Download End System Multicast

Introduction
 MANET
 Examples
 Performance Matrics
 Conclusions

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
Traditional network architectures
distinguish between two types of entities
› end systems (hosts) and the network (routers
and switches).

The key architectural question is: what
new features should be added to the IP
layer?
› Multicast and QoS
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Delivery of information to a group
 Creating copies only when the links to
the multiple destinations

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video-on-demand
 live media streaming
 video conferencing
 multiplayer games


Real time and large data flow
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
In deciding whether to implement
multicast services at the IP layer or at
end systems, there are two conflicting
considerations that we need to
reconcile.
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
First, IP Multicast requires routers to
maintain per group state
› violate the “stateless” architectural principle,
and introduce high complexity and serious
scaling.

Second, IP Multicast calls for changes at
the infrastructural level
› slows down the pace of deployment.
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
Finally, IP Multicast is providing higher
level features such as reliability,
congestion control, flow control, and
security has been shown to be more
difficult than in the unicast case.
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
We consider a model in which multicast
related features, such as group
membership, multicast routing and
packet duplication, are implemented at
end systems, assuming only unicast IP
service.
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An overlay approach to multicast,
however efficient, cannot perform as
well as IP Multicast.
 It is impossible to completely prevent
some redundant traffic on physical links.
 Communication between end systems
involves increasing latency.

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(b) naive unicast transmission.
 (c) the IP Multicast tree constructed by
DVMRP
 (d) an “intelligent” overlay tree

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Issues
IP multicast
Application multicast
efficiency in terms of
delay/bandwidth
High
Low — Medium
Complexity or
Overhead
Low
Medium — High
Ease of deployment
Low
Medium — High
OSI layer works
Network layer
Application layer
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
GROUP MANAGEMENT
› Mesh First vs. Tree First
› Source Specific Tree vs. Shared Tree
› Refinement

ROUTING MECHANISM
› Shortest Path
› Minimum Spanning Tree
› Clustering Structure
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
Tree-based
› Source node as the root, thus there is only
one single path between every pair of
sender and receiver.
› It’s very efficient since the routing
information needs to be maintained is very
little.

Mesh-based
› More than one path between each sender
and receiver pair exists.
› More robust but less efficient.
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
Source-tree-based
› It construct a multicast tree among all the member
nodes for each source node.(usually this is a shortest
path tree)
› More efficient.
› Too much routing information to maintain.

Shared-tree-based
› It constructs only one multicast tree for a multicast
group including several source nodes. (usually this is
a minimum spanning tree)
› Every source uses this tree to do multicast.
› Less efficient.
› It reduces the overhead greatly by maintaining less
routing information.
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
Constructed trees might be different
› Depending upon the order of joining
requests
› Construct the tree in real time and have no
a-priori knowledge of node arrivals

Local optimum to the global optimum
and improves the system’s performance
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A Shortest Path Tree constructs a
minimum cost path from a source node
to all its receivers
 A source-specific multicast tree or in
graph theoretic terms a rooted tree

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Construct a low cost tree
 Used by a shared tree

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Construct a hierarchical cluster of nodes
with each cluster having a head
 Advantages

› Reduction in control overhead
› Faster joining and leaving
› A sub-optimal tree
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Form a temporary and dynamic wireless
network on a wireless channel without
the fixed infrastructure
 Self-organizing collection of Mobile
Nodes
 Low bandwidth, mobility and low power
 Due to the limited transmission range,
multiple hops may be needed

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router vs. forwarding node
 traverse internet vs. multi-hops routing
 fixed vs. topology changes frequently

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
Proactive (table-driven)
› continuously evaluate routes
› maintain up-to-date routing information
› periodically flood its location to other nodes
› maintains a location table

Reactive (on-demand)
› routing creates routing only when desired
› in searching of the destination
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
Explicit
› Location update is sent to a defined subset
(update quorum)
› Location query is sent to a subset (query
quorum)

