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Versions: 00 01 03 draft-ietf-nfsv4-federated-fs-protocol

Network Working Group                                          D. Ellard
Internet-Draft                                               C. Everhart
Intended status: Standards Track                            NetApp, Inc.
Expires: February 6, 2009                                      R. Tewari
                                                                 M. Naik
                                                             IBM Almaden
                                                          August 5, 2008


                NSDB Protocol for Federated Filesystems
            draft-tewari-nfsv4-federated-fs-protocol-03.txt

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Copyright Notice

   Copyright (C) The IETF Trust (2008).











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Abstract

   This document describes a file system federation protocol that
   enables file access and namespace traversal across collections of
   independently administered fileservers.  The protocol specifies a set
   of interfaces by which fileservers and collections of fileservers
   with different administrators can form a fileserver federation that
   provides a namespace composed of the filesystems physically hosted on
   and exported by the constituent fileservers.


Table of Contents

   1.  Requirements notation  . . . . . . . . . . . . . . . . . . . .  4
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Protocol Goals . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Overview of Features and Concepts  . . . . . . . . . . . . . .  7
     3.1.  Namespace  . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.2.  Fileset  . . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.3.  Fileset Location (FSL) . . . . . . . . . . . . . . . . . .  8
       3.3.1.  Mutual Consistency across Fileset Locations  . . . . .  9
     3.4.  Namespace Repository (NSDB)  . . . . . . . . . . . . . . .  9
     3.5.  Mount Points, Junctions and Referrals  . . . . . . . . . . 10
     3.6.  Federation Root FileServers  . . . . . . . . . . . . . . . 11
     3.7.  Federation Root FileSet  . . . . . . . . . . . . . . . . . 11
     3.8.  Fileservers  . . . . . . . . . . . . . . . . . . . . . . . 11
     3.9.  File-access Clients  . . . . . . . . . . . . . . . . . . . 11
   4.  Interaction with NFSv4 . . . . . . . . . . . . . . . . . . . . 12
   5.  Finding the local NSDB . . . . . . . . . . . . . . . . . . . . 13
   6.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     6.1.  Create a Fileset and its FSL(s)  . . . . . . . . . . . . . 14
       6.1.1.  Creating a Fileset and a FSN . . . . . . . . . . . . . 14
       6.1.2.  Adding a Replica of a Fileset  . . . . . . . . . . . . 15
     6.2.  Junction Resolution  . . . . . . . . . . . . . . . . . . . 15
     6.3.  Example use case for fileset annotations . . . . . . . . . 16
   7.  Error Definitions  . . . . . . . . . . . . . . . . . . . . . . 17
   8.  Mapping the NSDB onto LDAP . . . . . . . . . . . . . . . . . . 19
     8.1.  Basic LDAP Configuration . . . . . . . . . . . . . . . . . 19
     8.2.  LDAP Attributes  . . . . . . . . . . . . . . . . . . . . . 19
       8.2.1.  fedfsUuid  . . . . . . . . . . . . . . . . . . . . . . 19
       8.2.2.  fedfsNetAddr . . . . . . . . . . . . . . . . . . . . . 20
       8.2.3.  fsnUuid  . . . . . . . . . . . . . . . . . . . . . . . 20
       8.2.4.  nsdbName . . . . . . . . . . . . . . . . . . . . . . . 20
       8.2.5.  fslHost  . . . . . . . . . . . . . . . . . . . . . . . 20
       8.2.6.  fslPath  . . . . . . . . . . . . . . . . . . . . . . . 20
       8.2.7.  annotation . . . . . . . . . . . . . . . . . . . . . . 21
       8.2.8.  descr  . . . . . . . . . . . . . . . . . . . . . . . . 21
       8.2.9.  fslUuid  . . . . . . . . . . . . . . . . . . . . . . . 21



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       8.2.10. junctionKey  . . . . . . . . . . . . . . . . . . . . . 21
       8.2.11. childFsnUuid . . . . . . . . . . . . . . . . . . . . . 21
       8.2.12. childNsdbName  . . . . . . . . . . . . . . . . . . . . 22
     8.3.  LDAP Objects . . . . . . . . . . . . . . . . . . . . . . . 22
       8.3.1.  FsnObject  . . . . . . . . . . . . . . . . . . . . . . 22
       8.3.2.  FslObject  . . . . . . . . . . . . . . . . . . . . . . 22
       8.3.3.  JunctionObject . . . . . . . . . . . . . . . . . . . . 22
   9.  NSDB Protocol Operations . . . . . . . . . . . . . . . . . . . 24
     9.1.  Administrative NSDB Operations . . . . . . . . . . . . . . 24
       9.1.1.  Creating an FSN  . . . . . . . . . . . . . . . . . . . 25
       9.1.2.  Deleting an FSN  . . . . . . . . . . . . . . . . . . . 26
       9.1.3.  Mount an FSN . . . . . . . . . . . . . . . . . . . . . 26
       9.1.4.  Unmount an FSN . . . . . . . . . . . . . . . . . . . . 27
       9.1.5.  Create an FSL  . . . . . . . . . . . . . . . . . . . . 28
       9.1.6.  Delete an FSL  . . . . . . . . . . . . . . . . . . . . 28
       9.1.7.  Update an FSL  . . . . . . . . . . . . . . . . . . . . 29
       9.1.8.  Examining an FSL . . . . . . . . . . . . . . . . . . . 29
       9.1.9.  Finding the children FSNs of a fileset . . . . . . . . 29
     9.2.  Fileserver to NSDB Operations  . . . . . . . . . . . . . . 30
       9.2.1.  Looking up FSLs for an FSN . . . . . . . . . . . . . . 30
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 31
   11. IANA Requirements  . . . . . . . . . . . . . . . . . . . . . . 32
   12. Conclusions  . . . . . . . . . . . . . . . . . . . . . . . . . 33
   13. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
   14. Normative References . . . . . . . . . . . . . . . . . . . . . 37
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 38
   Intellectual Property and Copyright Statements . . . . . . . . . . 39
























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1.  Requirements notation

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














































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2.  Introduction

   A federated filesystem enables file access and namespace traversal in
   a uniform, secure and consistent manner across multiple independent
   fileservers within an enterprise (and possibly across multiple
   enterprises) with reasonably good performance.

