Internet Engineering Task Force T. Tsou Internet-Draft Huawei Technologies (USA) Updates: RFC 3588 (if approved) T. Taylor, Ed. Intended status: Standards Track Huawei Technologies Expires: July 14, 2012 January 11, 2012 Realm-Based Redirection In Diameter draft-ietf-dime-realm-based-redirect-04 Abstract RFC 3588 allows a Diameter redirect agent to specify one or more individual hosts to which a Diameter message may be redirected by an upstream Diameter node. However, in some circumstances an operator may wish to redirect messages to an alternate domain without specifying individual hosts. This document specifies a mechanism by which this can be achieved. New applications may incorporate this capability by reference to the present document. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on July 14, 2012. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must Tsou & Taylor Expires July 14, 2012 [Page 1] Internet-Draft Realm-Based Redirection In Diameter January 2012 include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 2. Support of Realm-Based Redirection Within Applications . . . . 3 3. Realm-Based Redirection . . . . . . . . . . . . . . . . . . . . 3 3.1. Behaviour of Diameter Nodes . . . . . . . . . . . . . . . . 4 3.1.1. Behaviour at the Redirect Agent . . . . . . . . . . . . 4 3.1.2. Behaviour of Other Diameter Nodes . . . . . . . . . . . 5 3.2. The Redirect-Realm AVP . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 7. Normative References . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Tsou & Taylor Expires July 14, 2012 [Page 2] Internet-Draft Realm-Based Redirection In Diameter January 2012 1. Introduction The usual redirect indication, as described in Section 6.1.7 and Sections 6.12-6.14 of [RFC3588], returns one or more individual host names to the upstream Diameter node. However, consider the case where an operator has offered a specific service but no longer wishes to do so. The operator has arranged for an alternative domain to provide the service. To aid in the transition to the new arrangement, the original operator maintains a redirect server to indicate the alternative destination to upstream nodes. However, the original operator has no interest in configuring a list of hosts in the alternative operator's domain, and would prefer simply to provide redirect indications to the domain as a whole. Within this specification, the term "realm-based redirection" is used to refer to a mode of operation where the redirect indication specifies a realm and the upstream Diameter node reroutes the message to the realm rather than an individual host. 1.1. Requirements Language 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 [RFC2119]. 2. Support of Realm-Based Redirection Within Applications Because realm-based redirection is not part of base Diameter behaviour, support for realm-based redirection by the agent MUST be specified as part of particular applications. In this way, Diameter's capability negotiation mechanism can be used indirectly to indicate support for realm-based redirection by indicating support for the applications concerned. Designers of new applications MAY incorporate the mechanism specified here into their application by reference to this document. Note that a redirect agent will apply realm-based redirection only for those applications that it recognizes to be eligible for such treatment. In typical usage, where a realm has handed off specific applications to an alternate realm for processing, this is not an issue, since the operator can configure the redirect server for those specific applications. 3. Realm-Based Redirection This section specifies an extension to [RFC3588] to achieve realm- Tsou & Taylor Expires July 14, 2012 [Page 3] Internet-Draft Realm-Based Redirection In Diameter January 2012 based redirection. The elements of this solution are: o a new result code, DIAMETER_REALM_REDIRECT_INDICATION (3xxx TBD); o one new attribute-value pair (AVP), Redirect-Realm; and o associated behaviour at Diameter nodes implementing this specification. 