Mobile IP Registration 45
Reverse Tunneling Flag—The Mobile Node would like traffic to be reverse tunneled.
Lifetime—This is the length of time in seconds that the Mobility Agent can retain an
active binding. The lifetime value can range from 0 to 65,535 seconds. If the lifetime is 0,
the Mobile Node is deregistering. A lifetime value of 65,535 is infinite.
Home Address—This is the Mobile Node’s Home Address. If the Home Address is set to, the Mobile Node would like a Home Address to be dynamically allocated.
Home Agent—This is the IP address of the Mobile Node’s Home Agent. This can be if dynamic Home Agent assignment is being used.
CoA—This is the address that the Mobile Node would like all traffic tunneled to.
Identification—The identification field prevents replay attacks. It is usually represented
as an NTP-style timestamp.
Extensions—These begin with a type and length and then are followed by extension-
specific data.
Registration Reply Codes
A RRP is sent either by a FA or a Home Agent in response to a RRQ. In the case of an FA-CoA,
if the FA accepts the RRQ from the Mobile Node, it forwards the request to the Home Agent.
However, if the FA rejects the RRQ or cannot forward the request to the Home Agent, it
immediately sends a RRP with an appropriate error code, and does not propagate the reply to
the Home Agent. Similarly, if the FA receives a RRP from the Home Agent and deems the reply
to be invalid, it generates a new RRP with the appropriate error code. The possible FA reply
codes are as follows:
64 reason unspecified
65 administratively prohibited
66 insufficient resources
67 mobile node failed authentication
68 home agent failed authentication
69 requested Lifetime too long
70 poorly formed Request
71 poorly formed Reply
72 requested encapsulation unavailable
73 reserved and unavailable
77 invalid care-of address
78 registration timeout
80 home network unreachable (ICMP error received)
81 home agent host unreachable (ICMP error received)
82 home agent port unreachable (ICMP error received)
88 home agent unreachable (other ICMP error received)
The FA attempts to use a specific reply code so that the Mobile Node knows why the registration
was rejected. For example, the FA can send back error code 72 to indicate that the requested

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