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

2. 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. 1. MIH-capable mobile node (MN) communicating with MM over IP
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
Use Hard-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
Mobile Node
Cellular
WLAN
Mobility Manager 1
Power up: connect to WLAN
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) 7
Session continues
over cellular

8. Fragmentation, NAT Traversal, and Security
Trend in IEEE 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