Unicast Model Research Articles

Proof-labeling schemes: Broadcast, unicast and in between

We study the effect of limiting the number of different messages a node can transmit simultaneously on the verification complexity of proof-labeling schemes (PLS). In a PLS, each node is given a label, and the goal is to verify, by exchanging messages over each link in each direction, that a certain global predicate is satisfied by the system configuration. We consider a single parameter r that bounds the number of distinct messages that can be sent concurrently by any node: in the case r=1, each node may only send the same message to all its neighbors (the broadcast model), in the case r≥Δ, where Δ is the largest node degree in the system, each neighbor may be sent a distinct message (the unicast model), and in general, for 1≤r≤Δ, each of the r messages is destined to a subset of the neighbors.We show that message compression linear in r is possible for verifying fundamental problems such as the agreement between edge endpoints on the edge state. Some problems, including verification of maximal matching, exhibit a large gap in complexity between r=1 and r>1. For some other important predicates, the verification complexity is insensitive to r, e.g., the question whether a subset of edges constitutes a spanning-tree. We also consider the congested clique model. We show that the crossing technique [1] for proving lower bounds on the verification complexity can be applied in the case of congested clique only if r=1. Together with a new upper bound, this allows us to determine the verification complexity of MST in the broadcast clique. Finally, we establish a general connection between the deterministic and randomized verification complexity for any given number r.

All-to-All Broadcast in WDM Linear Array with 3-length Extension

All-to-all broadcast communication, distributing messages from each node to every other node, is a dense communication pattern and finds numerous applications in advanced computing and communication networks from the control plane to datacenters. In this article, a linear array is extended by directly linking all nodes which are separated by two intermediate nodes with additional fibers and this network is referred as linear array with 3-length extension. The wavelength allotment methods are proposed to realize all-to-all broadcast over WDM optical linear array with 3-length extension under multiple unicast routing model and the wavelength number needed atmost to establish all-to-all broadcast is determined. The wavelength number needed atmost to establish all-to-all broadcast in a linear array with 3-length extension is reduced by a minimum of 61% and a maximum of 66% when compared to a basic linear array. Similarly, the wavelength number needed atmost to establish all-to-all broadcast is reduced by a minimum of 24% and a maximum of 33% when compared to linear array with 2-length extension.

A Novel OBDD-Based Reliability Evaluation Algorithm for Wireless Sensor Networks on the Multicast Model

The two-terminal reliability calculation for wireless sensor networks (WSNs) is a #P-hard problem. The reliability calculation of WSNs on the multicast model provides an even worse combinatorial explosion of node states with respect to the calculation of WSNs on the unicast model; many real WSNs require the multicast model to deliver information. This research first provides a formal definition for the WSN on the multicast model. Next, a symbolic OBDD_Multicast algorithm is proposed to evaluate the reliability of WSNs on the multicast model. Furthermore, our research on OBDD_Multicast construction avoids the problem of invalid expansion, which reduces the number of subnetworks by identifying the redundant paths of two adjacent nodes ands-tunconnected paths. Experiments show that the OBDD_Multicast both reduces the complexity of the WSN reliability analysis and has a lower running time than Xing’s OBDD- (ordered binary decision diagram-) based algorithm.

Scalable Rekeying limited to Subgroup using Hybrid Key Trees

Maintaining security is a critical issue in any group communication protocols. The objective of security in a group communication is to ensure the access only to the legitimate members of the multicast group. The entry and eviction of the members are the main criteria to change the group key and to give them more assurance of a secret communication, which is known as re-keying. Since it is a frequently performed activity during a communication, the group key updating need to be done in a scalable and efficient manner. Earlier, client–server paradigm is the most predominantly used technique for applications like conferencing, chat groups, interactive video gaming, etc which use the concept of unicast for the transmission of data. Present day advancements in the Internet technologies, especially the increase of bandwidth are definitely encouraging environment for new developments. Unlike the old communication models, where the delivery of the packets are to be carried out in an unicast model, multicasting technique provides an efficient delivery service to larger user-community with effective and efficient network resource utilization. In the earlier schemes proposed for rekeying mechanism like LKH [4], FDLKH [7], DLPKH [9], the entire group will be disturbed with change in the membership. This paper proposes two new ideas: one with an objective of efficient re-keying and the other with an objective of disturbing only a subset of the group. Both the ideas don’t need the secure channel for the distribution of the key material like [4],[7] and also does not reveal the private keys like [9]. The number of keys maintained at each member in this scheme, number of messages sent, size of the messages and number of encryption and decryptions are always constant unlike the other schemes which typically depends on the height of the tree.

Optimization-based congestion control for multicast communications

This article outlines an approach for multicast congestion control based on an economic model that has been successfully applied to unicast congestion control. In this model, congestion signals are interpreted as prices and congestion-controlled sessions as utility maximizing agents. A naive extension of the unicast model fails to achieve a reasonable balance between providing the incentives necessary to promote the use of multicast and ensuring that multicast sessions do not interact too aggressively with unicast sessions. We extend the model by introducing a rational definition of multicast utility. The revised model provides a basis for multicast congestion control protocols that provide incentives to use multicast but are necessarily unfair to unicast traffic. We show, however, that the degree of unfairness can be controlled by appropriately setting a design parameter with a limiting case of strict fairness.

Small group multicast: a new solution for multicasting on the Internet

The Internet's global ubiquity has fostered numerous applications that use many different communications models. Applications like FTP Web browsing, and e-mail employ a unicast model where two parties exchange data over logical point-to-point connections. In other applications, such as multiparty audio/video conferencing and collaborative gaming, a source sends data to multiple parties. One way to support multiparty communications is with unicast connections between the source and all of the receivers. If a group has N parties, then a source must set up N-1 unicast connections and transmit the data N times over the network. When N is large, scalability becomes an issue for the source and the network. IP multicast solves this problem by sending a single copy of the data over a distribution tree that is rooted at the source and that branches out to the various destinations. Because the source transmits a single copy of the data, only one copy of the data appears on the branches in the distribution tree.