LMS: A Router Assisted Scheme for Reliable Multicast
Christos C. Papadopoulos, Guru M. Parulkar, George Varghese · 2001
Building on the success of unicast IP, IP Multicast adopted a simple, open, best-effort delivery model with broadcast-within-a-group semantics. Despite several years of effort, the research community has been unable to produce scalable and reliable end-to-end transport on top of this model. Proposed solutions are either not flexible or incur high control overhead. Many of these problems can be significantly simplified and perhaps solved with network assistance, an approach which had been dismissed until recently due to concerns about violating the end-to-end argument. Such violation occurs when network elements perform transport level operations. We claim that network assistance is possible without violating the end-to-end argument. We present Light-weight Multicast Services (LMS), which enhance the existing multicast model with simple forwarding services that do not require transport level actions. Using LMS, routers tag and steer transport-level control packets to selected endpoints, thus preserving the location advantage of the routers while pushing transport processing to the edges. LMS facilitates very efficient solutions (compared to pure end-to-end schemes) to problems like scalable reliable multicast. We show that shifting the processing from routers to endpoints has minimal impact on efficiency (compared to the idealized transport-aware network solution), while offering significant gains in terms of scalability, reduced application complexity and ease of deployment. What distinguishes LMS from other scheme is its ability to easily handle dynamic groups and the minimal overhead it incurs at the network and the receivers.