Diameter Maintenance and M. Jones
Extensions (DIME) Bridgewater Systems
Internet-Draft J. Korhonen
Updates: 3588 (if approved) Nokia Siemens Networks
Intended status: Standards Track September 2, 2010
Expires: March 6, 2011
Diameter Extended NAPTR
draft-ietf-dime-extended-naptr-02
Abstract
This document describes an extended format for the S-NAPTR
Application Service Tag used in dynamic Diameter agent discovery.
The extended format allows NAPTR queries to contain Diameter
Application-Id information.
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].
Status of this Memo
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Extended NAPTR Service Field Format . . . . . . . . . . . . . . 4
4. Extended NAPTR-based Diameter Peer Discovery . . . . . . . . . 5
5. Usage Guidelines . . . . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
6.1. IETF Diameter Application Service Tags . . . . . . . . . . 7
6.2. Vendor-Specific Diameter Application Service Tags . . . . . 7
6.3. Diameter Application Protocol Tags . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
The Diameter base protocol [RFC3588] specifies three mechanisms for
the Diameter peer discovery. One of these involves the Diameter
implementation performing a NAPTR query [RFC3403] for a server in a
particular realm. These NAPTR records provide a mapping from a
domain, to the SRV record [RFC2782] or A/AAAA record
[RFC1035][RFC3596] for contacting a server with the specific
transport protocol in the NAPTR services field.
The extended NAPTR usage for Diameter peer discovery defined by this
document is based on the Straightfoward-NAPTR (S-NAPTR) Dynamic
Delegation Discovery System (DDDS) Application defined in [RFC3958].
This document updates the Diameter peer discovery procedure described
in Section 11.6 of [RFC3588] and defines S-NAPTR Application Service
and Application Procotol Tag values that permit the discovery of
Diameter peers that support a specific Diameter application and
transport protocol.
2. Terminology
The Diameter base protocol specification (Section 1.4 of RFC 3588)
defines most of the terminology used in this document.
3. Extended NAPTR Service Field Format
The NAPTR Service Field format defined by the S-NAPTR DDDS in
[RFC3958] consists of a S-NAPTR Application Service tag and a S-NAPTR
Application Protocol tag delimited by a single colon (":") character.
The S-NAPTR Application Service Tag ABNF specification for the
discovery of Diameter agents supporting a specific Diameter
application is show below.
appln-svc-tag = iana-appln-tag / experimental-appln-tag
iana-appln-tag = "aaa+ap" appln-id
experimental-appln-tag = "x-aaa+ap" appln-id
appln-id = *DIGIT
; Application identifier expressed as a
; decimal integer.
As stated in [RFC3958], application service tags that start with "x-"
are considered experimental, and no provision is made to prevent
duplicate use of the same string. Implementors use them at their own
risk.
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The S-NAPTR Application Protocol Tag ABNF specification for the
discovery of Diameter agents supporting a specific Diameter transport
protocol is shown below.
appln-protocol-tag = "diameter." app-protocol
app-protocol = "tcp" / "sctp" / "tls.tcp"
For example, a NAPTR service field value of:
'aaa+ap6:diameter.sctp'
Means that the Diameter node in the SRV or A/AAAA record supports
the Diameter Session Initiation Protocol (SIP) Application ('6')
and SCTP as the transport protocol.
The maximum length of the NAPTR service field is 256 octets including
one octet length field (see Section 4.1 of RFC 3403 and Section 3.3
of [RFC1035]). The DNS administrator of some domain SHOULD also
provision base RFC 3588 style NAPTR records [RFC2915] in order to
guarantee backwards compatibility with legacy RFC 3588 compliant
Diameter peers. If the DNS administrator provisions both extended
S-NAPTR records as defined in this specification and legacy RFC 3588
NAPTR records, then the extended S-NAPTR records MUST have higher
priority (e.g. lower order and/or preference values) than legacy
NAPTR records.
4. Extended NAPTR-based Diameter Peer Discovery
The basic Diameter Peer Discover principles are described in Section
5.2 of [RFC3588]. This specification updates the NAPTR query
procedure in the Diameter peer discovery mechanism by allowing the
querying node to determine which applications are supported by
resolved Diameter peers.
The extended format NAPTR records provide a mapping from a domain, to
the SRV record or A/AAAA record for contacting a server supporting a
specific transport protocol and Diameter application. The resource
record will contain an empty regular expression and a replacement
value, which is the SRV record or the A/AAAA record for that
particular transport protocol. If the server supports multiple
transport protocols, there will be multiple NAPTR records, each with
a different Services Field value and potentially different list of
supported Diameter applications.
The assumption for this mechanism to work is that the DNS
administrator of the queried domain has first provisioned the DNS
with extended format NAPTR entries. The steps below replace the
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NAPTR query procedure steps in Section 5.2 of [RFC3588].
a. The Diameter implementation performs a NAPTR query for a server in
a particular realm. The Diameter implementation has to know in
advance which realm to look for a Diameter agent in and which
Application Identifier it is interested in. The realm could be
deduced, for example, from the 'realm' in a NAI that a Diameter
implementation needed to perform a Diameter operation on.
b. If the returned NAPTR service fields contain entries formatted as
"aaa+apX:Y" where "X" indicates the Application Identifier and "Y"
indicates the transport protocol, the target realm supports the
extended format for NAPTR-based Diameter peer discovery defined in
this document.
If "X" contains the required Application Identifier and "Y"
matches a transport protocol supported by the client, the
client resolves the "replacement" field entry to a target host
using the lookup method appropriate for the "flags" field.
