Modification to Default Values of SOL_MAX_RT and INF_MAX_RT
obsoleted by
- rfc-8415 — Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
updates
- rfc-3315 — Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
Extracted elements (17)
The default values of SOL_MAX_RT and INF_MAX_RT were raised from 120 seconds to 3600 seconds because deployments observed unacceptably high aggregated DHCPv6 traffic when many clients sent Solicit messages to a server configured not to respond. The change reduces long-term retransmission frequency from every 2 minutes to every hour.
There are no additional requirements for DHCPv6 relay agents with respect to SOL_MAX_RT and INF_MAX_RT options; relays handle these options transparently.
A client MUST ignore any Advertise message that includes a Status Code option with NoAddrsAvail, except that it MUST process an included SOL_MAX_RT option and MUST process an included INF_MAX_RT option. This updates RFC 3315 Section 17.1.3.
A DHCPv6 client MUST include the INF_MAX_RT option code in any Option Request option it sends, as required by RFC 3315.
A DHCPv6 client MUST include the SOL_MAX_RT option code in any Option Request option it sends, as required by RFC 3315.
A DHCPv6 client MUST silently ignore any SOL_MAX_RT or INF_MAX_RT option values that are less than 60 or more than 86400.
If a DHCPv6 client receives a message containing an INF_MAX_RT option with a valid value, the client MUST set its internal INF_MAX_RT parameter to that value, which is then used by the retransmission mechanism in RFC 3315 Sections 14 and 18.1.5.
If the server will not assign any addresses, it MUST send an Advertise with NoAddrsAvail and MAY also include SOL_MAX_RT and/or INF_MAX_RT options. This updates RFC 3315 Section 17.2.2.
The default value of INF_MAX_RT is updated from 120 seconds to 3600 seconds, reducing the maximum Information-request retransmission interval for clients that do not receive a satisfactory response.
The default value of SOL_MAX_RT is updated from 120 seconds to 3600 seconds, reducing the maximum Solicit retransmission interval for clients that do not receive a satisfactory response.
Updated SOL_MAX_RT and INF_MAX_RT values apply only to the network interface on which the client received the corresponding options; they do not propagate to other interfaces.
The DHCPv6 server MAY include the INF_MAX_RT option in any response to a client that requested it via Option Request option. The option MUST be sent in the main body of the message, not encapsulated inside IA_NA, IA_TA, or IA_PD options.
The DHCPv6 server MAY include the SOL_MAX_RT option in any response to a client that requested it via Option Request option. The option MUST be sent in the main body of the message, not encapsulated inside IA_NA, IA_TA, or IA_PD options.
IANA assigned option code 82 for OPTION_SOL_MAX_RT and option code 83 for OPTION_INF_MAX_RT from the 'DHCP Option Codes' table of the DHCPv6 registry.
A malicious DHCPv6 server could set SOL_MAX_RT and INF_MAX_RT to unreasonably high values, causing undue delays in a client completing its DHCPv6 transaction when no other valid response is received. If a valid server also responds, large override values have no effect.
The INF_MAX_RT option (OPTION_INF_MAX_RT, option-code 83) carries a 32-bit unsigned integer INF_MAX_RT value in seconds, with option-len fixed at 4. The value MUST be in the range 60 to 86400 seconds.
The SOL_MAX_RT option (OPTION_SOL_MAX_RT, option-code 82) carries a 32-bit unsigned integer SOL_MAX_RT value in seconds, with option-len fixed at 4. The value MUST be in the range 60 to 86400 seconds.