   The first requirement of a federated filesystem is the ability to
   traverse the data exported by different fileservers without requiring
   a static client configuration.  The second requirement is that the
   location of the data should be dynamically discovered and the
   discovery process should be transparent to the clients.  The third
   requirement is that it should be possible for all clients, with
   sufficient privilege, to view the same namespace regardless of the
   fileserver they connect to.

   Traditionally, fileserver collections are administered by a single
   entity.  Fileservers may provide proprietary management tools and in
   some cases an administrator may be able to use the proprietary tools
   to build a shared namespace out of the exported filesystems.  Relying
   on vendor-proprietary tools does not work in larger enterprises or
   when collaborating across enterprises because it is likely that the
   system will contain fileservers running different software, each with
   their own interfaces, with no common protocol to manage the namespace
   or exchange namespace information.  There may also be independently-
   administered singleton servers that export some or all of their
   filesystem resources.  A filesystem federation protocol enables the
   interoperation across multi-vendor fileservers managed by the same
   administrative entity, across singleton independent fileservers, and
   across independent administrative entities that may manage a
   collection of fileservers.  The scope of the filesystem federation
   protocol is limited to NFSv4 capable fileservers.  The support for
   NFSv3 fileservers is optional.

2.1.  Protocol Goals

   The objective of this draft is to specify a set of interfaces by
   which fileservers and collections of fileservers with different
   administrators can form a fileserver federation that provides a
   namespace composed of the filesystems physically hosted on and
   exported by the fileservers of the federation.  It should be
   possible, using a system that implements the interfaces, to share a
   common namespace across all the fileservers in the federation.  It
   should also be possible for different fileservers in the federation
   to project different namespaces and enable clients to traverse them.
   Such a federation may contain an arbitrary number of namespace
   repositories, each belonging to a different administrative entity,
   and each rendering a part of the namespace.  Such a federation may



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   also have an arbitrary number of administrative entities responsible
   for administering disjoint subsets of the fileservers.  In the rest
   of the document the term fileserver implies a fileserver that is part
   of the federation.  A fileserver not part of the federation is called
   an external fileserver.














































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3.  Overview of Features and Concepts

3.1.  Namespace

   The goal of a unified namespace is to make all managed data available
   to all clients via the same path in a common filesystem-like
   namespace.  This should be achieved with minimal or zero client
   configuration.  In particular, updates to the common namespace should
   not require configuration changes at the client.  Filesets, which are
   the unit of data management, are a set of files and directories
   accessible from a single mount.  Depending on the implementation,
   they may be anything between an individual directory of an exported
   filesystem to an entire exported filesystem at a fileserver.  From
   the perspective of the clients, the common namespace is constructed
   by logically mounting filesets that are physically located on
   different fileservers.  The namespace, which is defined in terms of
   fileset definitions, fileset identifiers, the location of each
   fileset in the namespace, and the physical location of the
   implementation(s) of each fileset, is stored in a set of namespace
   repositories, each managed by an administrative entity.  The
   namespace schema defines the model used for populating, modifying,
   and querying the namespace repositories.  It is not required by the
   federation that the namespace be common across all fileservers.  It
   should be possible to have several independently rooted namespaces
   that should permit traversal into another namespace at defined
   junction points.

3.2.  Fileset

   A fileset is defined to be a container of data and is the basic unit
   of data management.  It is uniquely represented by the fileset name
   (FSN).  An FSN is considered unique across the federation.  An FSN
   contains information sufficient to locate the namespace repository
   (NSDB) that holds authoritative information about it and an
   identifier, called fsn_uuid, that identifies it on that NSDB.  After
   an FSN is created, it is associated with a fileset location (FSL) on
   a fileserver.  A fileset can be implemented by one or more FSLs.  The
   attributes of an FSN are:

   NsdbName:  the fully qualified domain name of an NSDB location that
      contains authoritative information for this FSN.

   FsnUuid:  a 128-bit UUID (universally unique identifier), conforming
      to [RFC4122], that is used to uniquely identify an FSN.







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3.3.  Fileset Location (FSL)

   An FSL represents the location where the fileset data resides.  Each
   FSL maps to a host:path pair on a file server.  An FSL may also have
   additional attributes.  Each location has an associated type that
   determines the protocol(s) that may be used to access its data.  Type
   information can be used to decide the list of locations that will be
   returned to the client.  It also has associated status information.
   Other attributes associated with an FSL are based on the NFSv4.1
   fs_locations_info attribute[RFCTBD].

       struct FSL {
          utf8string    host_fqdn;
          utf8string    pathname;
          FSL_ATTR      attrs;
       };

   Each FSL consists of:

   host_fqdn:  the name of the host fileserver storing the physical data

   pathname:  the exported pathname at that host fileserver

   attrs:  additional attributes for this FSL, as described in the
      FSL_ATTR structure


       struct FSL_ATTR {
           protocol_t   type;
           int32_t      currency;
           annotation_t annotations<>;
           fs_status_t  status;
           opaque_t     info<>;
       }

   The attributes associated with each FSL are:

   type:  the protocol(s) supported by the fileserver hosting this FSL

   currency:  the time lag of this FSL represented as the number of time
      units it lags the latest version as defined by the NFSv4.1
      fs_locations_info attribute.  A currency value of 0 represents the
      latest version.  Currency values are less than or equal to zero

   annotations:  a list of name/value pairs that can be interpreted by
      an individual NSDB.  The semantics of the name/value pair is not
      defined by this protocol and is intended to be used by higher-
      level administration protocols



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   status:  fls_status as defined by the NFSv4.1 status attribute

   info:  as defined in NFSv4.1 fs_locations_info attribute

3.3.1.  Mutual Consistency across Fileset Locations

   All of the FSLs that have the same FSN (thereby reference the same
   fileset) are equivalent from the point of view of client access; the
   different locations of a fileset represent the same data, though
   potentially at different points in time.  Fileset locations are
   equivalent but not identical.  Locations may either be read- only or
   read-write.  Typically, multiple read-write locations are backed by a
   clustered filesystem while read-only locations are replicas created
   by a federation-initiated or external replication.  Read-only
   locations may represent consistent point-in-time copies of a read-
   write location.  The federation protocols, however, cannot prevent
   subsequent changes to a read-only location nor guarantee point-in-
   time consistency of a read-only location if the read-write location
   is changing.

