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Application Layer Multicast for Small Groups:Status and Research Direction

Bobby BhattacharjeeUniversity of Maryland

John BufordPanasonic Digital Networking Laboratory

March 16, 2006

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Topics Problem statement

Mostafa Ammar. Why Johnny Can’t Multicast Lessons about the Evolution of the Internet. Keynote - NOSDAV 03.

Background and summary of current ALM research Yang-hua Chu, Sanjay G. Rao, Srinivasan Seshan and Hui Zhang. A Case for End

System Multicast. IEEE J on Selected Areas in Communications, 2002 Suman Banerjee, Bobby Bhattacharjee. A Comparative Study of Application Layer

Multicast Protocols. Submitted. ALM and Mobile IP

A. Garyfalos and K. Almeroth, A Flexible Overlay Architecture for Mobile IPv6 Multicast", J on Sel Areas in Communications Special Issue on Wireless Overlay Networks Based on Mobile IPv6, vol. 23, num. 11, pp. 2194-2205, Nov 2005.

A. Garyfalos, K. Almeroth, and J. Finney. A comparison of network and application layer multicast for mobile IPv6 networks. MSWIM '03.

Hybrid multi-destination and host-group multicast Qi He, Mostafa Ammar, "Dynamic Host-Group/Multi-Destination Routing for

Multicast Sessions," J. of Telecommunication Systems, vol. 28, pp. 409-433, 2005. Research issues for proposed SSGM activity

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Problem StatementMostafa Ammar. Why Johnny Can’t Multicast Lessons about the Evolution of the Internet. Keynote - NOSDAV 03..

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Application Layer Multicast (End System Multicast)

Scalability with number of groups Routers maintain per-group state Analogous to per-flow state for QoS

guarantees Aggregation of multicast addresses is

complicated

Supporting higher level functionality is difficult IP Multicast: best-effort multi-point delivery service End systems responsible for handling higher level

functionality Reliability and congestion control for IP Multicast

complicated

Deployment is difficult and slow ISP’s reluctant to turn on IP Multicast

Y. Chu, S. Rao and H. Zhang. A Case for End System Multicast. IEEE Journal on Selected Areas in Communications, 2002

Y. Chu, S. Rao and H. Zhang. A Case for End System Multicast. (Keynote) ACM SIGMETRICS Performance Evaluation Review, 2000

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Application Layer Multicast

Potential Benefits Scalability

Routers do not maintain per-group state End systems do, but they participate in very few groups

Easier to deploy Potentially simplifies support for higher level functionality

Leverage computation and storage of end systems For example, for buffering packets, transcoding, ACK aggregation Leverage solutions for unicast congestion control and reliability

End System Multicast is a promising alternative approach for multi-point delivery Narada: A distributed protocol for constructing efficient overlay trees among end systems Simulation and Internet evaluation results to demonstrate that Narada can achieve good

performance Consider applications with small and sparse groups

Around tens to hundreds of members

Y. Chu, S. Rao and H. Zhang. A Case for End System Multicast. IEEE Journal on Selected Areas in Communications, 2002

Y. Chu, S. Rao and H. Zhang. A Case for End System Multicast. (Keynote) ACM SIGMETRICS Performance Evaluation Review, 2000

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Application Layer MulticastY. Chu, S. Rao and H. Zhang. A Case for End System Multicast. IEEE Journal on Selected Areas in Communications, 2002

Y. Chu, S. Rao and H. Zhang. A Case for End System Multicast. (Keynote) ACM SIGMETRICS Performance Evaluation Review, 2000

3 topologies, various group sizessimulation results (JSAC 2002)Internet measurements (SIGMETRICS 2000)

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Application Layer Multicast

Mesh-first protocols are efficient for small multicast groups, while implicit protocols scale well with increasing group sizes.

Tree-first protocols are less suited for latency sensitive (e.g. real-time) applications but are useful to implement for high-bandwidth data transfers.

