# Networking of Multi-Robot Systems: Architectures and Requirements
## 4 Communication Issues and Requirements for MRS Systems
### MRS Networking Protocol Issues and Requirements
* Connection to backbone: In the cases where the MRS network needs to be connected to a backbone network or to the Internet, there is a need to map the QoS and other networking parameters of the R2R and R2I traffic from the header of the MRS packet to the corresponding parameters in the headers of the upper layers in the backbone network. This should be done in a way that ensures seamless integration of the two systems, which does not lead to appreciable changes in the QoS of the associated MRS traffic. * Mobility: Nodes in an MRS network are typically mobile. However, the mobility degree and pattern can vary widely between different applications. For example, MRS networks with nodes consisting of UAVs are expected to move at considerably higher speeds than nodes in an MRS with nodes consisting of robots moving on rough terrain in a search-and-rescue mission. Consequently, the routing protocol that is chosen for the MRS network must be characterized by higher efficiency for the mobility degree and pattern of the particular MRS network. * Handoff and roaming: MRS networks with a very large number of nodes (hundreds or thousands) typically need to have multiple layers of hierarchy as indicated earlier. Robots in a particular cluster usually transmit their data to an elected CH or a gateway node that provides connection to the rest of the robots in the MRS or a backbone network. However, when a particular robot goes out of range of its designated or current gateway and into the range of another gateway, a handoff process needs to take place. When robots require changing their connection from a particular network to another one due to geographic movement a roaming mechanism must take place (for example, the MRS might be using cellular connections). Such considerations are important to keep in mind at the network design and configuration phases. * Security: Depending on the nature, confidentially, and criticality of the MRS application, secure communication might be an essential requirement to ensure its success. Certain MRS networks that perform military, or sensitive commercial services might be subject to many kinds of attacks. The attacks can be internal or external to the network. Consequently, the communication protocol that is chosen must have security provisioning to ensure protection against possible attacks. Such attacks can be passive or active. Passive attacks include eavesdropping, and traffic analysis. Active attacks include masquerade, replay, modification of message content, and denial or service (DoS). * Reliability: To varying degrees of importance, reliability of the communication process is an important aspect of certain MRS networks. For certain types of applications, R2R and R2I communication cannot tolerate interruptions, which might lead to mission disruption, or failure, which in turn can result in high financial losses or cause life-threatening conditions. Subsequently, the MRS network protocol need to include reliability features such as fail-safe provisioning, redundancy of critical communication components, or designated nodes to replace other communication-critical nodes in case of malfunctioning or failure.