Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Relay Agent Subscriber-ID Option
Extracted elements (10)
The format and encoding of subscriber-id data is intentionally not standardized because the option is only intended for use within a single administrative domain, exchanged only between relay agents and DHCPv6 servers within that domain. No semantic requirements are imposed on the data.
The subscriber-id is intended to be stable as customers connect through different paths and as network changes occur, decoupling subscriber identity from physical network topology. This allows service providers to assign subscriber-specific actions (addresses, prefixes, DNS, accounting) without reconfiguration when a subscriber moves between access points.
In environments where both DHCPv4 and DHCPv6 are deployed, it may be beneficial to use NVT ASCII encoding for the subscriber-id, consistent with the DHCPv4 Subscriber-ID suboption (RFC 3993).
DHCPv6 relay agents MAY be configured to include a Subscriber-ID option in relayed (RELAY-FORW) DHCPv6 messages.
The DHCPv6 server MAY use the Subscriber-ID option information, if available, in addition to other relay agent option data, client options, and physical network topology to assign addresses, delegate prefixes, and configuration parameters.
There is no requirement that a server return the Subscriber-ID option and its data in a RELAY-REPLY message.
The Relay Agent Subscriber-ID option (OPTION_SUBSCRIBER_ID, code 38) carries a variable-length subscriber identity value. It consists of a 2-octet option-code, 2-octet option-len, and a subscriber-id field of at least 1 octet.
IANA assigned DHCPv6 option code 38 for the Relay Agent Subscriber-ID Option (OPTION_SUBSCRIBER_ID).
Since the Subscriber-ID option is only exchanged between relay agents and DHCPv6 servers, RFC 3315 Section 21.1 provides details on securing DHCPv6 messages between servers and relay agents, and Section 23 covers general DHCPv6 security considerations.
The Subscriber-ID option encodes as: OPTION_SUBSCRIBER_ID (38) in 16 bits, option-len in 16 bits (minimum 1), followed by the variable-length subscriber-id field. The encoding of the subscriber-id data is not standardized by this specification.