Diameter Maintenance and Extensions L. Bertz
Internet-Draft Sprint
Intended status: Standards Track June 29, 2017
Expires: December 31, 2017

Diameter Predicted Units


This document specifies the conveyance of predicted usage information for proper dimensioning of network services that use Diameter based authorization.

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 December 31, 2017.

Copyright Notice

Copyright (c) 2017 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 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.

This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English.

Table of Contents

1. Introduction

When a User is authorized to use a service via Diameter applications such as [RFC4006] or [RFC7155], the Client is not aware of the average load placed upon it by the User. This can lead to overload situations or Diameter Clients being too conservative and denying services to valid Users even whose presence would not overload the service.

Given virtualization and the use of many software based services the service capacity varies on a service instance, i.e. Diameter Client, basis. Even though the Diameter Client is the same softawre it will vary in terms of the load it can accept. Thus, a Diameter Server cannot depend upon consistent capacities of a Diameter Client.

This specification introduces the Predicted-Service-Units Attribute Value Pair (AVP). This information conveys the predicted usage introduced on the service by the authorized User. Such information can be used by the Diameter Client to estimate future load and proactively manage its resources.

Although this informaiton is conveyed from the Diameter Server to the Client several system aspects are out of the scope of this document:

When the value(s) or multiple types of Costs are provided they are represented by the Time-Of-Day-Condition AVP defined in [RFC5777] and contained in a Predicted-Service-Units-Series AVP. This AVP contains one or more Predicted-Service-Units. Multiple Cost types, e.g. CC-Total-Octets and CC-Time, may be represented in the same Predicted-Service-Units entry and in the same Predicted-Service-Units-Series so long as no overlapping times exist for the same Cost Type.

2. Terminology

In this document, the key words "MAY", "MUST", "MUST NOT", "OPTIONAL", "RECOMMENDED", "SHOULD", and "SHOULD NOT", are to be interpreted as described in [RFC2119].

3. Predicted Service AVPs

3.1. Predicted-Service-Units

The Predicted-Service-Units AVP (AVP Code TBD1) is of type Grouped and contains the amount of units that the Diameter Client can expect to provide to the end user until the service must be released or the new service authorizatoin request, e.g. Credit-Control-Request, must be sent if a Granted-Service-Unit AVP [RFC4006] has been applied to the user's service. A client is not required to implement all of the unit types, and it MUST ignore unknown or unsupported unit types.

The Predicted-Service-Units AVP is defined as follows (per the grouped- avp-def of [RFC6733]):

         Predicted-Service-Units ::= < AVP Header: TBD1 >
                                    [ CC-Time ]
                                    [ CC-Money ]
                                    [ CC-Total-Octets ]
                                    [ CC-Input-Octets ]
                                    [ CC-Output-Octets ]
                                    [ CC-Service-Specific-Units ]
                                    [ Time-Of-Day-Condition ]
                                   *[ AVP ]

The Time-Of-Day-Condition AVP is defined in [RFC5777], all other AVPs are defined in [RFC4006].

The presence of this information is provided as anticipated load information to the Diameter Client and is not intended to be prescriptive in any manner regarding the user's service.

When the Time-Of-Day-Condition AVP is not present, the value(s) are assumed to apply for the duration of the authorized session until this value is updated as part of the Diameter application, e.g. a Diameter Re-Auth-Request/Answer (RAR/RAA) message [RFC6733].

3.2. Predicted-Service-Units-Series

The Predicted-Service-Units-Series AVP (AVP Code TBD2) is of type Grouped, and contains one or more Predicted-Service-Units with non-overlapping times for each specific Cost type.

A client is not required to implement all of the unit types, and it MUST ingore unknown or unsupported unit types.

It is defined as follows (per the grouped-avp-def of [RFC6733]):

          Predicted-Service-Units-Series ::= < AVP Header: TBD2 >
                                    1*{ Predicted-Service-Units }

For each specific type of Cost, e.g. CC-Time, any two Predicted-Service-Units values in the series MUST NOT contain overlapping time windows specified in their Time-Of-Day-Condition values. When an entry has no Time-Of-Day-Condition present it is assumed to apply at all times.

4. Usage Examples

When Predicted-Service-Units are returned as part of an authorization per [RFC7155] or [RFC4006], the client MAY use this information as guidance on projected load the new user will generate on the service.

If the client supports/understnds the information provided in the Predicted-Service-Units AVP, it can update its projected load. Based upon this information it MAY take one or more of the following actions (this is not exhaustive):

5. IANA Considerations

IANA allocated AVP codes in the IANA-controlled namespace registry specified in Section 11.1.1 of [RFC6733] for the following AVPs that are defined in this document.

AVP AVP Code Section Defined Data Type
Predicted-Service-Units TBD1 Section 3.1 GROUPED
Predicted-Service-Units-Series TBD2 Section 3.2 GROUPED

6. Security Considerations

The Diameter base protocol [RFC6733] requires that each Diameter implementation use underlying security; i.e., TLS/TCP, DTLS/SCTP or IPsec. These mechanisms are believed to provide sufficient protection under the normal Internet threat model; that is, assuming that the authorized nodes engaging in the protocol have not been compromised, but that the attacker has complete control over the communication channels between them. This includes eavesdropping, message modification, insertion, and man-in-the-middle and replay attacks. Note also that this application includes a mechanism for application layer replay protection by means of the Session-Id from [RFC6733]. In these environments, the use of TLS/TCP, DTLS/SCTP or IPsec is sufficient. The details of TLS/TCP, DTLS/SCTP or IPsec related security considerations are discussed in the [RFC6733].

Because this application conveys past usage information (directly or indirectly), it increases the interest for various security attacks. Therefore, all parties communicating with each other MUST be authenticated, including, for instance, TLS client-side authentication. In addition, authorization of the client SHOULD be emphasized; e.g., that the client is allowed to perform credit- control for a certain user. The specific means of authorization are outside of the scope of this specification but can be, for instance, manual configuration.

The attributes provided by this solution MUST be assumed to be privacy sensitive by both the client and server.

7. References

7.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M. and J. Loughney, "Diameter Credit-Control Application", RFC 4006, DOI 10.17487/RFC4006, August 2005.
[RFC5777] Korhonen, J., Tschofenig, H., Arumaithurai, M., Jones, M. and A. Lior, "Traffic Classification and Quality of Service (QoS) Attributes for Diameter", RFC 5777, DOI 10.17487/RFC5777, February 2010.
[RFC6733] Fajardo, V., Arkko, J., Loughney, J. and G. Zorn, "Diameter Base Protocol", RFC 6733, DOI 10.17487/RFC6733, October 2012.

7.2. Informative References

[RFC7155] Zorn, G., "Diameter Network Access Server Application", RFC 7155, DOI 10.17487/RFC7155, April 2014.

Author's Address

Lyle Bertz Sprint 6220 Sprint Parkway Overland Park, KS 66251 United States EMail: lylebe551144@gmail.com