# 5G Network Slice Isolation
## 4 Model of Network Slice Isolation
### Network Slice Planning Procedures  
An overview of network slice deployment planning procedures is provided as follows. We begin with Figure 5(a), which gives the network slice isolation plan based on Quality of Service (QoS) satisfaction. Basically, the QoS satisfaction shall be conducted and aggregate individual QoS parameters. We take the reliability as an example, which is shown in Figure 5(a). The three horizontal lines on the graph represent the minimal reliability requirements of a specific type of network slice service. More specifically, the level of the service reliability requirement of an enhanced Mobile Broadband (eMBB) network slice is the lowest among the three because eMBB may accept high-latency network QoS and a certain level of packet loss. The level of service reliability of a massive Machine-Type Communications (mMTC) network slice is on a mid-level since mMTC deploys a large number of device connections with short messages transmission and no re-transmission policy characteristics since the duty cycle of mMTC devices may be very short. These features of mMTC are asking for a better service reliability than that of the eMBB network slice. Last but not the least, the highest service reliability is an Ultra-Reliable Low-Latency Communications (URLLC) network slice, which very often applies to deliver critical infrastructure while commonly providing a certain level of defense mechanisms. Figure 5(b) gives another network slice deployment consideration. We often see the network slice deployment using air-gap isolation, logical isolation or a combination of isolation methods. Obviously, each network slice would have a set of constrains with different protocol stacks that can be controlled by tenant or MNO.From the MNO point of view, when the tenant has more control of the network slice, it is better to apply air-gap isolation because there is better reliability than logical isolation. Figure 5(b) provides the result of comparing air-gap (bare-metal) isolation and logical isolation. Therefore, in terms of considering isolation, when we have the same isolation level, the reliability increases with the tenant control level. On the other hand, a network slice that has the maximal tenant control level requires the isolation level to be maximal as well. It can use air-gap isolation, which is shown in the Figure 5(b).  
Figure 6: _Cont._  
According to the results, obviously, the tenant can remove some of the isolation options. For example, in general, logical isolation would not be possible for deployment in URLLC services due to performance requirements; the only possible solution would be to apply air-gap isolation with physical resources. We can further to discuss the trade-off, which is shown in Figure 6b. Basically, the tenant can choose from all the available options with regard to its cost of security and defense preference. Typically, the tenant may demand a security-hardening network slice, but the cost of isolation would be directly proportional to security hardening, which is shown in Figure 6a. Figure 6b also indicates the upper bound of the security level related to the upper bound of the tenant control level, i.e., by the isolation level, bare-metal isolation can achieve more than logical isolation. In order to achieve a better level of security, it is always better to use air-gap (bare-metal) isolation rather than logical isolation. However, it may cost more and have less flexibility.