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Cellular IP: A new Paradigm in Internet Host Mobility

Cellular IP: A new Paradigm in Internet Host Mobility. P R E S E N T E D B Y Venu Pragada Abhinav Anand. Overview. Introduction Cellular IP & Mobile IP Paging Routing Handoff Performance Summary. What is Cellular IP ??. Cellular IP

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Cellular IP: A new Paradigm in Internet Host Mobility

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  1. Cellular IP: A new Paradigm in Internet Host Mobility P R E S E N T E D B Y Venu Pragada Abhinav Anand C e l l u l a r I P

  2. Overview • Introduction • Cellular IP & Mobile IP • Paging • Routing • Handoff • Performance • Summary C e l l u l a r I P

  3. What is Cellular IP ?? C e l l u l a r I P

  4. Cellular IP • new robust, simple, and flexible protocol for highly mobile hosts • CIP supports local mobility & efficiently interworks with Mobile IP • can accommodate large no. of users by separating idle from active hosts • requires no new packet formats, encapsulations, or address space allocations C e l l u l a r I P

  5. Why bother for Cellular IP?When we have Mobile IP... because.. • Mobile IP is optimized only for: • macro level mobility and • relatively slow moving hosts C e l l u l a r I P

  6. Mobile IP and Cellular IP *Cell sizes smaller *Migration freq faster *User population greater Hierarchical Mobility Management *Faster & smooth handoff *Less load on Internet *Cheap-passive connectivity C e l l u l a r I P

  7. G C E A Gateway Internet with Mobile IP F R R Beacon signal MH Home agent of MH Wireless Access network Model D B C e l l u l a r I P

  8. Current Foreign Agent Previous Foreign Agent Mobile Node Home Agent Correspondent node New c/o address Registration Registration Notification Packet Packet Binding Update Packet Packet Packet What if MH moves from one Access Network to another *Handoff sequence between two Access Networks C e l l u l a r I P

  9. 5 key Features of CIP • Easy Global Migration • Cheap Passive Connectivity • Efficient Location Management & • Flexible Handoff • Simple Memory less Mobile hosts C e l l u l a r I P

  10. Easy Global Migration • Migration should be transparent to the user • This is achieved by: • allowing the BS to emit beacon signals • when MH connects the access network it must inform its HA as required by MIP • for global reachability, the MH uses a local C/O address, but within the access network its identified by its home IP C e l l u l a r I P

  11. Cheap Passive connectivity • mechanism of keeping track of idle MHs. • allows max. no users connected to a network • reduces the network load C e l l u l a r I P

  12. PC RC 1 2 3 4 Mobile Host X X X Service Area Efficient Location Management PAGING & ROUTING Two parallel structures of mappings (PC &RC) 1 - idle MH keeps PC upto-date 2 - PC mappings used to find the loc of idle MH 3 - maintains RC mappings until actively connected 4 - routing of data packets to MH C e l l u l a r I P

  13. PROTOCOL DETAILS C e l l u l a r I P

  14. Protocol Parameters C e l l u l a r I P

  15. Different Packet Formats used • Data packets • Route up-date packets • paging up-date packets • paging tear-down packets *All the control packets have the same format Control Packets C e l l u l a r I P

  16. IP header ICMP message 8 bit TYPE 8 bit CODE 16 bit CHECKSUM Contents 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Timestamp (64 bits long) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | CU |S| AType | Auth. Length | CU | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Authentication (variable length) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Control information (variable length) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Control Packet(s) Format Is an ICMP packet - source address : IP of sending MH - destination addr : gateway - type : cellular IP - code : control (eg: route up-date) Timestamp : determines order of pkts CU : currently unused S flag( =1) : indicates semi-soft handoff A Type : denotes auth. method used Auth. Length : length of authentication Type : type of control information Length : length of following data Data : determined by Type & Length C e l l u l a r I P

  17. Beacon Signal Structure • Transmitted by each BS periodically • Info carried: • CIP network identifier • IP address of the GW • ID of the paging area C e l l u l a r I P

  18. Paging What is paging & how is it done? process of keeping track of MHs in idle state and promoting to active state upon receiving data • idle MHs periodically generate paging-update messages • paging-update messages travel up the GW • Nodes with PC updates PC mappings • finally GW discards the paging-update packets C e l l u l a r I P

