1. 1 IEEE 802.21 MEDIA INDEPENDENT HANDOVER DCN: 21-06-0734-00-0000 Title: MIH Protocol State Machine Date Submitted: September 13, 2006 Presented at IEEE 802.21 session in Melbourne, Australia Authors or Source(s): Y. Alice Cheng, Miriam Tauil, Kenichi Taniuchi, Subir Das, Yoshihiro Ohba, Ashutosh Dutta, Victor Fajardo Abstract: This contribution proposes MIH protocol state machine both for source and receiver nodes. In particular, this reflects our experience in Information Service implementation.

2. 2 IEEE 802.21 presentation release statements This document has been prepared to assist the IEEE 802.21 Working Group. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.21. The contributor is familiar with IEEE patent policy, as outlined in Section 6.3 of the IEEE-SA Standards Board Operations Manual and in Understanding Patent Issues During IEEE Standards Development http://standards.ieee.org/board/pat/guide.html> Section 6.3 of the IEEE-SA Standards Board Operations Manualhttp://standards.ieee.org/guides/opman/sect6.html#6.3 http://standards.ieee.org/board/pat/guide.html

3. 3 Introduction The state transition diagrams are specified per MIH protocol specification in draft D01- 09 Intended to stimulate further discussions and create state machines that help MIH implementers Current State Machines reflect all MIH Services Possible inclusion as Annex in the specification

4. 4 Design Considerations The ACK request and response are used for providing reliability in sending/receiving MIH message –If the underlying protocol is reliable, such as TCP, the states that involve ACK are not required Current State diagrams reflects only the transactions in the MIH protocol operation –Session operation is not considered Requests received after the transaction is terminated with the same transaction ID are considered as new requests

5. 5 Timers Retransmission timer –Defined in D01-09 Two additional timers are introduced: –Abandon Timer (Abn.timer)- Time to wait for transaction to be completed E.g., ‘Response’ after request is sent from the source node –Cache Timer Cache ACK Timer (Cack.timer): Time to keep the ACK of a message in memory after sending the ACK, in case the message is received again and the ACK should be re-send. This is applicable to Client State only. Cache Response Timer (Cres.timer): Time to wait before discarding the response, after its first transmission. This is applicable to Server State only Cack.timer and Cres.timer are equivalent and may be realized with a single timer

6. 6 Need for Cache Timers When MIH is transmitting over unreliable transport and the destination failed to reach the source as depicted in figure –The destination shall not treat the same request as new transaction request. This corresponds to –The “Sent” state described in the MIH Request Sender state diagram, and –The “Completed” state described in the MIH Request Receiver state diagram. The value of the Cache Response Timer is relevant to the Retransmission Timer RtX.max –Cres.timer > Σ(Rtx.timer) 0 Cache ACK Timer triggered in the “Completed” state of the source state diagram has the similar effect. Rtx.timer Req w/ AckReq ACK Rsp w/ AckRsp Cres.timer Rsp w/ AckRsp SourceDestination Abn.timer

7. 7 MIH State Diagrams Each State Diagram represents ONE transaction Following cases are being addressed: MIH Request Sender Client sends Request w/ or w/o AckReq Client receives Response w/ or w/o AckReq MIH Request Receiver Server receives Request w/ or w/o AckReq Server responds w/ or w/o AckReq MIH Indication Sender MIH Indication Receiver

8. 8 Legends Timers –Retransmission Timer (Rtx.timer) Time to wait for ACK before retransmitting message –Abandon Timer (Abn.timer) Time to wait for server response after request is sent or after the ACK of the request is received –Cache ACK Timer (Cack.timer) Time to keep the ACK of a message in memory after sending the ACK response, in case the message is received again and the ACK should be re- send –Cache Response Timer (Cres.timer) Time to wait before discarding the response, after its first transmission Variables –Retransmission Count (Rtx.count) The number retransmissions occurred –Maximum Retransmission Count (Rtx.max) The maximum number of retransmission RtX.Max NOTE: Cack.timer or Cres.timer > Σ(Rtx.timer) 0

