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