  19. X : from G X : from C Internet with E G Mobile IP GW C Paging-update D A X F R B MH Illustration of Paging I don’t have a PC Paging-update packets create mappings in PCs C e l l u l a r I P

  20. X : from C X : from G Internet with E Mobile IP G G times out GW C D A X F R B MH PCs updated for a moving host No change in PC at A X : from F X : from F,G C e l l u l a r I P

  21. X : from C Internet with X : from F Mobile IP GW E G C D A F R B X MH Paging packets are routed to the mobile host by PCs X C e l l u l a r I P

  22. Paging & Routing caches C e l l u l a r I P

  23. Routing • Basic operation: Same as that of paging • Routing & Paging are separated by two intrinsic time scales • Routing deals with active hosts only • MHs actively receiving data must send route-update packets periodically • PCs do not stop tracking active MHs C e l l u l a r I P

  24. N O D E Dn-links Up-link GW CIP Routing CIP nodes: need to implement the Up-link and Dn-link routing algorithms (only) Packets routed on a hop-by-hop basis How are uplinks configured? • by using a simple shortest path algorithm • Gateway beacon packet are sent C e l l u l a r I P

  25. Uplink Routing • Packet arriving from a Dn-link first updates RC and PC mappings and is then forwarded on Up-link • 5-tuples (mappings) {IP-address, interface, MAC address, exp.time, timestamp} • DATA packets only refresh the caches(RC &PC) but do not change them • A mapping is refreshed only when one exists and the exp.timer is reset ; else pkt dropped exp.time = current time + route-timeout C e l l u l a r I P

  26. Uplink Routing (contd..) • Route-update packets, both refresh and create new mappings in RCs • PCs are updated the same way but uses paging-timeout instead of route-timeout • If it’s a paging-teardown packet, then the mappings from both RC and PC are purged • Finally after the cache modifications the control packet is forwarded on the Uplink C e l l u l a r I P

  27. no no no Pkt from Uplink yes yes yes Downlink Routing • Packet arriving from the Uplink is assumed to be destined to the MH Check for valid mapping in RC Check for PC Broadcast on all links, except the one it came on Forward it to the Dnlink neighbor Check for valid mapping in PC Packet dropped Downlink routing Mechanism C e l l u l a r I P

  28. Handoff in Cellular IP Defn: a change of access point during active data transmission or reception . Types: • Hard Handoff • Semi Soft Handoff C e l l u l a r I P

  29. Hard handoff • Initiated by the mobile host (MH). • Based on signal strength measurements of Beacon Signal from the BS. • MH has capability to listen to only one BS at a time. • During the Handoff Latency the downlink packets are lost. • Not suitable for applications where loss of packets are not tolerated. C e l l u l a r I P

  30. X : from F X : from C X : from E Internet with Mobile IP E G GW C D A X F R B Handoff X : from D X : from D, E C e l l u l a r I P

  31. Semi soft Handoff • Improvement over Hard Handoff ; NO packet loss & smooth handoff. • Trade off: Packets are received in duplication. Mechanism: • Host’s radio device is capable of listening to two logical channels. • Reduces handoff latency by sending semisoft packet to the new BS while listening to the old BS. • The regular handoff occurs after a semisoft delay which is arbitrary value between mobile -GW round trip time and route -timeout. C e l l u l a r I P

  32. Semi soft handoff contd... For smooth handoff 6 5 4 Crossover point BS GW BS GW Crossover pt Need for buffering at the cross over point : 3 NBS 2 OBS 1 NBS OBS Case I Case II Depending on the network topology the time to transmit packets From the cross over point to the new BS and old BS will differ C e l l u l a r I P

  33. Soft handoff mechanism Contd.... • To ensure smooth handoff, a constant delay is introduced temporarily to compensate, with high probability, the time difference between two streams. • Mapping created by the semisoft packet has a flag to indicate that downlink packets must pass through a delay device. • After handoff the flag is cleared and all the packets in delay device is delivered with no further delaying of packets. Goals accomplished: • no packet loss • smooth handoff C e l l u l a r I P

