SGi-LAN (SGi Local Area Network) is network infrastructure connected to a 3GPP (Third Generation Partnership Project) LTE (Long-Term Evolution) network over the SGi or Gi reference point (i.e., interface) that provides different value-added IP-based services to user data as it flows through the network [3GPP]. These value-added services may include, among others [3GPP, Cisco, Intel-1]:
In the future, SGi-LAN will also need to address the growing use of encrypted traffic. It might also include different forms of proxies and interworking functions for IoT [Cisco].
In an LTE network, SGi-LAN is positioned between the Evolved Packet Core (EPC; the LTE core network) and a PDN (Packet Data Network) Gateway such as an Internet or IMS (IP Multimedia Subsystem) gateway. A typical SGi-LAN supports several million subscribers [Intel-1].
SGi-LAN is the home of Service Function Chains (SFC), which are not standardized by 3GPP [IETF]. Traditional mobile deployments of SGi-LAN services simply chain all the functions together in a serial and static manner [HPE]. The limitations of this approach include that (1) each function has to process all the traffic, (2) introducing new functions or upgrading existing ones takes a lot of time and effort, (3) a failure of a single function may interrupt the overall service for all subscribers, and (4) the introduction of new services is slowed down.
Service Function Chaining (SFC) makes it possible to dynamically configure user plane traffic to be routed through a chain of network components which provide value-added services [SS]. As an example, traffic of a certain customer may be passed through a protocol optimization component (e.g., for video) or a security function such as parental control. SFC, when combined with SDN (Software-Defined Networking) and NFV (Network Functions Virtualization), can be used to remove the limitations mentioned in the previous paragraph and enable optimal use of data center resources, scalability to cope with ever-increasing traffic, and optimal steering of traffic through SGi-LAN network functions [Intel-2]. In fact, virtualization of the SGI-LAN is often a first step for mobile operators towards network virtualization [HPE]. It allows the virtualized SGi-LAN functions to be run as VNFs (Virtualized Network Functions) on standard x86 server hardware in the operator’s cloud infrastructure.
3GPP is defining the integration of 3GPP policy standards with external policy standards, including policies for SDN controllers. A new interface (St) has been defined between the PCRF (Policy and Charging Rules Function) and a new Service Chain Traffic Controller Function (SCTCF) [Intel-2]. The St interface allows the PCRF to interface to the SFC controller functions in order to provide traffic description filters that enable more coordinated and comprehensive implementation of service chains in SGi-LAN.
But what is the role of the SGi-LAN in 5G networks? According to some visions, in 5G networks, the integration of SGi-LAN network functions will be seamless, and the traditional separation between the network functions placed in the SGi-LAN and other parts of the network will be removed [NOK], allowing the SGi-LAN functions to be either integrated with the basic connectivity and policy enforcement functions, or still be deployed independently in the SGi-LAN. Among other things, this will allow service function chaining to take advantage of edge clouds - virtualized SGi-LAN functions can be placed where needed [AF]. As an example, SGi-LAN functions could be placed on router-based compute blades, on COTS (Common Off-The-Shelf) x86 servers on an edge node (e.g, one could place a CDN cache on an edge node to move traffic closer to the edge), or in a central data center. The placement decision is made by a central orchestration system, which can steer traffic into service chains for example on a per application, subscriber, bearer or device basis, or based on some combination of them.
Finally, SGi-LAN may also be referred to as (S)Gi-LAN, Gi-LAN, GiLAN, vGiLAN (virtualized GiLAN), SGiLAN, Gi LAN or SGi LAN.
[3GPP] 3GPP TS 23.203 V14.3.0 (2017-03), Technical Specification, 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects;
Policy and charging control architecture (Release 14)
https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=810
[AF] Designing 5G-Ready Mobile Core Networks, https://www.affirmednetworks.com/wp-content/themes/renden/pdf/5G_Whitepaper_Heavy_Reading.pdf
[Cisco] The Cisco 5G Strategy Series: Packet Core, Transport, and Identity Management, http://www.cisco.com/c/dam/en/us/solutions/collateral/service-provider/ultra-services-platform/5g-strategy-series.pdf
[HPE] Virtualization of Gi-LAN Functions, https://www.hpe.com/h20195/v2/GetPDF.aspx/4AA6-3417ENN.pdf
[IETF] Service Function Chaining Use Cases in Mobile Networks, draft-ietf-sfc-use-case-mobility-07, https://tools.ietf.org/html/draft-ietf-sfc-use-case-mobility-07
[Intel-1] Etisalat and Intel – Virtualizing the Internet Gateway Gi-LAN for Flexibility, https://builders.intel.com/docs/networkbuilders/Etisalat-and-Intel-virtualizing-the-internet-gateway-Gi-LAN-for-service-flexibility.pdf
[Intel-2] Gi-LAN and Dynamic Service Function Chaining for Communications Service Providers, https://builders.intel.com/docs/networkbuilders/Gi-LAN-and-dynamic-service-function-chaining-for-communication-service-providers-ra.pdf
[NOK] 5G - a System of Systems for a programmable multi-service architecture, http://resources.alcatel-lucent.com/asset/200012
[SS] The Road from EPC to 5G, https://www.slideshare.net/AlbertoDiez4/mobile-plots-from-epc-to-5g a
- NAT (Network Address Translation)
- Anti-malware
- Parental control
- DDoS (Distributed Denial of Service) protection
- Firewall
- Policy and charging enforcement
- Traffic detection (PCEF/TDF; Policy and Charging Enforcement Function / Traffic Detection Function)
- Content Delivery Network (CDN) caches
- Video transparent caching and optimization
- TCP optimization (e.g., to prepare the traffic for the Radio Access Network)
- Shaping traffic with Deep Packet Inspection (DPI)
- HTTP header enrichment to support partner services
- Providing analytics information
- Differentiated charging
In the future, SGi-LAN will also need to address the growing use of encrypted traffic. It might also include different forms of proxies and interworking functions for IoT [Cisco].
