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Network Working Group                                            M. WahlRequest for Comments: 2829                        Sun Microsystems, Inc.Category: Standards Track                                  H. Alvestrand                                                             EDB Maxware                                                               J. Hodges                                                             Oblix, Inc.                                                               R. Morgan                                                University of Washington                                                                May 2000Authentication Methods for LDAPStatus of this Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2000).  All Rights Reserved.Abstract   This document specifies particular combinations of security   mechanisms which are required and recommended in LDAP [1]   implementations.1. Introduction   LDAP version 3 is a powerful access protocol for directories.   It offers means of searching, fetching and manipulating directory   content, and ways to access a rich set of security functions.   In order to function for the best of the Internet, it is vital that   these security functions be interoperable; therefore there has to be   a minimum subset of security functions that is common to all   implementations that claim LDAPv3 conformance.   Basic threats to an LDAP directory service include:      (1)   Unauthorized access to data via data-fetching operations,Wahl, et al.                Standards Track                     [Page 1]

RFC 2829            Authentication Methods for LDAP             May 2000      (2)   Unauthorized access to reusable client authentication            information by monitoring others' access,      (3)   Unauthorized access to data by monitoring others' access,      (4)   Unauthorized modification of data,      (5)   Unauthorized modification of configuration,      (6)   Unauthorized or excessive use of resources (denial of            service), and      (7)   Spoofing of directory: Tricking a client into believing that            information came from the directory when in fact it did not,            either by modifying data in transit or misdirecting the            client's connection.   Threats (1), (4), (5) and (6) are due to hostile clients.  Threats   (2), (3) and (7) are due to hostile agents on the path between client   and server, or posing as a server.   The LDAP protocol suite can be protected with the following security   mechanisms:      (1)   Client authentication by means of the SASL [2] mechanism            set, possibly backed by the TLS credentials exchange            mechanism,      (2)   Client authorization by means of access control based on the            requestor's authenticated identity,      (3)   Data integrity protection by means of the TLS protocol or            data-integrity SASL mechanisms,      (4)   Protection against snooping by means of the TLS protocol or            data-encrypting SASL mechanisms,      (5)   Resource limitation by means of administrative limits on            service controls, and      (6)   Server authentication by means of the TLS protocol or SASL            mechanism.   At the moment, imposition of access controls is done by means outside   the scope of the LDAP protocol.   In this document, the term "user" represents any application which is   an LDAP client using the directory to retrieve or store information.Wahl, et al.                Standards Track                     [Page 2]

RFC 2829            Authentication Methods for LDAP             May 2000   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 inRFC 2119 [3].2.  Example deployment scenarios   The following scenarios are typical for LDAP directories on the   Internet, and have different security requirements. (In the   following, "sensitive" means data that will cause real damage to the   owner if revealed; there may be data that is protected but not   sensitive).  This is not intended to be a comprehensive list, other   scenarios are possible, especially on physically protected networks.      (1)   A read-only directory, containing no sensitive data,            accessible to "anyone", and TCP connection hijacking or IP            spoofing is not a problem.  This directory requires no            security functions except administrative service limits.      (2)   A read-only directory containing no sensitive data; read            access is granted based on identity.  TCP connection            hijacking is not currently a problem. This scenario requires            a secure authentication function.      (3)   A read-only directory containing no sensitive data; and the            client needs to ensure that the directory data is            authenticated by the server and not modified while being            returned from the server.      (4)   A read-write directory, containing no sensitive data; read            access is available to "anyone", update access to properly            authorized persons.  TCP connection hijacking is not            currently a problem.  This scenario requires a secure            authentication function.      (5)   A directory containing sensitive data.  This scenario            requires session confidentiality protection AND secure            authentication.3.  Authentication and Authorization:Definitions and Concepts   This section defines basic terms, concepts, and interrelationships   regarding authentication, authorization, credentials, and identity.   These concepts are used in describing how various security approaches   are utilized in client authentication and authorization.Wahl, et al.                Standards Track                     [Page 3]

