## 1 Introduction
In order to reserve communication resources and provide real-time communication between two end-points based on the required bandwidth, we use the D-SAR protocol [11]: a Distributed Scheduling Algorithm for Real-time applications based on concepts derived from Asynchronous Transfer Mode (ATM) networks [12]. The distributed nature of our resource reservation scheme, makes it feasible to change the reservation based on possible changes in the network connectivity, caused by the interference and dynamic link quality between the devices, in a timely manner. This capability together with the Clear Channel Assessment (CCA), re-transmission and channel hopping schemes in the data link layer, provide reliability in the network. As a response, D-MSR can address both the real-time and reliable communication requirements in a harsh industrial environment. In the network layer, we use RPL (Routing Protocol for Low power and Lossy Networks [13]). In the transport layer we define, the _end-to-end connection manager_ that establishes connections to either enable management communications (e.g., network layer control messages between network devices and gateway) or sensor/process data communications, through the D-SAR protocol. The sensors publish periodic data to actuators (the term \"sensor to actuator\", \"peer-to-peer\" and \"point-to-point\" communication are used interchangeably) for process control applications, or to gateway for monitoring applications. In case of node or edge failures, the _end-to-end connection manager_ releases the previously allocated communication resources along the old path, reserves new resources (in this paper \"resources\" means communication resources in the network) and establishes a new connection between the pairs through the new path, by applying the D-SAR protocol. We compare via simulation the performance of D-MSR with that of WirelessHART (given the similarities between WirelessHART and ISA100.11a, the same result can be obtained by comparing D-MSR with ISA100.11a) in a typical industrial environment with high packet losses. We evaluate the end-to-end data delivery delay and compare the communication schedule and network throughput of D-MSR with that of WirelessHART. Furthermore, we evaluate the relationship between the packet delivery ratio and increased internal and external interference in the network. We show that in case of extensive external interference, D-MSR requires less time to reach a stable data delivery ratio value in comparison with WirelessHART. We compare the power consumption in the D-MSR network with that of WirelessHART. We show that by applying D-MSR, we can achieve higher efficiency in network management in terms of latency and overhead during node joining, resource reservation, end-to-end connection establishment, and when coping with dynamic situations (e.g., node or edge failure). Section 2 provides background information about the MAC layer that is used in D-MSR. Section 3 describes D-MSR protocol stack architecture. Section 4 provides details about the functional description of D-MSR algorithms in different protocol layers. We provide details on the different phases of a network node from joining to publishing its sensor data, in Section 5. Section 6 elaborates on performance evaluation for real-time communication schedule construction, network throughput, data delivery in case of lossy networks, and management efficiency (in terms of delay, communication overhead), by comparing D-MSR with WirelessHART performance. Finally, Section 7 concludes the paper and summarizes our future research in this area.