
   many, if not all, Data Labels.

   For those edge TRILL switch nodes, a hybrid model should be
   considered.  That is the Push Model is used for some Data Labels or
   addresses within a Data Lable while the Pull Model is used for other
   Data Labels or addresses within a Data Label. It is the network
   operator's decision by configuration as to which Data Labels' mapping
   entries are pushed down from directories and which Data Labels'
   mapping entries are pulled.

   For example, assume a data center where hosts in specific Data
   Labels, say VLANs 1 through 100, communicate regularly with external
   peers.  Probably, the mapping entries for those 100 VLANs should be
   pushed down to the data center gateway routers. For hosts in other
   Data Labels that only communicate with external peers occasionally
   for management interface, the mapping entries for those VLANs should
   be pulled down from directory when the need comes up.

   Similarly, it could be that within a Data Label that some addresses,
   such as the addresses of gateways, file, DNS, or database server
   hosts are commonly referenced by most other hosts but those other
   hosts, perhaps compute engines, are typically only referenced by a
   few hosts in that Data Label. In that case, the address information
   for the commonly referenced hosts could be pushed as an incomplete
   directory while the addresses of the others are pulled when needed.

   The mechanisms described above for Push and Pull Directory services
   make it easy to use Push for some Data Labels or addresses and Pull
   for others. In fact, different TRILL switches can even be configured
   so that some use Push Directory services and some use Pull Directory
   services for the same Data Label if both Push and Pull Directory
   services are available for that Data Label. And there can be Data
   Labels for which directory services are not used at all.

   There are a wide variety of strategies that a TRILL switch can adopt
   for making use of directory assistance. A few suggestions are given
   below.

      -  Even if a TRILL switch will normally be operating with
      information from a complete Push Directory server, there will be a
      period of time when it first comes up before the information it
      holds is complete.  Or, it could be that the only Push Directories
      that can push information to it are incomplete or that they are
      just starting and may not yet have pushed the entire directory.


D. Eastlake, et al                                             [Page 32]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


      Thus, it is RECOMMENDED that all TRILL switches have a strategy
      for dealing with the situation where they do not have complete
      directory information. Examples are to send a Pull Directory query
      or to revert to [RFC6325] behavior.

      -  If a TRILL switch receives a native frame X resulting in
      seeking directory information, a choice needs to be made as to
      what to do if it does not already have the directory information
      it needs. In particular, it could (1) immediately flood the TRILL
      Data packet resulting from ingressing X in parallel with seeking
      the directory information, (2) flood that TRILL Data packet
      delayed, if it fails to obtain the directory information, or (3)
      discard X if it fails to obtain the information. The choice might
      depend on the priority of frame X since the higher that priority,
      the more urgent the frame is and the greater the probability of
      harm in delaying it. If a Pull Directory request is sent, it is
      RECOMMENDED that its priority be derived from the priority of the
      frame X with the derived priority configurable and having the
      following defaults:


          Ingressed     If Flooded    If Flooded
          Priority      Immediately   After Delay
          --------      -----------   -----------
            7             5             6
            6             5             6
            5             4             5
            4             3             4
            3             2             3
            2             0             2
            0             1             0
            1             1             1

   Priority 7 is normally only used for urgent messages critical to
   adjacency and so SHOULD NOT be the default for directory traffic.
   Unsolicited updates are sent with a priority that is configured per
   Data Label that defaults to priority 5.















D. Eastlake, et al                                             [Page 33]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


5. Security Considerations

   Incorrect directory information can result in a variety of security
   threats including the following:

      Incorrect directory mappings can result in data being delivered to
      the wrong end stations, or set of end stations in the case of
      multi-destination packets, violating security policy.

      Missing or incorrect directory data can result in denial of
      service due to sending data packets to black holes or discarding
      data on ingress due to incorrect information that their
      destinations are not reachable.

   Push Directory data is distributed through ESADI-LSPs [RFC7357] that
   can be authenticated with the same mechanisms as IS-IS LSPs. See
   [RFC5304] [RFC5310] and the Security Considerations section of
   [RFC7357].

   Pull Directory queries and responses are transmitted as RBridge-to-
   RBridge or native RBridge Channel messages [RFC7178]. Such messages
   can be secured as specified in [ChannelTunnel].

   For general TRILL security considerations, see [RFC6325].




























D. Eastlake, et al                                             [Page 34]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


6. IANA Considerations

   This section gives IANA assignment and registry considerations.



