The Mobile Node shall attempt the registration with only one Foreign Agent at a time. The storage allocation of the Challenges at the Mobile Node received from different Foreign Agents is implementation specific.
The following text modifications are proposed in section 2 to clarify the above point:
The Challenge extension, illustrated in figure 1, is inserted in the Agent Advertisements by the Foreign Agent, in order to communicate the latest challenge value that can be used by the mobile node to compute an authentication for its next registration request message. The challenge is selected by the foreign agent to provide local assurance that the mobile node is not replaying any earlier registration request. Eastlake, et al. [5] provides more information on generating pseudo-random numbers suitable for use as values for the challenge.
The Challenge extension, illustrated in figure 1, is inserted in the Agent Advertisements by the Foreign Agent, in order to communicate the latest challenge value that can be used by the mobile node to compute an authentication for its next registration request message. The challenge is selected by the foreign agent to provide local assurance that the mobile node is not replaying any earlier registration request. Eastlake, et al. [5] provides more information on generating pseudo-random numbers suitable for use as values for the challenge.
Note that the storage of different Challenges received in Agent Advertisements from multiple Foreign Agents is implementation specific and hence, out of scope for this specification.