   Regardless of the type, all locations exist at the same mount point
   in the namespace and, thus, one client may be referred to one
   location while another is directed to a different location.  Since
   updates to each fileset location are not controlled by the federation
   protocol, it is the responsibility of administrators to guarantee the
   functional equivalence of the data.

   The federation protocol does not guarantee that the different
   locations are mutually consistent in terms of the currency of the
   data.  It relies on the client file-access protocol (i.e., NFSv4) to
   contain sufficient information to help the clients determine the
   currency of the data at each location in order to ensure that the
   clients do not revert back in time when switching locations.  This
   raises a concern for NFSv3 fileservers, which the federation protocol
   may support, that may lack such control.

3.4.  Namespace Repository (NSDB)

   The NSDB service is a federation-wide service that provides
   interfaces to define, update, and query FSN information and FSN to
   FSL mapping information.  An individual repository of namespace
   information is called an NSDB location.  Each NSDB location is
   managed by a single administrative entity.  A single admin entity can
   manage multiple NSDB locations.

   The difference between the NSDB service and an NSDB location is
   analogous to that between the DNS service and a particular DNS
   server.



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   The term local NSDB is shorthand for an NSDB location that is known a
   priori to a server.  It is typically located within the same
   federation member as the server, but this is not required.  A local
   NSDB is not required.

   Each NSDB location stores the definition of the FSNs for which it is
   authoritative.  It also stores the definitions of the FSLs associated
   with those FSNs.  An NSDB location is authoritative for the filesets
   that it defines.  An NSDB location can cache information from a peer
   NSDB location.  The fileserver can always contact a local NSDB
   location (if it has been defined) or directly contact any NSDB
   location to resolve a junction.  Each NSDB location supports an LDAP
   interface and can be accessed by an LDAP client.

3.5.  Mount Points, Junctions and Referrals

   A mount point is a directory in a parent fileset where a target
   fileset may be attached.  If a client traverses the path leading from
   the root of the namespace to the mount point of a fileset it should
   be able to access the data in that fileset (assuming appropriate
   permissions).

   The directory where a fileset is mounted is represented by a junction
   in the underlying filesystem.  In other words, a junction can be
   viewed as a reference from a directory in one fileset to the root of
   the target fileset.  A junction can be implemented as a special
   marker on a directory that is interpreted by the fileserver as a
   mount point, or by some other mechanism in the underlying file
   system.

   What data is used by the underlying file system to represent the
   junction is not defined by this protocol.  The essential property is
   that the server must be able to find, given the junction, the FSN for
   the target fileset.  The FSN (as described earlier) contains both the
   NSDB location of the authoritative NSDB location and the FsnUuid (a
   UUID for the fileset).

   When a client traversal reaches a junction, the client is referred to
   a list of FSLs associated with the FSN that was the target of the
   junction.  The client can then redirect its connection to one of the
   FSLs.  This act is called a referral.  For NFSv4 clients, the FSL
   information is returned in the fs_locations or fs_locations_info
   attributes.

   The federation-fs interfaces do not limit where and how many times a
   fileset is mounted in the namespace.  Filesets can be nested -- a
   fileset can be mounted under another fileset.




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3.6.  Federation Root FileServers

   A set of designated fileservers that render the common federation-
   wide namespace are called the federation root fileservers.  The
   federation protocol does not mandate that federation root fileservers
   be defined.  When a client mounts the root of the namespace from a
   root fileserver it can traverse the entire federation-wide namespace.
   It is not required for a client to mount from one of the root
   fileservers.  If a client mounts from a non-root fileserver then it
   can traverse the part of the namespace that is visible starting from
   that fileserver.  A client can mount multiple individual filesets
   from multiple non-root fileservers and chose to navigate the
   namespace in any manner.  How the client discovers the root
   fileserver(s), if one is defined, is not in the scope of the
   federation protocol.  Numerous external techniques such as DNS SRV
   records can be used for this.

3.7.  Federation Root FileSet

   The root fileset is the optional, top-level fileset of the
   federation-wide namespace.  The root of the namespace is the top
   level directory of this fileset.  The fileset can contain an
   arbitrary number of virtual directories.  The leaf directories of the
   root fileset serve as the mount points for other filesets.  It is
   desirable that the leaf directories not contain data.  The root
   fileset is a simple combination of internal nodes and leaf nodes
   where each leaf node is a junction to a target fileset.  The root
   fileset is replicated at all the root fileservers.  The recommended
   replication protocols for root fileset replication are: an external
   protocol such as rsync or NDMP.

3.8.  Fileservers

   Fileservers are NFSv4 servers that store the physical fileset data or
   fileservers that refer the client to other fileservers.

3.9.  File-access Clients

   File access clients are standard off-the-shelf NAS clients that
   access file data using the NFSv4 protocol.











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4.  Interaction with NFSv4

   The federation protocol is compatible with the requirements of NFSv4
   referral mechanisms as defined in [RFC3530].















































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5.  Finding the local NSDB

   The local NSDB may be used for finding the mapping from the server's
   local representation of a junction to an FSN.  How the mapping is
   resolved is implementation-specific.  The fed-fs protocol does not
   mandate how and if a local NSDB is defined or located.  A fileserver
   could choose to have a special configuration setup for defining the
   local or default NSDB in a manner similar to a resolv.conf file for
   DNS.










































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6.  Examples

   In this section we provide examples and discussion of the basic
   operations facilitated by the federated file system protocol:
   creating a fileset, adding a replica of a fileset, resolving a
   junction, and creating a junction.