6.1 ESADI-Parameter Data Extensions

   Action 1: IANA will assigned a two bit field [bits 1-2 suggested]
   within the ESADI-Parameter TRILL APPsub-TLV flags for "Push Directory
   Server Status" (PDSS) and will create a sub-registry in the TRILL
   Parameters Registry as follows:

      Sub-Registry: ESADI-Parameter APPsub-TLV Flag Bits

      Registration Procedures: Standards Action

      References: [RFC7357] [This document]

         Bit  Mnemonic  Description                    Reference
         ---  --------  -----------                    ---------
           0    UN      Supports Unicast ESADI         ESDADI [RFC7357]
         1-2    PDSS    Push Directory Server Status   [this document]
         3-7    -       Available for assignment

   Action 2: In addition, the ESADI-Parameter APPsub-TLV is optionally
   extended, as provided in its original specification in ESADI
   [RFC7357], by one byte as show below. Therefore [this document]
   should be added as a second reference to the ESDAI-Parameter APPsub-
   TLV in the "TRILL APPsub-TLV Types under IS-IS TLV 251 Application
   Identifier 1" Registry.

                +-+-+-+-+-+-+-+-+
                | Type          |           (1 byte)
                +-+-+-+-+-+-+-+-+
                | Length        |           (1 byte)
                +-+-+-+-+-+-+-+-+
                |R| Priority    |           (1 byte)
                +-+-+-+-+-+-+-+-+
                | CSNP Time     |           (1 byte)
                +-+-+-+-+-+-+-+-+
                | Flags         |           (1 byte)
                +---------------+
                |PushDirPriority|           (optional, 1 byte)
                +---------------+
                | Reserved for expansion    (variable)
                +-+-+-+-...

   The meanings of all the fields are as specified in ESDADI [RFC7357]
   except that the added PushDirPriority is the priority of the


D. Eastlake, et al                                             [Page 35]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


   advertising ESADI instance to be a Push Directory as described in
   Section 2.3. If the PushDirPriority field is not present (Length = 3)
   it is treated as if it were 0x40. 0x40 is also the value used and
   placed here by an TRILL switch whose priority to be a Push Directory
   has not been configured.



6.2 RBridge Channel Protocol Number

   Action 3: IANA will allocate a new RBridge Channel protocol number
   for "Pull Directory Services" from the range allocable by Standards
   Action and update the subregistry of such protocol number in the
   TRILL Parameters Registry referencing this document.



6.3 The Pull Directory (PUL) and No Data (NOD) Bits

   Action 4: IANA is requested to assign a currently reserved bit in the
   Interested VLANs field of the Interested VLANs sub-TLV [suggested bit
   18] and the Interested Labels field of the Interested Labels sub-TLV
   [suggested bits 6] [RFC7176] to indicate Pull Directory server (PUL).
   This bit is to be added, with this document as reference, to the
   "Interested VLANs Flag Bits" and "Interested Labels Flag Bits"
   subregistries created by [RFC7357].

   Action 5: IANA is requested to assign a currently reserved bit in the
   Interested VLANs field of the Interested VLANs sub-TLV [suggested
   bits 19] and the Interested Labels field of the Interested Labels
   sub-TLV [suggested bits 7] [RFC7176] to indicate No Data (NOD, see
   Section 3.7). This bit is to be added, with this document as
   reference, to the "Interested VLANs Flag Bits" and "Interested Labels
   Flag Bits" subregistries created by [RFC7357].



6.4 TRILL Pull Directory QTYPEs

   Action 6: IANA is requested to create a new Registry on the
   "Transparent Interconnection of Lots of Links (TRILL) Parameters" web
   page as follows:

      Name: TRILL Pull Directory QTYPEs"
      Registration Procedure: IETF Review
      Reference: [this document]
      Initial contents as in Section 3.2.1.





D. Eastlake, et al                                             [Page 36]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


6.5 Pull Directory Error Code Registries

   Actions 7, 8, and 9: IANA is requested to create a new Registry and
   two new SubRegistries on the "Transparent Interconnection of Lots of
   Links (TRILL) Parameters" web page as follows:

   Registry
      Name: TRILL Pull Directory Errors
      Registration Procedure: IETF Review
      Reference: [this document]
      Initial contents as in Section 3.5.1.

      Sub-Registry
         Name: Sub-codes for TRILL Pull Directory Errors 1 and 3
         Registration Procedure: Expert Review
         Reference: [this document]
         Initial contents as in Section 3.5.2.

      Sub-Registry
         Name: Sub-codes for TRILL Pull Directory Errors 128 and 131
         Registration Procedure: Expert Review
         Reference: [this document]
         Initial contents as in Section 3.5.3.





























D. Eastlake, et al                                             [Page 37]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


Normative References

   [RFC826] - Plummer, D., "An Ethernet Address Resolution Protocol",
         RFC 826, November 1982.

   [RFC903] - Finlayson, R., Mann, T., Mogul, J., and M. Theimer, "A
         Reverse Address Resolution Protocol", STD 38, RFC 903, June
         1984

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

   [RFC3971] - Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
         "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005.

   [RFC4861] - Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
         "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
         September 2007.

   [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
         Authentication", RFC 5304, October 2008.

   [RFC5310] - Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
         and M. Fanto, "IS-IS Generic Cryptographic Authentication", RFC
         5310, February 2009.

   [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.

