Mobile IP: Multicast Service

Reference: “Multicast routing protocol in mobile networks”; Hee-Sook Shin; Young-Joo Suh;, Proc. IEEE International Conference on Communications (ICC), 2000; pp. 1416 -1420 (MobileIPMulticast-1.pdf)

Reference: “Multicast routing by mobility prediction for mobile hosts”; Young-Joo Suh; Dong-Hee Kwon, and Woo-Jae Kim, Proc. IEEE ICC, 2003; pp. 865 -869 (MobileIPMulticast-7.pdf)

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Related Work• Foreign agent-based multicast

– Remote subscriptionA mobile host has to subscribe to multicast groups

whenever it moves to a foreign net.

Simple, not required any encapsulations

Offering an optimal routing path

Non-existence of duplicated packets

Mobility expensive multicast service

Extra delay incurred from rebuilding a multicast tree

can create the possibility of a disruption in multicast

data delivery

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Related Work (cont)• Home agent-based multicast

– Bi-directional tunnelingData delivery is achieved by unicast Mobile IP tunnlei

ng via the home agent

When the HA receives a multicast packet destined for a mobile host, it encapsulates the packet twice (with 1. the mobile host address and 2. the care-of-address of the mobile host) and then transmits the packet to the mobile host as a unicast packet

If multiple mobile hosts that belong to the same home network visit the same foreign network, duplicate copies of multicast packets will arrive at the foreign network (see the figure on next slide)

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Multicast data duplication problem in HA-based multicast

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Related Work (cont)

• MoM (Mobile Multicast)- Ref.8 ACM MOBICOM’97

– Improve home agent-based multicast protocol

– A HA forwards only one copy of the multicast packet to each foreign network that contains its mobile hosts

– Upon receiving the multicast packet, a FA delivers it to mobile hosts using link-level multicasting

– Tunnel convergence problem

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Tunnel convergence problem

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Tunnel convergence problem• Solution

– The FA appoints one HA as the DMSP (Designated Multicast Service Provider) for the given multicast group

– The DMSP forwards only one packet into the tunnel, while other HAs that are not the DMSP do not forward the packet

– Drawback: multicast packets from both the DMSP and a multicast router can cause a duplication since it is possible that local static hosts in the foreign network are members of the same group as the visiting mobile hosts (see the figure on next slide)

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Duplication problem for DMSP scheme

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Non-optimal delivery route for DMSP scheme

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Proposed Protocol• MMA (Multicast by Multicast Agent)

– Multicast Agent (MA), Multicast Forwarder (MF)

– MAs provide multicast service to mobile hosts

– Each MA has one MF per multicast group and the MF of an MA is the MA that forwards multicast packets to it

– The MF of an MA may be the MA itself when its local network is included in the multicast tree

– Or the MF can be an MA in another network that belongs to the multicast group

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Proposed Protocol (cont)• Example

– A mobile host moves from N1 to N2

– 1. The mobile host send its MF information to the MA in N2 during registration, which is used by the MA for selecting the new MF

– 2. If N2 belongs to the multicast delivery tree, the MA itself becomes the MF

– 3. If the MA in N2 does not belong to the multicast delivery tree, the MF value that the mobile host had in N1 is used as the MF in N2

– 4. Optionally, the MA in N2 selects one that is closer to it, between the MF information that the MA had and the MF that the mobile host had in N1

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Proposed Protocol (cont)

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Proposed Protocol: data structure

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Algorithm: when a MH arrives

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Algorithm: when a multicast datagram arrives

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Algorithm: when a MH (member) leaves the current network

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Algorithm: a control packet from another MA arrives

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Discussion

• The proposed MMA protocol offers better (sub-optimal) delivery route than HA-based protocols since the MF is generally located in an adjacent network that is included in the multicast delivery tree

• The MMA protocol reduces the number of duplicated packets and total amount of tunneling since multicast packets can be forwarded directly from the multicast router in the current network

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Performance Evaluation

• Compare: MMA, MoM, HA-based protocol

• Criteria

– Amount of multicast data traffic

Traffic on the multicast tree + traffic occurred by tun

neling from MF to the mobile host

– Average delivery path length

– Scalability with multicast group size

– Comparison of DMSP handoff with MF handoff

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Simulation Parameters

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Discussion- Tunneling

• The number of tunneling is proportional to

– 1. The number of mobile hosts in the HA-based multicast protocol

– 2. The number of foreign networks which has mobile hosts having multicast membership in the MoM protocol

– 3. The number of MAs which receive data forwarded by an MF (for MMA protocol)

– See the figure on next slide

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Simulation result- Fig. 8

T = 50, MR=3

# o

f tu

nn

elin

g

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Simulation result- Fig. 9

• MMA shows an improved performance and the difference becomes larger for large tree sizes

MoM sparse

MMA sparse

Optimal

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Simulation result- Fig. 10

+

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Discussion- Fig. 10

• MoM shows shorter tree path length than MMA, but MoM shows much more tunnel path length than MMA

• As a result, MMA shows less total path length than MoM

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Simulation result- Handoff

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Discussion- Fig. 11

• MF handoff frequency in MMA is much less than DMSP handoff frequency

• Problem of frequent DMSP handoff– Cause much traffic in network

– Increase network overhead

– Cause performance degradation due to the out-of service period during handoff

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Extended work (ICC2003)

• Remote-subscription vs. MA-based Tunneling

• Allow necessary join operations– Reduce packet delivery length– Minimize the number of unnecessary join

• Necessary join– Only when the mobile host is expected to

remain in the network relatively long period of time

– Staying time at the previous network(s)– Threshold value for join

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Extended work (example)

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Host Mobility Prediction

• Speed: GPS (not always available)

• Expected staying time

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Simulation: Network Model

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Simulation: Parameters

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Simulation result: Fig. 3#

of

tun

nel

ing

MMA with join option

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Simulation result: Fig. 4

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Simulation result: Fig. 5

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Simulation result: Fig. 6a

# of MAs that currently have no visiting MHs subscribing multicast groups that MAs join for the MHs