Network Working Group E. Lear Internet-Draft K. Crozier Expires: March
10,29, 2006 Cisco Systems September 6,25, 2005 Using the NETCONF Protocol over Blocks Extensible Exchange Protocol (BEEP) draft-ietf-netconf-beep-06draft-ietf-netconf-beep-07 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on March 10,29, 2006. Copyright Notice 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). 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 1. Introduction The NETCONF protocol  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)  . 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 . 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) . The SASL profile used by BEEP allows for a simple and direct mapping to the existing security model for CLI, while transportlayer security (TLS)  provides a strong well tested encryption mechanism with either server or server and client-side authentication. 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 . It is anticipated that the SASL PLAIN mechanism will be heavily used in conjunction with TLS. 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: (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  Section 8.1: A: MSG 1 0 . 0 436442 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:base:1.0#startupurn: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 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 . 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:  message semantics:  Contact Information: c.f., the "Author's Address" section of this memo. 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 , and they MAY support other profiles such as OTP. 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. 4. IANA Considerations The IANA requested to assign a TCP port for NETCONF, and to register the BEEP profile contained here-in. 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. 6. References 6.1 Normative References  Enns, R., "NETCONF Configuration Protocol", draft-ietf-netconf-prot-07 (work in progress), June 2005.  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.  Myers, J., "Simple Authentication and Security Layer (SASL)", RFC 2222, October 1997.  Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A., and P. Kocher, "The TLS Protocol Version 1.0", RFC 2246, January 1999.  Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC 2595, June 1999.  Leach, P. and C. Newman, "Using Digest Authentication as a SASL Mechanism", RFC 2831, May 2000.  Rose, M., "The Blocks Extensible Exchange Protocol Core", RFC 3080, March 2001.  Rose, M., "Mapping the BEEP Core onto TCP", RFC 3081, March 2001. 6.2 Informative References  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.  Newman, C., "The One-Time-Password SASL Mechanism", RFC 2444, October 1998. Authors' Addresses Eliot Lear Cisco Systems Glatt-com Glattzentrum, Zurich 8301 CH Email: email@example.com Ken Crozier Cisco Systems 170 W. Tasman Dr. San Jose, CA 95134-1706 US Email: firstname.lastname@example.org 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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