1. Formal Approach to Mobility Modeling IETF 78 – IRTF MOBOPTS Ashutosh Dutta Bryan Lyles Henning Schulzrinne 1

2. Outline Motivation Abstract functions of mobility event Why mobility model Next Steps? 2

3. Motivation Cellular mobility typically involves handoff across homogeneous access technology –Optimization techniques are carefully engineered to improve the handoff performance IP-based mobility involves movement across access technologies, administrative domains, at multiple layers and involve interaction between multiple protocols –Mechanisms and design principles for optimized handover need better analysis –Currently there are ad hoc solutions for IP mobility optimization, not engineering practice –No formal methodology to systematically discover or evaluate mobility optimizations –No methodology for systematic evaluation or prediction of "run-time" cost/benefit tradeoffs 3

4. Backbone Administrative Domain B L2 PoA Corresponding Host 128.59.10.7 IP ch 207.3.232.10 210.5.240.10 128.59.11.8 N2 N1 N2 N1- Network 1 (802.11) N2- Network 2 ( CDMA/GPRS) Configuration Agent L3 PoA 207.3.232.10 Mobile Host Authentication Agent Authorization Agent Registration Agent Registration Agent Administrative Domain A Configuration Agent Authorization Agent Signaling Proxy Authentication Agent Signaling Proxy Layer 3 PoA L2 PoA Layer 2 PoA Layer 2 PoA L3 PoA Mobility Illustration in IP-based 4G network 128.59.9.6 L3 PoA A B C D 900 ms media interruption 802.11 h/o delay 900 ms 802.11 4 Seconds media interruption h/o delay 4 s 18 Seconds media interruption h/o delay 18 s 4

5. Mobility/ Function Access Type Network Discovery Resource Discovery Triggering Technique Detection Technique ConfigurationKey exchange/ Authentic ation EncryptionBinding Update Media Rerouting GSMTDMABCCHFCCHChannel Strength SCHTMSISRES/A3DESMSC Contld. Anchor WCDMA CDMA PILOTSYNC Channel Strength FrequencyTMSISRES/A 3 AESNetwork Control Anchor IS-95CDMAPILOTSYNC channel Channel Strength RTCTMSIDiffie- Hellman AKA KasumiMSC Contld. Anchor MSC CDMA 1X- EVDO EVDOPILOT Channel SYNC Channel Strength RTCTMSI Diffie- Hellman/ CAVE AESMSCPDSN/MSC 802.11CSMA/ CA Beacon 11R 802.21 SNR at Mobile Scanning. Channel Number, SSID SSID, Channel number Layer 2 authentic ate 802.1X EAP WEP/WP A 802.11i AssociateIAPP Cell IPAnyGateway beacon Mobile msmt. AP beacon ID GW Beacon MAC Address AP address IPSec Route Update Intermediat ey Router MIPv4AnyICMP Router adv. FA adv. ICMP Router Adv. FA adv. L2 triggering FA advFA-CoA Co-CoA IKE/PA NA AAA IPSecMIP Registratio n FA RFA HA MIPv6AnyStateless Proactive CARD 802.21 11R Router Adv. Router Prefix CoAIKE/PA NA AAA IPSECMIP update MIP RO CH MAP HA SIPMAnyStateless ICMP Router 802.21 11R L3 Router Adv. Router Prefix, ICMP CoA AOR Re-Register INVITE exchange /AAA IPSEC/ SRTP/ S/MIME Re-INVITEB2BUA CH RTPtrans Abstraction of mobility functions 5

6. Handover Event Network discovery & selection Network attachment ConfigurationSecurity association Binding update Media reroute Channel discovery L2 association Router solicitation Domain advertisement Identifier acquisition Duplicate Address Detection Address Resolution Authentication (L2 and L3) Key derivation Identifier update Identifier mapping Binding cache Tunneling Buffering Forwarding Bi-casting/ Multicasting Server discovery Identifier Verification Subnet discovery P1 P2P3 P4P5 P6 P11 P13 P12 P21 P22 P23 P31 P32 P33 P41 P42 P51 P52 P53 P54 P61 P62 P63 P64 System decomposition of handover process 6

7. Dependency analysis among handover operations 7

8. Resource usage per mobility events 8

9. Why Mobility Model ? Problem: In the absence of any formal mechanism it is difficult to predict or verify the systems performance of un-optimized handover or any specific handoff optimization technique Specific expected results –Generate automatic schedule of handoff operations given a set of resource constraints, performance objectives and dependence relationship –A methodology to verify the systems performance of a specific optimization technique as well as systems behavior (e.g., deadlocks) –Ability to design a customized mobility protocol that will define its own set of elementary operations for each of the desired handoff functions –Specification of the functional components of mobility protocols and tools that search for context specific optimizations, such as caching, proactive feature and cross layer techniques

10. Possible Next Steps? In order to transition ad hoc optimization approaches to engineering best practice we need the following: –Framework or model that can analyze the mobility event in a systematic way, can verify and predict the performance under systems resource constraints –A set of fundamental design principles to optimize handoff components across layers –A set of well defined methodologies to verify the optimization techniques for mobility in an IP-based network –Need best current practices for mobility deployment Write a document with mobility design principles and systematic approach to building a mobility model –cite some sample illustrative models if possible 10