请教开销总线中的开销字节计算问题

holi

<p>在学习华为光传输设备中，一个关于开销的问题我不太明白。2500+中，有两组开销，分别为2M，32路64K。这没有问题。但是后来有个结论：“<span style="FONT-SIZE: 10.5pt; LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;; mso-bidi-font-family: &quot;Times New Roman&quot;; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA;">若要保证一个光口所有功能的正常实现，至少需要</span><span lang="EN-US" style="FONT-SIZE: 10.5pt; LINE-HEIGHT: 150%; FONT-FAMILY: &quot;Times New Roman&quot;; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-fareast-font-family: 宋体;">20</span><span style="FONT-SIZE: 10.5pt; LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;; mso-bidi-font-family: &quot;Times New Roman&quot;; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA;">个字节”。这个20个字节是怎么算出来的？</span></p><p><span style="FONT-SIZE: 10.5pt; LINE-HEIGHT: 150%; FONT-FAMILY: 宋体; mso-ascii-font-family: &quot;Times New Roman&quot;; mso-hansi-font-family: &quot;Times New Roman&quot;; mso-bidi-font-family: &quot;Times New Roman&quot;; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA;">我特别数了数开销中的字节，有30个。这里的“至少需要20个字节”是怎么算出来的呢？</span></p>