[Mip4] Regarding MN-AAA extension

Hi all,

I have a doubt regarding MN-AAA extension. Please help me to solve this.

When the mobile node has sent a request with MN-AAA extension, what are the
parameters to be filled in each field of the Radius request? 

The draft draft-ietf-mobileip-radius-challenge-00 says: 

The CHAP-ID octet of the RADIUS CHAP-password attribute will contain the
last byte of the Challenge value from MIP FA Challenge extension[6].  The
authenticator from the MN-AAA Authentication extension MUST be used as the
CHAP-Password attribute. The User-Name attribute MUST be populated with the
user-name attribute from the AMR message. The following data stream, as
described earlier, MUST be included in the CHAP- Challenge attribute:

Preceding Mobile IP data || Type, Length, SPI.

We made CHAP-ID as the last byte of the challenge value from MIP FA
Challenge extension, Password as the authenticator from MN-AAA extension,
and username attribute is also correct. In CHAP-Challenge field, currently
we are filling the MD5 checksum of the preceding mobile ip data || Type,
Length, SPI. Is this correct? How can we fill the preceding mobile IP data
as it is since size of the data can vary each time?

Now the radius server is rejecting the request every time. What are the
correct parameters to be filled?

Please do reply.

Thanks & Regards

Manju

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