If "X" does not contain the required Application Identifier or
"Y" does not match a transport protocol supported by the
client, the peer discovery is abandoned.
c. If the returned NAPTR service fields contain entries formatted as
"AAA+D2X" where "X" indicates the transport protocol, the target
realm supports the NAPTR-based Diameter peer discovery defined in
[RFC3588].
If "X" matches a transport protocol supported by the client,
the client continues processing the NAPTR as described in
[RFC3588] and [RFC2915].
If "X" does not match a transport protocol supported by the
client, the peer discovery is abandoned.
d. If the target realm does not support NAPTR-based Diameter peer
discovery, the client proceeds with the next peer discovery
mechanism described in Section 5.2 of [RFC3588].
5. Usage Guidelines
Diameter is a peer to peer protocol whereas most of the applications
that extend the base protocol behave like client/server applications.
The role of the peer is not advertised in the NAPTR tags and not even
communicated during Diameter capability negotiation (CER/CEA). For
this reason, NAPTR-based Diameter peer discovery for an application
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defining client/server roles should only be used by a client to
discover servers.
6. IANA Considerations
6.1. IETF Diameter Application Service Tags
IANA is requested to reserve the following S-NAPTR Application
Service Tags for existing IETF Diameter applications:
+------------------+----------------------------+
| Tag | Diameter Application |
+------------------+----------------------------+
| aaa+ap1 | NASREQ [RFC3588] |
| aaa+ap2 | Mobile IPv4 [RFC4004] |
| aaa+ap3 | Base Accounting [RFC3588] |
| aaa+ap4 | Credit Control [RFC4006] |
| aaa+ap5 | EAP [RFC4072] |
| aaa+ap6 | SIP [RFC4740] |
| aaa+ap7 | Mobile IPv6 IKE [RFC5778] |
| aaa+ap8 | Mobile IPv6 Auth [RFC5778] |
| aaa+ap9 | QoS [RFC5866] |
| aaa+ap4294967295 | Relay [RFC3588] |
+------------------+----------------------------+
Future IETF Diameter applications MUST reserve the S-NAPTR
Application Service Tag corresponding to the allocated Diameter
Application ID.
6.2. Vendor-Specific Diameter Application Service Tags
Vendor-Specific Diameter Application IDs are allocated by IANA
according to the "First Come First Served" policy and do not require
an IETF specification. However, the S-NAPTR Application Service Tag
registry created by [RFC3958] defines a registration policy of
"Specification Required" with a further stipulation that the
"specification" is an RFC (of any category). If a Vendor-Specific
Diameter Application requires the functionality defined in this
document, an RFC of any category MUST be published which reserves the
S-NAPTR Application Service Tag corresponding to the Vendor-Specific
Diameter Application ID.
6.3. Diameter Application Protocol Tags
IANA is requested to reserve the following S-NAPTR Application
Protocol Tags for the Diameter transport protocols:
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+------------------+----------+
| Tag | Protocol |
+------------------+----------+
| diameter.tcp | TCP |
| diameter.sctp | SCTP |
| diameter.tls.tcp | TLS/TCP |
+------------------+----------+
7. Security Considerations
This document specifies an enhancement to RFC 3588 Diameter base
protocol defined NAPTR service field format and also modifications to
the NAPTR processing logic defined. The enhancements and
modifications are based on the S-NAPTR, which is actually a
simplification of the NAPTR, and therefore the same security
considerations described in RFC 3588 are applicable to this document.
No further extensions are required beyond the security mechanisms
offered by RFC 3588. However, a malicious host doing S-NAPTR queries
learns applications supported by Diameter agents in a certain realm
faster, which might help the malicious host to scan potential targets
for an attack more efficiently when some applications have known
vulnerabilities.
8. References
8.1. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[RFC3403] Mealling, M., "Dynamic Delegation Discovery System (DDDS)
Part Three: The Domain Name System (DNS) Database",
RFC 3403, October 2002.
[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
[RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,
"DNS Extensions to Support IP Version 6", RFC 3596,
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October 2003.
[RFC3958] Daigle, L. and A. Newton, "Domain-Based Application
Service Location Using SRV RRs and the Dynamic Delegation
Discovery Service (DDDS)", RFC 3958, January 2005.
[RFC4004] Calhoun, P., Johansson, T., Perkins, C., Hiller, T., and
P. McCann, "Diameter Mobile IPv4 Application", RFC 4004,
August 2005.
[RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J.
Loughney, "Diameter Credit-Control Application", RFC 4006,
August 2005.
[RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible
Authentication Protocol (EAP) Application", RFC 4072,
August 2005.
[RFC4740] Garcia-Martin, M., Belinchon, M., Pallares-Lopez, M.,
Canales-Valenzuela, C., and K. Tammi, "Diameter Session
Initiation Protocol (SIP) Application", RFC 4740,
November 2006.
[RFC5778] Korhonen, J., Tschofenig, H., Bournelle, J., Giaretta, G.,
and M. Nakhjiri, "Diameter Mobile IPv6: Support for Home
Agent to Diameter Server Interaction", RFC 5778,
February 2010.
[RFC5866] Sun, D., McCann, P., Tschofenig, H., Tsou, T., Doria, A.,
and G. Zorn, "Diameter Quality-of-Service Application",
RFC 5866, May 2010.
8.2. Informative References
[RFC2915] Mealling, M. and R. Daniel, "The Naming Authority Pointer
(NAPTR) DNS Resource Record", RFC 2915, September 2000.
Authors' Addresses
Mark Jones
Bridgewater Systems
Email: mark@azu.ca
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Jouni Korhonen
Nokia Siemens Networks
Email: jouni.nospam@gmail.com
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