Deep packet inspection (DPI) is a technique that has seen success in traffic management, security, and network analysis. It is a technology that performs content analysis of network packets at line speed but is different from header or metadata-based packet inspection, which is typically performed by switches, firewalls, and IDS/IPS devices. A general DPI solution provides deep packet inspection for different applications.
Header-only processing limits what you can see from packet processing and hence cannot detect content-based threats or differentiate applications using common communication platforms. DPI inspects the content/payload of the packet and can extract content-level information, such as malware, specific data, and application types that are otherwise unavailable.
As network operators, Internet service providers (ISPs), and corporations alike are increasingly dependent on the efficiency of their networks and the applications that run on them, the need to manage bandwidth and control the complexity and security of communications becomes paramount. DPI provides exactly the means for such purposes. User organisations that seek better network management and compliance should view DPI as an essential technology.
DPI technology works by first reassembling packets into network flows. Data processing, including protocol classification, then kicks in and extracts information from the flow content. Flow reassembly and content extraction both require heavyweight-processing capabilities, especially in high-volume data streams. A successful DPI technology must therefore provide fundamental features like high performance computing and flexible support for analysis tasks.
A DPI-processing unit must provide scalability and performance that is in accordance with the performance of the communication network. Deep content inspection requires heavier processing than mere header inspection. As such, DPI often uses a parallel processing architecture to speed up computational tasks. A DPI technology ultimately provides users with information extracted from the network flow. The actual content processing can vary widely depending on the information extracted. DPI technology should behave somewhat like a platform-providing the utility (the "how") for content processing, but letting users decide "what" is to be processed.
Service providers use DPI to segment network traffic. Many service providers are now using DPI to separate traffic into low-latency (voice), guaranteed-latency (Web traffic), guaranteed-delivery (application traffic), and best-effort-delivery applications (file sharing). Using this classification, they can better optimise their resources for mission-critical traffic, police use of noncritical ones, and minimise network congestion. Because of cheaper bandwidth, service providers can add value-added services for additional revenues, including security, peak-usage management, content-based billing, and targeted advertising. These all require deep visibility into the network traffic stream.
Large enterprises can use DPI to manage network performance. Enterprises with large networks covering many geographic regions have very diverse traffic types running across their internal networks. Beyond controlling costs and bandwidth usage, security is a constant challenge that requires an understanding of application traffic on the network. These enterprises are beginning to see the benefits of DPI analysis. For example, a network administrator can use DPI technology to rate limit certain application traffic when the network performance is low, and raise the limit when the performance goes back to normal.