Internet Engineering Task Force T. Tsou
Internet-Draft T. Taylor, Ed.
Updates: RFC 3588 Huawei Technologies
(if approved) July 12, 2010
Intended status: Standards Track
Expires: January 13, 2011
Realm-Based Redirection In Diameter
draft-ietf-dime-realm-based-redirect-03
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.
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This Internet-Draft will expire on January 13, 2011.
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to this document. Code Components extracted from this document must
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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 . . . . . . . . . . . 4
3.2. The Redirect-Realm AVP . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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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 cannot be
guaranteed without advertisement at the application level. Designers
of new applications wishing to include support for realm-based
redirection can incorporate the mechanism specified here by reference
to this document.
3. Realm-Based Redirection
This section specifies an extension to [RFC3588] to achieve realm-
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.
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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 home server identities, the redirect agent MUST proceed
as follows:
o If the peer from which the request was received did not advertise
an application incorporating the realm-based routing capability in
the CER/CEA exchange, the redirect agent SHOULD set the 'E' bit in
the answer and set the Result Code to DIAMETER_UNABLE_TO_DELIVER.
As an alternative, the redirect agent MAY if so configured provide
a host-based redirect as described in Section 6.1.7 of [RFC3588].
o Otherwise, if an application supporting the use of realm-based
redirection was negotiated with the peer, the redirect agent MUST
set the Result-Code AVP to DIAMETER_REALM_REDIRECT_INDICATION
rather than DIAMETER_REDIRECT_INDICATION. Furthermore, the
redirect agent MUST a Redirect-Realm AVP containing the realm from
the routing table entry in its answer message instead of one or
more Redirect-Host AVPs. To prevent confusion at Diameter nodes
receiving the answer message, the message MUST include the Error-
Reporting-Host AVP if the host setting the Result-Code AVP is
different from the identity encoded in the Origin-Host AVP, in
conformity with Section 7.1 of [RFC3588]. All other aspects of
Section 6.1.7 remain the same as for host-based redirection.
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
SHOULD attempt to reroute the request to the indicated realm using
normal discovery procedures to find an appropriate destination host.
The receiving Diameter node SHOULD update its cache of routing
entries according to the direction provided by the Redirect-Max-
Cache-Time AVP, if present. The cache entry SHOULD be associated
with a redirect usage of REALM_AND_APPLICATION.
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
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containing the result code value DIAMETER_REALM_REDIRECT_INDICATION
and the Redirect-Realm AVP SHOULD route the original request. The V
flag for the Redirect-Realm AVP MUST NOT be set.
Section 6.14 of [RFC3588] is modified to permit the Redirect- Max-
Cache-Time AVP to be used also to specify the persistence of cache
entries created by the Redirect-Realm AVP.
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
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, and Jouni Korhonen 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.
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Authors' Addresses
Tina Tsou
Huawei Technologies
Bantian, Longgang District
Shenzhen 518129
P.R. China
Email: tena@huawei.com
Tom Taylor (editor)
Huawei Technologies
Ottawa
Canada
Email: tom111.taylor@bell.net
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