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Control and User Plane Separation in Brocade Virtual Core for Mobile

by Heeseon ‎02-17-2016 12:48 PM - edited ‎02-17-2016 01:00 PM (6,328 Views)

Mobile networks have come a long way from circuit switched GSM network to carry voice. GSM architectures, being the first mobile networks, became a basis of all the mobile network generations following it – with a hierarchical structure among multiple physical entities, connected through different interfaces using mobile-specific protocols.   This architecture worked perfect when voice and narrowband data was the main content transported among a limited number of phones. 


Then came the era of mobile broadband data, smartphones, and IoT devices where support of diverse spectrum of use cases in an efficient and agile way became critical:

  • The network should continue to support increasing amounts of data and various applications for subscribers.
  • There may be large number of IoT devices an order of magnitude larger than subscribers, which would incur higher signaling transactions but generate only small amount of data, like power meters.
  • They demand large throughput of mission critical data from a small number of devices like video monitoring at the mining site, etc.
  • The mobility nature of the services, from stationary device support like surveillance camera to a high speed mobile device support like connected vehicles.


To support this wide range of use cases, completely new way of thinking is needed in mobile network architecture beyond the evolution of GSM based architecture. Brocade VCM provides a fresh view of the mobile network architecture to support the increasing variance of use-cases while still maintaining compliance to industry standards.


Network Transformation by Brocade VCM through modular architecture

 Brocade VCM (Virtual Core for Mobile) is designed with a very simple goal – to have two or more parties to exchange digital contents in the most efficient way.   And this, of course, is a very obvious goal for any communication.  The question is on “how”.   We are exchanging all sorts of data through Internet which has a very flat architecture with routers and switches using one protocol - IP.  Compare this with mobile architecture where data is exchanged through multiple different types of physical nodes using multiple different protocols.


Brocade VCM transforms the mobile network from GSM-era architecture to more Internet like architecture.   It does so by looking at the mobile packet core as one service rather than a group of different physical nodes.  We broke the boundaries of physical nodes of packet core, looked at the functions that used to be performed by physical nodes, consolidated those functions, and came up with core set of functions that need to be performed at mobile networks.  The result is a flat and function (or service) based modular architecture.


Old Physical node based EPC Architecture

Figure 1: Old Physical node based EPC architecture


Transformation of phycial node based architecture into function based architecture

Transformation of phycial node based architecture into function based architecture

Figure 2: Transformation of physical node based architecture into function based architecture


One of the biggest changes this architecture brings is a separation of control plane and user plane.   Traditional architecture has control and user plane supported all in the same box even though there was lots of attempt to separate these functions.  In fact, in LTE the control plane node (MME) and user plane node (S-GW and P-GW) are separated but S-GW and P-GW still have significant signaling portion in them.  Brocade VCM architecture is all about decomposition and re-composition.  We had decomposed the EPC into functional level, not into node level, then re-composed those functions into meaningful groups.  All the control functions of MME, S-GW, and P-GW becomes a “control function of an EPC”.  In the same way, user plane functions of S-GW and P-GW becomes a consolidated “user plane function of EPC”.    By consolidating the similar functions into one module, Brocade VCM minimizes the overhead, latency, and duplicates.


Location Independence of Control and User Plane in VCM

Complete separation of the control and user plane allows mobile service operators to have great flexibility of where to locate each function according to their needs and use cases.  Specifically, it becomes easier to place the user plane very close to the edge.  With its easiness to locate the user plane anywhere, Brocade VCM’s user plane is called ‘Portable User Plane (PUP)’.   The following diagram represents Brocade VCM’s internal architecture featuring PUP.   With the decomposition and re-composition, the complete EPC service is architected into an interface layer, control plane, user plane (PUP), and database layer, managed by the internal management function.  This allows a direct mapping of mobile workload into compute resources and makes the independent scalability per functional module available while optimizing the underlying resource utilization.   Portability of the user plane allows distribution of data to the edge of the network while maintaining control of each session centrally.

Brocade VCM architecture with Portable User Plane (PUP) Figure 3: Brocade VCM architecture with Portable User Plane (PUP)


The 3rd Generation Partnership Project (3GPP) recently approved the study item for Control and User Plane Separation (CUPS).   Other SDOs are also moving to address this aspect, including ONF and IETF.  Brocade VCM already implemented this framework and has proven its performance and flexibility for deployment in multiple customer environments.   Brocade VCM’s architecture with control and user plane separation provides the following benefits:

  • Reduced latency and improved subscriber experience
  • Minimize the cost associated with increased EPC interfaces to OSS/BSS, including PCRF, OCS, and OFCS by having centralized interface and control plane
  • Optimal routing for MNOs and MVNOs
  • Localization of mobile-to-mobile communications at different hierarchies
  • Minimize scaling challenges inherent with Internet of Things
  • Eliminated mobility support to devices that don’t need it


With this modular architecture that has a built-in control and user plane separation, challenge to support wide range of use cases mentioned above is addressed.  


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