Transcript MobOpts-2x
Formal Approach to Mobility Modeling IETF 78 – IRTF MOBOPTS Ashutosh Dutta Bryan Lyles Henning Schulzrinne 1 Outline • Motivation • Abstract functions of mobility event • Why mobility model • Next Steps? 2 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 Mobility Illustration in IP-based 4G network Administrative Domain A Administrative Domain B Authorization Agent Registration Agent Authorization Agent Authentication Agent Authentication Agent Configuration Agent Signaling Proxy N1 Registration Agent Configuration Agent N2 N1 Backbone IPch Signaling Proxy L3 PoA Corresponding Host Layer 2 PoA 207.3.232.10 A L2 PoA L3 PoA N2 128.59.11.8 L2 PoA Layer 3 PoA B C D L3 PoA 128.59.10.7 Mobile Host N1- Network 1 (802.11) N2- Network 2 ( CDMA/GPRS) Layer 2 PoA 207.3.232.10 802.11 802.11 210.5.240.10 128.59.9.6 802.11 Handoff Delay ~ 18 s CDMA 802.11 802.11 900 ms media interruption h/o delay 900 ms 4 h/o delay 18 s 18 Seconds media interruption 4 Seconds media interruption h/o delay 4 s Abstraction of mobility functions Mobility/ Function Access Type Network Discovery Resource Discovery Triggering Technique Detection Technique Configuration Key exchange/ Authentic ation Encryption Binding Update Media Rerouting GSM TDMA BCCH FCCH Channel Strength SCH TMSI SRES/A3 DES MSC Contld. Anchor WCDMA CDMA PILOT SYNC Channel Channel Strength Frequency TMSI SRES/A 3 AES Network Control Anchor IS-95 CDMA PILOT SYNC channel Channel Strength RTC TMSI DiffieHellman AKA Kasumi MSC Contld. Anchor MSC CDMA 1XEVDO EVDO PILOT Channel SYNC Channel Channel Strength RTC TMSI DiffieHellman/ CAVE AES MSC PDSN/MSC 802.11 CSMA/ CA Beacon 11R 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 Associate IAPP Cell IP Any Gateway beacon Mobile msmt. AP beacon ID GW Beacon MAC Address AP address IPSec IPSec Route Update Intermediat ey Router MIPv4 Any ICMP Router adv. FA adv. ICMP Router Adv. FA adv. L2 triggering FA adv FA-CoA Co-CoA IKE/PA NA AAA IPSec MIP Registratio n FA RFA HA MIPv6 Any Stateless Proactive CARD 802.21 11R Router Adv. Router Prefix CoA IKE/PA NA AAA IPSEC MIP update MIP RO CH MAP HA SIPM Any Stateless ICMP 802.21 11R L3 Router Router Prefix, CoA AOR INVITE exchange IPSEC/ SRTP/ Re-INVITE B2BUA CH 5 System decomposition of handover process Handover Event P1 P2 Network discovery & selection P11 Channel discovery P13 P3 Network attachment P12 Subnet discovery P21 L2 association Server discovery P4 Configuration P5 Security association P6 Media reroute Binding update P31 Identifier acquisition P23 Domain advertisement P22 Router solicitation P33 Address Resolution P32 Duplicate Address Detection P41 Authentication (L2 and L3) P53 Identifier mapping P42 Key derivation P51 Identifier update P62 P61 Tunneling P54 Binding cache Forwarding P63 Buffering P64 P52 Identifier Verification Bi-casting/ Multicasting 6 Dependency analysis among handover operations Handoff Process P11 – Channel Discovery P12 – Subnet discovery Precedence Relationship P00 P21,P22 P13 – Server discovery P12 P21- Layer 2 association P11 P22- Router solicitation P23- Domain advertisement P21, P12 P13 P31 – Identifier acquisition P23,P12 P32 – Duplicate address detection P33 – Address resolution P41 – Authentication P42 – Key Derivation P51 – Identifier update P31 P52 – Identifier verification P53 – Identifier mapping P31 P51 P54 – Binding cache P61 – Tunneling P53 P51 P62 – Forwarding P63 – Buffering P64 – Multicasting/Bicasting P51, P53 P62, P51 P51 P32, P31 P13 P41 P31,P52 Data it depends on Signal-to-Noise Ratio value Layer 2 beacon ID L3 router advertisement Subnet address Default router address Channel number MAC address Authentication key Layer 2 binding Server configuration Router advertisement Default gateway Subnet address Server address ARP Router advertisement New identifier Address of authenticator PMK (Pairwise Master Key) L3 Address Uniqueness of L3 address Completion of COTI Updated MN address at CN and HA New Care-of-address mapping Tunnel end-point address Identifier address New address of the mobile New identifier acquisition New identifier acquisition 7 Resource usage per mobility events Sub Sub-operations transitions Resource Consumption Bytes exchanged CPU samples Power (nano joules) t00 t01 t11 t12 t13 t21 t22 t23 t31 t32 t33 t41 t42 t43 t51 Layer 2 un-reachability test Layer 3 unreachability Discover layer 2 channel Discover layer 3 subnet Discover server Layer 2 association Router solicitation Domain advertisement Identifier acquisition Duplicate address detection Address resolution Layer 2 open authentication Layer 2 EAP Four-way handshake Master key derivation (PMK) 43 86 109 110 126 99 70 226 1426 164 60 94 2842 504 0 5 3 3 4 5 2 4 4 5 6 3 3 6 4 10 51600 103200 130800 132000 540000 118800 84000 271200 1711200 196800 72000 112800 3410400 604800 0 t52 t61 t62 t63 t64 t71 t72 t81 t82 t83 t91 t92 Session key derivation (PTK) Identifier update Identifier verification Identifier mapping Binding cache Fast binding update Local caching Tunneling Forwarding Buffering Local id mapping Multicasting/bicasting 0 204 148 0 0 110 0 60 100 120 40 192 6 4 6 8 3 3 6 2 2 3 4 2 0 422400 177600 0 0 132000 0 72000 120000 144000 48000 230400 8 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 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