It is possible for a mobile node to solicit agent advertisement to avoid waiting for an agent to advertise. Some may choose not to advertise at all, for example, agents residing on a link where some form of agent discovery is possible through the use of a link layer protocol. This is permitted by the Mobile IP standard.
Mobile IP agent advertisements uses the same procedures, defaults and constants as specified for ICMP router discovery (advertisement and solicitation) except for the following :
Solicitations should only be sent by the MN in the absence of agent advertisements and when a care-of address have not been determined by other means. For example, through some link-layer protocol or when using a colocated care-of address acquired through DHCP. When using solicitations the MN has to obey the same rules as a node sending normal ICMP router discovery solicitations. Except that the MN may solicit more often than once every three seconds and a mobile node that is not connected to a FA may solicit more than MAX_SOLICITATIONS (see ).
A MN is required to limit the rate at which it sends solicitations. It may initially send three solicitations once a second, after this it must use a exponential backoff algorithm to reduce the rate until a maximum delay has been reached. The MN uses the mobility agent advertisement extension to distinguish between mobility agent advertisements and normal uses of the ICMP protocol.