Dynamics
Mobile Node Signaling State Machine	$Revision: 1.3 $	State approved
Date 08-Dec-1998	Author Jari Hautio
Review date 10-Dec-1998	Reviewed by Jouni Malinen
Approval date 10-Dec-1998	Approved by Jouni Malinen

$Id: mn_machine.html,v 1.3 1998/12/09 23:46:03 jkmaline Exp $

Mobile Node Signaling State Machine

Signaling State machine has following states:

Startup - Initial state, mobility variables are uninitalized
Disconnected - Mobility variables have been initialized, but tunneling is not activated.
Find_agent - Mobile Node seeks mobility agent for tunneling and sends Solicitation messages
Passive_find - Mobile Node waits for an advertisement message passively.
Request_tunnel - Mobile tries to register tunnel nd waits for Registration Reply
Forced_request - Mobile tries to confirm the tunnel using Registration request messages
Connected - The tunnel has been established, timer is used to refresh the tunnel when half of the remaining lifetime is left.
Close_for_Home - Mobile in Home network, closing tunnel
At_home - Mobile is in home network, no tunneling, but if mobile moves to another network tunnel is automatically established
Error - An unrecoverable error has been encountered and machine will be restarted

Transitions are presented state by state. For all transitions are stated input conditions for the transition, output when the transition occurs and changes to variables. Changes to variables must be done before any output is processed. All states have transition to Error state, which is taken when an error occurs. If no transition is available for a message or input, nothing is done, and current state is kept.

Objects and variables used in state machine:

FA - Address of closest foreign agent
Sequence Number - Storage for last heard Mobility Agent Advertisement message
Timer - Timer, which generates a timer expiration event to machine input, when in times out.
Lifetime_left - Variable indicating lifetime left for the tunnel
Adv_timer - Timer, which indicates advertisement lifetime left for a heard advertisement
Reply_timer - Timer to measure time needed for registration.

State Machine

State: Startup

Transition: Initialize

Input: -
Output: Log agent startup message
Variables: Read configuration information from ini-file and initialize variables
Next State: Disconnected

State: Disconnected

Transition: Create_Tunnel

Input: API Call "Create Tunnel"
Output: Broadcast Mobile Agent Solicitation Message
Variables: Set Timer to X
Next State: Find_agent

State: Find_agent

Transition: Timer

Input: Timer expires
Output: Broadcast Mobile Agent Solicitation message
Variables: Set Timer to X
Next State: Find_agent

Transition: Foreign_Advertisement

Input: Mobile Agent Advertisement message from foreign agent
Output: Send Registration Request to FA
Variables: Set Timer to X, set FA to advertised agent, Store Sequence Number, start Reply_timer, set Adv_timer
Next State: Request_Tunnel

Transition: Home_Advertisement

Input: Mobile Agent Advertisement message from home agent
Output: -
Variables:
Next State: At_Home

Transition: Disconnect

Input: API Call "Disconnect"
Output:
Variables: -
Next State: Disconnected

Transition: Location_Update

Input: API Call "Location Update"
Output: Mobile Agent Solicitation message
Variables: Set Timer to X
Next State: Find_agent

Transition: Too_Many_Retries

Input Retry counter expires
Output: -
Variables: -
Next State: Passive_Find

Transition: Home_Update

Input: Api Call "Home Update"
Output: -
Variables:
Next State: At_Home

State: Request_Tunnel

Transition: Timer

Input: Timer expires
Output: Send Registration Request to FA
Variables: Set Timer to X
Next State: Request_Tunnel

Transition: Adv_Lifetime Ends

Input: Adv_timer for MA Advertisement expires
Output: Broadcast Mobile Agent Solicitation message
Variables: Set Timer to X
Next State: Find_Agent

Transition: Disconnect

Input: API Call "Disconnect"
Output:
Variables: -
Next State: Disconnected

Transition: Location_Update

Input: API Call "Location Update"
Output: Mobile Agent Solicitation message
Variables: Set Timer to X
Next State: Find_agent

Transition: Reply_Accept

Input: Registration Reply, accepting the tunnel
Output: -
Variables: Set Lifetime_left to replied lifetime - Reply_timer,
Set Timer to Lifetime / 2,
Start tunneling
Next State: Connected

