1. I-D: draft-rahman-mipshop-mih-transport-01.txt Transport of Media Independent Handover Messages Over IP 67 th IETF Annual Meeting MIPSHOP Working Group

2. Key Concepts Re-use existing well proven Internet protocols for –Discovery of MIH nodes –Transport of MIH messages –Security –Etc. Use functionalities already provided by MIH (IEEE 802.21) & focus on transport mechanism Define new functionality at MIH application layer where needed

3. Network Model Cellular Network WLAN Network WiMAX Network Internet Mobility Manager #1 Cellular BS WLAN AP WiMAX BS Mobile Node Mobility MN contains MIH application & multiple access technologies An MIH application enabled node that supports and/or manages MNs for seamless HO Mobility Manager #N MIH Proxy Contains MIH Proxy Function Signaling over IP L2 Signaling

4. Summary of Proposal Hard coding or DHCP to discover Mobility Manager (MM) –Mobile Node (MN) discovers MM at initialization –Depends on number of MMs –DHCP as per draft-daniel-dhc-mihis-opt-02.txt (Park, et al.) UDP as MIH transport mechanism between MM and MN –Easy to implement, simple & fast, used by many other control protocols e.g. SIP IPSec for security mechanism Existing MIH functionalities in order to –Setup and keep track of MIH node identifiers, session and transaction identifiers –Discover capabilities of MIH peers –Provide reliability with optional ACK bit fields Retransmission timers at MIH application layer to complement UDP for reliability –And associated congestion control mechanism

5. An MIH Enabled Mobile Node The MIH application shall have a newly defined port number (from IANA) WLANCellular IP UDP MIH App.Other App. New Port Number WLAN Interface Cellular Interface

6. Transport Mechanism for Reliable MIH Message Delivery Sender of MIH message may request an acknowledgement –Done by setting ACK Request bit in MIH message Sender sets retransmission timer based on type of MIH message (i.e. Information, Event, Command) –If ACK does not arrive within timeout period then retransmit –If ACK arrives within timeout then assume message delivered correctly If ACK Request bit was set, the receiver shall send an ACK message –Done by setting ACK Respond bit in MIH message –ACK can be piggy backed with data

7. MIH Application Retransmission Timers Three retransmission timers defined for Information Service (IS), Event Service (ES), and Command Service (ES) Message Content Associated Retransmission Timer Example Value Notes IS Information Timer (T1)1000 ms T1 > T2 Least time Sensitive ES Event Timer (T2) 500 msT3 < T2 < T1 CS Command Timer (T3) 100 ms T3 < T2 Most time sensitive

8. MIH Signaling Example 1: Directly Over UDP/IP Mobile NodeCellularWLANMobility Manager Power up: connect to WLAN Send a request for IS (e.g. NL) and set application timer T1 ACK not received timeout after T1 Retransmit request for IS and re-set application timer T1 Send IS response (with piggy backed ACK) and set application timer T1 Send ACK Send ‘Link Up’ ES to inform about HO completion (no ACK required) Session continues over cellular 1 2 3 4 5 6 7 MN then decides to move to cellular (based on radio conditions) Obtain Neighbor List

9. MIH Signaling Example 1: Via WLAN MIH Proxy Mobile NodeCellular WLAN (Proxy) Mobility Manager Power up: connect to WLAN Send a request for IS (e.g. NL) Inter-work L2 message to UDP/IP message 1 2 3 4 5 6 7 Obtain Neighbor List Forward IS request ACK not received timeout after T1 Retransmit IS request Send ACK Send IS response Send ACK Inter-work UDP/IP message to L2 message Forward IS response 8

10. NAT Traversal, Fragmentation, & Security MNs can be behind NATs –If MNs behind NATs initiate sessions with MM then there will be no NAT traversal problems Trend in IEEE 802.21 is to use small MIH messages –ES and CS: small and will not require fragmentation –IS can be large: use IP fragmentation when needed together with retransmission timers for reliability Use relevant IPSec features i.e. Encapsulated Security Payload and/or Authentication Header for secure messaging

11. Conclusions Re-use existing protocols as much as possible and define new functionalities only where needed Use UDP: existing, fast, & simple to use transport protocol –Used by other protocols e.g. SIP commonly uses UDP, CAPWAP also uses UDP, & the IETF NETLMM Working Group also considers UDP for transport Use existing MIH (IEEE 802.21) functionalities: –Provides options for ACKs, sessions & transactions management Use MIH Application Retransmission timers for reliability