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  1. 1. VoIP Mobility Pavan Kundhavaram
  2. 2. Contents <ul><li>Introduction. </li></ul><ul><li>VoIP Mobility. </li></ul><ul><li>Issues. </li></ul><ul><li>Conclusion. </li></ul><ul><li>References. </li></ul>
  3. 3. VoIP Introduction <ul><li>VoIP is Voice Over IP. </li></ul><ul><li>VoIP is the routing of voice conversations over the internet or any other IP-based network. </li></ul><ul><li>Voice Calls are transmitted over Packet switched Network instead of Public Switched Telephone Network(PSTN). </li></ul><ul><li>VoIP allows users to travel anywhere in the world and still make and receive phone calls. </li></ul>
  4. 4. How It Works <ul><li>VoIP converts the voice signal from telephone into a digital signal that travels over the internet then converts it back at the other end . </li></ul><ul><li>A broadband connection is required in order to place VoIP call. </li></ul>
  5. 5. VoIP Mobility <ul><li>Mobility include : </li></ul><ul><ul><li>Terminal Mobility. </li></ul></ul><ul><ul><li>User Mobility. </li></ul></ul><ul><ul><li>Service Mobility. </li></ul></ul>
  6. 6. Issues <ul><li>Optimizing the Handover Delay . </li></ul><ul><li>Mobility Management for VoIP Traffic. </li></ul><ul><li>VoIP Seamless Handover. </li></ul>
  7. 7. Issue#1:Optimizing Handover Delay <ul><li>The support of IP-based real time services in the next-generation systems require coupling of mobility with QOS. </li></ul><ul><li>Coupling host mobility and quality of service is one of main challenges. </li></ul><ul><li>The mobile node can experience disruptions or intermittent disconnections of on going real-time session due to handovers. </li></ul>
  8. 8. Issue#1 contd.. <ul><li>The time or duration of such interruption is called disruption time. </li></ul><ul><li>The handover delay is the time interval from when the handover process starts to when the first data packet is received by MN. </li></ul><ul><li>The handover delay can heavily affect the user satisfaction . </li></ul>
  9. 9. Proposed Solution <ul><li>First step : Simple model that takes into account the delay increases between the different entities involved in the handover. </li></ul><ul><li>Second step: Considers FER of the wireless link and the retransmissions strategies of the different protocols to overcome the losses. </li></ul>
  10. 10. Simple Model for Analysis
  11. 11. Analysis contd.. <ul><li>the delay between the MN and the Radio Access Network (RAN) is tmr. </li></ul><ul><li>the delay between the MN and the Access Router (AR)is ts . </li></ul><ul><li>the delay between the MN and the FA/MAP is tmf . </li></ul><ul><li>the delay between the MN and its HA is assumed to be th . </li></ul><ul><li>the delay between the MN and the CN is tmc . </li></ul><ul><li>the delay between the MN’s home network and the CN is thc. </li></ul>
  12. 12. Assumptions <ul><li>ts<th. </li></ul><ul><li>In MIPv4 FACoA instead of CCoA is used therefore MN’s incoming and outgoing traffic is relayed by the FA. </li></ul><ul><li>The MN sends regularly solicitations after leaving one network. </li></ul><ul><li>For each binding update (BU) message sent ,Binding Acknowledge (BA) is expected to be received. </li></ul><ul><li>For MIPv6 registration we do not consider the time needed by Duplicate Address Detection (DAD) process. </li></ul>
  13. 13. MIPv4 handoff <ul><li>The MN detects the IP subnet by exchanging Agent Solicitation and Agent Advertisement messages which takes 2 tmf . </li></ul><ul><li>Then, the MN sends a MIP Registration Request to the HA and gets a Registration Reply, which takes 2 th . </li></ul><ul><li>At this MN starts receiving downlink packets. </li></ul><ul><li>The MIPv4 handoff takes 2 tmf + 2 th . </li></ul>
