Network Working Group E. Lear
Internet-Draft K. Crozier
Expires: March 29, 2006 Cisco Systems
September 25, 2005
Using the NETCONF Protocol over Blocks Extensible Exchange Protocol
(BEEP)
draft-ietf-netconf-beep-07
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Copyright (C) The Internet Society (2005).
Abstract
This document specifies an application protocol mapping for the
NETCONF protocol over the Blocks Extensible Exchange Protocol (BEEP).
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Why BEEP? . . . . . . . . . . . . . . . . . . . . . . . . 3
2. BEEP Transport Mapping . . . . . . . . . . . . . . . . . . . . 4
2.1 NETCONF Session Establishment . . . . . . . . . . . . . . 4
2.2 Starting a Channel for NETCONF . . . . . . . . . . . . . . 4
2.3 NETCONF Session Usage . . . . . . . . . . . . . . . . . . 6
2.4 NETCONF Session Teardown . . . . . . . . . . . . . . . . . 6
2.5 BEEP Profile for NETCONF . . . . . . . . . . . . . . . . . 6
3. Security Considerations . . . . . . . . . . . . . . . . . . . 8
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1 Normative References . . . . . . . . . . . . . . . . . . . 11
6.2 Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 11
A. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Intellectual Property and Copyright Statements . . . . . . . . 14
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1. Introduction
The NETCONF protocol [1] defines a simple mechanism through which a
network device can be managed. NETCONF is designed to be usable over
a variety of application protocols. This document specifies an
application protocol mapping for NETCONF over the Blocks Extensible
Exchange Protocol (BEEP) [7] .
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [2].
1.1 Why BEEP?
Use of BEEP is natural as an application protocol for transport of
XML. As a peer to peer protocol, BEEP provides an easy way to
implement NETCONF, no matter which side of the connection was the
initiator. This "bidirectionality" allows for either manager or
agent to initiate a connection. This is particularly important to
support large number of intermittently connected devices, as well as
those devices that must reverse the management connection in the face
of firewalls and network address translators (NATs).
BEEP makes use of the Simple Authentication and Security Layer (SASL)
[3]. The SASL profile used by BEEP allows for a simple and direct
mapping to the existing security model for CLI, while transportlayer
security (TLS) [4] provides a strong well tested encryption mechanism
with either server or server and client-side authentication.
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2. BEEP Transport Mapping
All NETCONF over BEEP implementations MUST implement the profile and
functional mapping between NETCONF and BEEP as described below.
2.1 NETCONF Session Establishment
Managers may be either BEEP listeners or initiators. Similarly,
agents may be either listeners or initiators. Thus the initial
exchange takes place without regard to whether a manager or the agent
is the initiator. After the transport connection is established, as
greetings are exchanged, they SHOULD each announce their support for
TLS and optionally SASL. Once greetings are exchanged, if TLS is to
be used and available by both parties, the listener STARTs a channel
with the TLS profile.
Once TLS has been started, a new greeting is sent by both initiator
and listener, as required by the BEEP RFC.
At this point, if SASL is desired, the initiator starts a BEEP
channel to perform a SASL exchange to authenticate itself. Upon
completion of authentication the channel is closed. That is, the
channel is exclusively used to authenticate.
Examples of both TLS and SASL profiles can be found in [7].
It is anticipated that the SASL PLAIN mechanism will be heavily used
in conjunction with TLS.[5] In such cases, in accordance with RFC
2595 the PLAIN mechanism MUST NOT be advertised in the first BEEP
<greeting>, but only in the one following a successful TLS
negotiation. This applies only if TLS and SASL PLAIN mechanisms are
both to be used. The SASL PLAIN mechanism MUST NOT be used
unencrypted channels to avoid risk of eavesdropping. More specifics
about the use of SASL and TLS are mentioned in Security
Considerations below.
Once authentication has occurred, there is no need to distinguish
between initiator and listener. We now distinguish between manager
and agent, and it is assumed that each knows its role in the
conversation.
2.2 Starting a Channel for NETCONF
The manager now establishes new channel and specifies the single
NETCONF profile. For example:
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(M = Manager ; A = Agent )
M: MSG 0 1 . 10 48 101
M: Content-type: application/beep+xml
M: <start number="1">
M: <profile uri="http://iana.org/beep/netconf" />
M: </start>
M: END
A: RPY 0 1 . 38 87
A: Content-Type: application/beep+xml
A:
A: <profile uri="http://iana.org/beep/netconf" />
A: END
At this point we are ready to proceed on BEEP channel 1 with NETCONF
operations.
Next the manager and the agent exchange NETCONF <hello> elements on
the new channel so that each side learns the other's capabilities.
This occurs through a MSG. Each side will then respond with
positively. The following example is adapted from [1] Section 8.1:
A: MSG 1 0 . 0 442
A: Content-type: application/beep+xml
A:
A: <hello xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
A: <capabilities>
A: <capability>
A: urn:ietf:params:xml:ns:netconf:base:1.0
A: </capability>
A: <capability>
A: urn:ietf:params:xml:ns:netconf:capability:startup:1.0
A: </capability>
A: <capability>
A: http:/example.net/router/2.3/core#myfeature
A: </capability>
A: </capabilities>
A: <session-id>4</session-id>
A: </hello>
A: END
M: RPY 1 0 . 0 0
M: END
Certain NETCONF capabilities may require additional BEEP channels.
When such capabilities are defined, a BEEP mapping must be defined as
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well.
At this point, the NETCONF session is established, and capabilities
have been exchanged.
