WDIFF

draft-ietf-nntpext-tls-nntp-06.txt --> draft-ietf-nntpext-tls-nntp-07.txt

NNTP Extensions Working Group K. Murchison
Internet Draft Oceana Matrix Ltd.
Expires: November December 2005 J. Vinocur
Cornell University
C. Newman
Sun Microsystems
May
June 2005

Using TLS with NNTP
draft-ietf-nntpext-tls-nntp-06
draft-ietf-nntpext-tls-nntp-07

Status of this memo

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Abstract

This memo defines an extension to the Network News Transport
Protocol [NNTP] (NNTP) to provide connection-based security (via allow an NNTP client and server to use Transport
Layer Security [TLS]). (TLS). The primary goal is to provide encryption
for single-link confidentiality purposes, but data integrity,
(optional) certificate-based peer entity authentication, and

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(optional) data compression are also possible.

Note to the RFC Editor

The normative references to RFC 2234, RFC 2246, and RFC 3546, and the
informative reference to RFC 2222 may
be replaced by draft-crocker-abnf-rfc2234bis,
draft-ietf-tls-rfc2246-bis draft-ietf-tls-rfc3526bis, and
draft-ietf-sasl-rfc2222bis
respectively should any or all of those documents reach RFC status
before this one.

The normative reference to [NNTP] and the informative reference to
[NNTP-AUTH] are documents which are expected to be published
simultaneously with this one and so can be replaced by references
to the resulting RFCs.

Table of Contents

0. Changes from Previous Version ............................ 2

1. Introduction ............................................. 3 2
1.1. Conventions Used in this Document ................... 3
2. The STARTTLS Extension ................................... 3
2.1. Advertising the STARTTLS Extension .................. 3
2.2. STARTTLS Command .................................... 4
2.2.1. Usage .......................................... 4
2.2.2. Description .................................... 4
2.2.2.1. Processing After the STARTTLS Command ..... 5
2.2.2.2. Result of the STARTTLS Command ............ 6
2.2.3. Examples ....................................... 7 6
3. Augmented BNF Syntax for the STARTTLS Extension .......... 8
3.1. Commands ............................................ 8
3.2. Capability entries .................................. 9 8
4. Summary of Response Codes ................................ 9 8
5. Security Considerations .................................. 9
6. IANA Considerations ...................................... 11
7. References ............................................... 12
7.1. Normative References ................................ 12
7.2. Informative References .............................. 12
8. Authors' Addresses ....................................... 12
9. Acknowledgments .......................................... 13
10. Intellectual Property Rights ............................ 13
11. Copyright ............................................... 14

0. Changes from Previous Version

Changed:
o Made Ken the primary author.
o Updated to RFC 3978/3979 boilerplate.
o Fixed CAPABILITIES responses (specifically LIST arguments) in
examples.
o Section 5: Consolidated two paragraphs to coincide with language
in [NNTP-AUTH].

Clarified:
o Section 2.1: STARTTLS MUST NOT be advertised once a TLS layer
is active or after successful authentication.
o Section 3: This document extends the ABNF in [NNTP], and the
[NNTP] ABNF must be imported first before validating the
STARTTLS ABNF (based on recommendations of AD regarding
IMAPEXT I-Ds).

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1. Introduction

Historically, unencrypted NNTP [NNTP] connections were satisfactory
for most purposes. However, sending passwords unencrypted over the
network is no longer appropriate, and sometimes strong encryption integrity and/or
confidentiality protection is desired for the entire connection.

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The STARTTLS extension TLS protocol (formerly known as SSL) provides a way to use secure
an application protocol from tampering and eavesdropping. Although
advanced SASL authentication mechanisms [NNTP-AUTH] can provide a
lightweight version of this service, TLS is complimentary to both
simple authentication-only SASL mechanisms and deployed clear-text
password login commands.

In some existing implementations, TCP port 563 has been dedicated
to NNTP over TLS. These implementations begin the popular TLS [TLS]
service negotiation
immediately upon connection, and then continue with the existing initial
steps of an NNTP protocol. The current
(unstandardized) session. This use of TLS for NNTP is most commonly on a
dedicated TCP port; this practice separate port is
discouraged for the reasons documented in section 7 of "Using TLS
with IMAP, POP3 and ACAP" [TLS-IMAPPOP]. Therefore, this

This specification formalizes the STARTTLS command already in
occasional use by the installed base.

