mà chủ yếu là chương trình lớp phủ điều hành DOS và cho phép các máy trạm trên mạng để chia sẻ ổ đĩa và các thiết bị ngoại vi. DOS, cũng được phát triển bởi Microsoft, khóa tập tin và ghi lại IBM máy tính mạng chương trình DOS hoặc trên máy tính bộ chuyển đổi với NETBIOS | bridging and switching methods and performance issues 347 mode while the other switch would have both ports in a forwarding mode of operation. To obtain the ability to control the spanning tree most switches permit a number of parameters to be altered from their management console. Those parameters include the forwarding delay that governs the time the switch will wait before forwarding a packet the aging time the switch waits for the receipt of a hello packet before initiating a topology change the Hello time interval between the transmission of BPDU frames and the path cost assigned to each port. Switch Type As previously discussed a switch will either support one or multiple addresses per port. If it supports one address per port it is a port-based switch. In comparison if it supports multiple addresses per switch it is considered to be a segment-based switch even if only one end station is connected to some or all ports on the switch. Switching Mode Ethernet switches can be obtained to operate in a cut-through store-and-forward or hybrid operating mode. As previously discussed in this section the hybrid mode of operation represents toggling between cut-through and store-and-forward based upon a frame error rate threshold. That is a hybrid switch might initially be set to operate in a cut-through mode and compute the CRC for each frame on-the-fly comparing its computed values with the CRCs appended to each frame. When a predefined frame error threshold is reached the switch would change its operating mode to store-and-forward enabling erroneous frames to be discarded. Some switch vendors reference a hybrid switch mode as an error-free cut-through operating mode. Virtual LAN Support A virtual LAN can be considered to represent a broadcast domain created through the association of switch ports MAC addresses or a network layer parameter. Thus there are three basic types of vLAN creation methods you can evaluate when examining the functionality of an Ethernet .