Implicit
› Location servers are chosen via a hashing
function
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Multicast On-demand Distance Vector
routing protocol
 This protocol uses broadcast to find the
route in an on-demand way and
constructs a shared routing tree.
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Group Join Process
Multicast
Broadcast
Activation
- RREQ
Broadcast
Group
Hello
Only GM Responds
Group
member
Multicast Tree member
Ordinary node
Potential Group
member
Multicast link
Communication link
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Leaving a Multicast Group
Group
member
Multicast Tree member
Non leaf Node
Must remain as a Tree member
Ordinary node
Potential Group
member
Multicast link
Communication link
Leaf Node
Can remove
itself from
Again
Leaf Node
MTfrom MT
Remove himself
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Node must periodically hear from active
neighbors to know they are still within
range
 Every time hear broadcast, update
lifetime
 If no broadcast with hello_interval,
broadcast Hello packet
 Failure to hear from a neighbor for

› (1 + allowed_hello_loss ) * hello_lifetime
indicates loss of link
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
Source broadcasts
› Route Request(RREQ)
› <J_flag, R_flag, Bcast_ID,
RREQ
Src_Addr, Src_Seq#, Dst_Addr,
Source
Dst_Seq#, HopCnt>
 Node can reply to RREQ if
› – It is the destination
› – It has a “fresh enough” route to
the destination


Nodes create reverse route
entry
Record Src IP Addr / Broadcast
ID to prevent multiple
processing
Destination
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
Source broadcasts
› Route Request(RREQ)

Node can reply to RREQ
if
Source
› – It is the destination
› – It has a “fresh enough”
route to the destination


Nodes create reverse
route entry
Record Src IP Addr /
Broadcast ID to prevent
multiple processing
RREP
Destination
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
Source broadcasts
› Route Request(RREQ)

Node can reply to
RREQ if
Source
› – It is the destination
› – It has a “fresh enough”
route to the destination
Nodes create reverse
route entry
 Record Src IP Addr /
Broadcast ID to prevent
multiple processing

Destination
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Nodes along path
create forward
route to dest
 Source begins
sending data when
receives first RREP

Source
Destination
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
GROUP MANAGEMENT
› Tree First
› Shared Tree
› No refinement

ROUTING MECHANISM
› Minimum Spanning Tree

MANET ROUTING
› Reactive
› Flat
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
Latency
› end-to-end delay

Bandwidth
› throughput at the receiver

Stress
› number of identical copies of a packet
carried by a physical link
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
Resource Usage
› 57 / 30 / 32

Protocol Overhead
› total bytes of non-data traffic
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Although, MANET multicast is an ALM,
using wired mech. cannot perform well.
 Actually, there is no a “one-for-all”
scheme that works well with different
scenarios.
 Highly dynamic environment, nodes
move arbitrarily, thus network topology
changes frequently and unpredictably
 Moreover, bandwidth and battery
power are limited.
 Make multicast extremely challenging

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Tu, W. & Jia, W., “An End Host Multicast Protocol for Peerto-Peer Networks,” LCN '05: Proceedings of the The IEEE
Conference on Local Computer Networks 30th
Anniversary IEEE Computer Society, 2005, pp. 392-399
 Hosseini, M., Ahmed, D., Shirmohammadi, S. & Georganas,
N., “A Survey of Application-Layer Multicast Protocols,”
Communications Surveys & Tutorials, IEEE, 2007, Vol. 9(3),
pp. 58-74
 Junhai, L., Danxia, Y., Liu, X. & Mingyu, F., “A survey of
multicast routing protocols for mobile Ad-Hoc networks,”
Communications Surveys Tutorials, IEEE, 2009, Vol. 11(1), pp.
78 -91
 Perkins, C. & Royer, E., “Ad-hoc on-demand distance
vector routing,” Mobile Computing Systems and
Applications, 1999. Proceedings. WMCSA '99. Second IEEE
Workshop on, 1999, pp. 90 -100

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