Scalable Multicasting in Mobile Ad Hoc Networks

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Scalable Multicasting in Mobile Ad Hoc Networks

• Chao Gui, Prasant Mohapatra
• Networks Lab.
• Computer Science Department
• University of California, Davis

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Ad Hoc Network Applications
Law Enforcement
Scientific Exploration
First Response
Personal Communication
Group communication is more important!
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Agenda

• Introduction
• Multicast scalability in MANET
• Two hierarchical Multicast Methods
• Domain-based
• Overlay-driven
• Performance Evaluation

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Hierarchical Routing and Scalability

• Hierarchical routing on Internet
• Unicast
• BGP Intra-domain Routing
• Multicast
• HDVMRP Intern-domain Intra-domain multicast
• Hierarchical routing achieves scalability
• Shrinks the multicast routing table
• aka. reduces protocol state
• Faster forwarding
• Two types of scalability
• Vertical scalability increase of group size
• Horizontal scalability increase of number of
  groups

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Multicast Protocol State Maintenance

• Protocol state is the multicast routing tables at
  each node
• Multicast routing tree/mesh is maintained by
  protocol states
• In MANET, protocol state maintenance takes much
  control overhead
• Multicast scalability is more important in MANET

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Protocol state reduction and constraining

• Overlay multicast
• AMRouteLiu99, PAST-DMGui03
• Backbone-based multicast
• MCEDARSinha99
• Stateless multicast
• DDMJi01, LGTChen02, RDGLuo03

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State Maintenance Overlay Multicast

• Method
• Virtual topology
• Minimal function at IP layer
• Multicast function at overlay layer
• Protocol state
• Constrain its distribution only on group members
• Compare with MAODV or ODMRP
• Pro con
• Pro Robustness against mobility
• Con Data delivery not efficient

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State Maintenance Backbone-based

• Method
• Form clusters, build virtual backbone on
  cluster-heads
• Multicast routing within backbone
• Cluster-heads further deliver to all group
  members
• Protocol State
• Reduce its size simple topology at backbone
• Constrain its distribution only on cluster-heads
• Pro Con
• Pro Backbone topo. more simple stable
• Pro Good for large group size
• Con Not good for horizontal scalability
  traffic bottleneck at the cluster-heads

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State Maintenance Stateless Multicast

• DDM Method
• Source put the addr. of all receivers into packet
  header
• Intermediate nodes consult unicast protocol to
  know how to duplicate/forward the packet
• Protocol state
• No state at any node, only stay within packet
  headers
• Pro Con
• Pro Good at supporting many multicast groups
• Con Packet header overhead
• Con Only good for small groups
• Opposite of backbone-based multicast

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Agenda

• Introduction
• Multicast scalability in MANET
• Two hierarchical Multicast Methods
• Domain-based
• Overlay-driven
• Performance Evaluation

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Hierarchical Multicast in MANET

• Goal
• Explore hierarchical multicast methods different
  than backbone-based multicast
• All multicast groups share same backbone
• Support both vertical and horizontal scalability
• More flexible maintenance of protocol state
• Propose two methods
• Domain based
• Overlay driven

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Domain-based Hierarchical MCast

• Method
• Partition a large mcast group into sub-groups
• Within each sub-group, one node is chosen to be
  sub-root
• The sub-roots together form the upper level mcast
  group
• Source first deliver data packet to sub-roots
  using upper level mcast protocol
• Sub-roots further deliver the packet within its
  sub-group using lower level mcast protocol

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Domain-based Hierarchical MCast
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An example Hierarchical DDM

• Goal
• Make DDM scale up for bigger groups
• Flexible control on amount and distribution of
  protocol states

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Hierarchical DDM

• Sub-root selection and group partition
• Goal adjacent members in same sub-group

leaf node
i
source
(2)
(1)
Packet header

• Source generate HIER_REQ packet.
• Forwarding set includes all group members.
• In this packet, source specifies desired
  sub-group size.
• (2) The packet is forwarded to any intermediate
  node.
• Forwarding set is shrinking while being forwarded.

Packet payload
Forwarding set (in the header)
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Hierarchical DDM

• Sub-root selection and group partition

(4)
i
source
(4)
(5)
(3)
(3)At node i, the forwarding set size matches the
sources desired sub-group size. Node i become
sub-root candidate. (4)Node I send back source
HIER_REP packet, including its forwarding
set. Source will receive HIER_REP packets from
other nodes as well. (5)Source collect HIER_REP
packets and forwarding sets. Based on
them, source makes partition on group member
list, and select sub-roots. (6)If node i is
selected as sub-root, source send it a SR_Confirm
packet, containing sub-group list for node i.
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Hierarchical DDM

• Sub-root selection and group partition

i
(6)
source
(7)
(6)If node i is selected as sub-root, source send
it a SR_Confirm packet, containing sub-group list
for node i. (7)Node i records its sub-group list.
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Hierarchical DDM

• Further details
• Hierarchy maintenance
• Join and leave operations
• Dynamic partitioning

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Summery

• Introduction
• Multicast scalability in MANET
• Two hierarchical Multicast Methods
• Domain-based
• Overlay-driven
• Performance Evaluation

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Overlay Driven Hierarchical MCast

• Upper level mcast
• Build an overlay multicast tree on all group
  members
• In overlay mcast tree, each non-leaf node is a
  forking point, assigned with an FORK_ID

4
S
2
3
1
a)Overlay mcast tree
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Overlay Driven Hierarchical MCast

• Lower level mcast
• At each forking point, form a lower level group
• Source of this group is the forking point,
  receivers are its children in overlay tree

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1
4
3
S
b)Overlay driven hierarchical mcast tree
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Implementation

• Implementation
• Upper level AMRoute
• Lower level DDM
• Operations
• Use AMRoute maintain overlay mcast tree
• Source use DDM to deliver data packet to its
  children in overlay tree
• Compared to using multiple unicasts
• Each children nodes continue to use DDM to
  deliver packet to their children

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Agenda

• Introduction
• Multicast scalability in MANET
• Two hierarchical Multicast Methods
• Domain-based
• Overlay-driven
• Performance Evaluation

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Performance v.s. Group Size
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Performance v.s. Group Size
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Performance v.s. Group Size
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Performance v.s. Group Size
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Performance v.s. Groups
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Performance v.s. Groups
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Performance v.s. Groups
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Performance v.s. Groups
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Summery

• Introduction
• Multicast scalability in MANET
• Two hierarchical Multicast Methods
• Domain-based
• Overlay-driven
• Performance Evaluation

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Introduction

• Mobile Ad Hoc Network
• On-the-fly deployment
• Low power
• Numerous app.