● 以太网的数据帧封装如下图所示，包含TCP段中的数据部分最长应该是 （18） 字节。  <table style="border: medium none; width: 581px; border-collapse: collapse; height: 35px; margin-left: -23.4pt;" _dj="MsoNormalTable" border="1" cellpadding="0" cellspacing="0"><tbody><tr style="height: 20.85pt;"><td style="border: 1pt solid windowtext; padding: 0cm 5.4pt; width: 94.35pt; height: 20.85pt;" width="126">   目的MAC地址</td><td style="border-width: 1pt 1pt 1pt medium; border-style: solid solid solid none; border-color: windowtext windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt; width: 90pt; height: 20.85pt;" width="120">源MAC地址</td><td style="border-width: 1pt 1pt 1pt medium; border-style: solid solid solid none; border-color: windowtext windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt; width: 54pt; height: 20.85pt;" width="72">协议类型</td><td style="border-width: 1pt 1pt 1pt medium; border-style: solid solid solid none; border-color: windowtext windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt; width: 38.55pt; height: 20.85pt;" width="51">IP头</td><td style="border-width: 1pt 1pt 1pt medium; border-style: solid solid solid none; border-color: windowtext windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt; width: 42.45pt; height: 20.85pt;" width="57">TCP头</td><td style="border-width: 1pt 1pt 1pt medium; border-style: solid solid solid none; border-color: windowtext windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt; width: 36pt; height: 20.85pt;" width="48">数据</td><td style="border-width: 1pt 1pt 1pt medium; border-style: solid solid solid none; border-color: windowtext windowtext windowtext -moz-use-text-color; padding: 0cm 5.4pt; width: 33.55pt; height: 20.85pt;" width="45">CRC</td></tr></tbody></table> <br class="bogusBR">