Implicit protocols are particularly beneficial when the size of the multicast group is very large, and can be adapted for both latency-sensitive applications (due to their short path lengths) and high-bandwidth applications (due to low tree degree).

Suman Banerjee, Bobby Bhattacharjee. A Comparative Study of Application Layer Multicast Protocols. Submitted

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ALM & Mobile IP

Mobility introduces several new challenges for ALM that do not exist in wired networks. System stability,heterogeneity and node capability become critical problems since

mobile nodes may be less capable or more constrained in their ability to act as ALM end hosts.

Moreover, in terms of network performance IP Multicast outperforms ALM both for low and high speeds.

Approach hybrid system in which inter-domain multicast support is provided using ALM and

intra-domain support is provided using native multicast.

A. Garyfalos and K. Almeroth, A Flexible Overlay Architecture for Mobile IPv6 Multicast", J on Selected Areas in Communications Special Issue on Wireless Overlay Networks Based on Mobile IPv6, vol. 23, num. 11, pp. 2194-2205, November 2005.

A. Garyfalos, K. Almeroth and J. Finney, "A Comparison of Network and Application Layer Multicast for Mobile IPv6 Networks", ACM Workshop on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM), San Diego, California, USA, September 2003.

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ALM & Mobile IP

In terms of throughput, low mobility gives no major advantage to IP multicast. However, as nodes start to increase their speed, ALM experiences additional packet loss. At its worst, ALM suffers about 4 times the loss of IP multicast.

In terms of RDP (Relative Delay Penalty), Low mobility causes IP multicast to perform much better: on the order of 4 to 5

times better than ALM. High mobility, IP multicast still performs better, but the improvement is less: an

RDP ratio of 2 to 1. Overall, ALM suffers both when mobility is low and when it is high.

Low mobility gives better robustness but very high RDP. High mobility gives better RDP values, but robustness is poor.

A. Garyfalos and K. Almeroth, A Flexible Overlay Architecture for Mobile IPv6 Multicast", J on Selected Areas in Communications Special Issue on Wireless Overlay Networks Based on Mobile IPv6, vol. 23, num. 11, pp. 2194-2205, November 2005.

A. Garyfalos, K. Almeroth and J. Finney, "A Comparison of Network and Application Layer Multicast for Mobile IPv6 Networks", ACM Workshop on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM), San Diego, California, USA, September 2003.

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Hybrid Multi-Destination & Host-group Multicast Routing

“One criticism against Xcast is that it involves more router processing due to multiple unicast route lookups. The Xcast community(Xcast (2004)) has argued that the cost would not be substantial given the small session sizes Xcast is intended for. On the other hand, Xcast developers strive to optimize the processing cost in their designs, tunneling being one of the approaches they adopt. Given that most (80% according to (Chalmers and Almeroth (2001))) of the routers on typical multicast trees are non-branching, tunneling between branching routers could reduce the SGM processing cost by a large fraction. It should be clear from the description of the transition protocol how we exploit the tunnels to save processing costs.” (p. 12)

Future work: Target an implementation of the dynamic SGM/split-

group SGM/PIM routing system. Our goal will be to investigate issues in router performance and processing overheads.

Assume Internet support for both host-group multicast routing to very large groups and multi-destination routing to small and medium size groups

Protocol to switch between SGM and PIM-SSM (Single Source Multicast)

Protocol for dynamic join/leave using tunnel management

Qi He, Mostafa Ammar, "Dynamic Host-Group/Multi-Destination Routing for Multicast Sessions," Journal of Telecommunication Systems, vol. 28, pp. 409-433, 2005.

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Hybrid Multi-Destination & Host-group Multicast Routing

Qi He, Mostafa Ammar, "Dynamic Host-Group/Multi-Destination Routing for Multicast Sessions," Journal of Telecommunication Systems, vol. 28, pp. 409-433, 2005.

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Research Issues for Proposed SSGM Activity

For small groups, topology optimization/adaptation is not as crucial

Assume millions of groups, then different set of assumptions drive solutions for Bootstrapping Group management and group formation Group level churn

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Questions?