# On the Rollout of Network Slicing in Carrier Networks: A Technology Radar
## 2 Network Slicing: Concept, System Architecture and Deployment
### Network Slice Description  
One of the main business cases for network slicing is Network Slice as a Service (NSaaS) [17]. In this business model, an industry vertical (acting as the network slice customer) requests the network operator (acting as the network slice provider) to allocate a dedicated network slice satisfying a particular set of service requirements. With a large variety of emerging verticals in the market, it is fundamental for the operator to define a unified ability to interpret service requirements from different verticals, and to represent them in a common language. This unification will help the operator capture vertical-specific service requirements and translate them into appropriate network slice provisioning actions.  
In this regard, the GSM Alliance (GSMA) has promoted the idea of having a universal slice blueprint providing a point of convergence between telco and vertical industries on network slicing understanding. This blueprint, known as the Generic network Slice Template (GST) [21], contains a set of attributes that allow the characterization of any network slice. The most representative GST attributes are included in Table 1.  
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multirow{2}{*}{**GST Attribute**} & \multicolumn{4}{c}{**Network Domain**} & \multicolumn{2}{c}{**mloT NEST**} & \multicolumn{2}{c}{**eMBB NEST**} & \multicolumn{2}{c}{**uRLLC NEST**} \\ \cline{2-7}  & **RAN** & **TN** & **CN** & & & & \\ \hline Availability & X & X & X & 99.9 & 99.99 & 99.999 \\ \hline Session and Service Continuity & & & & X & SSC Mode 1: the IP address is preserved & SSC Mode 1: the IP address is preserved & SSC Mode 1: the IP address is preserved \\ (SSC) support & & & & & is preserved & is preserved \\ \hline Maximum DL (UL) throughput & X & & X & 2 (4) Mbps & 200 (200) Mbps & 40 (40) Mbps \\ \hline QP (UL) throughput per slice & X & X & X & Maximum: 30 (60) Gbps & Guaranteed: 300 (200) Gbps & Maximum: 20 (20) Gbps \\ Maximum number of PDU & & & & X & 500,000 & 80,000 & 1500 \\ sessions & & & & & & \\ \hline Slice Quality of Service (QoS) & X & X & X & 3 GPP SQL 9 & 3 GPP SQL: 12,5,6,7,8,9 & 3 GPP SQL: 82 \\ Maximum supported packet size & X & X & X & 300 bytes & 1500 bytes & 160 bytes \\ \hline UE density (per km\({}^{2}\)) & X & & X & 100,000 & 500 & 80 \\ \hline \multirow{3}{*}{Simultaneous use of the slice} & \multirow{3}{*}{X} & \multirow{3}{*}{X} & \multirow{3}{*}{X} & Can be used simultaneously & Can be used simultaneously & \multirow{3}{*}{Canned be used simultaneously} \\  & & & & with any slices with same SD with any slices with same SST & with any another slice \\ \cline{1-1} \cline{5-5}  & & & & & value but different SD values & \\ \hline Supported device velocity & X & & X & 10 km/h-Pedestrian & 500 km/h-High speed vehicular & 120 km/h-Vehicular \\ \hline \multicolumn{7}{l}{NOTE 1: Slice QoS parameters attribute defines all the QoS relevant parameters supported by the network slice, including priority level, packet delay budget (i.e., maximum allowed latency), packet error rate,} \\ \multicolumn{7}{l}{} \\ \end{tabular}
\end{table}
Table 1: Examples of NESTs for the three slices represented in Figure 2.  
A Network Slice Type (NEST) is the result of filling GST attributes with values according to the service requirements. In essence, a NEST is a filled-in version of a GST, and can be used by an operator and a vertical customer to agree on the Service Level Agreement (SLA). Different NESTs allow the description of different network slices. For slices based on 3 GPP 5G service categories, the operator may have a set of standardized NESTs (S-NESTs). For slices addressing specific industry use cases, the operator can define additional NESTs (P-NESTs) [22].  
Table 1 provides one example with three NESTs, one for each slice represented in Figure 2. The table also qualifies the impact of the NEST attributes on every technical domain.