6.1.  Create a Fileset and its FSL(s)

   A fileset is the abstraction of a set of files and their containing
   directory tree.  The fileset abstraction is the fundamental unit of
   data management in the federation.  This abstraction is implemented
   by an actual directory tree whose root location is specified by a
   fileset location (FSL).

   In this section, we describe the basic requirements for starting with
   a directory tree and creating a fileset that can be used in the
   federation protocols.  Note that we do not assume that the process of
   creating a fileset requires any transformation of the files or the
   directory hierarchy.  The only thing that is required by this process
   is assigning the fileset a fileset name (FSN) and expressing the
   location(s) of the implementation of the fileset as FSL(s).

   There are many possible variations to this procedure, depending on
   how the FSN that binds the FSL is created, and whether other replicas
   of the fileset exist, are known to the federation, and need to be
   bound to the same FSN.

   It is easiest to describe this in terms of how to create the initial
   implementation of the fileset, and then describe how to add replicas.

6.1.1.  Creating a Fileset and a FSN

   1.  Choose the NSDB node that will keep track of the FSL(s) and
       related information for the fileset.

   2.  Request that the NSDB node register a new FSN for the fileset.

       The FSN may either be chosen by the NSDB node or by the server.
       The latter case is used if the fileset is being restored, perhaps
       as part of disaster recovery, and the server wishes to specify
       the FSN in order to permit existing junctions that reference that
       FSN to work again.

       At this point, the FSN exists, but its location is unspecified.

   3.  Send the FSN, the local volume path, the export path, and the
       export options for the local implementation of the fileset to the



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       NSDB node.  Annotations about the FSN or the location may also be
       sent.

       The NSDB node records this info and creates the initial FSL for
       the fileset.

6.1.2.  Adding a Replica of a Fileset

   Adding a replica is straightforward: the NSDB node and the FSN are
   already known.  The only remaining step is to add another FSL.

   Note that the federation interfaces do not include methods for
   creating or managing replicas: this is assumed to be a platform-
   dependent operation (at least at this time).  The only interface
   required is the ability to register or remove the registration of
   replicas for a fileset.

6.2.  Junction Resolution

   A fileset may contain references to other filesets.  These references
   are represented by junctions.  If a client requests access to a
   fileset object that is a junction, the server resolves the junction
   to discover the FSL(s) that implements the referenced fileset.

   There are many possible variations to this procedure, depending on
   how the junctions are represented and how the information necessary
   to perform resolution is represented by the server.  In this example,
   we assume that the only thing directly expressed by the junction is
   the junction key; its mapping to FSN can be kept local to the server
   hosting the junction.

   Step 5 is the only step that interacts directly with the federation
   interfaces.  The rest of the steps may use platform-specific
   interfaces.

   1.  The server determines that the object being accessed is a
       junction.

   2.  The server determines the junction key for the junction.

   3.  Using the junction key, the server does a local lookup to find
       the FSN of the target fileset.

   4.  Using the FSN, the server finds the NSDB node responsible for the
       target object.

   5.  The server contacts that NSDB node and asks for the set of FSLs
       that implement the target FSN.  The NSDB node responds with a set



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       of FSLs.

6.3.  Example use case for fileset annotations

   The fileset annotations can be used to define relationships between
   filesets that can be used by an auxiliary replication protocol.
   Consider the scenario where a fileset is created and mounted at some
   point in the namespace.  A snapshot of the read-write FSL of that
   fileset is taken periodically at different frequencies say a daily
   snapshot or a weekly snapshot.  The different snapshots are mounted
   at different locations in the namespace.  The daily snapshots are
   considered as a different fileset from the weekly ones but both are
   related to the source fileset.  For this we can define an annotation
   labeling the filesets as source and replica.  The replication
   protocol can use this information to copy data from one or more FSLs
   of the source fileset to all the FSLs of the replica fileset.  The
   replica filesets are read-only while the source fileset is read-
   write.

   This follows the traditional AFS model of mounting the read-only
   volume at a path in the namespace different from that of the read-
   write volume.

   The federation protocol does not control or manage the relationship
   among filesets.  It merely enables annotating the filesets with user-
   defined relationships.

























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7.  Error Definitions

   ERR_OK  Indicates the operation completed successfully.

   ERR_ACCESS  Permission denied.  The caller does not have the correct
      permission to perform the requested operation.  Contrast this with
      ERR_PERM, which restricts itself to owner or privileged user
      permission failures.

   ERR_BADCHAR  A UTF-8 string contains a character which is not
      supported in the context in which it being used.

   ERR_BADNAME  A name string in a request consists of valid UTF-8
      characters supported by the server but the name is not supported
      by the server as a valid name for current operation.

   ERR_BADTYPE  An attempt was made to create an object of a type not
      supported by the server.

   ERR_DENIED  An attempt to lock a file is denied.  Since this may be a
      temporary condition, the client is encouraged to retry the lock
      request until the lock is accepted.

   ERR_EXIST  Object exists.  The object specified already exists.

   ERR_INVALID  Invalid argument or unsupported argument for an
      operation.

   ERR_IO  I/O error.  A hard error (for example, a disk error) occurred
      while processing the requested operation.

   ERR_NAMETOOLONG  The filename in an operation was too long.

   ERR_NOENT  No such object.  The object being accessed does not exist.

   ERR_NOTDIR  Not a directory.  The caller specified a non- directory
      in a directory operation.

   ERR_NOTEMPTY  An attempt was made to remove an object that was not
      empty.  An FSN which has FSLs still defined for it.

   ERR_NOTSUPP  Operation is not supported.

   ERR_PERM  Not owner.  The operation was not allowed because the
      caller is either not a privileged user (root) or not the owner of
      the target of the operation.





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   ERR_WRONGSEC  The security mechanism being used by the client for the
      operation does not match the server's security policy.  The client
      should change the security mechanism being used and retry the
      operation.

