n as Forward Explicit Congestion Notification (FECN), and Backward Explicit Congestion Notification (BECN). EFCI is a technique used to convey congestion notification information from the destination to the source via communication to its peer in the higher protocol layers. The source can therefore take appropriate action to reduce additional traffic through the present channel. The problem with this method is that at least a one-way propagation delay is required to notify the source of the congestion. BECN is a faster mechanism than EFCI since a congested network can use this technique to send congestion information in the reverse direction of the network flow to indicate the problem without requiring peer notification. However, like the EFCI technique, BECN is also subject to long propagation delays if the congestion is occurring at the destination. Bandwidth ManagementSince bandwidth for satellites is limited, proper bandwidth management in the ATM over satellite system is critical. A substantial degradation of the overall performance of the combined terrestrial and satellite system will severely inhibit its usefulness. Applications requiring high bandwidth allocations are particularly affected by this issue.Bandwidth management is a difficult matter to handle within a satellite network. One possible way to help with this problem is to allocate bandwidth for the channel at the connection setup phase by using a Burst Time Plan (BTP). This traffic assignment scheme is a mapping tool that indicates the position and lengths of bursts in the transmission frame. The BTP restricts the number of ATM cells in bursts or subbursts that each earth station can transmit. The number of Virtual Paths (VP) and Virtual Channels (VC) of the ATM connection can also be restricted by the BTP to help with bandwidth management. SUMMARY The usefulness of a combination ATM and satellite network will be determined by its ability to maintain the QO...
