Functionality
The Control-Plane functional element (e.g. PGW-C, SMF) controls the packet processing and forwarding in the User-Plane functional elements (e.g. PGW-U, UPF), by establishing, modifying or deleting PFCP Sessions.
User plane packets shall be forwarded between the CP and UP functions by encapsulating the user plane packets using GTP-U encapsulation (see 3GPP TS 29.281 [3]). For forwarding data from the UP function to the CP function, the CP function shall provision Packet Detection Rules (PDR) per PFCP session context, with the Packet Detection Information (PDI) identifying the user plane traffic to forward to the CP function and with a Forwarding Action Rule (FAR) set with the Destination Interface "CP function side" and set to perform GTP-U encapsulation and to forward the packets to a GTP-u F-TEID uniquely assigned in the CP function per PFCP session and PDR. The CP function shall then identify the PDN connection and the bearer to which the forwarded data belongs by the Fully Qualified TEID (F-TEID) in the header of the encapsulating GTP-U packet. For forwarding data from the CP function to the UP function, the CP function shall provision one or more PDR(s) per PFCP session context, with the PDI set with the Source Interface "CP function side" and identifying the GTP-u F-TEID uniquely assigned in the UP function per PDR, and with a FAR set to perform GTP-U decapsulation and to forward the packets to the intended destination. URRs and QERs may also be configured.
Per session multiple PDRs, FARs, QoS Enforcement Rules (QER), Usage Reporting Rules (URR) and/or Buffering Action Rules (BAR) are sent.
Here are the main concepts used, organized in their logical association model:
- PDRs - Packet Detection Rules - contain information for matching data packets to certain processing rules. Both outer encapsulation and inner user-plane headers can be matched. The following rules can be applied on positive matching:
- FARs - Forwarding Action Rules - whether and how the packets matching PDRs should be dropped, forwarded, buffered or duplicated, including a trigger for first packet notification; it includes packet encapsulation or header enrichment rules. In case of buffering, the following rules can be applied:
- BARs - Buffering Action Rules - how much data to buffer and how to notify the Control-Plane.
- QERs - QoS Enforcement Rules - rules for providing Gating and QoS Control, flow and service level marking.
- URRs - Usage Reporting Rules - contain rules for counting and reporting traffic handled by the User-Plane function, generating reports to enable charging functionality in the Control-Plane functions.
Transport
Very similar to GTP-C, PFCP uses UDP. Port 8805 is reserved. [5]
For reliability, a similar re-transmission strategy as for GTP-C is employed, lost messages being sent N1-times at T1-intervals. Transactions are identified by the 3-byte long Sequence Number, the IP address and port of the communication peer.
The protocol includes an own Heart-beat Request/Response model, which allows monitoring the availability of communication peers and detecting restarts (by use of a Recovery-Timestamp Information Element).
For User-Plane packet exchanges between the Control and User Plane functional elements, GTP-U for the Sx-u interface, or alternatively a simpler UDP or Ethernet encapsulation for the N4-u interface (to be confirmed, as standards are still incomplete).
General Packet Radio Service (GPRS), also called 2.5G, is a packet orientated mobile data standard on the 2G cellular communication network's global system for mobile communications (GSM). GPRS was established by European Telecommunications Standards Institute (ETSI) in response to the earlier CDPD and i-mode packet-switched cellular technologies. It is now maintained by the 3rd Generation Partnership Project (3GPP).
A router is a computer and networking device that forwards data packets between computer networks, including internetworks such as the global Internet.
In IEEE 802 LAN/MAN standards, the medium access control (MAC), also called media access control, is the layer that controls the hardware responsible for interaction with the wired or wireless transmission medium. The MAC sublayer and the logical link control (LLC) sublayer together make up the data link layer. The LLC provides flow control and multiplexing for the logical link, while the MAC provides flow control and multiplexing for the transmission medium.
The GPRS core network is the central part of the general packet radio service (GPRS) which allows 2G, 3G and WCDMA mobile networks to transmit Internet Protocol (IP) packets to external networks such as the Internet. The GPRS system is an integrated part of the GSM network switching subsystem.
The Radio Network Controller (RNC) is a governing element in the UMTS radio access network (UTRAN) and is responsible for controlling the Node Bs that are connected to it. The RNC carries out radio resource management, some of the mobility management functions and is the point where encryption is done before user data is sent to and from the mobile. The RNC connects to the Circuit Switched Core Network through Media Gateway (MGW) and to the SGSN in the Packet Switched Core Network.
