Jean-Michel Combes | 9 Dec 17:17 2010

RFC3971: clarification about destination address for CPS messages


I have an issue with text in RFC3971 regarding the ADD process and
especially the destination address for CPS messages sent by a host.

Section 6.4.6 mentions:
"When soliciting certificates for a router, a host MUST send
Certification Path Solicitations either to the All-Routers multicast
address, if it has not selected a default router yet, or to the
default router's IP address, if a default router has already been

Section 6.4.1 confirms that destination address is either All-Routers
multicast address or the default router's IP address:
"Destination Address
         Typically the All-Routers multicast address, the
Solicited-Node multicast address, or the address of the host's default

I don't understand why the CPS message is not sent directly (i.e.
unicast address) to the router advertising the RA message (which
triggers the sending of the CPS message) received by the host.

Thanks in advance for any clarification!

Best regards.