RFC 2829            Authentication Methods for LDAP             May 20003.1.  Access Control Policy   An access control policy is a set of rules defining the protection of   resources, generally in terms of the capabilities of persons or other   entities accessing those resources.  A common expression of an access   control policy is an access control list.  Security objects and   mechanisms, such as those described here, enable the expression of   access control policies and their enforcement.  Access control   policies are typically expressed in terms of access control   attributes as described below.3.2.  Access Control Factors   A request, when it is being processed by a server, may be associated   with a wide variety of security-related factors (section 4.2 of [1]).   The server uses these factors to determine whether and how to process   the request.  These are called access control factors (ACFs).  They   might include source IP address, encryption strength, the type of   operation being requested, time of day, etc.  Some factors may be   specific to the request itself, others may be associated with the   connection via which the request is transmitted, others (e.g. time of   day) may be "environmental".   Access control policies are expressed in terms of access control   factors.  E.g., a request having ACFs i,j,k can perform operation Y   on resource Z. The set of ACFs that a server makes available for such   expressions is implementation-specific.3.3.  Authentication, Credentials, Identity   Authentication credentials are the evidence supplied by one party to   another, asserting the identity of the supplying party (e.g. a user)   who is attempting to establish an association with the other party   (typically a server).  Authentication is the process of generating,   transmitting, and verifying these credentials and thus the identity   they assert.  An authentication identity is the name presented in a   credential.   There are many forms of authentication credentials -- the form used   depends upon the particular authentication mechanism negotiated by   the parties.  For example: X.509 certificates, Kerberos tickets,   simple identity and password pairs.  Note that an authentication   mechanism may constrain the form of authentication identities used   with it.Wahl, et al.                Standards Track                     [Page 4]

RFC 2829            Authentication Methods for LDAP             May 20003.4.  Authorization Identity   An authorization identity is one kind of access control factor.  It   is the name of the user or other entity that requests that operations   be performed.  Access control policies are often expressed in terms   of authorization identities; e.g., entity X can perform operation Y   on resource Z.   The authorization identity bound to an association is often exactly   the same as the authentication identity presented by the client, but   it may be different.  SASL allows clients to specify an authorization   identity distinct from the authentication identity asserted by the   client's credentials.  This permits agents such as proxy servers to   authenticate using their own credentials, yet request the access   privileges of the identity for which they are proxying [2].  Also,   the form of authentication identity supplied by a service like TLS   may not correspond to the authorization identities used to express a   server's access control  policy, requiring a server-specific mapping   to be done.  The method by which a server composes and validates an   authorization identity from the authentication credentials supplied   by a client is implementation-specific.4. Required security mechanisms   It is clear that allowing any implementation, faced with the above   requirements, to pick and choose among the possible alternatives is   not a strategy that is likely to lead to interoperability. In the   absence of mandates, clients will be written that do not support any   security function supported by the server, or worse, support only   mechanisms like cleartext passwords that provide clearly inadequate   security.   Active intermediary attacks are the most difficult for an attacker to   perform, and for an implementation to protect against.  Methods that   protect only against hostile client and passive eavesdropping attacks   are useful in situations where the cost of protection against active   intermediary attacks is not justified based on the perceived risk of   active intermediary attacks.   Given the presence of the Directory, there is a strong desire to see   mechanisms where identities take the form of a Distinguished Name and   authentication data can be stored in the directory; this means that   either this data is useless for faking authentication (like the Unix   "/etc/passwd" file format used to be), or its content is never passed   across the wire unprotected - that is, it's either updated outside   the protocol or it is only updated in sessions well protected against   snooping.  It is also desirable to allow authentication methods toWahl, et al.                Standards Track                     [Page 5]

