Comparison of IP Micromobility Protocol Wireless/Mobile Network Lab 이 진 우

Contents qIntroduction qClassification of protocols qA Generic Model qSimulation Model qHandoff Quality qRoute Control Messaging qImproved Handoff Schemes qConclusion

Introduction qMicormobility protocols l Motivation à Predominance of pico-cellular environment in the future – small cell size, large number of access points à Efficiency problem of Mobile IP for real-time application within a single domain : high handoff latency, high signaling overhead and transient packet loss à No paing capability in Mobile IP l Main functions à Path setup mechanism, Fast handoff mechanism, Paging mechanism qPresentation l Performance comparison of CIP(Cellular IP), Hawaii, Hierarchical Mobile IP(HMIP) based on the Columbia IP Micromobility Software(CIMS) ns-2 extension

Classification of protocols qHierarchical Tunnel-based Approach l Location database is maintained in a distributed form by set of FAs in the access network l Tunneling corresponding to FA toward MH’s AP l BCMP, IDMP, 3G UMTS/CDMA2000, HMIP qMobile-Specific Routing Approach l Avoidance of the overhead introduced by decapsulation and reencapsulation schemes without tunneling and address conversion l Use home address and co-located COA in access network l Cellular IP, Hawaii

Figure 1. Two approach Hierarchical Tunneling ApproachMobile-Specific Routing Approach

A Generic Model (Cont.) qThe use of MRP (mobile routing point) l MSR to refer to nodes that participate in the procedure l Each MSR contains a list of hosts whose data path traverses the MSR qFigure 2-a l Data packet addressed to MH0 are forwarded by using “IP-in IP” encapsulation l Use Hierarchical tunneling such as HMIP qFigure 2-b l Internal address (MH0’s identifier) remain unchanged while external address (the next MRP’s address) is replaced by each MRP l IP Packets are encapsulated in L2 frames such as CIP and Hawaii Figure 2 : a) A network of mobile routing points ; b) a full network with intermediate nodes

A Generic Model

Simulation Model qCIMS ( Columbia IP Micromobility Software) l Micromobility extension for the ns-2 network simulator l Support separate models for CIP, Hawaii, HMIP à CIP : Hard and semisoft handoff, Paging and security à Hawaii : UNF (unicast nonforwarding) and MSF (multiple stream forwarding) handoff l Hawaii à BaseStatioinNode object instead of AP à Hawaii router are implemented in special HawaiiAgent object l HMIP à Use a GFAAgent object to implement a single GFA and FAs in each AP Figure 3. The simulated network topology

Handoff Quality (Cont.) qUDP l MH moves periodically between neighboring AP at a speed of 20 m/s l Use UDP probing traffic between CH and MH and count the average number of packet loss during handoff l Results of Figure 4 à CIP hard handoff and Hawaii UNF are very similar and handoff delay is related to the packet delay between the APs and the cross-over node à HMIP cannot benefit from crossover distance Figure 4. UDP packet loss at handoff

Handoff Quality qTCP l At 14.75s into the simulation a CIP hard handoff occurs l Packet loss caused by the handoff results in a TCP timeout Figure 5. TCP sequence numbers at the time of CIP hard handoff

Route Control Messaging qAccording to Tree topologies l CIP and Hawaii are similar for tree topologies l Difference for non-tree topologies à Suboptimal in Hawaii à Optimal in CIP qTrade-off of suboptimal routing l Cause performance bottleneck and signaling load at the common section l Discard update message at crossover MRP

Improved Handoff Schemes (Cont.) qPacket loss reduction techniques l Bi-casting techniques of CIP à Semisoft handoff by allowing a MH to set up routing to new AP prior to handoff à Delay device for a fixed period amount of time (T ss ) before transmission l Buffering and forwarding techniques of Hawaii à MSF operates after handoff à Old AP forwards packet to new AP during handoff à Store all packet received for a certain period (T msf ) l HMIP à Operate along similar lines, bi-casting and buffering and forwarding

Improved Handoff Schemes (Cont.) Figure 8. UDP packet loss and duplication ; this is for packet interarrival times of 5 ms and 10 ms CIP semisoft handoffHawaii MSF handoff

Improved Handoff Schemes (Cont.) Figure 9. TCP sequence numbers at the time of a Cellular IP semi-soft handoff (Tss = 50 ms)semi-soft handoff (Tss = 100 ms)

Improved Handoff Schemes qDifference between CIP and Hawaii l Packet reordering l TCP protocol reacts adversely to Hawaii MSF qNewReno congestion control l Applying NewReno congestion control represents a different approach to improving handoff performance l NewReno can be advatageous in case of batch losses due to radio fading Figure 6. Application level TCP throughput in periodic handoffs

Conclusion qOpen issue l Support the delivery of a variety of traffic including best effort and real-time traffic l Work on a suitable QoS model for micromobility qWorking group l IETF Mobile IP WG l IETF Seamoby WG à Low-latency handoff, IP paging