  14. 14. MIPv6 handoff <ul><li>The MN detects the IP subnet by exchanging with AR Router Solicitation and Router Advertisement messages that takes 2 ts . </li></ul><ul><li>MN sends to HA a Binding Update and gets a Binding Acknowledge that takes 2 th . </li></ul><ul><li>Finally, the MN sends to the CH a Binding Update and gets a Binding Acknowledge that takes 2 tmc . </li></ul><ul><li>The MIPv6 handoff delay is 2 ts + 2 th + 2 tmc . </li></ul>
  15. 15. Second Step Assumptions <ul><li>A random error process. </li></ul><ul><li>An Agent/Router Advertisement is sent only if a Agent/Router Solicitation has been previously received. </li></ul><ul><li>An Registration Reply/Binding Acknowledge is sent only if a Registration Request/Binding Update has been received previously. </li></ul><ul><li>Error correction mechanisms and processing /queuing times are not considered here. </li></ul>
  16. 16. Second Step contd.. <ul><li>Probability of the frame being erroneous in the air link is p. </li></ul><ul><li>For k frames in MIP packet ,the packet loss rate is </li></ul><ul><li>(1 − (1 − p ) k ) . </li></ul><ul><li>We denote τ as the inter frame time. D as the frame propagation delay through the RAN. </li></ul><ul><li>Propagation delay from MN to RAN for a MIP message is </li></ul><ul><li>D + ( k − 1) τ . </li></ul>
  17. 17. Adaptive Retransmission timer <ul><li>The retransmission timers for all the MIP-based protocols follow the exponential back-off mechanism. </li></ul><ul><li>Tr (1) be the initial back-off timer. </li></ul><ul><li>The back-off timer upon the ith transmission Tr ( i ) doubles after each retransmission </li></ul><ul><li>Tr ( i ) = 2 ( i− 1) · Tr (1) </li></ul>
  18. 18. contd.. <ul><li>the initial retransmission timer Tr (1) is a crucial parameter which should be optimized </li></ul><ul><li>It should not be too short. </li></ul><ul><li>It should not be too long. </li></ul><ul><li>It is proportional to the transmission time of the messages involved in the handover transaction. </li></ul>
  19. 19. Back-off interval timer
  20. 20. Retransmission Probability <ul><li>The probability of retransmission q is the probability of a </li></ul><ul><li>transaction having failed </li></ul><ul><li>The probability of having a retransmission of Solicitation is: </li></ul><ul><li>q = 1 − ((1 − p ) k 1+ k 2 ) </li></ul>
  21. 21. Average Handover Delay <ul><li>Let Nm be the maximum number of transmissions. </li></ul><ul><li>The average delay for a successful transaction is the average delay for successfully transmitting and receiving the corresponding acknowledgement of an MIP message. </li></ul><ul><li>The average handover delay Tt MIP is given as: </li></ul><ul><li>Tt MIP = ∑ Tt ( i ) MIP </li></ul>
  22. 22. contd.. Tt ( i ) MIP =1/1 − q Nm · [(1 − q ) ( D + ( k − 1) τ ) +(1 − q ) q ( Tr (1) + D + ( k − 1) τ ) +(1 − q ) q 2 · (3 Tr (1) + D + ( k − 1) τ ) + · · · +(1 − q ) q Nm− 1 · ((2 Nm− 1 − 1) Tr (1) + D + ( k − 1) τ )] = D + ( k − 1) τ − Tr (1) + ((1 − q )(1 − (2 q ) Nm ))/(1 − q Nm )(1 − 2 q )) · Tr (1)
  23. 23. MIPv4 Handover Delay <ul><li>MIPv4 average handover delay is </li></ul><ul><li>TtMIPv 4 = Tt ( AgSol ) + Tt ( AgAdv ) + 2 trf </li></ul><ul><li>+2 trh + Tt ( RegReq ) + Tt ( RegRep ). </li></ul><ul><li>Where trf is the delay between the RAN and the FA </li></ul><ul><li>( trf = tmf − tmr ) and trh is the delay between the RAN </li></ul><ul><li>and the HA ( trh = th − tmr). </li></ul>
  24. 24. MIPv6 Handover Delay <ul><li>MIPv6 average handoff delay is as follows: </li></ul><ul><li>TtMIPv 6 = Tt ( RSol ) + Tt ( RAdv ) + 2 trf </li></ul><ul><li>+2 trh + 2 trc + 2 Tt ( BU ) + 2 Tt ( BA). </li></ul><ul><li>where trc is the delay between the RAN and the CN trc = tmc − tmr . </li></ul>where trc is the delay between the RAN and the CN trc = tmc − tmr ).