RFC 2829            Authentication Methods for LDAP             May 2000   carry authorization identities based on existing forms of user   identities for backwards compatibility with non-LDAP-based   authentication services.   Therefore, the following implementation conformance requirements are   in place:      (1)   For a read-only, public directory, anonymous authentication,            described insection 5, can be used.      (2)   Implementations providing password-based authenticated            access MUST support authentication using the DIGEST-MD5 SASL            mechanism [4], as described insection 6.1.  This provides            client authentication with protection against passive            eavesdropping attacks, but does not provide protection            against active intermediary attacks.      (3)   For a directory needing session protection and            authentication, the Start TLS extended operation [5], and            either the simple authentication choice or the SASL EXTERNAL            mechanism, are to be used together.  Implementations SHOULD            support authentication with a password as described insection 6.2, and SHOULD support authentication with a            certificate as described insection 7.1.  Together, these            can provide integrity and disclosure protection of            transmitted data, and authentication of client and server,            including protection against active intermediary attacks.   If TLS is negotiated, the client MUST discard all information about   the server fetched prior to the TLS negotiation.  In particular, the   value of supportedSASLMechanisms MAY be different after TLS has been   negotiated (specifically, the EXTERNAL mechanism or the proposed   PLAIN mechanism are likely to only be listed after a TLS negotiation   has been performed).   If a SASL security layer is negotiated, the client MUST discard all   information about the server fetched prior to SASL.  In particular,   if the client is configured to support multiple SASL mechanisms, it   SHOULD fetch supportedSASLMechanisms both before and after the SASL   security layer is negotiated and verify that the value has not   changed after the SASL security layer was negotiated.  This detects   active attacks which remove supported SASL mechanisms from the   supportedSASLMechanisms list, and allows the client to ensure that it   is using the best mechanism supported by both client and server   (additionally, this is a SHOULD to allow for environments where the   supported SASL mechanisms list is provided to the client through a   different trusted source, e.g. as part of a digitally signed object).Wahl, et al.                Standards Track                     [Page 6]

RFC 2829            Authentication Methods for LDAP             May 20005. Anonymous authentication   Directory operations which modify entries or access protected   attributes or entries generally require client authentication.   Clients which do not intend to perform any of these operations   typically use anonymous authentication.   LDAP implementations MUST support anonymous authentication, as   defined insection 5.1.   LDAP implementations MAY support anonymous authentication with TLS,   as defined insection 5.2.   While there MAY be access control restrictions to prevent access to   directory entries, an LDAP server SHOULD allow an anonymously-bound   client to retrieve the supportedSASLMechanisms attribute of the root   DSE.   An LDAP server MAY use other information about the client provided by   the lower layers or external means to grant or deny access even to   anonymously authenticated clients.5.1. Anonymous authentication procedure   An LDAP client which has not successfully completed a bind operation   on a connection is anonymously authenticated.   An LDAP client MAY also specify anonymous authentication in a bind   request by using a zero-length OCTET STRING with the simple   authentication choice.5.2. Anonymous authentication and TLS   An LDAP client MAY use the Start TLS operation [5] to negotiate the   use of TLS security [6].  If the client has not bound beforehand,   then until the client uses the EXTERNAL SASL mechanism to negotiate   the recognition of the client's certificate, the client is   anonymously authenticated.   Recommendations on TLS ciphersuites are given insection 10.   An LDAP server which requests that clients provide their certificate   during TLS negotiation MAY use a local security policy to determine   whether to successfully complete TLS negotiation if the client did   not present a certificate which could be validated.Wahl, et al.                Standards Track                     [Page 7]

