TcpMaxDataRetransmissions đặt số lượng tối đa truyền lại của một phân đoạn TCP có chứa các dữ liệu trước khi kết nối là bị bỏ rơi. Bản tóm tắt sau đây của khung 5-12 của mạng Capture Màn hình 13-01, bao gồm trong \ Captures thư mục trên đồng hành CD-ROM), cho thấy số lượng tối đa của truyền lại và tăng gấp đôi của RTO giữa | 274 Part III Transport Layer Protocols 2. After RTO number of seconds when the RTO expires the segment RTO is set to twice the RTO for the segment s previous transmission and retransmitted. Step 2 is repeated for the maximum number of retransmissions before the TCP connection is abandoned. The TcpMaxDataRetransmissions registry value controls the maximum number of retransmissions for TCP in Windows Server 2008 and Windows Vista. TcpMaxDataRetransmissions Location HKEY_LOCAL_MACHINE SYSTEM CurrentControlSet Servi ces Tcpip Parameters Data type REG_DWORD Valid range 0-0xFFFFFFFF Default value 5 Present by default No TcpMaxDataRetransmissions sets the maximum number of retransmissions of a TCP segment containing data before the connection is abandoned. The following summary of Frames 5-12 of Network Monitor Capture 13-01 included in the Captures folder on the companion CD-ROM shows the maximum number of retransmissions and the doubling of the RTO between successive retransmissions Frame Time Offset Time Delta Description 5 FTP Data Transfer To Server 6 FTP Data Transfer To Server 7 FTP Data Transfer To Server 8 FTP Data Transfer To Server 9 FTP Data Transfer To Server 10 FTP Data Transfer To Server 11 FTP Data Transfer To Server 12 FTP Data Transfer To Server This Network Monitor trace was captured from a File Transfer Protocol FTP client on which the uploading of a file was in progress and the cable connecting the network adapter of the FTP server was pulled. Frames 8 through 12 show the retransmission behavior of TCP. Notice how the initial RTO is seconds and successive retransmissions have RTOs that are doubled. After the last retransmission the FTP server waits 16 seconds before abandoning the connection and recovering the connection s resources. It takes a total of seconds to abandon the connection. The .
