A Comparison of Mechanisms for Improving Mobile IP Handoff Latency for End-to-End TCP MobiCom 2003 Robert Hsieh and Aruna Seneviratne School of Electrical Engineering and Telecommunications The University of New South Wales 26th February, 2004 Presented by Sookhyun, Yang

Contents Introduction Related Works Experimental Methodology Experimental Results Conclusion

Mobility Related Terminology INTRODUCTION Mobility Related Terminology Mobile node (MN) Handoff (Handover) Layer 2 handoff Beacon message Access router (AR) Access network (AN) Mobile IP (MIP) Handoff latency Home network (HN) Foreign (Visited) network Home Agent (HA) Foreign agent (FA) Correspondent node (CN) Internet draft: http://www.ietf.org/internet-drafts/draft-ietf-seamoby-mobility-terminology-06.txt

Mobile IP (MIP) When a MN moves and attach itself to another network INTRODUCTION Mobile IP (MIP) When a MN moves and attach itself to another network Need to obtain a new IP address All existing IP connections to the MN need to be terminated and then reestablished Solution to this problem at MIP Indirection provided with a set of network agents Handoff latency Address reconfiguration procedure HA registration process No modification to existing routers or end correspondent nodes Foreign network (FN) reconfiguration IP’ COS (Care-of-address) CN FA tunneling binding IP intercept Binding!!! HA IP IP Home network (HN) Mobile node (MN) Access point (AP)

Motivation Effects of Mobile IP (MIP) handoff latency INTRODUCTION Motivation Effects of Mobile IP (MIP) handoff latency Packet losses Severe End-to-End TCP performance degradation Mitigation of these effects with MIPv6 extensions Hierarchical registration management Address pre-fetching Local retransmission mechanism No comparative studies regarding the relative performance amongst MIPv6 extensions TCP performance degradation Perceive these losses as congestion Cause source throttling or retransmission

INTRODUCTION Overview Evaluate the impact of layer-3 handoff latency on End-to-End TCP for various MIPv6 extensions Hierarchical MIPv6 MIPv6 with Fast-handover Hierarchical MIPv6 with Fast-handover Simultaneous Bindings Seamless handoff architecture for MIP (S-MIP) Propose an evaluation model examining the effect of linear and ping-pong movement on handoff latency and TCP goodput Optimize S-MIP by further eliminating the possibility of packets out of order

Hierarchical Mobile IPv6 (HMIPv6) RELATED WORKS Hierarchical Mobile IPv6 (HMIPv6) Minimize HA registration delay!! Internet CN HA RCOA_1 MAP Mobility Anchor Point (MAP) AR RCOA_2 AR binding binding AR AR AR AR AR AR AR AR AP MAP act like a local home agent RCOA_1 LCOA’ AP AP Macro mobility Micro mobility RCOA_2 LCOA’’ Access network Access network RCOA_1 LCOA Internet draft - http://www.ietf.org/internet-drafts/draft-ietf-mipshop-hmipv6-01.txt

Local Handoff Latency Reduction RELATED WORKS Local Handoff Latency Reduction Low latency address configuration Reduce address reconfiguration time Configure an address for MN in an network likely to move to before it moves Use L2 trigger Method Pre-registration Perform L3 handoff before completion of L2 handoff Post-registration Setup a temporary bi-directional tunnel between oFA and nFA Allow MN to continue using oFA while registration at the time or later MIPv6 with Fast-Handover Combined method of pre-registration and post-registration Three phases Handover initiation Tunnel establishment Packet forwarding Pre-registration: perform L3 handoff before it completes the L2 handoff Beacon signal -> L2 trigger from link-layer ->

MIPv6 with Fast-Handover RELATED WORKS MIPv6 with Fast-Handover MN oFA nFA Beacon L2 trigger RtSolPr(Router solicitation proxy) Handover initiation 1 PrRtAdv(Proxy router advertisement) HI(Handover initiation) Tunnel Establishment btw oFA & nFA 2 F-BU(Fast-binding update) with COA Hack(Handover ack) F-Back(Fast-binding ack) F-BAck Disconnect Forward packets Packet forwarding phase 3 Connect F-NA(Fast neighbor advertisement) Deliver packets Internet draft - http://www.ietf.org/internet-drafts/draft-ietf-mipshop-fast-mipv6-01.txt

HMIPv6 with Fast-handover RELATED WORKS HMIPv6 with Fast-handover Combine HMIPv6 with Fast-handover Reduce latency due to address configuration and HA registration Relocate the forwarding anchor point from oAR to the MAP Internet CN HA MAP MAP Forwarding Forwarding Low latency handoff == fast handover in Mobile IPv6 AR AR AR AR nAR AR nAR oAR Access network Access network

Simultaneous Bindings RELATED WORKS Simultaneous Bindings Reduce packet losses N-casting packets with multiple bindings Forward packets for a short period to the MN’s current location and to n-other locations where the MN is expected move to Forwarding carried by oAR, MAP or HA nAR1 Simultaneous binding MAP oAR nAR2 AP (Access point) Internet draft- http://www.ietf.org/internet-drafts/draft-elmalki-mobileip-bicasting-v6-05.txt

Seamless Handoff for MIP (S-MIP) RELATED WORKS Seamless Handoff for MIP (S-MIP) Provide a different approach to solve the timing ambiguity problem Build on HMIPv6 with Fast-Handover Use MN location and movement pattern to instruct MN when and how handoff is initiated Decision engine (DE) Store the history of MN locations Determine movement pattern Make “handoff decision” for MN MAP DE nAR2 oAR nAR1 MN