RFC 2829            Authentication Methods for LDAP             May 20006. Password-based authentication   LDAP implementations MUST support authentication with a password   using the DIGEST-MD5 SASL mechanism for password protection, as   defined insection 6.1.   LDAP implementations SHOULD support authentication with the "simple"   password choice when the connection is protected against   eavesdropping using TLS, as defined insection 6.2.6.1. Digest authentication   An LDAP client MAY determine whether the server supports this   mechanism by performing a search request on the root DSE, requesting   the supportedSASLMechanisms attribute, and checking whether the   string "DIGEST-MD5" is present as a value of this attribute.   In the first stage of authentication, when the client is performing   an "initial authentication" as defined in section 2.1 of [4], the   client sends a bind request in which the version number is 3, the   authentication choice is sasl, the sasl mechanism name is "DIGEST-   MD5", and the credentials are absent.  The client then waits for a   response from the server to this request.   The server will respond with a bind response in which the resultCode   is saslBindInProgress, and the serverSaslCreds field is present.  The   contents of this field is a string defined by "digest-challenge" in   section 2.1.1 of [4].  The server SHOULD include a realm indication   and MUST indicate support for UTF-8.   The client will send a bind request with a distinct message id, in   which the version number is 3, the authentication choice is sasl, the   sasl mechanism name is "DIGEST-MD5", and the credentials contain the   string defined by "digest-response" in section 2.1.2 of [4].  The   serv-type is "ldap".   The server will respond with a bind response in which the resultCode   is either success, or an error indication.  If the authentication is   successful and the server does not support subsequent authentication,   then the credentials field is absent.  If the authentication is   successful and the server supports subsequent authentication, then   the credentials field contains the string defined by "response-auth"   in section 2.1.3 of [4].   Support for subsequent authentication is   OPTIONAL in clients and servers.Wahl, et al.                Standards Track                     [Page 8]

RFC 2829            Authentication Methods for LDAP             May 20006.2. "simple" authentication choice under TLS encryption   A user who has a directory entry containing a userPassword attribute   MAY authenticate to the directory by performing a simple password   bind sequence following the negotiation of a TLS ciphersuite   providing connection confidentiality [6].   The client will use the Start TLS operation [5] to negotiate the use   of TLS security [6] on the connection to the LDAP server.  The client   need not have bound to the directory beforehand.   For this authentication procedure to be successful, the client and   server MUST negotiate a ciphersuite which contains a bulk encryption   algorithm of appropriate strength.  Recommendations on cipher suites   are given insection 10.   Following the successful completion of TLS negotiation, the client   MUST send an LDAP bind request with the version number of 3, the name   field containing the name of the user's entry, and the "simple"   authentication choice, containing a password.   The server will, for each value of the userPassword attribute in the   named user's entry, compare these for case-sensitive equality with   the client's presented password.  If there is a match, then the   server will respond with resultCode success, otherwise the server   will respond with resultCode invalidCredentials.6.3. Other authentication choices with TLS   It is also possible, following the negotiation of TLS, to perform a   SASL authentication which does not involve the exchange of plaintext   reusable passwords.  In this case the client and server need not   negotiate a ciphersuite which provides confidentiality if the only   service required is data integrity.7. Certificate-based authentication   LDAP implementations SHOULD support authentication via a client   certificate in TLS, as defined insection 7.1.7.1. Certificate-based authentication with TLS   A user who has a public/private key pair in which the public key has   been signed by a Certification Authority may use this key pair to   authenticate to the directory server if the user's certificate is   requested by the server.  The user's certificate subject field SHOULD   be the name of the user's directory entry, and the Certification   Authority must be sufficiently trusted by the directory server toWahl, et al.                Standards Track                     [Page 9]

RFC 2829            Authentication Methods for LDAP             May 2000   have issued the certificate in order that the server can process the   certificate.  The means by which servers validate certificate paths   is outside the scope of this document.   A server MAY support mappings for certificates in which the subject   field name is different from the name of the user's directory entry.   A server which supports mappings of names MUST be capable of being   configured to support certificates for which no mapping is required.   The client will use the Start TLS operation [5] to negotiate the use   of TLS security [6] on the connection to the LDAP server.  The client   need not have bound to the directory beforehand.   In the TLS negotiation, the server MUST request a certificate.  The   client will provide its certificate to the server, and MUST perform a   private key-based encryption, proving it has the private key   associated with the certificate.   As deployments will require protection of sensitive data in transit,   the client and server MUST negotiate a ciphersuite which contains a   bulk encryption algorithm of appropriate strength.  Recommendations   of cipher suites are given insection 10.   The server MUST verify that the client's certificate is valid. The   server will normally check that the certificate is issued by a known   CA, and that none of the certificates on the client's certificate   chain are invalid or revoked.  There are several procedures by which   the server can perform these checks.   Following the successful completion of TLS negotiation, the client   will send an LDAP bind request with the SASL "EXTERNAL" mechanism.8. Other mechanisms   The LDAP "simple" authentication choice is not suitable for   authentication on the Internet where there is no network or transport   layer confidentiality.   As LDAP includes native anonymous and plaintext authentication   methods, the "ANONYMOUS" and "PLAIN" SASL mechanisms are not used   with LDAP.  If an authorization identity of a form different from a   DN is requested by the client, a mechanism that protects the password   in transit SHOULD be used.   The following SASL-based mechanisms are not considered in this   document: KERBEROS_V4, GSSAPI and SKEY.Wahl, et al.                Standards Track                    [Page 10]

