on Works DPI is able to provide information on network conditions because of its capability to see more fields in packets than only the "send to" address. Discerning only a packet's address is analogous to looking at the address of an envelope. DPI provides the capa- bility to determine which application the packet is using by examining patterns within packets. It can distinguish Voice over Internet Protocol (VoIP) traffic from data, gam- ing, and video traffic SO that video or gaming traffic within a carrier network can be given the treatment required to maintain optimum performance. DPI software develops a database of patterns, also referred to as signatures. Each signature or pattern is associated with a particular application such as peer-to-peer music sharing or protocols such as VoIP. It can also be associated with traffic from certain hackers or even terrorists attempting to launch malicious attacks with a goal of disrupting Internet or government sites. The DPI software matches its own database of patterns found in packets to those associated with particular applications, and network attacks. DPI software can be installed in stand-alone switches connected to an ISP or car- rier's network or as part of routers (see Figures 1-3 and 1-4). Routers are used to con- nect traffic to the Internet as well as to select routes to other networks. Sandvine 24000 Policy Traffic Switch Dual Ethernet interfaces to Dual console interfaces for connections to local distant administrative terminals administrative terminals Status lights PTS 24000 sandvine Network ports* Redundant fans, hard drives, and power supplies (which convert AC electrical current to DC) * Network ports interface with third-party systems, such as billing and charging operations, DPI applications, and subscriber profile databases. Figure 1-3 A Sandvine DPI switch. (Courtesy Sandvine, Inc.) Deep Packet Inspection: Traffic Management and Monitoring Policy Traffic Switch (PTS) Manages Traffic in an ISP's Networks On-deck services = Access device (DSLAM) an