1.1. The STARTTLS command
rectifies a number of the problems with using a separate port for a
"secure" protocol variant, and is the preferred way of using TLS
with NNTP.

1.1. Conventions Used in this Document

The notational conventions used in this document are the same as
those in [NNTP] and any term not defined in this document has the
same meaning as in that one.

The key words "REQUIRED", "MUST", "MUST NOT", "SHOULD", "SHOULD
NOT", "MAY", and "OPTIONAL" in this document are to be interpreted
as described in "Key words for use in RFCs to Indicate Requirement
Levels" [KEYWORDS].

In the examples, commands from the client are indicated with [C],
and responses from the server are indicated with [S].

2. The STARTTLS Extension

This extension provides a new STARTTLS command and has the
capability label STARTTLS.

2.1. Advertising the STARTTLS Extension

A server supporting the STARTTLS command as defined in this
document will advertise the "STARTTLS" capability label in response
to the CAPABILITIES command. However, this capability MUST NOT be
advertised once a TLS layer is active (see section 2.2.2.2), or
after successful authentication [NNTP-AUTH]. This capability MAY
be advertised both before and after any use of MODE READER, with
the same semantics.

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As the STARTTLS command is related to security, cached results of
CAPABILITIES from a previous session MUST NOT be relied on, as per
section 12.6 of [NNTP].

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Example:

[C] CAPABILITIES
[S] 101 Capability list:
[S] VERSION 2
[S] READER
[S] IHAVE
[S] STARTTLS
[S] LIST ACTIVE NEWSGROUPS
[S] .

2.2. STARTTLS Command

2.2.1. Usage

This command MUST NOT be pipelined.

Syntax
STARTTLS

Responses

382 Continue with TLS negotiation
502 Command unavailable [1]
580 Can not initiate TLS negotiation

[1] If a TLS layer is already active, or authentication has
occurred, STARTTLS is not a valid command (see section 2.2.2.2).

NOTE: Notwithstanding section 3.2.1 of [NNTP], the server MUST NOT
return either 480 or 483 in response to STARTTLS.

2.2.2. Description

A client issues the STARTTLS command to request negotiation of TLS.
The STARTTLS command is usually used to initiate session security,
although it can also be used for client and/or server certificate
authentication and/or data compression.

An NNTP server returns the 483 response to indicate that a secure
or encrypted connection is required for the command sent by the
client. Use of the STARTTLS command as described below is one way
to establish a connection with these properties. The client MAY
therefore use the STARTTLS command after receiving a 483 response.

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If a server advertises the STARTTLS capability, a client MAY
attempt to use the STARTTLS command at any time during a session to
negotiate TLS without having received a 483 response. Servers

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SHOULD accept such unsolicited TLS negotiation requests.

If the server is unable to initiate the TLS negotiation for any
reason (e.g. a server configuration or resource problem), the
server MUST reject the STARTTLS command with a 580 response.
Otherwise, the server issues a 382 response and TLS negotiation
begins. A server MUST NOT under any circumstances reply to a
STARTTLS command with either a 480 or 483 response.

If the client receives a failure response to STARTTLS, the client
must decide whether or not to continue the NNTP session. Such a
decision is based on local policy. For instance, if TLS was being
used for client authentication, the client might try to continue
the session in case the server allows it to do so even with no
authentication. However, if TLS was being negotiated for
encryption, a client that gets a failure response needs to decide
whether to continue without TLS encryption, to wait and try again
later, or to give up and notify the user of the error.

After

Upon receiving a 382 response to a STARTTLS command, the client
MUST start the TLS negotiation before giving any other NNTP
commands. The TLS negotiation begins for both the client and
server with the first octet following the CRLF of the 382 response.
If, after having issued the STARTTLS command, the client finds out
that some failure prevents it from actually starting a TLS
handshake, then it SHOULD immediately close the connection.

