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
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This Internet-Draft will expire on July 14, 2012.
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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 . . . . . . . . . . . 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
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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 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-
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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.
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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
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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
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Tom Taylor (editor)
Huawei Technologies
Ottawa
Canada
Email: tom.taylor.stds@gmail.com
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