Transition: Reply_Deny

Input: Registration Reply, tunnel rejected
Output: Log error
Variables: Stop tunneling
Next State: Depends on error Disconnected, if unrecovarable error, else Find Agent or Reques Tunnel

Transition: Home_Update

Input: Api Call "Home Update"
Output: Send Registration Request with zero lifetime to HA
Variables: Set Timer to X
Next State: Close_for_Home

State: Connected

Transition: Timer

Input: Timer expires
Output: Registration Request
Variables: Set Timer to Max(Lifetime_left / 2,Min_Timeout),
Set Lifetime_left toLifetime_left /2
Next State: Connected

Transition: Location_Update

Input: API Call "Location Update"
Output: Mobile Agent Solicitation message
Variables: Set Timer to X, stop tunneling
Next State: Find_Agent

Transition: Home_Update

Input: Api Call "Home Update"
Output: Send Registration Request with zero lifetime to HA
Variables: Set Timer to X
Next State: Close_for_Home

Transition: Agent_Reboot

Input: Mobility Agent Advertisement with lower Sequence Number than last time (stored seq.n.)
Output: Send Registration Request to FA
Variables: Set Timer to X, Store Sequence Number, start Reply_timer, set Adv_timer
Next State: Request_Tunnel

Transition: Forced_Request

Input: API call "Confirm"
Output: Send Registration Request with force bit on
Variables: Set call variables, Set Timer to Retry interval
Next State: Forced_Request

State: Forced_Request

Transition: Timer

Input: Timer expires
Output: Registration Request, force bit on
Variables: Set Timer to retry interval
Next State: Forced_Request

Transition: Location_Update

Input: API Call "Location Update"
Output: Mobile Agent Solicitation message
Variables: Set Timer to X, stop tunneling
Next State: Find_Agent

Transition: Agent_Reboot

Input: Mobility Agent Advertisement with lower Sequence Number than last time (stored seq.n.)
Output: Send Registration Request to FA, force bit on
Variables: Set Timer to X, Store Sequence Number, start Reply_timer, set Adv_timer
Next State: Forced_Request

Transition: Reply_Home

Input: Accepting Registration Reply from Home Agent
Output: Return Api Call with success
Variables: Set lifetime_left and Set Timer to Lifetime / 2
Next State: Connected

Transition: Home_Update

Input: Api Call "Home Update"
Output: Send Registration Request with zero lifetime to HA
Variables: Set Timer to X
Next State: Close_for_Home

State: Error

Transition: Reset

Input: -
Output: Log error
Variables: Stop tunneling
Next State: Startup

State: Close_for_Home

Transition: Timer

Input: Timer expires
Output: Registration Request, lifetime = 0
Variables: Set Timer to X
Next State: Close_for_Home

Transition: Location_Update

Input: API Call "Location Update"
Output: Mobile Agent Solicitation message
Variables: Set Timer to X
Next State: Find_Agent

Transition: Home_Reply

Input: Registration Reply from HA
Output: -
Variables: -
Next State: At_Home

State:At_Home

Transition: Location_Update

Input: API Call "Location Update"
Output: Broadcast Mobile Agent Solicitation message
Variables: Set Timer to X
Next State: Find_Agent

Transition: Disconnect

Input: API Call "Disconnect"
Output: -
Variables: -
Next State: Disconnected

State: Passive_Find

Transition: Foreign_Advertisement

Input: Mobility Agent Advertisement from FA (different than HA)
Output: Send Registration Request to FA
Variables: Set Timer to X, Set FA to advertised agent, Store Sequence Number, start Reply_timer, set Adv_timer
Next State: Request_Tunnel

Transition: Location_Update

Input: API Call "Location Update"
Output: Broadcast Mobile Agent Solicitation message
Variables: Set Timer to X
Next State: Find_Agent

Transition: Disconnect

Input: API Call "Disconnect"
Output:
Variables: -
Next State: Disconnected

Transition: Home_Advertisement

Input: Mobile Agent Advertisement message from HA
Output: Send Registration Request with zero lifetime to HA
Variables: Set Timer to X
Next State: Close_for_Home

Transition: Home_Update

Input: Api Call "Home Update"
Output: Send Registration Request with zero lifetime to HA
Variables: Set Timer to X
Next State: Close_for_Home