RFC 2829            Authentication Methods for LDAP             May 2000   The "EXTERNAL" SASL mechanism can be used to request the LDAP server   make use of security credentials exchanged by a lower layer. If a TLS   session has not been established between the client and server prior   to making the SASL EXTERNAL Bind request and there is no other   external source of authentication credentials (e.g.  IP-level   security [8]), or if, during the process of establishing the TLS   session, the server did not request the client's authentication   credentials, the SASL EXTERNAL bind MUST fail with a result code of   inappropriateAuthentication.  Any client authentication and   authorization state of the LDAP association is lost, so the LDAP   association is in an anonymous state after the failure.9. Authorization Identity   The authorization identity is carried as part of the SASL credentials   field in the LDAP Bind request and response.   When the "EXTERNAL" mechanism is being negotiated, if the credentials   field is present, it contains an authorization identity of the   authzId form described below.   Other mechanisms define the location of the authorization identity in   the credentials field.   The authorization identity is a string in the UTF-8 character set,   corresponding to the following ABNF [7]:   ; Specific predefined authorization (authz) id schemes are   ; defined below -- new schemes may be defined in the future.   authzId    = dnAuthzId / uAuthzId   ; distinguished-name-based authz id.   dnAuthzId  = "dn:" dn   dn         = utf8string    ; with syntax defined inRFC 2253   ; unspecified userid, UTF-8 encoded.   uAuthzId   = "u:" userid   userid     = utf8string    ; syntax unspecified   A utf8string is defined to be the UTF-8 encoding of one or more ISO   10646 characters.   All servers which support the storage of authentication credentials,   such as passwords or certificates, in the directory MUST support the   dnAuthzId choice.Wahl, et al.                Standards Track                    [Page 11]

RFC 2829            Authentication Methods for LDAP             May 2000   The uAuthzId choice allows for compatibility with client applications   which wish to authenticate to a local directory but do not know their   own Distinguished Name or have a directory entry.  The format of the   string is defined as only a sequence of UTF-8 encoded ISO 10646   characters, and further interpretation is subject to prior agreement   between the client and server.   For example, the userid could identify a user of a specific directory   service, or be a login name or the local-part of anRFC 822 email   address. In general a uAuthzId MUST NOT be assumed to be globally   unique.   Additional authorization identity schemes MAY be defined in future   versions of this document.10. TLS Ciphersuites   The following ciphersuites defined in [6] MUST NOT be used for   confidentiality protection of passwords or data:         TLS_NULL_WITH_NULL_NULL         TLS_RSA_WITH_NULL_MD5         TLS_RSA_WITH_NULL_SHA   The following ciphersuites defined in [6] can be cracked easily (less   than a week of CPU time on a standard CPU in 1997).  The client and   server SHOULD carefully consider the value of the password or data   being protected before using these ciphersuites:         TLS_RSA_EXPORT_WITH_RC4_40_MD5         TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5         TLS_RSA_EXPORT_WITH_DES40_CBC_SHA         TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA         TLS_DH_RSA_EXPORT_WITH_DES40_CBC_SHA         TLS_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA         TLS_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA         TLS_DH_anon_EXPORT_WITH_RC4_40_MD5         TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA   The following ciphersuites are vulnerable to man-in-the-middle   attacks, and SHOULD NOT be used to protect passwords or sensitive   data, unless the network configuration is such that the danger of a   man-in-the-middle attack is tolerable:Wahl, et al.                Standards Track                    [Page 12]

