Hard vs. Soft Network Slicing: What’s the Difference (Part 1)

Hard vs. Soft Network Slicing: What’s the Difference (Part 1)

In our recent webinar with Jennifer Clark of Heavy Reading, Leveraging the Cloud in the New 5G Edge, we discussed the importance of network slicing in 5G. And, we went into detail about the difference between hard and soft network slicing. The webinar is available on demand here.

5G supports a new generation of applications with diverse and stringent requirements in terms of capacity, latency, level of mobility, number of users, and user density. 5G actually defines three types of applications based on how their data needs to be treated:

  • Ultra Reliable Low Latency Communications (URLLC)
    • Requires support for 1 ms latencies, 0.001% packet loss, user mobility up to 100km/h
    • E.g., autonomous driving
  • Massive Machine Type Communications (mMTC)
    • Requires support for 1 million devices per square kilometer, tens of bps bandwidth, and latency minimization for battery life optimization
    • E.g., Massive IoT
  • Enhanced Mobile Broadband (eMBB)
    • Requires Gbps bandwidth, real time or not
    •  E.g., immersive UIs based on Augmented Reality / Virtual Reality

5G is a cellular access network technology where the Radio Access Network (RAN) is just one component. The other two components are the Mobile Core (MC) and the backhaul network that interconnects the RAN with the MC:

  • The Radio Access Network (RAN)  is specified within 5G, and it covers everything related to the air interface between the user element and the base station.
  • The Mobile Core (MC) is also specified within 5G, and its main role is to act as a gateway for user traffic to and from the greater internet (user plane), to manage user mobility, authentication, registration, etc (control plane), and to establish per-user tunnels between user plane and base stations for each different traffic type
  • The Backhaul Network is the network that interconnects the RAN with the MC. It is not part of the 5G specification, so it is up to each network operator to decide how to implement it. It requires functionalities such as QoS, timing synchronization, MPLS, and segment routing.
5G cellular network
5G cellular network

5G enables network operators to ensure the same network can fulfill the heterogeneous requirements of these diverse types of applications by determining how network resources are assigned to application traffic. This is defined as network slicing. 5G actually specifies a standard set of network slices, denoted Standardized Slice Type (SST), in order to determine how resources need to be assigned at the RAN and at the MC level to fulfill the requirements of different types of applications. For example, SST1 applies to eMBB, SST2 applies to URLLC, and SST3 to mMTC.

Network slicing capabilities need to be available across all components of the 5G cellular network (RAN, MC, Backhaul network) in order to ensure this differentiated treatment end to end, for example from the moment user traffic enters the RAN to the moment it exits the MC user plane towards the Internet. 5G specifies how network slicing is implemented in RAN and MC, but it does not specify how the backhaul network achieves it, so it is up to each network operator to determine how to accomplish it.

5G specifies two mechanisms for network slicing. The first one is based on QoS techniques, by applying a dynamic allocation of available network resources to different classes of traffic, and it is denoted as soft network slicing. The second one takes advantage of the software-based, cloud-based architecture of 5G, as well as component disaggregation, and achieves slicing through 5G component virtualization and replication. This second approach is denoted hard network slicing.

In the next post, I’ll look into more detail on both soft and hard network slicing, compare their merits, and describe how hard network slicing relies on Multi-Access Edge Computing (MEC) for realizing its full potential.