Diameter Predicted Units

When a User is authorized to use a service via Diameter applications such as or , the Client is not aware of the average load placed upon it by User. This can lead to overload situations or the Diameter Client redirecting or denying services to valid Users even though their presence may 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. 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: How the Diameter Server acquired the information contained in the Predicted-Service-UnitsAVP. How the values in the Predicted-Service-Units AVP were determined. The accuracy or validity of the values in the Predicted-Service-Units AVP. Specific actions the Diameter Client should take when its service functions are overloaded. Specific actions the Diameter Client takes to bring itself in/out of service for new or existing Users.

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

The Predicted-Service-Units AVP (AVP Code TBD1) is of type Grouped and contains the amount of units that the Diameter credit-control client can expect to provide to the end user until the service must be released or the new Credit-Control-Request must be sent, if a Granted-Service-Unit AVP has been applied to the user's service. A client is not required to implement all of the unit types, and it must ingore unknown or unsupported unit types. The Predicted-Service-Units AVP is defined as follows (per the grouped- avp-def of ):

[ CC-Time ] [ CC-Money ] [ CC-Total-Octets ] [ CC-Input-Octets ] [ CC-Output-Octets ] [ CC-Service-Specific-Units ] *[ Service-Cost-Information ] *[ AVP ] ]]> With the exception of the Service-Cost-Information AVP, all AVPs are defined in . 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.

The Service-Cost-Information AVP (AVP Code TBD2) is of type Grouped, and it is used to return the service cost information, which the client can use, if it understands it, for various purposes inclduing load prediction and sizing. 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]):

{ Unit-Value } { Cost-Unit } { Service-Dimension } ]]> Unit-Value and Cost-Unit are defined in .

The Service-Dimension AVP (AVP Code TBD3) is of type UTF8String. It specifies the applicable service type (dimension) to the Service-Cost-Information.

When Predicted-Service-Units are returned as part of an authorization per or , 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 it's projected load. Based upon this information it MAY take one or more of the following actions (this is not exhaustive): Redirect at the service / protocol level any new service requests. Begin enforcing mechanisms to reduce the amount of service load on a subset of services already established. Remove itself from any system that directs new service requests to it. Initiate administrative functions to increase its capacity or start the process of creating new intances to service requests.

IANA allocated AVP codes in the IANA-controlled namespace registry specified in Section 11.1.1 of for the following AVPs that are defined in this document. AVP AVP Code Section Defined Data Type Predicted-Service-Units TBD1 GROUPED Service-Cost-Information TBD2 GROUPED Service-Dimension TBD3 UTF8String

The Diameter base protocol 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 and CC- Request-Number, which is specified in this document. The Diameter credit-control application is often used within one domain, and there may be a single hop between the peers. 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 . 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; i.e., 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.