9. 9. Received Response WITH AckReq/ Pass Response to MIH User, Send ACK, Stop Abn.timer, Start Cack.timer.. Sent Request WITH AckReq/ Start Rtx.timer, Rtx.count = 0 Init MIH Request Sender (Source Node) Completed Processing Received ACK message/ Stop Rtx.timer, Start Abn.timer. Sent.. Received Response WITH AckReq/ Pass Response to MIH User, Send ACK, Start Cack.timer Cases addressed: Client sends Req. w/ AckReq Server responds w/ AckReq Client sends Req. w/ AckReq Server responds w/o AckReq Client sends Req. w/o AckReq Server responds w/ AckReq Client sends Req. w/o AckReq Server responds w/o AckReq Timers used: Rtx.timer Abn.timer Cack.timer Terminated Cack.timer expires Rtx.timer expires & Rtx.count < Rtx.max/ Retransmit Request, Restart Rtx.timer. Rtx.count++ Received Response WITHOUT AckReq/ Pass Response to MIH User, End transaction Abn.timer expires/ End transaction Received Response WITHOUT AckReq/ Pass Response to MIH User, End transaction Rtx.timer expires & Rtx.count == Rtx.max/ End transaction Received duplicate Response / Retransmit ACK Sent Request WITHOUT AckReq/ Start Abn.timer

10. 10 Sender States Description Init –Initial state before the transaction starts Sent –The state of which a request message is sent –If this message needs to be retransmitted, the client still stays at this state –Once the client receives a message from the server or abandons the request, the state is transited Processing –The state of which the client is waiting for a response –Once the client receives a response or abandons the request, the state is transited Completed –The state of which a response with AckReq was received –The client stays in this state until Cache Ack timer expires Terminated –Final state when the transaction is terminated –Notify the application if transaction fails

11. 11. Send Response WITH AckReq set/ Start Rtx.timer, Rtx.count = 0 Received Request/ Pass Request to MIH User, if AckReq set, Send ACK Init Completed Wait ACK Terminated Received same Request/ Send ACK if AckReq set Processing Rtx.timer expires & Rtx.count == Rtx.max/ End transaction Received ACK / End transaction Rtx.timer expires & Rtx.count < Rtx.max / Retransmit response, Start Rtx.timer, Rtx.count ++ Received same Request / Send Response Send Response WITHOUT AckReq & Received Request WITH AckReq/ Start Cres.timer Completed Cres.timer expires / End transaction Received same Request/ Send Response Cases addressed: Server receives Req. w/o AckReq Server respond w/ AckReq Server receives Req. w/ AckReq Server respond w/ AckReq Server receives Req. w/ AckReq Server respond w/o AckReq Server receives Req. w/o AckReq Server respond w/o AckReq Timers used: Rtx.timer Cres.timer MIH Request Receiver (Destination Node) Send Response WITHOUT AckReq & Received Request WITHOUT AckReq/ End Transaction Notes: The AckRsp should be set for all the response message if the request has the AckReq bit set.

12. 12 Receiver States Description Init –Initial state before the transaction starts Processing –The state of which a request was received –If the same request is received again, the server stays at this state –The state is transited when a response is sent Completed Wait ACK –The state of which a response with AckReq was sent –The server stays in this state until an ACK is received or re-transmission mechanism timed out Completed –The state of which a request with AckReq was received and a response without AckReq was sent. –The server stays in this state while until cache response timer expires Terminated –Final state when the transaction is terminated –Notify the application if transaction fails

13. 13.. Sent Indication WITH AckReq / Start Rtx.timer, Rtx.count = 0 Init MIH Indication Sender Received ACK / End transaction Sent.. Timers used: Rtx.timer Terminated Rtx.timer expires & Rtx.count < Rtx.max / Retransmit Indication, Restart Rtx.timer, Rtx.count++ Rtx.timer expires & Rtx.count == Rtx.max / End transaction Sent Indication WITHOUT AckReq / End transaction

14. 14 Ind. Sender States Description Init –Initial state before the transaction starts. Sent –The state of which an indication with AckReq was sent. –The Indication Sender stays in this state until the ACK is received or Abandon Timer expires. Terminated –Final state when the transaction is terminated –Notify the application if transaction fails

15. 15. Received Indication WITH AckReq / Pass Indication to MIH User, Send ACK, Start Cack.timer Init... Terminated.. Received Indication WITHOUT AckReq/ Pass Indication to MIH User, End transaction Completed Cack.timer expires / End transaction Received same Indication / Send ACK MIH Indication Receiver Timers used: Cack.timer

16. 16 Ind. Receiver States Description Init –Initial state before the transaction starts. Completed –The state of which an indication with AckReq was received. –The Indication Sender stays in this state until the Cache ACK Timer expires. Terminated –Final state when the transaction is terminated –Notify the application if transaction fails