Servers MUST be able to understand backwards-compatible TLS Client
Hello messages (provided that client_version is TLS 1.0 or later),
and clients MAY use backwards-compatible Client Hello messages.
Neither clients nor servers are required to actually support Client
Hello messages for anything other than TLS 1.0. However, the TLS
extension for Server Name Indication ("server_name") [TLS-EXT]
SHOULD be implemented by all clients; it also SHOULD be implemented
by any server implementing STARTTLS that is known by multiple names
(otherwise it is not possible for a server with several hostnames
to present the correct certificate to the client).

Although current use of TLS most often involves

The server remains in the dedication of
port 563 for NNTP over TLS, non-authenticated state, even if client
credentials are supplied during the continued use of TLS on a separate
port is discouraged for negotiation. The AUTHINFO
SASL command [NNTP-AUTH] with the reasons documented in section 7 of
"Using EXTERNAL mechanism [SASL] MAY be
used to authenticate once TLS with IMAP, POP3 and ACAP" [TLS-IMAPPOP].

2.2.2.1. Processing After client credentials are successfully
exchanged, but servers supporting the STARTTLS Command

After the TLS handshake has been completed, both parties MUST
immediately command are not
required to support AUTHINFO in general or that mechanism in
particular. The server MAY use information from the client
certificate for identification of connections or posted articles
(either in its logs or directly in posted articles).

If the client receives a failure response to STARTTLS or if the TLS
negotiation fails, the client must decide whether or not to
continue the NNTP session. Such a decision is based on local
policy. For instance, if TLS was being used for client
authentication, the
authentication and privacy achieved (if any). The NNTP client and might try to continue the session in
case the server allows it to do so even with no authentication.
However, if TLS was being negotiated for encryption, a client that

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server may

gets a failure response needs to decide whether to move ahead even if the TLS negotiation ended
without authentication and/or without privacy because NNTP services
are often performed continue without authentication or privacy, but some
NNTP clients
TLS encryption, to wait and try again later, or servers may want to continue only if a particular
level give up and
notify the user of authentication and/or privacy was achieved.

If the NNTP client decides that error.

If the level of authentication or
privacy server is not high enough for it unable to continue, it SHOULD issue a
QUIT command immediately after initiate the TLS negotiation is complete. If or if the NNTP server decides that
TLS negotiation fails, the level of authentication or privacy
is not high enough for it to continue, it server SHOULD either reject subsequent
restricted NNTP commands from the client with a 483 response code
(possibly with a text string such as "Command refused due to lack
of security"), or reject a command with a 400 response code
(possibly with a text string such as "Connection closing due to
lack of security") and close the connection.

The decision of whether or not to believe the authenticity of the
other party in a TLS negotiation is a local matter. However, some
general rules for the decisions are:

o The client MAY check that the identity presented in the server's
certificate matches the intended server hostname or domain.
This check is not required (and may fail in the absence of the
TLS "server_name" extension [TLS-EXT], as described above), but
if it is implemented and the match fails, the client SHOULD
either request explicit user confirmation, or terminate the
connection but allow the user to disable the check in the
future.
o Generally an NNTP server would want to accept any verifiable
certificate from a client, however authentication can be done
using the client certificate (perhaps in combination with the
SASL EXTERNAL mechanism [NNTP-AUTH], although an implementation
supporting STARTTLS is not required to support SASL in general
or that mechanism in particular). The server MAY use
information about the client certificate for identification of
connections or posted articles (either in its logs or directly
in posted articles).

2.2.2.2. Result of the STARTTLS Command

Upon successful completion of the TLS handshake, the NNTP protocol
is reset to the state immediately after the initial greeting
response (see 5.1 of [NNTP]) has been sent, with the exception that
if a MODE READER command has been issued, the effects of it (if
any) are not reversed. In this case, as no greeting is sent, the
next step is for the client to send a command. The server MUST
discard any knowledge obtained from the client, such as the current

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newsgroup and article number, that was not obtained from the TLS
negotiation itself. Likewise, the client SHOULD discard and MUST
NOT rely on any knowledge obtained from the server, such as the
capability list, which was not obtained from the TLS negotiation
itself.

