AVP (Attribute Value Pair) is a fundamental data structure in Diameter protocol, used to communicate configuration and control information. AVPs contain specific data attributes that are necessary for managing user sessions, authentication, authorization, accounting, and other functions in network communications. Here’s a breakdown:
- Structure of an AVP:
- An AVP has three main components: the Attribute (what type of data the AVP represents), the Value (the data itself), and optional metadata for the AVP’s behavior or attributes.
- AVPs are identified by a unique AVP Code and are designed to be flexible. They can contain values such as strings, integers, IP addresses, or other data types.
- Purpose:
- AVPs convey specific information or attributes between Diameter nodes (e.g., clients and servers).
- They define policy and control parameters that handle the various aspects of network sessions, such as user identity, bandwidth usage, quality of service, or PDN type.
- Behavior and Flags:
- Each AVP can have several flags (e.g., Mandatory, Vendor-Specific), which help govern how the AVP should be processed. For instance:
- Mandatory Flag: Indicates that a Diameter node must understand and process this AVP; otherwise, it rejects the message.
- Vendor-Specific Flag: Signifies that the AVP is defined by a specific vendor and may be interpreted differently based on the vendor’s protocol.
- Each AVP can have several flags (e.g., Mandatory, Vendor-Specific), which help govern how the AVP should be processed. For instance:
- Examples of AVPs:
- User-Name AVP: Contains a user identifier for authenticating a session.
- Session-Timeout AVP: Specifies the time after which a session should expire.
- PDN-Type AVP: Indicates the type of IP version support available on the PDN (e.g., IPv4, IPv6).