RFC 2829            Authentication Methods for LDAP             May 2000         TLS_DH_anon_EXPORT_WITH_RC4_40_MD5         TLS_DH_anon_WITH_RC4_128_MD5         TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA         TLS_DH_anon_WITH_DES_CBC_SHA         TLS_DH_anon_WITH_3DES_EDE_CBC_SHA   A client or server that supports TLS MUST support at least   TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA.11. SASL service name for LDAP   For use with SASL [2], a protocol must specify a service name to be   used with various SASL mechanisms, such as GSSAPI.  For LDAP, the   service name is "ldap", which has been registered with the IANA as a   GSSAPI service name.12. Security Considerations   Security issues are discussed throughout this memo; the   (unsurprising) conclusion is that mandatory security is important,   and that session encryption is required when snooping is a problem.   Servers are encouraged to prevent modifications by anonymous users.   Servers may also wish to minimize denial of service attacks by timing   out idle connections, and returning the unwillingToPerform result   code rather than performing computationally expensive operations   requested by unauthorized clients.   A connection on which the client has not performed the Start TLS   operation or negotiated a suitable SASL mechanism for connection   integrity and encryption services is subject to man-in-the-middle   attacks to view and modify information in transit.   Additional security considerations relating to the EXTERNAL mechanism   to negotiate TLS can be found in [2], [5] and [6].13. Acknowledgements   This document is a product of the LDAPEXT Working Group of the IETF.   The contributions of its members is greatly appreciated.Wahl, et al.                Standards Track                    [Page 13]

RFC 2829            Authentication Methods for LDAP             May 200014. Bibliography   [1] Wahl, M., Howes, T. and S. Kille, "Lightweight Directory Access       Protocol (v3)",RFC 2251, December 1997.   [2] Myers, J., "Simple Authentication and Security Layer (SASL)",RFC2222, October 1997.   [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement       Levels",BCP 14,RFC 2119, March 1997.   [4] Leach, P. and C. Newman, "Using Digest Authentication as a SASL       Mechanism",RFC 2831, May 2000.   [5] Hodges, J., Morgan, R. and M. Wahl, "Lightweight Directory Access       Protocol (v3): Extension for Transport Layer Security",RFC 2830,       May 2000.   [6] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",RFC2246, January 1999.   [7] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax       Specifications: ABNF",RFC 2234, November 1997.   [8] Kent, S. and R. Atkinson, "Security Architecture for the Internet       Protocol",RFC 2401, November 1998.Wahl, et al.                Standards Track                    [Page 14]

RFC 2829            Authentication Methods for LDAP             May 200015. Authors' Addresses   Mark Wahl   Sun Microsystems, Inc.   8911 Capital of Texas Hwy #4140   Austin TX 78759   USA   EMail: M.Wahl@innosoft.com   Harald Tveit Alvestrand   EDB Maxware   Pirsenteret   N-7462 Trondheim, Norway   Phone: +47 73 54 57 97   EMail: Harald@Alvestrand.no   Jeff Hodges   Oblix, Inc.   18922 Forge Drive   Cupertino, CA 95014   USA   Phone: +1-408-861-6656   EMail: JHodges@oblix.com   RL "Bob" Morgan   Computing and Communications   University of Washington   Seattle, WA 98105   USA   Phone: +1-206-221-3307   EMail: rlmorgan@washington.eduWahl, et al.                Standards Track                    [Page 15]

RFC 2829            Authentication Methods for LDAP             May 200016.  Full Copyright Statement   Copyright (C) The Internet Society (2000).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Wahl, et al.                Standards Track                    [Page 16]