Page 246 - 5G Basics - Core Network Aspects

1 Core network aspects

Appendix II

Problem statement of current mobile packet core network
(This appendix does not form an integrated part of this Recommendation.)

This clause focuses on the problem statement of the mobile packet core in the current network based on the
analysis of scenarios in Appendix I.

II.1 Problem in traffic steering

Faced with rapid increases of data traffic, MNOs want to and/or have to deploy many service function entities
such as URL filter, video optimization, content compression to improve the user's quality of experience (QoE),
to reduce the bandwidth pressure and to provide valued added services. Two kinds of service function entity
models, i.e., the static serial model and the hairpin model, are deployed [b-3GPP TR 22.808].
Static serial model is one where the service function entities are statically connected with one another, and
traffic goes through all the service function entities deployed on the chain. The access point name (APN) is
usually used to differentiate each service chain. However, this model has some drawbacks:

– The flows go through the service function entities that are not necessarily needed. As a result, a
transfer delay is added.

– All the capabilities on the chain have to be designed to be capable of handling maximum traffic
processing capacity, even though the capabilities may only be needed for part of the traffic.
– It is difficult to adjust the service chain if a service function entity is reused in multiple service chains,
e.g., a large number of configuration tasks becomes necessary when a shared service function entity
is changed.
Hairpin model is one where all service function entities are connected to a centralized traffic routing
controller, and the traffic goes back to the controller to decide the next hop after the previous service
function entity processing ends. However, this model has some drawbacks:
– All traffic always goes through the centralized controller to determine the next hop, which
significantly increases the load on the controller.
– The centralized processing network element becomes a single point of failure.

II.2 Problem caused by proprietary hardware
Network functions usually run on proprietary hardware appliances which require vendor-specific
configuration tools. Frequently, the deployment of a new service requires yet another hardware box to be
installed and configured. These issues add complexity to the operator's network management and service
deployment, and increase operating expenses (OPEX).

In addition, because proprietary hardware usually cannot be shared by different network functions, these
specialized hardware appliances suffer from short lifecycles due to the fast innovation in technology and
unexpected changes in customers' demands. This worsens the efficiency of capital expenditure (CAPEX) such
as hardware investment.

II.3 Problem statement of the mobile packet core gateway
The mobile packet core architecture has decoupled the control function and forwarding function partially by
splitting the mobility management function from the hybrid control and forwarding function into mobility
management function and gateway function. But the control function and forwarding function of the
gateways are still tightly coupled, especially for the tunnel control and forwarding [b-IEEE-Kostas]. The
current mobile gateways face some of the following issues:

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