2.3 NETCONF Session Usage
Nearly all NETCONF operations are executed through the <rpc> tag. To
issue an RPC, the manager transmits on the operational channel a BEEP
MSG containing the RPC and its arguments. In accordance with the
BEEP standard, RPC requests may be split across multiple BEEP frames.
Once received and processed, the agent responds with BEEP RPY
messages on the same channel with the response to the RPC. In
accordance with the BEEP standard, responses may be split across
multiple BEEP frames.
2.4 NETCONF Session Teardown
Upon receipt of <close-session> from the manager, once the agent has
completed all RPCs, it will close BEEP channel 0. When an agent
needs to initiate a close it will do so by closing BEEP channel 0.
Although not required to do so, the agent should allow for a
reasonable period for a manager to release an existing lock prior to
initiating a close. Once the agent has closed channel 0, all locks
are released, and each side follows tear down procedures as specified
in [8]. Having received a BEEP close or having sent <close-session>,
a manager MUST NOT send further requests. If there are additional
activities due to expanded capabilities, these MUST cease in an
orderly manner, and should be properly described in the capability
mapping.
2.5 BEEP Profile for NETCONF
Profile Identification: http://iana.org/beep/netconf
messages exchanged during Channel Creation: not applicable
Messages starting one-to-one exchanges: "hello", "rpc", "rpc-reply"
Messages in positive replies: "rpc-reply"
Messages in negative replies: "rpc-reply"
Messages in one-to-many exchanges: none
Message syntax: [1]
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message semantics: [1]
Contact Information: c.f., the "Author's Address" section of this
memo.
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3. Security Considerations
Configuration information is by its very nature sensitive. Its
transmission in the clear and without integrity checking leaves
devices open to classic so-called "person in the middle" attacks.
Configuration information often times contains passwords, user names,
service descriptions, and topological information, all of which are
sensitive. A NETCONF application protocol, therefore, must minimally
support options for both confidentiality and authentication.
The BEEP mapping described in this documents addresses both
confidentiality and authentication in a flexible manner through the
use of TLS and SASL profiles. Confidentiality is provided via the
TLS profile, and is used as discussed above. In addition, the server
certificate shall serve as the server's authentication to the client.
The client MUST be prepared to recognize a valid server certificate.
While distribution of such certificates is beyond the scope of this
document, the implementor is cautioned to be aware of any
interdependencies that may be placed on the network infrastructure
through the use of protocols that validate trust anchors.
For client-side authentication there are several options. The client
MAY provide a certificate during the initiation phase of TLS, in
which case the subject of that certificate shall be considered
principle for authentication purposes. Once again, server
implementors should be aware of any interdependencies that could be
created through protocols used to validate trust anchors.
In the case where the client has not authenticated through TLS, the
server SHOULD advertise one or more SASL profile, from which the
client will choose. In the singular case where TLS is established
the minimum profile MAY be PLAIN. Otherwise, implementations MUST
support the DIGEST-MD5 profile as described in [6], and they MAY
support other profiles such as OTP.[10]
Different environments may well allow different rights prior to and
then after authentication. An authorization model is not specified
in this document. When an operation is not properly authorized then
a simple rpc-error containing "permission denied" is sufficient.
Note that authorization information may be exchanged in the form of
configuration information, which is all the more reason to ensure the
security of the connection.
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4. IANA Considerations
The IANA requested to assign a TCP port for NETCONF, and to register
the BEEP profile contained here-in.
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5. Acknowledgments
This work is the product of the NETCONF IETF working group, and many
people have contributed to the NETCONF discussion. Most notably, Rob
Ens, Phil Schafer, Andy Bierman, Wes Hardiger, Ted Goddard, and
Margaret Wasserman all contributed in some fashion to this work,
which was originally to be found in the NETCONF base protocol
specification. Thanks also to Weijing Chen, Keith Allen, Juergen
Schoenwaelder, Marshall Rose, and Eamon O'Tuathail for their very
constructive participation.
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6. References
6.1 Normative References
[1] Enns, R., "NETCONF Configuration Protocol",
draft-ietf-netconf-prot-07 (work in progress), June 2005.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] Myers, J., "Simple Authentication and Security Layer (SASL)",
RFC 2222, October 1997.
[4] Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A., and
P. Kocher, "The TLS Protocol Version 1.0", RFC 2246,
January 1999.
[5] Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC 2595,
June 1999.
[6] Leach, P. and C. Newman, "Using Digest Authentication as a SASL
Mechanism", RFC 2831, May 2000.
[7] Rose, M., "The Blocks Extensible Exchange Protocol Core",
RFC 3080, March 2001.
[8] Rose, M., "Mapping the BEEP Core onto TCP", RFC 3081,
March 2001.
6.2 Informative References
[9] Bray, T., Paoli, J., Sperberg-McQueen, C., and E. Maler,
"Extensible Markup Language (XML) 1.0 (Second Edition)", W3C
REC REC-xml-20001006, October 2000.
[10] Newman, C., "The One-Time-Password SASL Mechanism", RFC 2444,
October 1998.
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Authors' Addresses
Eliot Lear
Cisco Systems
Glatt-com
Glattzentrum, Zurich 8301
CH
Email: lear@cisco.com
Ken Crozier
Cisco Systems
170 W. Tasman Dr.
San Jose, CA 95134-1706
US
Email: kcrozier@cisco.com
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Appendix A. Change Log
07: Match URN changes to core draft (one change).
06: Changes (fix references, IANA section) from AD comments.
05: improved advice on use of tls and SASL profiles.
04: complete revamp of the profile. Added <hello> as well as
examples.
03: minor gnits relating to <close-session>
02: added comments about locking
01: Removed management channel, rpc-status, rpc-abort, and associated
profile changes.
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