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Implementing an IP priority scheme with off the shelf products Disclosure Number: IPCOM000019917D
Original Publication Date: 2003-Oct-10
Included in the Prior Art Database: 2003-Oct-10
Document File: 3 page(s) / 48K

Publishing Venue



A combination of a suitably configured router and a simple state of the art private branch exchange (ISDN-switch) can be used to implement a layer 3 (IP) or layer 4 (TCP / UDP) priority scheme.

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Implementing an IP priority scheme with off the shelf products


A priority scheme for the IP (OSI layer 3) and TCP / UDP (OSI layer 4) layers can be implemented by a suitably configured and interconnected state of the art private branch exchange in combination with a standard router.


    Due to technical and financial restrictions adjacent IP routers in an Intra- or Internet are usually connected with limited bandwidth long distance links. If the traffic volume increases beyond a certain threshold, the observable quality of service e.g. for time critical Voice over IP applications will deteriorate. At higher utilization rates individual IP data packets will be discarded. With today's commercially used technologies this frequently leads to a further deterioration of the network traffic, because automatically timer triggered retransmissions will increase the offered network load. In certain distress situations - e.g. a denial of service attack - this situation does even prevent necessary counter measures as network management commands to reconfigure names servers, router configuration tables or firewalls can not reach their destinations.

    Several years ago the internet community has already identified the need for a priority scheme to avoid such problems. Unfortunately however there is neither a final specification for an implementation nor a universally accepted simple approach to implement such a scheme with existing commercially available products.


    It is assumed that a state of the art private branch exchange provides the capability for individual access lines or calls to specific destination numbers to preempt regular connections established by regular access lines (or connected to normal non-privileged destination numbers). In military digital branch exchanges a more advanced priority scheme providing four levels of priority is standard for years.

    For current...