3.1. Behaviour of Diameter Nodes 3.1.1. Behaviour at the Redirect Agent This specification modifies Section 2.7 of [RFC3588] to permit REDIRECT routing table entries to contain an alternative realm instead of individual home server identities. This specification modifies Section 6.1.7 of [RFC3588]. If the realm-based routing table for a request contains a realm rather than one or more server identities, the redirect agent MUST proceed as follows: o If the request contains a Destination-Host AVP or if the request is for an application that does not support realm-based redirection, the redirect agent MUST set the 'E' bit in the answer and set the Result Code to DIAMETER_UNABLE_TO_DELIVER. Note that the latter case is actually a matter of misconfiguration at the redirect server. o Otherwise, if the request is for an application supporting realm- based redirection, the redirect agent MUST set the Result-Code AVP to DIAMETER_REALM_REDIRECT_INDICATION rather than DIAMETER_REDIRECT_INDICATION. Furthermore, the redirect agent MUST include a Redirect-Realm AVP containing the realm from the routing table entry in its answer message instead of one or more Redirect-Host AVPs. All other aspects of Section 6.1.7 remain the same as for host-based redirection. The redirect agent MAY include a copy of the Redirect-Host-Usage AVP, which SHOULD be set to REALM_AND_APPLICATION. If this AVP is added, the Redirect-Max-Cache-Time AVP MUST also be included. Note that these AVPs apply to the peer discovered by a node acting on the redirect agent's response, as described in the next section. Sections 6.13 and 6.14 of [RFC3588] are modified to permit the Redirect-Host-Usage and Redirect-Max-Cache-Time AVPs to be used also to specify the persistence of cache entries created by the Redirect-Realm AVP. Tsou & Taylor Expires July 14, 2012 [Page 4] Internet-Draft Realm-Based Redirection In Diameter January 2012 3.1.2. Behaviour of Other Diameter Nodes A Diameter node conforming to this specification which receives an answer with the result code value DIAMETER_REALM_REDIRECT_INDICATION MUST take the following steps: 1. Verify that the new realm is authorized to provide the requested service. 2. If successful, locate and establish a connection to a peer in the realm given by the Redirect-Realm AVP, using normal discovery procedures as described in Section 5.2 of [RFC3588]. 3. If again successful: * update its cache of routing entries for the realm and application to which the original request was directed, taking into account the Redirect-Host-Usage and Redirect-Max-Cache- Time AVPs, if present in the answer. * Remove the Destination-Host (if present) and Destination-Realm AVPs from the original request and add a new Destination-Realm AVP containing the realm identified by the Redirect-Realm AVP in the answer. * Forward the modified request. Note that the implementation of realm-based redirection will disrupt any stateful sessions being served by the given application in the interdicted realm. The transition to realm-based redirection thus needs to be managed to minimize the ensuing disruption. 3.2. The Redirect-Realm AVP The Redirect-Realm AVP (code TBD) is of type DiameterIdentity. It specifies a realm to which a node receiving a redirect indication containing the result code value DIAMETER_REALM_REDIRECT_INDICATION and the Redirect-Realm AVP SHOULD route the original request. The M flag for the Redirect-Realm AVP MUST be set, and the V flag MUST NOT be set. 4. Security Considerations Because realm-based redirection implies a change in business relationships, the node acting on the redirect indication SHOULD verify that the new realm is authorized to perform the requested service. Similarly the originator of the request SHOULD perform an Tsou & Taylor Expires July 14, 2012 [Page 5] Internet-Draft Realm-Based Redirection In Diameter January 2012 authorization check of the path as described in Section 2.10 of [RFC3588]. 5. IANA Considerations This specification adds a new AVP code [TBD] Redirect-Realm in the AVP Code registry under Authentication, Authorization, and Accounting (AAA) Parameters. This specification allocates a new Result-Code value DIAMETER_REALM_REDIRECT_INDICATION (3xxx TBD) in the Result-Code AVP Values (code 268) - Protocol Errors registry under Authentication, Authorization, and Accounting (AAA) Parameters. 6. Acknowledgements Glen Zorn, Sebastien Decugis, Wolfgang Steigerwald, Mark Jones, Victor Fajardo, Jouni Korhonen, Avi Lior, and Lionel Morand contributed comments that helped to shape this document. 7. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. Arkko, "Diameter Base Protocol", RFC 3588, September 2003. Authors' Addresses Tina Tsou Huawei Technologies (USA) 2330 Central Expressway Santa Clara, CA 95050 USA Phone: +1 408 330 4424 Email: Tina.Tsou.Zouting@huawei.com URI: http://tinatsou.weebly.com/contact.html Tsou & Taylor Expires July 14, 2012 [Page 6] Internet-Draft Realm-Based Redirection In Diameter January 2012 Tom Taylor (editor) Huawei Technologies Ottawa Canada Email: tom.taylor.stds@gmail.com Tsou & Taylor Expires July 14, 2012 [Page 7]