   ERR_WRONGNSDB  The NSDB location is not the one to be used for this
      operation.












































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8.  Mapping the NSDB onto LDAP

   This section describes the LDAP schema used to define the LDAP
   implementation of the NSDB service.  The first part of the section
   describes the basic properties of the LDAP configuration that MUST be
   used in order to ensure compatibility between different
   implementations.  The second section defines the new LDAP attribute
   types and the subsequent sections describe the new object types and
   specifies how the distinguished name of each object instance MUST be
   constructed.

8.1.  Basic LDAP Configuration

   The base name (or suffix) for all of DNs used by the NSDB schema is
   "dc=fed-fs,dc=com".

   The DN of the priviledged LDAP user is, by convention,
   "cn=admin,dc=fed-fs,dc=com".  This user is able to modify the
   contents of the LDAP database.  It is permitted to use a different DN
   (or add additional priviledged users) but if a different DN is used
   then every admin entity that needs to modify the contents of the
   database or view privilidged information must be made aware of the
   new DN.

   It MUST be possible for the anonymous (unauthenticated) user perform
   LDAP queries that access the NSDB data.

   All implementation SHOULD use the same schema, or, at minimum, a
   schema that includes all of the objects, with each of the attributes,
   named in the following sections.  The complete schema SHOULD be
   defined as part of the protocol (or as a separate RFC) when its
   definition is complete.

8.2.  LDAP Attributes

   This section describes the required attributes of the NSDB LDAP
   schema.

8.2.1.  fedfsUuid

   A fedfsUuid is the base type for all of the universally unique
   identifiers (UUIDs) used by the federated file system protocols.

   This SHOULD be defined in terms of the text representation of the
   standard UUID (as defined in [RFC4122]).

   It MAY also be useful, for purposes of debugging or annotation, to
   permit a fedfsUuid to include members of a more general class of



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   strings.

   A fedfsUuid is a single-valued attribute.

8.2.2.  fedfsNetAddr

   An fedfsNetAddr is the locative name of a TCP/IP-based network
   service.  It MUST be able to express network locations as IPv4, IPv6,
   and DNS FQDN notations.  It may include a port specifier, or the port
   may be implicit in context.

   There MAY be a special syntax at some point for specifying a SVR
   record (for a DNS FQDN).

   This attribute is single-valued.

8.2.3.  fsnUuid

   A fsnUuid represents the fsnUuid component of an FSN.

   The fsnUuid is a subclass of fedfsUuid.

   This attribute is single-valued.

8.2.4.  nsdbName

   A nsdbName is the NSDB component of an FSN.

   The nsdbName attribute is a subclass of fedfsNetAddr.

   This attribute is single-valued.

8.2.5.  fslHost

   A fslHost is the hostname/port component of an FSL.

   The fslHost attribute is a subclass of fedfsNetAddr.

   This attribute is single-valued.

8.2.6.  fslPath

   The path component of an FSL.

   This attribute is single-valued.






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8.2.7.  annotation

   An annotation of an NSDB object.

   This attribute is multi-valued; an object type that permits
   annotations may have any number of annotations per instance.

   This attribute is a placeholder; it has not been well-defined at the
   date of this draft.

8.2.8.  descr

   A descriptive attribute containing information about an NSDB object.

   This attribute is single-valued.

   This attribute is a placeholder; it has not been well-defined at the
   date of this draft.

8.2.9.  fslUuid

   Each FSL must have a UUID associated with it, which serves as part of
   its DN.

   The fslUuid attribute is a subclass of fedfsUuid.

   This attribute is single-valued.

8.2.10.  junctionKey

   Each junction has a unique junctionKey that is used to distinguish it
   from other junctions that may refer to the same child fileset and/or
   appear within the same parent fileset.

   The junctionKey attribute is a subclass of fedfsUuid.

   This attribute is single-valued.

8.2.11.  childFsnUuid

   The fsnUuid of the target of a junction.

   The childFsnUuid attribute is a subclass of fsnUuid.

   This attribute is single-valued.






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8.2.12.  childNsdbName

   The nsdbName of the target of a junction.

   The childNsdbName attribute is a subclass of nsdbName.

   This attribute is single-valued.

8.3.  LDAP Objects

8.3.1.  FsnObject

   An FsnObject represents an FSN.

   The required attributes of an FsnObject are an fsnUuid and nsdbName.

   An FsnObject MAY also have descr and annotation attributes, but
   neither is required.

   The DN of an FSN is assumed to take the following form:
   "fsnUuid=FSNUUID,dc=fed-fs,dc=com", where fsnUuid is the UUID of the
   FSN.

   An FsnObject MAY also have additional attributes, but these
   attributes MUST NOT be referenced by any part of this draft.

8.3.2.  FslObject

   An FslObject represents an FSL.

   The required attributes of an FslObject are an fsnUuid, nsdbName,
   fslHost, fslPath, and fslUuid.

   An FslObject MAY also have descr and annotation attributes, but
   neither is required.

   The DN of an FSL is required to take the following form:
   "fslUuid=UUID,fsnUuid=FSNUUID,dc=fed-fs,dc=com".

   To find all the FSLs that match a given FSN, query for the children
   of the object with DN "fsnUuid=FSNUUID,dc=fed-fs,dc=com" with a
   filter for "objectType = fslObject".  (If you want to be doubly
   careful, you can also filter by the nsdbName.)

8.3.3.  JunctionObject

   An JunctionObject captures the relationship between a fileset and its
   children (if any).  The children FSNs are FSNs that appear in



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   junctions in the fileset named by the fsnUuid and nsdbName attributes
   of the parent FSN.

   The required attributes of a JunctionObject are a junctionKey,
   fsnUuid, nsdbName, childFsnUuid, and childNsdbName.

   A JunctionObject MAY also have descr and annotation attributes, but
   neither is required.

   The required form of a DN for an JunctionObject is:
   "junctionKey=KEY,fsnUuid=FSNUUID,dc=fed-fs,dc=com" where KEY is a
   unique key chosen for this relationship (the junctionKey) and FSNUUID
   is the fsnUuid of the parent fileset's FSN.