  25. 25. Numerical Results
  26. 26. Disruption time vs. FER
  27. 27. Issue#2: Mobility Management for VoIP Traffic <ul><li>IP based mobility management traditionally operate at the network layer and provide basic connectivity to the MN as they change their point of attachment. </li></ul><ul><li>MIP ensures ubiquitous connectivity by allowing MN to retain its permanent home address(PHoA) and by tunneling packets to temporarily care of address(CoA). </li></ul><ul><li>These solutions are necessary for VoIP application in dynamic tactical battlefield networks. </li></ul>
  28. 28. Issue contd.. <ul><li>MIP potentially high update latency makes it unsuitable for supporting seamless handoffs during ongoing call. </li></ul><ul><li>SIP at application layer offers many advantages over corresponding MIP but suffers a drawback of absence of mobility management hierarchy. </li></ul><ul><li>SIP and MIP use flat hierarchy in which every change in MN requires generation of global binding updates. </li></ul><ul><li>Updates incur high latency and make rapid handoffs impossible. </li></ul>
  29. 29. Draw backs of Flat Architecture <ul><li>On every change in subnet. </li></ul><ul><ul><li>MN refreshes its configuration information (COA) . </li></ul></ul><ul><ul><li>Generate global bindings to update remote nodes with new COA. </li></ul></ul><ul><li>In absence of hierarchy every update travel all the way to the remote node. </li></ul><ul><li>Update process can have high latency because of communication delay. </li></ul><ul><li>If there is packet loss latency becomes much higher at intermediate hops. </li></ul>
  30. 30. Solution:DMA Architecture <ul><li>The DMA Architecture is based on two-level mobility management hierarchy. </li></ul><ul><li>IDMP is used as the protocol for managing mobility within a domain. </li></ul><ul><ul><li>The Mobility Agent(MA) is similar to MIP foreign Agent (FA) excepts it resides higher in network hierarchy and acts as a domain-wide point for packet redirection. </li></ul></ul><ul><ul><li>A Subnet Agent (SA) is similar to MIP FA and provides subnet-specific mobility services. </li></ul></ul>
  31. 31. IDMP Architecture
  32. 32. contd.. <ul><li>Under IDMP MN has two concurrent CoAs: </li></ul><ul><ul><li>Global Care of Address(GCoA). </li></ul></ul><ul><ul><li>Local Care of Address (LCoA). </li></ul></ul><ul><li>Packets from a remote CN are forwarded to the GCoA and are intercepted by the MA. </li></ul><ul><li>The MA tunnels these packets to the MN’s current LCoA. </li></ul><ul><li>Global binding updates are generated only when the MN changes domains and obtains a new GCoA, </li></ul><ul><li>This approach drastically reduces the global signaling load. </li></ul>
  33. 33. Elements of DMA Architecture
  34. 34. Dynamic technique <ul><li>The DMA architecture defines a dynamic technique for assigning an MA to an MN when it first moves into the domain. </li></ul><ul><li>The architecture assumes the presence of multiple MAs and applies a load balancing technique for distributing the mobility load across the multiple MAs. </li></ul><ul><li>A central node called the Mobility Server (MS) implements different load balancing and MA-allocation strategies. </li></ul>
  35. 35. Contd.. <ul><li>The architecture also uses the Differentiated Services framework to dynamically provision domain resources and provide an MN QoS guarantees as it moves within the domain. </li></ul><ul><li>DMA requires MN to obtain a new LCoA if network mobility is confined to single mobility domain. </li></ul><ul><li>A group of 200 soldiers communicating with 5CNs would generate 1000 simultaneous global binding updates under flat architecture but only 200 local updates under DMA approach. </li></ul>
  36. 36. Signal Flow of VoIP Mobility
  37. 37. Issue#3:VoIP Seamless Handover <ul><li>The period from when the MN last receives data traffic via its old IP subnet to when it receives it new IP subnet is handover delay. </li></ul><ul><li>Delay is divided into four sub-delays: </li></ul><ul><ul><li>Layer 1/Layer 2 radio link switching delay. </li></ul></ul><ul><ul><li>L2 access re-authentication delay. </li></ul></ul><ul><ul><li>IP layer binding delay. </li></ul></ul><ul><ul><li>Application layer authentication and registration delay, </li></ul></ul>
  38. 38. Contd.. <ul><li>The Inter-AP handoff is reduced Inter-Access point protocol is proposed. </li></ul><ul><li>L2 re-authentication delay could be reduced during inter-AP roaming. </li></ul><ul><li>IP layer binding delay is due to allocation of dynamic IP address via DHCP followed by routing path update to new AP. </li></ul><ul><li>DHCP delay in Mobile IP and application layer authentication and registration delay in SIP mobility is a challenge. </li></ul>
