Transcript (b) Ad hoc Wireless

Multicast In Wireless Mobile
Environments
Reporter:江俊毅
Introduction
 Wireless Network Categories
 Multicasting for wireless mobile hosts in an
IP network is a challenging task
 We first introduce the issues involved in
providing multicast in a mobile environment
 Discuss details of proposed multicast
routing protocols
Wireless Network Categories
 Infrastructure Wireless:
base station network is connected to
the wired Internet.
 Ad hoc Wireless:
wireless nodes communicate directly
with one another.
Wireless LANs
(a) Infrastructure Wireless
(b) Ad hoc Wireless
Issues In Mobile Environments
 Multicast Forwarding Algorithm
 A source-based protocol like DVMRP ,DVMRP
forwards multicast packets only if it receives
them on the correct interface
 when mobile host (MH) moves to a new domain ,
its interface to the multicast router changes ,
resulting in the packets being dropped
Issues In Mobile Environments
 Dense or Sparse Model Protocol
 The dense mode protocols are useful if there
are a lot of users and bandwidth availabilitiy is
not a problem, whereas sparse mode protocols
are meant for widely distributed users with
limited bandwidth.
Issues In Mobile Environments
 Qos Provisioning
 Quality of service (QoS)-based wireless
multicasting is an open issue
 In this section we first describe Mobile-IP
based multicasting protocols
Proposals for Multicast over MIP
 Remote Subscription
 In remote subscription an MH resubscribes to
the multicast group each time it moves to a
new foreign network.
 It is the simplest way of providing multicast
through Mobile IP.
Remote Subscription
Out-of-synch problem
Proposals for Multicast over MIP
 Bidirectional Tunneling
 In this scheme MHs send and receive multicast
packets by way of their home agents (HAs),
using unicast Mobile IP tunnels from their HAs.
Bidirectional Tunneling
Tunnel convergence
Multicast support using Mobile IP
 Multicast support using Mobile IP (MoM)
 MoM is based on bidirectional tunneling
 MoM selected HA among the given set of HA is
called designated multicast service provider
(DMSP)
MoM
DMSP select
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Classify
1.Agent based
2.Count-based
3.Proximity-based
4.Random-based
RBMoM
 Range-Based Mobile Multicast (RBMoM)
 RBMoM provides a trade-off between the
shortest delivery path and the frequency of
multicast tree reconfiguration
 It selects a router called a multicast HA(MHA)
 Every MH can have only one MHA
 MHA(Multicast HA) is responsible for tunneling
multicast data to foreign networks
Select the new MHA
Proposals for Multicast over MIP
 Multicast for Mobility Protocols (MMP)
 MMP uses a sparse mode multicast routing
protocol Core Base Trees (CBT) to handle the
movement of mobile nodes within a foreign
network.
 This scheme uses a shared-tree, to and from a
centre point called the core of the network.
 MMP relies on Mobile IP Agent Discovery
procedure in order for mobile hosts to discover
relevant Mobility Agents and obtain a multicast
care-of-address.
MMP
1.BS transmit periodic beacons
with Agent Advertisement
messages
2.MN transmits a Registration
Request to the base station
3.BS will send a Join request
to the Core and create a
permanent group
4.MN moves to another cell,
it will initiate handoff when it
receives a stronger beacon
MobiCast
 MobiCast is designed for an internetwork
environment with small wireless cells, with
many cells grouped together and served by
domain FAs (DFAs).
MobiCast
WHEN MN JOIN GLOUP X
1.MN send IGMP message to
DFA
2.DFA instead MN join X
3. Construct multicast
group Y and MN join group Y
Y
Y
Y
4.X-> DFA-> Y-> all AP
Reliable Wireless Multicast Protocols
 Reliable Multicast Data Distribution Protocol (RMDP):
 Uses Forward Error Correction (FEC) and
Automatic Retransmission reQuest (ARQ)
information to provide reliable transfer.
Redundant information is inserted into the FEC,
often enabling a receiver to reconstruct the
original packet.
 In the event that such information is not enough,
an ARQ is sent to the multicast source which in
turn, multicasts the requested packet to all
receivers.
Reliable Wireless Multicast Protocols
 RM2
 RM2 is a reliable multicast protocol that can be
used for both wired and wireless environments.
 RM2 is a hierarchical protocol that divides a
multicast tree into subtrees where subcasting
within these smaller regions is applied using a
tree of retransmission servers (RSs)
Reliable Wireless Multicast Protocols
 RS having a retransmission subcast address
shared by its members and which may be
dynamically configured using the IETF’s
Multicast Address Dynamic Client Allocation
Protocol (MADCAP).
 The receivers are required to send negative
acknowledgments (NACKs), pointing out the
packets to be retransmitted.
RM2
compare
Conclusion
 This article is an attempt to give an overview of
current research in wired and wireless multicast
field and show that this area is rapidly growing
and evolving.
 Future directions in wireless multicast need to
consider QoS, security, and so on.
 Furthermore , a detailed investigation is
desirable for both unreliable and reliable
environments.
END
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