   Note that the reason why KEY might be something other than simply the
   fsnUuid of the child's FSN is that a child FSN may appear as the
   target of several junctions within the same fileset, and we must have
   a way to distinguish each of these junctions.

   To find all the junctions within a given fileset, query for the
   children of the object with DN "fsnUuid=FSNUUID,dc=fed-fs,dc=com" and
   filter for "objectType = JunctionObject".  (If you want to be doubly
   careful, you can also filter by the nsdbName.)




























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9.  NSDB Protocol Operations

   The operations defined by the protocol can be described as several
   sub-protocols that are used by entities within the federation to
   perform different roles.

   The first of these sub-protocols defines how the state of an NSDB
   location can be initialized and updated.  The primary use of this
   sub-protocol is by an administrator to add, edit, or delete filesets,
   their properties, and their fileset locations.

   The second of these sub-protocols defines the queries that are sent
   to an NSDB location in order to perform resolution (or find other
   information about the information stored within that NSDB location)
   and the responses returned by the NSDB location.  The primary use of
   this sub-protocol is by a fileset server in order to perform
   resolution, but it may also be used by an administrator to query the
   state of the system.

   The first and second sub-protocols are defined as LDAP operations,
   using the schema defined in the previous section.  If each NSDB
   location is a standard LDAP server, then, in theory, it is
   unnecessary to describe the LDAP operations in detail, because the
   operations are ordinary LDAP operations to query and update records.
   However, we do not require that an NSDB location implement a complete
   NSDB service, and therefore we define in these sections the minimum
   level of LDAP functionality required to implement an NSDB location.

   The NSDB sub-protocols are defined in the next two sub-sections.

   The third sub-protocol defines the queries or other requests that are
   sent to a fileset server in order to get information from it or to
   modify the state of the fileset server in a manner related to the
   federation protocols.  The primary purpose of this for an
   administrator to create or delete a junction or fileset or discover
   related information about a particular fileset server.

   The third sub-protocol is defined as ONC/RPC operations.  The reason
   for using a different RPC mechanism (instead of mapping these
   operations onto LDAP) is to minimize the changes required to the
   fileset server.  This protocol is described in a separate document.

9.1.  Administrative NSDB Operations

   The admin entity initiates and controls the commands to manage
   fileset and namespace information.  The admin entity, however, is
   stateless.  All state is maintained at the NSDB locations or at the
   fileserver.



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   We require that each NSDB location be able to act as an LDAP server
   and that the protocol used for communicating between the admin entity
   and each NSDB is LDAP.

   The names we assign to these operations are entirely for the purpose
   of exposition in this document, and are not part of the LDAP dialogs.

   In the description of the LDAP messages and LDIF, we use the
   following notation: constant strings and literal names are specified
   in lower or mixed case, while variables or values are specified in
   uppercase.  One important exception to this rule is that the names of
   the error codes follow the convention (used widely in other
   protocols, including NFS) of having names that are entirely
   uppercase.

   NEED TO UPDATE THE TEXT HERE TO REFER TO THE OTHER DRAFT. -DJE

9.1.1.  Creating an FSN

   The administrator uses this operation to create a new FSN by
   requesting the NSDB to create a new FsnObject in its LDAP database
   with an fsnUuid of FSNUUID and an NsdbName of NSDB.

   The NSDB location that receives the request SHOULD check that the
   NSDB matches its own value and return an ERR_WRONGNSDB error if does
   not.  This is to ensure that an FSN is always created by the NSDB
   location encoded within the FSN as its owner.

   The NSDB location that receives the request SHOULD check all of the
   attributes for validity and consistency, but this is not generally
   possible for LDAP servers because the consistency requirements cannot
   be expressed in the LDAP schema (although many LDAP servers can be
   extended, via plug-ins or other mechanisms, to add functionality
   beyond the strict definition of LDAP).

   PARAGRAPH DESCRIBING ERRORS

9.1.1.1.  LDAP Request

   The admin chooses the fsnUuid and NsdbName of the FSN.  The fsnUuid
   is a UUID and should be chosen via a standard process for creating a
   UUID (described in [RFC4122]).  The NsdbName is the name of the NSDB
   location that will serve as the source of definitive information
   about an FSN for the life of that FSN.  In the example below, the
   admin server chooses a fsnUuid of FSNUUID and the NsdbName of NSDB
   and then sends an LDAP ADD request, described by the LDIF below, to
   the NSDB location NSDB.  This will create a new FsnObject on that
   NSDB location with the given attributes in the LDAP database.



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       dn: fsnUuid=FSNUUID,dc=fed-fs,dc=com
       changeType: add
       objectClass: FsnObject
       fsnUuid: FSNUUID
       nsdbName: NSDB

9.1.2.  Deleting an FSN

   Deletes the Fileset with the given FSN.  This assumes that all the
   FSLs related to that FSN have already been deleted.  If FSL records
   for this FSN still exist in the database of the NSDB that receives
   this request, then this function MUST return with an ERR_NOTEMPTY
   error.

   Note that the FSN delete function only removes the fileset from the
   namespace (by removing the records for that FSN from the NSDB
   location that receives this request).  The fileset and its data are
   not deleted.  Any junction that has this FSN as its target may
   continue to point to this non-existent FSN.  A dangling reference may
   be detected when a client tries to resolve the target of a junction
   that refers to the deleted FSN and the NSDB returns ERR_NOTFOUND.

   PARAGRAPH DESCRIBING ERRORS

9.1.2.1.  LDAP Request

   The admin then sends an LDAP DELETE request to the NSDB server to
   remove the FsnObject from the NSDB server.  An example LDIF for the
   delete request is shown below.

       dn: fsnUuid=FSNUUID,dc=fed-fs,dc=com
       changeType: delete

9.1.3.  Mount an FSN

   NOTE: the semantics of this operation have changed significantly, and
   "mount" might be a quite unintuitive name at this point.

