Patent ID: 7840670

Claim:
In a packet network communications system, a method of passively analyzing packet-delivery performance during a communications session between a source and destination, the method comprising: detecting by a call signaling exchange the establishment of a communications session between a source and a destination, the communications session being that period between a call answer signal from the destination and a call termination condition during which data packets are sent between the source and the destination; sending in response to detecting the establishment of the communications session, diagnostic packets from the source during the established communication session, each packet eliciting a response from a router along a path between the source and destination; and analyzing the responses from routers along at least one path to produce a packet-delivery metric for one or more of the routers along one or more paths between the source and the destination, wherein each diagnostic packet is of the same format as data packets delivered during the communications session, each diagnostic packet is of the same length as data packets being transmitted in the communications session, and each diagnostic packet including: the same user datagram protocol (UDP) destination port number as data packets, the same differential services code point as the data packets, and a real time protocol (RTP) header that is valid for the data being transmitted in the communications session.