Performance of Priorities in Packet Switching

Master's thesis assignment

Philips Business Communications, Hilversum


The Internet Protocol (IP) is not only successful in data communications. IP emerges as the convergence layer for all forms of communication including voice, video or multimedia in general. The packet switched Internet is taking over the circuit switched Telephone network. The packet switched paradigm has great advantages in flexibility but it can (not yet) give the same Quality of Service (QoS) as circuit switching. Therefore, all over the world great effort is put into improving the QoS packet switched systems. Priorities are a key instrument in giving each communication flow the QoS that it asks (and pays) for.

Philips Business Communications (PBC) is an important supplier of Private Branch Exchanges (PBXs) providing wired and wireless communications for small to large enterprises. The shift of paradigm implies that the packet switched internetworking devices, that are part of the new PBX, must be able to distinguish between different communication flows and treat each flow according to its QoS requirements. Then, the following priorities can be exercised at each output buffer of an internetworking device:

  1. Service priority
  2. Storage priority

Here A. implies that a packet of one flow is transmitted on the outgoing link before a packet of another flow and B. that —when the buffer overflows— a packet of one flow can push out a packet of another flow.

In the Advanced Development (AD) department of PBC we have already methods for realizing different kinds of priorities, but the performance of those methods and the mapping of flows of different QoS classes to different priority levels must be further investigated. To this end, the master’s student will:

  1. Study internal reports and some external literature about new (wireless) PBX architectures, protocols and performance
  2. Extend the possibilities of mapping QoS classes to different priority levels
  3. Write Java applets that analyze with discrete event simulation the performance of the choices that can be made under 2.

Of course, the process of the steps above is accompanied by interaction with members of AD, interim reports and a final thesis and presentations at TU Delft and Philips. The student will be guided by Prof.dr. Frits Schoute of PBC and TU Delft (email: and, phone 035-6893593 and 015-2783544).