   The mount operation records that a given fileset (called the parent
   fileset) contains a junction.  The target of that fileset is called
   the child fileset.

   The NSDB of the parent fileset (as identified by the FSN of the
   parent) maintains this information.

   The parent/child relation is used to indicate how the filesets in the
   federation are related.  The names "parent" and "child" should not be
   taken literally.  A fileset can have no parent (if it is a root



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   fileset).  A fileset may also have any number of parents.  In theory,
   the parent of a fileset may also be its child, although in practice
   this is deprecated.

   A fileset may be mounted in multiple places, and may have the same
   parent multiple times.  For example, /home/ellard and /home/
   daniel.ellard might both be junctions from the /home fileset to the
   fileset that represents the home directory of user Daniel Ellard.  In
   order to be able to distinguish each mount, each mount is given a
   unique identifier (in addition to the fsnUuids of the parent and
   child).

   PARAGRAPH DESCRIBING ERRORS

9.1.3.1.  LDAP Request

   On fileset mount operation the admin will generate an LDAP ADD
   request to the NSDB server using the example LDIF below.  This
   creates a new FsnJunctionObject that establishes the mount
   relationship between the parent and target FSNs.

       dn: key=KEY,fsnUuid=FSNUUID,dc=fed-fs,dc=com
       changeType: add
       objectClass: JunctionObject
       fsnUuid: FSNUUID
       nsdbName: NSDBNAME
       childFsnUuid: CHILDFSNUUID
       childNsdbName: CHILDNSDB

9.1.4.  Unmount an FSN

   Removes the record of a junction between a parent and child fileset.

   PARAGRAPH DESCRIBING ERRORS

9.1.4.1.  LDAP Request

   In case a target_FSN is to be unmmounted, the associated
   JunctionObject is deleted from the NSDB maintaining the parent
   fileset.  An example delete request is shown below.

       dn: key=KEY,fsnUuid=FSNUUID,dc=fed-fs,dc=com
       changeType: delete








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9.1.5.  Create an FSL

   Creates a new Fileset location at the given location denoted by HOST
   and PATH for the given FSN.  An fsl_uuid may be provided as an
   optional UUID for the FSL.  Normally an FSL is identified by the
   HOST:PATH pair.  A UUID is an optional way to identify an FSL if it
   is recovered to a different HOST:PATH after a backup/restore.  If the
   FSL belongs to an FSN that has another FSN mounted under it then
   there would be a related junction_create operation.

   PARAGRAPH DESCRIBING ERRORS

   The FSL create command will result in the admin server sending an
   LDAP ADD request to create a new FslObject at the NSDB maintaining
   the given FSN.  The example LDIF is shown below.  The PATH is the
   pathname where the fileset is located on that host.

9.1.5.1.  LDAP Request

       dn:fslUuid=UUID,fsnUuid=FSNUUID,dc=fed-fs,dc=com
       changeType: add
       objectClass: FslObject
       fsnUuid: FSNUUID
       nsdbName: NSDB
       fslUuid: UUID
       fslHost: HOST
       fslPath: PATH
       type: nfs4
       version: VERSION

9.1.6.  Delete an FSL

   Deletes the given Fileset location.  The admin requests the NSDB
   location storing the FslObject to delete it from its database.  This
   operation does not result in the fileset location's data being
   deleted at the fileserver.

   PARAGRAPH DESCRIBING ERRORS

9.1.6.1.  LDAP Request

       dn: fslUuid=UUID,fsnUuid=FSNUUID,dc=fed-fs,dc=com
       changeType: delete








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9.1.7.  Update an FSL

   Update the attributes of a given FSL.  This command results in a
   change in the attributes of the FslObject at the NSDB server
   maintaining this FSL.  The attributes that must not change are the
   fslUuid and the fsnUuid of the fileset this FSL implements.

   PARAGRAPH DESCRIBING ERRORS

9.1.7.1.  LDAP Request

       dn: fslUuid=UUID,fsnUuid=FSNUUID,dc=fed-fs,dc=com
       changeType: modify
       replace: ATTRIBUTE-TYPE

9.1.8.  Examining an FSL

   Find all attributes of a given FSL from the FSLObject stored at the
   NSDB location.

   ERRORS: ERR_OK ERR_NOTFOUND ERR_INVALID ERR_PERM

   WHERE IS THE LDAP FOR THIS? -DJE

9.1.9.  Finding the children FSNs of a fileset

   The NSDB also tracks information about which filesets are "children"
   of others.  A fileset X is a child of fileset Y if there is a
   junction in fileset Y referencing fileset X. (note that this
   definition permits a fileset to be its own child, although this use
   is deprecated)

   In addition to keeping track of whether one fileset has another as
   its child, the NSDB also records additional information to simplify
   management -- each parent/child relation is associated with an
   additional key that is used to disambiguate the relationship.  For
   example, one fileset may have several junctions targeting the same
   child, but each has a seperate key that can be used to differentiate
   them.  This permits junctions to be removed without necessarily
   removing the underlying relationship.

   NOTE: if it is decided to require that there can only be one junction
   from one fileset to a second, then the key should simply be the FSN
   of the target.  This restriction would greatly simplify some aspects
   of the implementation (but it may also eliminate some very useful
   functionality).





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       LDAP Request
       Search base: fsnUuid=FSNUUID, dc=fed-fs, dc=com
       Search scope: onelevel
       Search filter:  (objectClass=JunctionObject)

9.2.  Fileserver to NSDB Operations

9.2.1.  Looking up FSLs for an FSN

   Return the list of FSLs for the FSN with an fsnUuid that matches the
   filter.  The fileserver will convert the list of FSLs to the NFSv4
   fs_locations.

   The filter may also specify the type of protocol (v4, v3), or type of
   data access (ro, rw).

