APPLICATION LAYER MULTICASTING BY D.Jayasakthi
Feb 23, 2016
APPLICATION LAYER MULTICASTING
BYD.Jayasakthi
Content The Evolution of Multicast Applications of Multicast IP Multicast Application Layer Multicast Application Layer Multicast Protocol
Design Conclusion
The Evolution of Multicast
Multicast Backbone (MBone)
Intra-Domain Multicast
Inter-Domain Multicast
Std IP Multicast Model1988
1992
1994
1997
Applications of Multicast
A scene from the famous network game “Shrine of the Ancient”
Distance Learning
Multimedia conferencing
Data Delivery Unicast:
One source to one destination Broadcast:
One source to all destination Multicast:
One source to many destinations(but not all) Many source to many destinations
Multi- UnicastUnicast Source
Router
Receiver
IP Multicast Distribute information to large audiences
over an IP network
IP Multicast
IP Multicast Source
Router
Receiver
Deployment Issues with IP Muticasting
IP Multicast-capable routers need to be installed at all levels of the network (from backbone to edge routers) for the multicasting service to work.
There also exist management and security issues related to the deployment of IP Multicast: The ease of flooding attacks via multicasting Unauthorized reception of data from a multicast session Preventing allocation of same multicast address for two sessions The difficulty of setting up firewalls while allowing multicasting.
The lack of network-level support for multicasting has thus led researchers and commercial entities to seek alternative ways of multicasting at the application layer.
Application Layer Multicasting(ALM) IP Multicast is not globally deployed. Application Layer/Level Multicast (or Overlay
Multicast) is hence proposed. Multicasting implemented at end hosts instead
of network routers Nodes form Unicast channels or tunnels
between themS
R1 R2
E1
E2 E3
Unicast
Unicast
Unicast
ALM Benefits• Easy to deploy– No change to network infrastructure
• Programmable end-hosts– Overlay construction algorithms at end hosts
can be easily applied– Easier maintenance.
IP Multicast vs. ALM
IP Multicast vs. ALM
APPLICATION LAYER MULTICAST PROTOCOL DESIGN
Application Domain Deployment Level Group Management Routing Mechanism
Application Domain Different classes of applications have different
sets of requirements regarding Reliability, Latency, Bandwidth, and Scaling. Such requirements in turn determine the design choices of ALM protocol regarding the group management mechanism it deploys.
The application domain therefore influences the ALM protocol.
Deployment Level 2 levels of Deployment:
Infrastructure Level End System Level
Group ManagementHow to manage a group of nodes in a multicast
session? Basic group management:
How users find out about multicast sessions? How they join a session? How they leave?
Centralized or Distributed way Mesh-first approach or a Tree-first approach Source Specific Tree or Shared Tree Whether the protocol will take advantage of
existing IP Multicast islands? Whether it is necessary to refine the multicast
tree to improve performance?
Routing Design of the routing mechanism typically
involves a (heuristic) solution to a graph theory problem.
The most important is the routing mechanisms. Some Common approaches to the routing
mechanism are 1: Shortest Path 2: Minimum Spanning Tree 3: Clustering Structure 4: Peer-to-Peer Structure
Shortest Path The aim is to construct degree constraint
minimum diameter spanning tree A Shortest Path Tree (SPT) constructs a minimum
cost path from a source node to all its receivers.
Minimum Spanning Tree Given a graph with a cost associated with each
edge (usually delay), a Minimum Spanning Tree (MST) is a tree with minimum total cost spanning all the members
2
Clustering Structure This group constructs a cluster of nodes
that can be used to construct trees.
Clustering Structure In order to better organize the overlay tree and
reduce control message overhead, some ALM protocols such as ZIGZAG and NICE construct a hierarchical cluster of nodes.
The advantage of a hierarchical clustering approach to multicast tree routing is the reduction in control overhead and faster joining.
Peer-to-Peer Structure In P2P structure, the routing is simply done
through reverse-path forwarding or forward- path forwarding or in some cases a combination of both type.
The advantage of these approaches includes low control overhead and distributed management of the multicast tree but they do not restrict the degree of each node and are suboptimal.
Conclusion Compared to IP multicasting, ALM has certain disadvantages
such as longer delays and less efficient traffic generation.
However, due to its overwhelming advantages for certain applications, such as immediate deploy-ability and application-specific adaptation, it can be a practical solution to many of the existing problems in multi-user communications.
The fact that an ALM protocol can be developed and deployed on the Internet without the need to make any changes to the existing network infrastructure, and the ability to evolve and apply modifications to the protocol quickly and easily at the application layer has helped the ALM approach to have a quicker start compared to other multi-user communications solutions.
References
"A Survey of Application-Layer Multicast Protocols", Mojtaba Hosseini, Dewan Tanvir Ahmed, Shervin Shirmohammadi, Nicolas D. Georganas, IEEE Communications Surveys & Tutorials, Vol. 9, no. 3, July 2007, pp. 58-74
S. Deering and D. Cheriton, “Multicast Routing in Datagram Internetworks and Extended LANS,” ACM Trans. Comp. Syst., vol. 8, no. 2, 1990, pp. 85–111.
C. Diot et al., “Deployment Issues for the IP Multicast Service and Architecture,” IEEE Network Mag., vol. 14, no. 1, 2000, pp. 78–88.
Thank You