Both the client and the server MUST know if there is a TLS session
active. A client MUST NOT attempt to start a TLS session if a TLS
session is already active. A server MUST NOT return the STARTTLS
capability label in response to a CAPABILITIES command received
after a TLS handshake has completed, and a server MUST respond with
a 502 response code if a STARTTLS command is received while a TLS
session is already active. Additionally, the client MUST NOT issue
a MODE READER command while a TLS session is active and a server
MUST NOT advertise the MODE-READER capability.

The capability list returned in response to a CAPABILITIES command
received after the a successful TLS handshake MAY be different than the
list returned before the TLS handshake. For example, an NNTP
server supporting SASL [NNTP-AUTH] might not want to advertise
support for a particular mechanism unless a client has sent an
appropriate client certificate during a TLS handshake.

2.2.3. Examples

Example of a client being prompted to use encryption and
negotiating it successfully (showing the removal of STARTTLS from
the capability list once a TLS layer is active), followed by a
successful selection of the group and an (inappropriate) attempt by

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the client to initiate another TLS negotiation:

[C] CAPABILITIES
[S] 101 Capability list:
[S] VERSION 2
[S] READER
[S] STARTTLS
[S] LIST ACTIVE NEWSGROUPS OVERVIEW.FMT
[S] OVER
[S] .
[C] GROUP local.confidential
[S] 483 Encryption or stronger authentication required
[C] STARTTLS
[S] 382 Continue with TLS negotiation
[TLS negotiation occurs here]
[Following successful negotiation, traffic is protected by TLS]
[C] CAPABILITIES
[S] 101 Capability list:
[S] VERSION 2

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[S] READER
[S] LIST ACTIVE NEWSGROUPS OVERVIEW.FMT
[S] OVER
[S] .
[C] GROUP local.confidential
[S] 211 1234 3000234 3002322 local.confidential
[C] STARTTLS
[S] 502 STARTTLS not allowed with active TLS layer

Example of a request to begin TLS negotiation declined by the
server:

[C] STARTTLS
[S] 580 Can not initiate TLS negotiation

Example of a failed attempt to negotiate TLS, followed by two
attempts at selecting groups only available under a security layer
(in the first case the server allows the session to continue, in
the second it closes the connection). Note that unrestricted
commands such as CAPABILITIES are unaffected by the failure:

[C] STARTTLS
[S] 382 Continue with TLS negotiation
[TLS negotiation is attempted here]
[Following failed negotiation, traffic resumes without TLS]
[C] CAPABILITIES
[S] 101 Capability list:
[S] VERSION 2
[S] READER

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[S] STARTTLS
[S] LIST ACTIVE NEWSGROUPS OVERVIEW.FMT
[S] OVER
[S] .
[C] GROUP local.confidential
[S] 483 Encryption or stronger authentication required
[C] GROUP local.private
[S] 400 Closing connection due to lack of security

3. Augmented BNF Syntax for the STARTTLS Extension

This section describes the formal syntax of the STARTTLS extension
using ABNF [ABNF]. It extends the syntax in section 9 of [NNTP],
and non-terminals not defined in this document are defined there.
The [NNTP] ABNF should be imported first before attempting to
validate these rules.

3.1. Commands

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This syntax extends the non-terminal "command", which represents an
NNTP command.

command =/ starttls-command

starttls-command = "STARTTLS"

3.2. Capability entries

This syntax extends the non-terminal "capability-entry", which
represents a capability that may be advertised by the server.

capability-entry =/ starttls-capability

starttls-capability = "STARTTLS"

4. Summary of Response Codes

This section contains a list of every new response code defined in
this document, whether it is multi-line, which commands can
generate it, what arguments it has, and what its meaning is.

Response code 382
Generated by: STARTTLS
Meaning: continue with TLS negotiation

Response code 580
Generated by: STARTTLS
Meaning: can not initiate TLS negotiation

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5. Security Considerations

Security issues are discussed throughout this memo.

In general, the security considerations of the TLS protocol [TLS]
and any implemented extensions [TLS-EXT] are applicable here; only
the most important are highlighted specifically below. Also, this
extension is not intended to cure the security considerations
described in section 12 of [NNTP]; those considerations remain
relevant to any NNTP implementation.

