RADIUS Delegated-IPv6-Prefix [RFC4818] AVPs
RADIUS Delegated-IPv6-Prefix Attribute
The RADIUS Delegated-IPv6-Prefix Attribute is defined to carry an IPv6 prefix that is delegated to a user for use within the user’s network. This attribute is particularly useful in scenarios such as DHCP Prefix Delegation, where a delegating router obtains an IPv6 prefix from a RADIUS server and then assigns it to a requesting router or node.
Purpose of the RADIUS Delegated-IPv6-Prefix Attribute
- IPv6 Prefix Delegation: The attribute carries an IPv6 prefix that can be assigned to a user’s network. For example, the delegated prefix may be further allocated to other nodes via DHCP Prefix Delegation.
- Enhanced Network Address Management: By providing a mechanism for dynamic prefix delegation, this attribute facilitates efficient IPv6 address management and ensures that users receive the appropriate subnet resources for their network operations.
Key Elements and Operational Workflow
Attribute Structure:
- Value Type: The Delegated-IPv6-Prefix attribute is defined as an OctetString, encapsulating the IPv6 prefix data.
- Coexistence with Other Attributes: The Framed-IPv6-Prefix attribute is not designed for delegating prefixes for use within the user's network. Therefore, both the Framed-IPv6-Prefix and Delegated-IPv6-Prefix attributes may appear together in the same RADIUS packet if needed.
Message Sequence for DHCP Prefix Delegation (In a typical deployment):
- A Requesting Router initiates the process by sending a solicitation for an IPv6 prefix.
- The Delegating Router forwards a request to the RADIUS server.
- The RADIUS server processes the request and responds with an accept message that includes the Delegated-IPv6-Prefix attribute.
- The Delegating Router then advertises the received prefix to the Requesting Router, completing the prefix delegation cycle.
Diameter Considerations
- Interoperability: When used in Diameter, the attribute is treated as a Diameter AVP within the RADIUS attribute compatibility space (Codes 1–255), meaning no additional Diameter Code values are needed.
- Translation and Consistency: The Delegated-IPv6-Prefix attribute is copied directly between RADIUS and Diameter, with only necessary changes in headers, alignment, and padding. The same applicability rules used in RADIUS for Access-Request, Access-Accept, and Accounting-Request also apply in Diameter (AA-Request, AA-Answer, and Diameter Accounting-Request).
- AVP Flag Rules: The attribute is subject to specific AVP flag rules which require it to be mandatory (MUST) in certain contexts, optionally present (MAY) in others, and must be encrypted (Encr: Y) as per the protocol specifications.
IANA Considerations
- IANA has assigned a Type value of 123 for the Delegated-IPv6-Prefix attribute in the RADIUS Attribute Types registry, ensuring its standardized identification and interoperability across different implementations.
For complete technical specification of RADIUS Delegated-IPv6-Prefix Attribute in Diameter protocol please refer to: [RFC4818]
package com.mobius.software.telco.protocols.diameter.primitives.rfc4818
|
Name |
AVP Code |
Data Type |
Vendor |
|
Delegated-IPv6-Prefix |
123 |
OctetString |
IETF |
|
Used to carry an IPv6 prefix that can be delegated to a client or network device. It provides information about the prefix length and the actual prefix data, enabling support for IPv6 address delegation scenarios. This AVP is primarily utilized in Access-Accept packets to assign prefixes to clients. It can also be included in Access-Request packets as a hint by the NAS (Network Access Server) to suggest preferred prefixes, although the server is not obligated to honor the hint. The format of the Delegated-IPv6-Prefix AVP is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | Prefix-Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Prefix +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Parameters: Type (8 bits): Fixed value 123 indicating the AVP type for Delegated-IPv6-Prefix. Length (8 bits): Specifies the length in bytes of the attribute. Minimum: 4 bytes for a 0-bit prefix. Maximum: 20 bytes for a 128-bit prefix. Reserved (8 bits): Set to zero by the sender and ignored by the receiver. Prefix-Length (8 bits): Represents the length of the prefix in bits. Range: 0 to 128 bits. A length of 128 specifies a single IPv6 address. Prefix (Variable): Contains the IPv6 prefix data. Only the required prefix bits are included, and the unused bits MUST be zero. The AVP can repeat multiple times to delegate more than one IPv6 prefix in the same session. |
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