Transport of media independent handover messages over ip
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Transport of Media Independent Handover Messages Over IP. I-D: draft-rahman-mipshop-mih-transport-01.txt. 67 th IETF Annual Meeting MIPSHOP Working Group. Key Concepts. Re-use existing well proven Internet protocols for Discovery of MIH nodes Transport of MIH messages Security Etc.

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Transport of Media Independent Handover Messages Over IP

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Transport of Media Independent Handover Messages Over IP

I-D: draft-rahman-mipshop-mih-transport-01.txt

67th IETF Annual Meeting MIPSHOP Working Group


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


Network Model

An MIH application enabled node that supports and/or manages MNs for seamless HO

Mobility Manager #1

Mobility Manager #N

Internet

Signaling over IP

Signaling over IP

WiMAX Network

WLAN Network

Cellular Network

Contains MIH Proxy Function

WLANAP

WiMAX BS

MIH Proxy

Cellular BS

L2 Signaling

MN contains MIH application & multiple access technologies

Mobile Node

Mobility


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


An MIH Enabled Mobile Node

  • The MIH application shall have a newly defined port number (from IANA)

New Port Number

MIH App.

Other App.

UDP

IP

WLAN

Cellular

Cellular Interface

WLAN Interface


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


MIH Application Retransmission Timers

  • Three retransmission timers defined for Information Service (IS), Event Service (ES), and Command Service (ES)


MIH Signaling Example 1: Directly Over UDP/IP

Mobile Node

Cellular

WLAN

Mobility Manager

Power up: connect to WLAN

1

Obtain

Neighbor List

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


MIH Signaling Example 1: Via WLAN MIH Proxy

WLAN (Proxy)

Mobile Node

Cellular

Mobility Manager

1

Power up: connect to WLAN

Obtain

Neighbor List

2

Send a request for IS (e.g. NL)

Inter-work L2 message

to UDP/IP message

3

Forward IS request

ACK not received

timeout after T1

4

Retransmit IS request

5

Send ACK

6

Send IS response

7

Send ACK

Inter-work UDP/IP

message to L2 message

8

Forward IS response


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


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


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