PCC, PCEF, DPI, EXTERNAL OR INTERNAL DPI

PCEF – Policy and Charging Enforcement Function, it comprises of:

·         Flow Based Charging

·         Policy Enforcement

·         Service Data Flow Detection Functionalities.

In the 3GPP standard, the PCEF function is realized by gateway element, e.g. GGSN in GPRS case. To realize the 3 main functions that are defined for the PCEF, a technology called DPI is used.

Deep Packet Inspection (DPI) is a form of computer network packet filtering that examines the data and/or header part of a packet as it passes an inspection point, searching for protocol to be aware of the service type or predefined criteria to decide if the packet can pass or if it needs to be routed to a different destination, or for the purpose of collecting statistical information.

According to the capabilities of inspecting the data packets, 3 levels of DPI are classified:

·         H-DPI (Heuristic Analysis DPI).

·         L3/L4 DPI

·         L7 DPI

The DPI function enables the PCEF to understand what types of traffic (e.g., http, mail, snapchat, whatsapp) are running on it, to classify them and perform traffic control and charging.

Neutrally speaking, there is no best solution but it is about the most proper solution. There are advantages and disadvantages for each of the solution; I will demistify afew below:

Firstly, clarity is needed about the DPI performance. 

Actually, DPI is a function, either it internal or external, it consume resources equally. Why we say DPI affect GGSN performance is because we claim our GGSN specification under normal traffic model. When we talk about GGSN DPI performance, everybody will say “Lots of stuff.....Waa  Waa Waa :) ”. For external DPI box, they claim specifications under normal traffic model, make you feel no performance drop.  But anyway from Hardware technical point of view, they are the same.

Secondly, i will talk about the Pros and Cons.

Internal DPI:

1. Compared to external DPI, internal DPI can provide E2E QoS for wireless network. It’s very important if you know how E2E QoS works (later I will introduce this concept as i discuss in these forums) Furthermore, in LTE phase, E2E QoS is mandatory.

2.  Can provide rich control policy (such as location based policy, multi-SIM) and precise charging (DPI box can’t control PDP deactivation, the PDP can be activated in GGSN even if there is no balance for this user).

External DPI:

1. Can provide convergent policy control and charging for both Fixed & Mobile networks.

2. Some external DPI boxes can provide more value-addeded solutions, such as Video optimization, Ad insertion, Caching etc. 

So, for the argument for the internal DPI and external DPI, we should state it clearly and not confuse our selves. But I think we just need to  put emphasis the E2E QoS.

#PerfectionIsANorm