Network Working Group G. Zorn
Internet-Draft Network Zen
Intended status: Standards Track K. Jiao
Expires: October 15, 2009 Huawei Technologies
April 13, 2009
The Diameter Capabilities Update Application
draft-zorn-dime-capablities-update-01.txt
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Abstract
This document defines a new Diameter application and associated
command codes. The Capabilities Update application is intended to
allow the dynamic update of Diameter peer capabilities while the
peer-to-peer connection is in the open state.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Specification of Requirements . . . . . . . . . . . . . . . . . 3
3. Diameter Protocol Considerations . . . . . . . . . . . . . . . 3
4. Capabilities Update . . . . . . . . . . . . . . . . . . . . . . 3
4.1. Command-Code Values . . . . . . . . . . . . . . . . . . . . 4
4.1.1. Capabilities-Update-Request . . . . . . . . . . . . . . 5
4.1.2. Capabilities-Update-Answer . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Application Identifier . . . . . . . . . . . . . . . . . . 6
5.2. Command Codes . . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
Capabilities exchange is an important component of the Diameter Base
Protocol [RFC3588], allowing peers to exchange identities and
Diameter capabilities (protocol version number, supported Diameter
applications, security mechanisms, etc.). As defined in RFC 3588,
however, the capabilities exchange process takes place only once, at
the inception of a transport connection between a given pair of
peers. Therefore, if a peer's capabilities change (due to software
update, for example), the existing connection(s) must be torn down
(along with all of the associated user sessions) and restarted before
the modified capabilities can be advertised.
This document defines a new Diameter application intended to allow
the dynamic update of Diameter peer capabilities over an existing
connection. Because the Capabilities Update application specified
here operates over an existing transport connection, modification of
the security mechanism in use is not allowed; if the security method
used between a pair of peers is changed the affected connection MUST
be restarted.
Discussion of this draft may be directed to the authors.
2. Specification of Requirements
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].
3. Diameter Protocol Considerations
This section details the relationship of the Diameter Capabilities
Update application to the Diameter Base Protocol.
This document specifies Diameter Application-ID <TBD1>. Diameter
nodes conforming to this specification MAY advertise support by
including the value of <TBD1> in the Auth-Application-Id of the
Capabilities-Exchange-Req and Capabilities-Exchange-Answer commands
[RFC3588].
4. Capabilities Update
When the capabilities of a Diameter node conforming to this
specification change, it SHOULD notify all of the nodes with which it
has an open transport connection using the Capabilities-Update-Req
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message (Section 4.1.1). This message allows the update of a peer's
identity and its capabilities (protocol version number, supported
Diameter applications, etc.).
The receiver only issues commands to its peers that have advertised
support for the Diameter application that defines the command. A
Diameter node MUST cache the supported applications in order to
ensure that unrecognized commands and/or AVPs are not unnecessarily
sent to a peer.
The receiver of the Capabilities-Update-Request (CUR) MUST determine
common applications by computing the intersection of its own set of
supported Application Id against all of the application identifier
AVPs (Auth-Application-Id, Acct-Application-Id and Vendor-Specific-
Application-Id) present in the CUR. The value of the Vendor-Id AVP
in the Vendor-Specific-Application-Id MUST NOT be used during
computation.
If the receiver of a Capabilities-Update-Req (CUR) message does not
have any applications in common with the sender then it MUST return a
Capabilities-Update-Answer (CUA) with the Result-Code AVP set to
DIAMETER_NO_COMMON_APPLICATION, and SHOULD disconnect the transport
layer connection; however, if active sessions are using the
connection, peers MAY delay disconnection until the sessions can be
redirected or gracefully terminated. Note that receiving a CUR or
CUA from a peer advertising itself as a Relay (see [RFC3588], Section
2.4) MUST be interpreted as having common applications with the peer.
The CUR and CUA messages MUST NOT be proxied, redirected or relayed.
Since the CUR/CUA messages cannot be proxied, it is still possible
that an upstream agent receives a message for which it has no
available peers to handle the application that corresponds to the
Command-Code. In such instances, the 'E' bit is set in the answer
message with the Result-Code AVP set to DIAMETER_UNABLE_TO_DELIVER to
inform the downstream peer to take action (e.g., re-routing requests
to an alternate peer).
4.1. Command-Code Values
This section defines Command-Code [RFC3588] values that MUST be
supported by all Diameter implementations conforming to this
specification. The following Command Codes are defined in this
document: Capabilities-Update-Request (CUR)Section 4.1.1 and
Capabilities-Update-Answer (CUA) Section 4.1.2.
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4.1.1. Capabilities-Update-Request
The Capabilities-Update-Request (CUR), indicated by the Command-Code
set to <TBD2> and the Command Flags' 'R' bit set, is sent to update
local capabilities. Upon detection of a transport failure, this
message MUST NOT be sent to an alternate peer.
When Diameter is run over SCTP [RFC2960], which allows connections to
span multiple interfaces and multiple IP addresses, the Capabilities-
Update-Request message MUST contain one Host-IP-Address AVP for each
potential IP address that may be locally used when transmitting
Diameter messages.
Message Format
<CUR> ::= < Diameter Header: TBD2, REQ >
{ Origin-Host }
{ Origin-Realm }
1* { Host-IP-Address }
{ Vendor-Id }
{ Product-Name }
[ Origin-State-Id ]
* [ Supported-Vendor-Id ]
* [ Auth-Application-Id ]
* [ Acct-Application-Id ]
* [ Vendor-Specific-Application-Id ]
[ Firmware-Revision ]
* [ AVP ]
4.1.2. Capabilities-Update-Answer
The Capabilities-Update-Answer indicated by the Command-Code set to
<TBD3> and the Command Flags' 'R' bit set, is sent in response to a
CUR message.
Message Format
<CUA> ::= < Diameter Header: TBD3 >
{ Origin-Host }
{ Origin-Realm }
{ Result-Code }
[ Error-Message ]
* [ AVP ]
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5. IANA Considerations
This section explains the criteria to be used by the IANA for
assignment of numbers within namespaces used within this document.
5.1. Application Identifier
This specification assigns the value <TBD1> from the Application
Identifiers namespace defined in RFC 3588. See section Section 3 for
the assignment of the namespace in this specification.
5.2. Command Codes
This specification assigns the values <TBD2> and <TBD3> from the
Command Codes namespace defined in RFC 3588. See section Section 4.1
for the assignment of the namespace in this specification.
6. Security Considerations
This document does not introduce any new vulnerabilities into the
Diameter protocol.
7. References
7.1. 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.
7.2. Informative References
[RFC2960] Stewart, R., Xie, Q., Morneault, K., Sharp, C.,
Schwarzbauer, H., Taylor, T., Rytina, I., Kalla, M.,
Zhang, L., and V. Paxson, "Stream Control Transmission
Protocol", RFC 2960, October 2000.
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Authors' Addresses
Glen Zorn
Network Zen
1310 East Thomas Street
#306
Seattle, Washington 98102
USA
Phone: +1 (206) 377-9035
Email: gwz@net-zen.net
Jiao Kang
Huawei Technologies
Section B1, Huawei Industrial Base
Bantian, Longgang District
Shenzhen 518129
P.R. China
Phone: +86 755 28786690
Email: kangjiao@huawei.com
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