In an LTE network, SGi-LAN is positioned between the Evolved Packet Core (EPC; the LTE core network) and a PDN (Packet Data Network) Gateway such as an Internet or IMS (IP Multimedia Subsystem) gateway. A typical SGi-LAN supports several million subscribers [Intel-1].
SGi-LAN is the home of Service Function Chains (SFC), which are not standardized by 3GPP [IETF]. Traditional mobile deployments of SGi-LAN services simply chain all the functions together in a serial and static manner [HPE]. The limitations of this approach include that (1) each function has to process all the traffic, (2) introducing new functions or upgrading existing ones takes a lot of time and effort, (3) a failure of a single function may interrupt the overall service for all subscribers, and (4) the introduction of new services is slowed down.
Service Function Chaining (SFC) makes it possible to dynamically configure user plane traffic to be routed through a chain of network components which provide value-added services [SS]. As an example, traffic of a certain customer may be passed through a protocol optimization component (e.g., for video) or a security function such as parental control. SFC, when combined with SDN (Software-Defined Networking) and NFV (Network Functions Virtualization), can be used to remove the limitations mentioned in the previous paragraph and enable optimal use of data center resources, scalability to cope with ever-increasing traffic, and optimal steering of traffic through SGi-LAN network functions [Intel-2]. In fact, virtualization of the SGI-LAN is often a first step for mobile operators towards network virtualization [HPE]. It allows the virtualized SGi-LAN functions to be run as VNFs (Virtualized Network Functions) on standard x86 server hardware in the operator’s cloud infrastructure.
3GPP is defining the integration of 3GPP policy standards with external policy standards, including policies for SDN controllers. A new interface (St) has been defined between the PCRF (Policy and Charging Rules Function) and a new Service Chain Traffic Controller Function (SCTCF) [Intel-2]. The St interface allows the PCRF to interface to the SFC controller functions in order to provide traffic description filters that enable more coordinated and comprehensive implementation of service chains in SGi-LAN.
But what is the role of the SGi-LAN in 5G networks? According to some visions, in 5G networks, the integration of SGi-LAN network functions will be seamless, and the traditional separation between the network functions placed in the SGi-LAN and other parts of the network will be removed [NOK], allowing the SGi-LAN functions to be either integrated with the basic connectivity and policy enforcement functions, or still be deployed independently in the SGi-LAN. Among other things, this will allow service function chaining to take advantage of edge clouds - virtualized SGi-LAN functions can be placed where needed [AF]. As an example, SGi-LAN functions could be placed on router-based compute blades, on COTS (Common Off-The-Shelf) x86 servers on an edge node (e.g, one could place a CDN cache on an edge node to move traffic closer to the edge), or in a central data center. The placement decision is made by a central orchestration system, which can steer traffic into service chains for example on a per application, subscriber, bearer or device basis, or based on some combination of them.
Finally, SGi-LAN may also be referred to as (S)Gi-LAN, Gi-LAN, GiLAN, vGiLAN (virtualized GiLAN), SGiLAN, Gi LAN or SGi LAN.
References
[3GPP] 3GPP TS 23.203 V14.3.0 (2017-03), Technical Specification, 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects;
Policy and charging control architecture (Release 14)
https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=810
[AF] Designing 5G-Ready Mobile Core Networks, https://www.affirmednetworks.com/wp-content/themes/renden/pdf/5G_Whitepaper_Heavy_Reading.pdf
[Cisco] The Cisco 5G Strategy Series: Packet Core, Transport, and Identity Management, http://www.cisco.com/c/dam/en/us/solutions/collateral/service-provider/ultra-services-platform/5g-strategy-series.pdf
[HPE] Virtualization of Gi-LAN Functions, https://www.hpe.com/h20195/v2/GetPDF.aspx/4AA6-3417ENN.pdf
[IETF] Service Function Chaining Use Cases in Mobile Networks, draft-ietf-sfc-use-case-mobility-07, https://tools.ietf.org/html/draft-ietf-sfc-use-case-mobility-07
[Intel-1] Etisalat and Intel – Virtualizing the Internet Gateway Gi-LAN for Flexibility, https://builders.intel.com/docs/networkbuilders/Etisalat-and-Intel-virtualizing-the-internet-gateway-Gi-LAN-for-service-flexibility.pdf
[Intel-2] Gi-LAN and Dynamic Service Function Chaining for Communications Service Providers, https://builders.intel.com/docs/networkbuilders/Gi-LAN-and-dynamic-service-function-chaining-for-communication-service-providers-ra.pdf
[NOK] 5G - a System of Systems for a programmable multi-service architecture, http://resources.alcatel-lucent.com/asset/200012
[SS] The Road from EPC to 5G, https://www.slideshare.net/AlbertoDiez4/mobile-plots-from-epc-to-5g a
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