Internet Engineering Task Force T. Tsou
Internet-Draft Huawei Technologies (USA)
Intended status: Standards Track R. Hao
Expires: January 17, 2013 Comcast Cable
T. Taylor, Ed.
Huawei Technologies
July 16, 2012
Realm-Based Redirection In Diameter
draft-ietf-dime-realm-based-redirect-05
Abstract
The Diameter protocol 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 January 17, 2013.
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
Tsou, et al. Expires January 17, 2013 [Page 1]
Internet-Draft Realm-Based Redirection In Diameter July 2012
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
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 . . . . . . . . . . . . . . . . . . . . 4
3.1. Configuration of the Redirecting Server . . . . . . . . . . 4
3.2. Behaviour of Diameter Nodes . . . . . . . . . . . . . . . . 4
3.2.1. Behaviour at the Redirecting Server . . . . . . . . . . 4
3.2.2. Proxy Behaviour . . . . . . . . . . . . . . . . . . . . 5
3.2.3. Client Behaviour . . . . . . . . . . . . . . . . . . . 6
3.3. The Redirect-Realm AVP . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
7. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
Tsou, et al. Expires January 17, 2013 [Page 2]
Internet-Draft Realm-Based Redirection In Diameter July 2012
1. Introduction
The usual redirect indication, as described in Section 6.1.8 and
Sections 6.12-6.14 of [RFC3588bis], 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.
As an example of another use case, consider a 3GPP IMS deployment
where subscriber data is provisioned in a geo-redundant Home
Subscriber Server (HSS) cluster for reliability. Each Application
Server (AS) needs to maintain redundant Diameter Sh links to both
cluster nodes for scalability. It is preferable that the AS should
go to the local HSS cluster node when it is available. It would be
useful for a cluster node to be able to redirect an AS request to its
partner node in the cluster without specifying the individual Sh link
to that alternate node. This could be accomplished by identifying
each cluster node with a separate realm and individual Sh links with
separate servers, and redirecting on the basis of realm rather than
individual server. There can be multiple geo-redundant HSS clusters,
in which case the Subscriber Location Function (SLF) performs the
redirection.
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 [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
Tsou, et al. Expires January 17, 2013 [Page 3]
Internet-Draft Realm-Based Redirection In Diameter July 2012
for the applications concerned. Designers of new applications can
incorporate the mechanism specified here into their application by
normative reference to this document.
The result of making realm-based redirection an application-specific
behaviour is that it cannot be performed by a redirect agent, but
instead must be performed by a Diameter server. However, despite the
change in executing role, the behaviour itself is a slight
modification of the behaviour of a redirect agent.
3. Realm-Based Redirection
This section specifies an extension to [RFC3588bis] 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.
3.1. Configuration of the Redirecting Server
A Diameter server MUST be configured as follows to execute realm-
based redirection:
o configured with an application that incorporates realm-based
redirection;
o the Local Action field of the routing table described in Section
2.7 of [RFC3588bis] is set to LOCAL;
o an application-specific field is set to indicate that the required
local action is to perform realm-based redirection;
o an associated application-specific field is configured with the
identities of one or more realms to which the request should be
redirected.
3.2. Behaviour of Diameter Nodes
3.2.1. Behaviour at the Redirecting Server
An application incorporating realm-based redirection may specify that
redirection applies for any request or only for the initial request
of a session (i.e., to prevent disruption of established sessions).
Tsou, et al. Expires January 17, 2013 [Page 4]
Internet-Draft Realm-Based Redirection In Diameter July 2012
If a server configured as described in Section 3.1 receives a request
for which the indicated local action is to perform realm-based
redirection, the server MUST proceed as follows:
o If the request contains a Destination-Host AVP, the server MUST
set the 'E' bit in the answer and set the Result-Code AVP to
DIAMETER_UNABLE_TO_DELIVER.
o Otherwise, the server MUST reply with an answer message with the
'E' bit set, while maintaining the Hop-by-Hop Identifier in the
header. The server MUST include the Result-Code AVP set to
DIAMETER_REALM_REDIRECT_INDICATION. The server MUST also include
the alternate realm identifiers with which it has been configured,
each in a separate Redirect-Realm AVP instance.
The server 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 server's response, as described in the next section.
3.2.2. Proxy Behaviour
A proxy conforming to this specification that receives an answer
message with the Result-Code AVP set to
DIAMETER_REALM_REDIRECT_INDICATION MAY attempt to reroute the
original request to a server in a realm identified by a Redirect-
Realm AVP instance in the answer message. If it does so, it MUST
take the following steps:
1. Select a specific realm from amongst those identified in
instances of the Redirect-Realm AVP in the answer message.
2. Verify that the new realm is authorized to provide the requested
service on behalf of the realm specified in the original request.
3. If successful, locate and establish a route to a peer in the
realm given by the Redirect-Realm AVP, using normal discovery
procedures as described in Section 5.2 of [RFC3588bis].
4. If again successful:
A. 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.
Tsou, et al. Expires January 17, 2013 [Page 5]
Internet-Draft Realm-Based Redirection In Diameter July 2012
B. Remove the Destination-Host (if present) and Destination-
Realm AVPs from the original request and add a new
Destination-Realm AVP containing the realm selected in the
initial step.
C. Forward the modified request.
5. If any of the preceding steps 2-4 fail and additional realms have
been identified in the original answer, select another instance
of the Redirect-Realm AVP in that answer and repeat steps 2-4 for
the realm that it identifies.
3.2.3. Client Behaviour
A client conforming to this specification MUST be prepared to receive
either an answer message containing a Result-Code AVP set to
DIAMETER_REALM_REDIRECT_INDICATION, or, as the result of proxy
action, some other result from a realm differing from the one to
which it sent the original request. In the case where it receives
DIAMETER_REALM_REDIRECT_INDICATION, the client SHOULD follow the same
steps prescribed in the previous section for a proxy, in order both
to update its routing table and to obtain service for the original
request. In other cases, the client SHOULD verify that the realm
from which it received the response is authorized to act on behalf of
the realm to which it directed the original request. If this
authorization fails, the response SHOULD be ignored.
3.3. 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
authorization check of the path as described in Section 2.10 of
[RFC3588bis].
Tsou, et al. Expires January 17, 2013 [Page 6]
Internet-Draft Realm-Based Redirection In Diameter July 2012
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.
[RFC3588bis]
Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,
"Diameter Base Protocol", June 2012.
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, et al. Expires January 17, 2013 [Page 7]
Internet-Draft Realm-Based Redirection In Diameter July 2012
Ruibing Hao
Comcast Cable
One Comcast Center
Philadelphia, PA 19103
USA
Phone: +1 215 286 3991(O)
Email: Ruibing_Hao@cable.comcast.com
Tom Taylor (editor)
Huawei Technologies
Ottawa
Canada
Email: tom.taylor.stds@gmail.com
Tsou, et al. Expires January 17, 2013 [Page 8]