Internet Engineering Task Force (IETF) has recently been discussing the possibility of using the M and O flags in Router Advertisements to control the CE Router's DHCP client. After hosting our third IPv6 Customer Edge (CE) Router Interoperability Test Event, held November 7-11, 2011, the UNH-IOL documented the findings below.
What is interesting about the findings indicted in the table is that router behavior varies based on the M and O flags' configuration. Some implementations treated the O flag as an indicator for turning on Prefix Delegation. However, this behavior is not conformant to RFC 6204, which states Prefix Delegation should be performed regardless of the M and O flags' state. Other implementations ignored the flags altogether and always started DHCP IA_NA and IA_PD acquisition. The latter behavior is acceptable per RFC 6204. RFC 6204 is being updated to 6204bis (currently in draft form), but it states that DHCP Prefix Delegation should be done when either the M or O Flag is set to one. The varied behavior of the devices observed indicates a need for further clarification in the IETF regarding the relationship between the M and O flags and DHCP in CE Router implementations. From these observations, it is evident that current requirements have led to devices that react differently depending on the M and O flags configured. This results in confusion and misconfiguration for both administrators and operators as to how DHCP clients are operating.
Currently, the UNH-IOL is working with the IPv6 Forum to create an IPv6 Ready CPE logo program. This program is intended to help operators and equipment manufacturers understand what features will aid them in the worldwide deployment in IPv6. If you are interested in learning more about the status of IPv6 in CE routers or would like further analysis of test event results, please download our IPv6 CE Interoperability Whitepaper (PDF). You may also contact Timothy Winters for more information or to schedule testing.
Timothy Winters, Senior IP Manager