Formal Approach to Mobility M odeling IETF 78 – IRTF MOBOPTS

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

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

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

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

5. Abstraction of mobility functions

6. System decomposition of handover process Handover Event P1 P2 P3 P4 P5 P6 Network discovery & selection Network attachment Configuration Security association Media reroute Binding update P12 P31 P11 Subnet discovery Identifier acquisition P62 Channel discovery P33 P61 P41 P53 Forwarding P21 P23 Address Resolution Tunneling Authentication (L2 and L3) Identifier mapping Domain advertisement P51 L2 association P32 P54 P63 P42 Identifier update P13 Binding cache Duplicate Address Detection Key derivation Buffering P22 Server discovery P64 Router solicitation Bi-casting/ Multicasting P52 Identifier Verification

7. Dependency analysis among handover operations

8. Resource usage per mobility events

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