  34. Implementation • CIP comprises of two protocol modules : the Node module & Mobile host modules. NODE module:(important functions) • paging update fn: maintains the paging cache • classifier: parses uplink packets and select those which update the routing cache. • route update fn: updates the routing cache • routing cache look up fn: parses downlink packets and searches the cache for mappings. • Paging cache look up fn C e l l u l a r I P

  35. Implementation contd. • forwarding engine: forwards downlink packets to the interface selected by RC or PC. • Delay device: temporarily inserted in the downlink route if a semisoft handoff is in progress. • Beacon generator for each wireless interface. MH module : • handoff controller: statistics of measured beacon strengths and deciding and performing handoff. • Protocol state machine: active and idle state. • Control packet generator: periodically transmitting route update packets or paging update packets as required by state machine. C e l l u l a r I P

  36. MH implementation contd. Paging packet arrives • Mobile host state machine idle active Sending route update packets Sending paging update All connections closed Assigning “Active state timer”: required to return to idle state. Timer setting depends on the nature of traffic. Trade off: • Higher active state timeout results in more route update packets. • Lesser active state timeout results in more paging packets. C e l l u l a r I P

  37. Gateway Schematic IP network GW controller GW packet filter CIP node • Three building blocks: • CIP node • GW packet filter • GW controller C e l l u l a r I P

  38. GW implementation • CIP node block: the RC and PC are updated by the uplink packets • GW filter: reads the destination IP address. Case 1: If GW’s address, then forwarded to the GW controller. Case II. If not GW’s address, then look up in RC and PC and if an entry is found, then treat the packet as downlink packet. Otherwise send the packet to Internet. • GW controller: control information is processed and the packet is dropped. Recommended that GW has both RC and PC to avoid loading the CIP n/w when no mapping in RC or PC. C e l l u l a r I P

  39. Performance of CIP Three major issues: • performance of Hard and semi soft handoff. Impact of handoff in TCP performance • the cost of setting ‘active state timeout’ at the MH. • Scalability limits of a BS based on Multi homed PC hardware. C e l l u l a r I P

  40. Performance contd... host router • Test configuration GW BS1 BS2 MH C e l l u l a r I P

  41. Performance contd... • In the testbed the BS are statically assigned frequencies. • The MH dynamically changes frequency to perform a handoff. • MH is a 300 MHz pentium PC notebook. • All the three nodes in the CIP are multi homed 300 MHz pentium PCs. • 100 Mbps full duplex links interconnects CIP nodes. C e l l u l a r I P

  42. Handoff performance • MH receives 100 bytes UDP packets at rates of 25 and 50 pps • MH continually make handoffs between BS every 5 seconds. Packet loss per handoff Mobile-GW round trip time (ms) C e l l u l a r I P

  43. Handoff performance contd... Inferences: • hard handoff causes packet loss proportional to the round trip time and to the downlink packet rate. • Semi soft handoff eliminates packet loss completely. C e l l u l a r I P

  44. Handoff performance on tcp throughput downlink TCP throughput [kbps) Number of handoffs per minute C e l l u l a r I P

  45. Handoff performance contd. Inferences: • as the handoff frequency increases, the performance of TCP degrades due to packet loss. • Semi-soft handoff reduced packet loss and significantly improved the throughput in relation to hard handoff. • Unlike the UDP traffic experiment, packet loss is not entirely eliminated which is reflected in in the decline of throughput. C e l l u l a r I P

  46. Active state timeout • This parameter determines the time a mobile host maintains a routing cache mappings after receiving a packet. • It reflects the expectation that one downlink packet may with high probability be soon followed by another and that it is worth keeping up-to-date routing information for sometime. • The trade off involved is the cost associated with transmitting route update packets for maintaining a higher value of timer and reducing paging traffic. C e l l u l a r I P

  47. Rate of paging traffic to mobile [bps] Active state timeout C e l l u l a r I P

  48. Active state timeout contd. Inferences : • paging traffic is reduced drastically by increasing the value of active state timeout timer. • Reducing the paging traffic saves the paging time and buffering requirement at the GW. C e l l u l a r I P

  49. Scalability • Main concern of scalability is the use of per host routes which is required for semi soft handoff. • In CIP scalability is achieved by separating the location management of idle host from active MH. • Thus CIP can accommodate large number of users. C e l l u l a r I P

  50. Scalability contd. throughput [Mbps] Number of entries in routing cache C e l l u l a r I P

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