   ERRORS: ERR_OK ERR_NOTFOUND ERR_INVALID ERR_PERM

       LDAP Request
       Search base: fsnUuid=FSNUUID, dc=fed-fs, dc=com
       Search scope: onelevel
       Search filter:  (objectClass=FslObject)

   The server can scan through the results and find results whose type
   corresponds to the type of the client on whose behalf the server is
   performing the request, extracting the fslHost and fslPath (and
   possibly additional attributes) and using them to create a list of
   fs_locations that the client can use.























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10.  Security Considerations

   To be added.
















































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11.  IANA Requirements

   This document has no actions for IANA.
















































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12.  Conclusions

   The federated filesystem protocol manages multiple independently
   administered fileservers to share namespace and referral information
   to enable clients to traverse seamlessly across them.














































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13.  Glossary

   Administrator:  user with the necessary authority to initiate
      administrative tasks on one or more servers.

   Admin entity:  A server or agent that administers a collection of
      fileservers and persistently stores the namespace information.

   Client:  Any client that accesses the fileserver data using a
      supported filesystem access protocol.

   Federation:  A set of server collections and singleton servers that
      use a common set of interfaces and protocols in order to provide
      to their clients a federated namespace accessible through a
      filesystem access protocol.

   Fileserver:  A server exporting a filesystem via a network filesystem
      access protocol.

   Fileset:  The abstraction of a set of files and their containing
      directory tree.  A fileset is the fundamental unit of data
      management in the federation.

      Note that all files within a fileset are descendants of one
      directory, and that filesets do not span filesystems.

   Filesystem:  A self-contained unit of export for a fileserver, and
      the mechanism used to implement filesets.  The fileset does not
      need to be rooted at the root of the filesystem, nor at the export
      point for the filesystem.

      A single filesystem MAY implement more than one fileset, if the
      client protocol and the fileserver permit this.

   Filesystem access protocol:  A network filesystem access protocol
      such as NFSv2 [RFC1094], NFSv3 [RFC1813], NFSv4 [RFC3530], or
      CIFS.

   FSL (Fileset location):  The location of the implementation of a
      fileset at a particular moment in time.  A FSL MUST be something
      that can be translated into a protocol-specific description of a
      resource that a client can access directly, such as a fs_location
      (for NFSv4), or share name (for CIFS).  Note that not all FSLs
      need to be explicitly exported as long as they are contained
      within an exported path on the fileserver.






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   FSN (Fileset name):  A platform-independent and globally unique name
      for a fileset.  Two FSLs that implement replicas of the same
      fileset MUST have the same FSN, and if a fileset is migrated from
      one location to another, the FSN of that fileset MUST remain the
      same.

   Junction:  A filesystem object used to link a directory name in the
      current fileset with an object within another fileset.  The
      server-side "link" from a leaf node in one fileset to the root of
      another fileset.

   Junction key:  The UUID of a fileset, used as a key to lookup an FSN
      within an NSDB node or a local table of information about
      junctions.

   Namespace:  A filename/directory tree that a sufficiently-authorized
      client can observe.

   NSDB (Namespace Database Service):  A service that maps FSNs to FSLs.
      The NSDB may also be used to store other information, such as
      annotations for these mappings and their components.

   NSDB Node:  The name or location of a server that implements part of
      the NSDB service and is responsible for keeping track of the FSLs
      (and related info) that implement a given partition of the FSNs.

   Referral:  A server response to a client access that directs the
      client to evaluate the current object as a reference to an object
      at a different location (specified by an FSL) in another fileset,
      and possibly hosted on another fileserver.  The client re-attempts
      the access to the object at the new location.

   Replica:  A replica is a redundant implementation of a fileset.  Each
      replica shares the same FSN, but has a different FSL.

      Replicas may be used to increase availability or performance.
      Updates to replicas of the same fileset MUST appear to occur in
      the same order, and therefore each replica is self-consistent at
      any moment.

      We do not assume that updates to each replica occur simultaneously
      If a replica is offline or unreachable, the other replicas may be
      updated.

   Server Collection:  A set of fileservers administered as a unit.  A
      server collection may be administered with vendor-specific
      software.




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      The namespace provided by a server collection could be part of the
      federated namespace.

   Singleton Server:  A server collection containing only one server; a
      stand-alone fileserver.














































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14.  Normative References

   [RFC1094]  Nowicki, B., "NFS: Network File System Protocol
              specification", RFC 1094, March 1989.

   [RFC1813]  Callaghan, B., Pawlowski, B., and P. Staubach, "NFS
              Version 3 Protocol Specification", RFC 1813, June 1995.

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

   [RFC2203]  Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol
              Specification", RFC 2203, September 1997.

   [RFC2743]  Linn, J., "Generic Security Service Application Program
              Interface Version 2, Update 1", RFC 2743, January 2000.

   [RFC3530]  Shepler, S., Callaghan, B., Robinson, D., Thurlow, R.,
              Beame, C., Eisler, M., and D. Noveck, "Network File System
              (NFS) version 4 Protocol", RFC 3530, April 2003.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              July 2003.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              July 2005.

   [RFC4346]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.1", RFC 4346, April 2006.

   [RFC4511]  Sermersheim, J., "Lightweight Directory Access Protocol
              (LDAP): The Protocol", RFC 4511, June 2006.

   [RFC4513]  Harrison, R., "Lightweight Directory Access Protocol
              (LDAP): Authentication Methods and Security Mechanisms",
              RFC 4513, June 2006.













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Authors' Addresses

   Daniel Ellard
   NetApp, Inc.
   1601 Trapelo Rd, Suite 16
   Waltham, MA  02451
   US

   Phone: +1 781-768-5421
   Email: ellard@netapp.com


   Craig Everhart
   NetApp, Inc.
   7301 Kit Creek Rd
   Research Triangle Park, NC  27709
   US

   Phone: +1 919-476-5320
   Email: everhart@netapp.com


   Renu Tewari
   IBM Almaden
   650 Harry Rd
   San Jose, CA  95120
   US

   Email: tewarir@us.ibm.com


   Manoj Naik
   IBM Almaden
   650 Harry Rd
   San Jose, CA  95120
   US

   Email: manoj@almaden.ibm.com













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Full Copyright Statement

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