Transport of Media Independent HO Messages over IP

1. 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 (akbar.rahman@interdigital.com) (ulises.olvera-hernandez@interdigital.com) (mahmoud.wafta@interdigital.com) (j.c.zuniga@ieee.org) (hwkim@sktelecom.com)

2. 802.21 Concepts • MIH uses a Common Header for Information, Command, and Event services (i.e. IS, CS, & ES) • No need to define headers for each of IS, CS, or ES • MIH protocol provides the following Identifiers: • 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

3. MIH Message Multiplexing MIH multiplexing taken care of by the MIH application layer Transport multiplexing taken care of by IP

4. Network Model 2. An MIH application enabled node providing IS, CS and ES for HO support Signalling over IP Signalling over IP 1. MIH-capable mobile node (MN) communicating with MM over IP L2 Signalling

5. 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 • UseHard-coding, or • DHCP for discovery as per draft-daniel-dhc-mihis-opt-02.txt • Use UDP as a transport mechanism for MIH messages • 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

6. MIH Message Transfer MIH Message MIH App. Other App. Sending… UDP datagram MIH App. uses a unique port number that is registered and obtained through IANA UDP Transport IP layer IP packet Receiving…

7. MIH Signaling: Directly Over UDP/IP Mobility Manager Mobile Node Cellular WLAN 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 Retransmit request for IS and re-set application timer T1 3 4 Send IS response (with piggy backed ACK) and set application timer T1 5 Send ACK MN then decides to move to cellular (based on radio conditions) 6 Send ‘Link Up’ ES to inform about HO completion (no ACK required) Session continues over cellular 7

8. Fragmentation, NAT Traversal, and Security • Trend in IEEE 802.21 is to use small MIH messages • 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 • 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 keep-alive 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

9. 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