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Transport of Media Independent HO Messages over IP 68th IETF MIPSHOP WG draft-rahman-mipshop-mih-transport-02.txt Akbar Rahman Ulises Olvera-Hernandez Mahmoud Wafta Juan Carlos Zuniga Hyun-Wook Kim ([email protected]) ([email protected]) ([email protected]) ([email protected]) ([email protected]) 802.21 Concepts MIH uses a Common Header for Information, Command, and Event services (i.e. IS, CS, & ES) MIH protocol provides the following Identifiers: No need to define headers for each of IS, CS, or ES MIHF ID: uniquely defines MIHF endpoints Transaction ID: an identifier used with every MIH request and its response message MIH messages provide ACK bits for optional reliability MIH Message Multiplexing MIH User 1 e.g. MIP MIH User 2 e.g. SIP MIH multiplexing taken care of by the MIH application layer MIH Function Transport e.g. UDP, TCP Transport multiplexing taken care of by IP MIH Transport IP IP Internet MIH Transport IP Network Model Mobility Manager (MM) 2. An MIH application enabled node providing IS, CS and ES for HO support Internet Cellular network Signalling over IP WLAN network Signalling over IP WiMax network MIH Proxy WLAN AP Cellular BS 1. MIH-capable mobile node (MN) communicating with MM over IP WiMax BS L2 Signalling MN Proposal The main objective is to keep the implementation of MIH transport as light as possible in both MN and MM MN discovers MM at initialization Use UDP as a transport mechanism for MIH messages Use Hard-coding, or DHCP for discovery as per draft-daniel-dhc-mihis-opt-02.txt Fast, simple and easy to use Used by many other control protocols Rely on existing MIH functionalities Common MIH header for IS, CS, & ES Discovery capabilities of MIH peers, e.g. Mobility Manager (MM) MIH ACK bits for optional reliability Use IPsec for secure message transport In the unlikely case of a large MIH message, use IP Fragmentation MIH Message Transfer MIH Message Sending… UDP datagram MIH App. Other App. UDP Transport IP layer Receiving… IP packet MIH App. uses a unique port number that is registered and obtained through IANA MIH Signaling: Directly Over UDP/IP Mobile Node Cellular WLAN Mobility Manager Power up: connect to WLAN 1 Obtain Neighbor List (after discovery and registration) 2 Send a request for IS (e.g. NL) and set application timer T1 ACK not received timeout after T1 3 4 5 Retransmit request for IS and re-set application timer T1 Send IS response (with piggy backed ACK) and set application timer T1 Send ACK MN then decides to move to cellular (based on radio conditions) 6 7 Send ‘Link Up’ ES to inform about HO completion (no ACK required) Session continues over cellular Fragmentation, NAT Traversal, and Security Trend in IEEE 802.21 is to use small MIH messages NAT Traversal ES and CS: small and will not require fragmentation IS could be large: use IP fragmentation when needed together with retransmission timers for reliability NAT traversal does not pose a problem in a typical operator deployment scenario, since MN is behind a NAT and MM is not Event reports can be setup in the MIH Function to perform keepalive functions and maintain the NAT binding Security Use existing IPsec ESP or AH for secure MIH messaging Use IPsec ESP with UDP encapsulation if MN is behind NATs Summary Use UDP as a transport mechanism Simple, easy and well known behaviour Fast transport for MIH messages Re-use existing MIH protocol functions as much as possible and define new functionalities only if needed Use MIH ACK bits and retransmission timers to ensure reliability whenever required Use periodic Event reports for keeping NAT binding Light implementation of MIH Transport over IP Use IPsec and IP Fragmentation