NNTP client and server implementations MUST implement the
TLS_RSA_WITH_RC4_128_MD5 [TLS] cipher suite, and SHOULD implement
the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA [TLS] cipher suite. This is
important as it assures that any two compliant implementations can
be configured to interoperate. All other cipher suites are
OPTIONAL.

Before the TLS handshake has begun, any protocol interactions are
performed in the clear and may be modified by an active attacker.
For this reason, clients and servers MUST discard any sensitive
knowledge obtained prior to the start of the TLS handshake upon the
establishment of a security layer. Furthermore, the CAPABILITIES
command SHOULD be re-issued upon the establishment of a security
layer, and other protocol state SHOULD be re-negotiated as well.

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It should be noted that NNTP is not an end-to-end mechanism. Thus,
if an NNTP client/server pair decide to add TLS privacy, confidentiality,
they are securing the transport only for that link. Similarly,
because delivery of a single piece of news may go between more than
two NNTP servers, adding TLS privacy confidentiality to one pair of servers
does not mean that the entire NNTP chain has been made private.
Furthermore, just because an NNTP server can authenticate an NNTP
client, it does not mean that the articles from the NNTP client
were authenticated by the NNTP client when the client received
them.

Both

During the TLS negotiation, the NNTP client and server must MUST check the result its understanding
of the TLS
negotiation server hostname against the server's identity as presented
in the server Certificate message, in order to see whether an acceptable degree of authentication
and privacy was achieved. Ignoring this step completely
invalidates using TLS for security. The decision about whether
acceptable authentication or privacy was achieved is made locally, prevent man-in-the-
middle attacks. Matching is implementation-dependent, and is beyond the scope of this
document. performed according to these rules:

- The NNTP client and MUST use the server should note carefully hostname it used to open the result of
connection (or the hostname specified in TLS negotiation. If "server_name"
extension [TLS-EXT]) as the negotiation results in no privacy, or if
it results value to compare against the server
name as expressed in privacy using algorithms or key lengths that are
deemed not strong enough, or if the authentication server certificate. The client MUST
NOT use any form of the server hostname derived from an insecure
remote source (e.g., insecure DNS lookup). CNAME

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canonicalization is not good
enough for either party, done.

- If a subjectAltName extension of type dNSName is present in the client may choose to end
certificate, it SHOULD be used as the NNTP
session with an immediate QUIT command, or source of the server may choose
not to accept any more NNTP commands.

The client and server should also server's
identity.

- Matching is case-insensitive.

- A "*" wildcard character MAY be aware that used as the TLS protocol
permits privacy and security capabilities to be renegotiated mid-
connection (see section 7.4.1 of [TLS]). left-most name
component in the certificate. For example, one of *.example.com would
match a.example.com, foo.example.com, etc. but would not match
example.com.

- If the
parties may desire minimal encryption after certificate contains multiple names (e.g. more than one
dNSName field), then a match with any authentication
steps have been performed. This underscores one of the fact that security fields is not present simply because TLS has been negotiated;
considered acceptable.

If the nature
of match fails, the established security layer must be considered. client SHOULD either ask for explicit user
confirmation, or terminate the connection with a QUIT command and
indicate the server's identity is suspect.

A man-in-the-middle attack can be launched by deleting the STARTTLS
capability label in the CAPABILITIES response from the server.
This would cause the client not to try to start a TLS session.
Another man-in-the-middle attack is to allow the server to announce
its STARTTLS capability, but to alter the client's request to start
TLS and the server's response. An NNTP client can partially
protect against these attacks by recording the fact that a
particular NNTP server offers TLS during one session and generating
an alarm if it does not appear in the CAPABILITIES response for a
later session (of course, the STARTTLS capability would not be
listed after a security layer is in place).

If the TLS negotiation fails or if the client receives a 483

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response, the client has to decide what to do next. The client has
to choose among three main options: to go ahead with the rest of
the NNTP session, to retry (re)try TLS later in the session, or to give
up and postpone newsreading/transport activity. If a failure or
error occurs, the client can assume that the server may be able to
negotiate TLS in the future, and should try to negotiate TLS in a
later session. However, if the client and server were only using
TLS for authentication and no previous 480 response was received,
the client may want to proceed with the NNTP session, in case some
of the operations the client wanted to perform are accepted by the
server even if the client is unauthenticated.