   [RFC7042] - Eastlake 3rd, D. and J. Abley, "IANA Considerations and
         IETF Protocol and Documentation Usage for IEEE 802 Parameters",
         BCP 141, RFC 7042, October 2013.

   [RFC7172] - Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R.,
         and D. Dutt, "Transparent Interconnection of Lots of Links
         (TRILL): Fine-Grained Labeling", RFC 7172, May 2014,
         <http://www.rfc-editor.org/info/rfc7172>.

   [RFC7176] - Eastlake 3rd, D., Senevirathne, T., Ghanwani, A., Dutt,
         D., and A. Banerjee, "Transparent Interconnection of Lots of
         Links (TRILL) Use of IS-IS", RFC 7176, May 2014,
         <http://www.rfc-editor.org/info/rfc7176>.

   [RFC7178] - Eastlake 3rd, D., Manral, V., Li, Y., Aldrin, S., and D.
         Ward, "Transparent Interconnection of Lots of Links (TRILL):
         RBridge Channel Support", RFC 7178, May 2014, <http://www.rfc-


D. Eastlake, et al                                             [Page 38]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


         editor.org/info/rfc7178>.

   [RFC7357] - Zhai, H., Hu, F., Perlman, R., Eastlake 3rd, D., and O.
         Stokes, "Transparent Interconnection of Lots of Links (TRILL):
         End Station Address Distribution Information (ESADI) Protocol",
         RFC 7357, September 2014, <http://www.rfc-
         editor.org/info/rfc7357>.

   [rfc7180bis] - D. Eastlake 3rd, M. Zhang, A. Banerjee, A. Ghanwani,
         and S. Gupta "Transparent Interconnection of Lots of Links
         (TRILL): Clarifications, Corrections, and Updates", RFC 7180,
         May 2014, <http://www.rfc-editor.org/info/rfc7180>.

   [IA] - Eastlake, D., L. Yizhou, R. Perlman, "TRILL: Interface
         Addresses APPsub-TLV", draft-ietf-trill-ia-appsubtlv, work in
         progress.



Informational References

   [RFC7067] - Dunbar, L., Eastlake 3rd, D., Perlman, R., and I.
         Gashinsky, "Directory Assistance Problem and High-Level Design
         Proposal", RFC 7067, November 2013.

   [ChannelTunnel] - D. Eastlake, M. Umair, Y. Li, "TRILL: RBridge
         Channel Tunnel Protocol", draft-ietf-trill-channel-tunnel, work
         in progress.

   [ARPreduction] - Y. Li, D. Eastlake, L. Dunbar, R. Perlman, I.
         Gashinsky, "TRILL: ARP/ND Optimization", draft-ietf-trill-arp-
         optimization, work in progress.




















D. Eastlake, et al                                             [Page 39]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


Acknowledgments

   The contributions of the following persons are gratefully
   acknowledged:

        TBD

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











































D. Eastlake, et al                                             [Page 40]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


Authors' Addresses

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

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


   Linda Dunbar
   Huawei Technologies
   5430 Legacy Drive, Suite #175
   Plano, TX 75024, USA

   Phone: +1-469-277-5840
   Email: ldunbar@huawei.com


   Radia Perlman
   EMC
   2010 256th Avenue NE, #200
   Bellevue, WA 98007 USA

   Email: Radia@alum.mit.edu


   Igor Gashinsky
   Yahoo
   45 West 18th Street 6th floor
   New York, NY 10011

   Email: igor@yahoo-inc.com


   Yizhou Li
   Huawei Technologies
   101 Software Avenue,
   Nanjing 210012 China

   Phone: +86-25-56622310
   Email: liyizhou@huawei.com









D. Eastlake, et al                                             [Page 41]


INTERNET-DRAFT                       TRILL: Directory Service Mechanisms


Copyright, Disclaimer, and Additional IPR Provisions

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.  The definitive version of
   an IETF Document is that published by, or under the auspices of, the
   IETF. Versions of IETF Documents that are published by third parties,
   including those that are translated into other languages, should not
   be considered to be definitive versions of IETF Documents. The
   definitive version of these Legal Provisions is that published by, or
   under the auspices of, the IETF. Versions of these Legal Provisions
   that are published by third parties, including those that are
   translated into other languages, should not be considered to be
   definitive versions of these Legal Provisions.  For the avoidance of
   doubt, each Contributor to the IETF Standards Process licenses each
   Contribution that he or she makes as part of the IETF Standards
   Process to the IETF Trust pursuant to the provisions of RFC 5378. No
   language to the contrary, or terms, conditions or rights that differ
   from or are inconsistent with the rights and licenses granted under
   RFC 5378, shall have any effect and shall be null and void, whether
   published or posted by such Contributor, or included with or in such
   Contribution.





















D. Eastlake, et al                                             [Page 42]


Html markup produced by rfcmarkup 1.114, available from https://tools.ietf.org/tools/rfcmarkup/