Stationary near the center RELATED WORKS Decision Engine MN location Tracking <- Signal strength Handoff Decision Linear Stochastic Stationary near the center Handoff mechanism

< SPS mechanism > RELATED WORKS Handoff Mechanism Linear movement Synchronized packet simulcasting (SPS) Optimized S-MIP Stochastical manner oAR and nAR are anticipation-mode Maintain MN’s binding with oAR, nAR before F-NA Reduce unnecessary re-setup Stationary state near the center Establish multiple bindings with ARs MN uses more than one COAs MAP optimization DE S-packet F-packet oAR nAR S-buffer F-buffer MN < SPS mechanism >

Optimized S-MIP Elimination of the possibility of packets out of order RELATED WORKS Optimized S-MIP Elimination of the possibility of packets out of order Upon sending the F-BU to the oAR, MN must immediately switch to the nAR After receiving F-BU, oAR must immediately forward packets to the nAR oAR only needs to send the FBAck to the nAR IP packet filtering mechanism at nAR oAR incorrectly forwards IP packets with the S-bit set as f-packets Compare IP packets within the s-buffer and f-buffer at nAR Discard identical packets in s-buffer [optimized] Examine 16 bit identification, fragment offset, and flag fields in IP header Already send..-_- f-packet으로 인식하므로..따라서 s-buffer에서 삭제

EXPERIMENTAL METHODOLOGY Implementation Simulator Network Simulator version 2 (ns-allinone2.1b6a) Patch with the ns wireless extension module allowing basic MIPv4 Extension to the ns-2 Mobile IPv6 protocol Hierarchical Mobile IPv6 protocol Fast-handover protocol Simultaneous bindings protocol Optimized S-MIP protocol Modification Infrastructure mode: WaveLan with connection monitor (CMon) Additional handoff algorithm: Midway handoff WaveLan: developed for simulation of wireless ad-hoc networks (broadcast mode) 이 실험에서는 infrastructure mode가 필요하므로 Connection monitor를 추가하여 Cmon이 MN의 packet 수신을 컨트롤한다. 즉, MN이 새로운 access router로 L2-handoff를 시작하면 L2 handoff가 완료될 때까지 모든 패킷을 버린다. S-MIP의 경우는 MN이 access network의 중간부분에 위치하였을 때 핸드오프를 initiation한다 이와 비슷하게 다른 프로토콜들도 동작하도록 한다

Simulation Network Topology EXPERIMENTAL METHODOLOGY Simulation Network Topology Max num of packets received by the receiver in sequence Drop policy in router – Drop_tail / RED < Performance focus > Handoff delay TCP goodput CN’s Congestion window Overall handoff delay (D) = time(first-transmitted~retransmitted) +time(CN->MN) Micro mobility Linear / ping-ping

EXPERIMENTAL RESULT – Handoff delay MIPv6 & HMIPv6 Sender (CN)’s view Time (seconds) TCP sequence number a: MIPv6 (resolution time 100ms) b~e: HMIPv6 (resolution time 100ms) f~I: HMIPv6 (resolution time 200ms) address resolution L2 handoff BU at MAP Out-of-sequence packet MIP’s D = 814ms HMIPv6’s D = 326ms

EXPERIMENTAL RESULT – Handoff delay Fast-Handover Sender (CN)’s view Time (seconds) TCP sequence number Proportional to distance (FA~HA) f ~ i : fast-handover (resolution time 100ms) RtSolPr~PrRtAdv BU L2 handoff D = 358ms Even though forwarding mechanism, MN is unable to receive packets until the binding update is completed

HMIPv6 with Fast-Handover EXPERIMENTAL RESULT – Handoff delay HMIPv6 with Fast-Handover < CN’s cwnd > Receiver (MN)’s view TCP sequence number D = 270ms Packet forwarding Out-of-sequence packet Packet loss due to L2 handoff send (ack) receive (data) Time (seconds)

EXPERIMENTAL RESULT – Handoff delay S-MIP Hand off = 100ms No packet loss No out-of-sequence packet TCP sequence number Sender (CN)’s view Time (seconds) <- Optimized S-MIP Time (seconds) TCP sequence number MAP으로 BU를 보낸 이후에 곧바로 네트웍을 바꾸므로 HMIPv6 with Fast handover == Simultaneous bindings 차이: No packet loss Out-of-sequence packet Non optimized S-MIP ->

< Ping-pong case > EXPERIMENTAL RESULT Handoff Delay MIP HMIPv6 MIPv6 with Fast-handover HMIPv6 with Simultaneous Bindings S-MIP (nonop) S-MIP 814ms 326ms 358ms 270ms 268ms 0ms < Linear case > < Ping-pong case > Completely break down Affected to a lesser extent Severe throttling Excellent resilience

MN is stationary near the PAR EXPERIMENTAL RESULT TCP Goodput Linear : 1.447s PP: 14.23s No handoff: MN is stationary near the PAR MN is stationary near the PAR

Congestion Window EXPERIMENTAL RESULT Linear movement Ping-ping movement S-MIP Simultaneous Binding

Correspondent node (CN) Conclusion Analyze various handoff latency reduction framework Show the possibility of significantly reducing the latency by S-MIP Optimize the S-MIP scheme Future works S-MIP under multiple connection scenarios Scalability of the Decision Engine (DE) Design more sophisticated positioning schemes for S-MIP Correspondent node (CN)