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6. IANA Considerations

This section gives a formal definition of the STARTTLS extension as
required by Section 3.3.3 of [NNTP] for the IANA registry.

o The STARTTLS extension provides connection-based security via
the Transport Layer Security (TLS).

o The capability label for this extension is "STARTTLS".

o The capability label has no arguments.

o This extension defines one new command, STARTTLS, whose
behavior, arguments, and responses are defined in Section 2.2.

o This extension does not associate any new responses with pre-
existing NNTP commands.

o This extension does affect the overall behavior of both server
and client, in that after successful use of the STARTTLS
command, all communication is transmitted with the TLS layer as
an intermediary.

o This extension does not affect the maximum length of commands or
initial response lines.

o This extension does not alter pipelining, but the STARTTLS
command cannot be pipelined.

o Use of this extension does alter the capabilities list; once the
STARTTLS command has been used successfully, the STARTTLS
capability can no longer be advertised by CAPABILITIES.
Additionally, the MODE-READER capability MUST NOT be advertised
after a successful TLS negotiation.

o This extension does not cause any pre-existing command to

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produce a 401, 480, or 483 response.

o This extension is unaffected by any use of the MODE READER
command, however the MODE READER command MUST NOT be used in the
same session following a successful TLS negotiation.

o Published Specification: This document.

o Author, Change Controller, and Contact for Further Information:
Author of this document.

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7. References

7.1. Normative References

[ABNF] Crocker, D., Overell, P., "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.

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

[NNTP] Feather, C., "Network News Transport Protocol",
draft-ietf-nntpext-base-*.txt, Work in Progress.

[TLS] Dierks, T., Rescorla, E., Allen, C., "The TLS Protocol Version 1.1",
draft-ietf-tls-rfc2246-bis-*.txt, Work in Progress. 1.0",
RFC 2246, January 1999.

[TLS-EXT] Blake-Wilson, S., Nystrom, M., Hopwood, D.,
Mikkelsen, J., Wright, T., "Transport Layer Security (TLS)
Extensions", draft-ietf-tls-rfc3546bis-*.txt, Work in Progress. RFC 3546, June 2003.

7.2. Informative References

[NNTP-AUTH] Vinocur, J., Murchison, K., Newman, C., "NNTP Extension
for Authentication", draft-ietf-nntpext-auth-*.txt, Work in
Progress.

[SASL] Myers, J., "Simple Authentication and Security Layer
(SASL)", RFC 2222, October 1997.

[TLS-IMAPPOP] Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC
2595, June 1999.

8. Authors' Addresses

Kenneth Murchison
Oceana Matrix Ltd.
21 Princeton Place
Orchard Park, NY 14127 USA

Email: ken@oceana.com

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Jeffrey M. Vinocur
Department of Computer Science
Upson Hall
Cornell University
Ithaca, NY 14853

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EMail: vinocur@cs.cornell.edu

Chris Newman
Sun Microsystems
1050 Lakes Drive, Suite 250
West Covina, CA 91790

EMail: cnewman@iplanet.com Chris.Newman@sun.com

9. Acknowledgments

A significant amount of the STARTTLS text in this document was lifted from
RFC 2595 by Chris Newman and RFC 3207 by Paul Hoffman.

Special acknowledgment goes also to the people who commented
privately on intermediate revisions of this document, as well as
the members of the IETF NNTP Working Group for continual insight in
discussion.

10. Intellectual Property Rights

The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed
to pertain to the implementation or use of the technology described
in this document or the extent to which any license under such
rights might or might not be available; nor does it represent that
it has made any independent effort to identify any such rights.
Information on the procedures with respect to rights in RFC
documents can be found in BCP 78 and BCP 79.

Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use
of such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository
at http://www.ietf.org/ipr.

The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.

11. Copyright

Murchison, et. al. Expires November December 2005 [Page 13]

Internet Draft TLS for NNTP May June 2005

ietf-ipr@ietf.org.

11. Copyright

This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.

This document and the information contained herein are provided on
an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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.

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