(CAC), and deliberate (selective) cell dropping. Although these methods work well for the land-based systems, they need to be modified for acceptable use with an ATM over satellite network and to maintain the appropriate QOS. Traffic shaping changes the characteristics of cell streams to improve performance. Some examples of traffic shaping are peak cell rate reduction, burst length limiting, and reduction of Cell Delay Variation (CDV) by positioning cells in time and queue service schemes. The limitation of this scheme in relation to the ATM satellite environment is the inability to dynamically change the traffic parameters during network congestion.CAC is an effective traffic control mechanism when used with systems that experience occasional congestion. This method is a set of actions that the system can take to allow or disallow a network ATM connection to be established based on the amount of network congestion at the present moment. In the ATM satellite system, however, this scheme seems to be effective during the ATM connection phase only. The long propagation delay of the satellite portion of the system precludes this technique from being useful during transmission. If the system faces more than occasional congestion, the performance suffers from the inability to establish ATM connections.The deliberate or selective cell dropping technique is based on the idea of potentially dropping a cell when the network becomes congested. The determining factor concerning which cells are to be dropped is the Cell Loss Priority (CLP) bit contained in the cell. (See Figure 2 for the location of the CLP bit in the ATM cell.) This scheme is not suited for the ATM satellite environment since it can cause many dropped cell retransmissions over long propagation delays thereby hindering overall performance.Two additional schemes proposed for use with ATM over satellite networks are Explicit Forward Congestion Indication (EFCI), also know...