  39. 39. Solution:VPN Technology <ul><li>The MN is identified by its static private IP address regardless of its current point of attachment to the subnets. </li></ul><ul><li>This allows the MN to use the same IP address during handover. </li></ul><ul><li>When the mobile host hands off to any other AP the new AP receives session information in advance hindering further messages. </li></ul><ul><li>The delay of re-authentication for the MN is reduced. </li></ul>
  40. 40. Link Layer <ul><li>The packet loss and end to end transmission delays can be reduced. </li></ul><ul><li>MN moves from one subnet to another subnet without interruption only if </li></ul><ul><ul><li>MN should communicate simultaneously with multiple APs. </li></ul></ul><ul><ul><li>The network must duplicate and correctly merge the IP flows from the CN to the MN through different APs. </li></ul></ul>
  41. 41. Multi-Homing Concept <ul><li>The multi-homing feature enables the MN to support seamless handover by simultaneous binding of two different addresses. </li></ul><ul><li>The packets are multicast to MN and MIP agents without need to tunnel packets to the NAR form the PAR as in Mobile IPv6 networks. </li></ul><ul><li>The packet loss is reduced during the handover. </li></ul>
  42. 42. Mobile Agent Technology <ul><li>The MA is software component which can be transferred from one network element to another while carrying on its status of execution. </li></ul><ul><li>MA technology can diminish network traffic and can maintain load balancing thus improving network performance specially in mobile environment. </li></ul><ul><li>MA technology in VoIP services includes reducing control packets, processing the SIM-based authentication via the VPN tunnel at new location of attachment and secure packet tranmission. </li></ul>
  43. 43. Mobile Agents to support seamless VoIP service <ul><li>Both IP layer binding delay and application layer authentication and registration delay are major parts of the overall handover delay. </li></ul><ul><li>The delay of IP address renewal (> 2s) has significant effect on the overall handover performance. </li></ul><ul><li>The application layer authentication and registration delay is harder to reduce than the DHCP delay and cannot be ignored due to security consideration. </li></ul>
  44. 44. Seamless Handover Architecture
  45. 45. Solution C ontd.. <ul><li>Layer 2 Tunneling Protocol (L2TP) VPN tunnels are </li></ul><ul><li>constructed between the L2TP Network Server (LNS) and all </li></ul><ul><li>L2TP Access Concentrators (LACs). </li></ul><ul><li>Service and authentication requests and data packets are </li></ul><ul><li>protected under IPSec tunnels while transmitted between the </li></ul><ul><li>MN and LNS. </li></ul><ul><li>They are further encapsulated into L2TP VPN tunnels during </li></ul><ul><li>transmission between the LNS and LAC. </li></ul>
  46. 46. contd.. <ul><li>The LNS function as a service proxy to forward the service requests from the MN to the application server. </li></ul><ul><li>To minimize the DHCP delay, IP binding delay and application layer authentication delay there are three techniques </li></ul><ul><ul><li>VPN with a private static IP address. </li></ul></ul><ul><ul><li>Multi-homing. </li></ul></ul><ul><ul><li>Mobile Agent. </li></ul></ul>
  47. 47. contd.. <ul><li>L2TP VPN can be implemented as an Intranet. </li></ul><ul><li>It can have the static private IP addresses assigned to its private MNs regardless of their location. </li></ul><ul><li>The fast handover for Mobile IPv6 tries to minimize the period of service disruption by the packet tunneling mechanisms while performing network layer handover. </li></ul><ul><li>The multi-homing concept is used to minimize the disruption time and packet loss ratio. </li></ul>
  48. 48. Message flows During Handover
  49. 49. Conclusion <ul><li>The issues discussed above deal with the various VoIP protocols and various standard both at the network layer and application layer. </li></ul><ul><li>In order to achieve transmission during roaming is a challenge and this can be achieved with proper hand over of the signal to the next BS. </li></ul>
  50. 50. References <ul><li>Fathi, Chakraborty, Prasad .”Mobility management for VoIP: Evaluation of Mobile IP-based protocols”.IEEE ,2005. </li></ul><ul><li>Misra ,Das,Anthony.”Hierarchical Mobility Management for VoIP Traffic”.IEEE 2001. </li></ul><ul><li>Lin ,Shun Yang.” Mobile Intelligent Agent Technologies to Support VoIP Seamless Mobility”.IEEE 2005 . </li></ul><ul><li>T. T. Kwon, M. Gerla, and S. Das, “Mobility Management for VoIP service: Mobile IP vs. SIP,” IEEE Wireless Communications, vol. 9, no. 5,pp. 66–75, October 2002 . </li></ul>