The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem (IMS) is a standardised architectural framework for delivering IP multimedia services. Historically, mobile phones have provided voice call services over a circuit-switched-style network, rather than strictly over an IP packet-switched network. Various voice over IP technologies are available on smartphones; IMS provides a standard protocol across vendors.
Assisted GNSS (A-GNSS) is a GNSS augmentation system that often significantly improves the startup performance—i.e., time-to-first-fix (TTFF)—of a global navigation satellite system (GNSS). A-GNSS works by providing the necessary data to the device via a radio network instead of the slow satellite link, essentially "warming up" the receiver for a fix. When applied to GPS, it is known as assisted GPS or augmented GPS. Other local names include A-GANSS for Galileo and A-Beidou for BeiDou.
In telecommunications networks, RANAP is a protocol specified by 3GPP in TS 25.413 and used in UMTS for signaling between the Core Network, which can be a MSC or SGSN, and the UTRAN. RANAP is carried over Iu-interface.
GPRS Tunnelling Protocol (GTP) is a group of IP-based communications protocols used to carry general packet radio service (GPRS) within GSM, UMTS, LTE and 5G NR radio networks. In 3GPP architectures, GTP and Proxy Mobile IPv6 based interfaces are specified on various interface points.
Packet Data Convergence Protocol (PDCP) is specified by 3GPP in TS 25.323 for UMTS, TS 36.323 for LTE and TS 38.323 for 5G. PDCP is located in the Radio Protocol Stack in the UMTS/LTE/5G air interface on top of the RLC layer.
The Radio Resource Control (RRC) protocol is used in UMTS, LTE and 5G on the Air interface. It is a layer 3 protocol used between UE and Base Station. This protocol is specified by 3GPP in TS 25.331 for UMTS, in TS 36.331 for LTE and in TS 38.331 for 5G New Radio. RRC messages are transported via the PDCP-Protocol.
In routing, the data plane, sometimes called the forwarding plane or user plane, defines the part of the router architecture that decides what to do with packets arriving on an inbound interface. Most commonly, it refers to a table in which the router looks up the destination address of the incoming packet and retrieves the information necessary to determine the path from the receiving element, through the internal forwarding fabric of the router, and to the proper outgoing interface(s).
System Architecture Evolution (SAE) is the core network architecture of mobile communications protocol group 3GPP's LTE wireless communication standard.
GTP' is an IP based protocol used within GSM and UMTS networks. It can be used with UDP or TCP. GTP' uses the same message structure as GTP, but it is largely a separate protocol. GTP' uses registered UDP/TCP port 3386.
Proxy Mobile IPv6 is a network-based mobility management protocol standardized by IETF and is specified in RFC 5213. It is a protocol for building a common and access technology independent of mobile core networks, accommodating various access technologies such as WiMAX, 3GPP, 3GPP2 and WLAN based access architectures. Proxy Mobile IPv6 is the only network-based mobility management protocol standardized by IETF.
Access network discovery and selection function (ANDSF) is an entity within an evolved packet core (EPC) of the system architecture evolution (SAE) for 3GPP compliant mobile networks. The purpose of the ANDSF is to assist user equipment (UE) to discover non-3GPP access networks – such as Wi-Fi or WIMAX – that can be used for data communications in addition to 3GPP access networks and to provide the UE with rules policing the connection to these networks.
A Home eNodeB, or HeNB, is the 3GPP's term for an LTE femtocell or Small Cell.
QoS Class Identifier (QCI) is a mechanism used in 3GPP Long Term Evolution (LTE) networks to ensure carrier traffic is allocated appropriate Quality of Service (QoS). Different carrier traffic requires different QoS and therefore different QCI values. QCI value 9 is typically used for the default carrier of a UE/PDN for non privileged subscribers.
Polaris Networks is a privately held company founded in 2003 and located in San Jose, California. It focuses on developing networking protocol software, and its products primarily include wireless protocol test tools and emulators for 3GPP LTE networks.
5G network slicing is a network architecture that enables the multiplexing of virtualized and independent logical networks on the same physical network infrastructure. Each network slice is an isolated end-to-end network tailored to fulfill diverse requirements requested by a particular application.
