tcp - Ethereal 转储中的 TSV 和 TSER 字段是什么意思？

Question

Ethereal 转储中的 TSV 和 TSER 字段是什么意思？我尝试使用谷歌搜索但找不到答案。

Answer 1

TSV 是 Timestamp Value 字段。它与序列号结合使用以唯一标识段(因为序列号可能会换行)。

TSER 是 Timestamp Echo Reply 字段。这用于 ACK 消息。它保存收到的最后一个 TSV 值的副本。它可用于往返时间估计(RTT = 当前时间 - TSER)。

字段在 RFC 1323 (TCP Extensions for High Performance) 中正式描述:

  TCP Timestamps Option (TSopt):

     Kind: 8

     Length: 10 bytes

      +-------+-------+---------------------+---------------------+
      |Kind=8 |  10   |   TS Value (TSval)  |TS Echo Reply (TSecr)|
      +-------+-------+---------------------+---------------------+
          1       1              4                     4

     The Timestamps option carries two four-byte timestamp fields.
     The Timestamp Value field (TSval) contains the current value of
     the timestamp clock of the TCP sending the option.

     The Timestamp Echo Reply field (TSecr) is only valid if the ACK
     bit is set in the TCP header; if it is valid, it echos a times-
     tamp value that was sent by the remote TCP in the TSval field
     of a Timestamps option.  When TSecr is not valid, its value
     must be zero.  The TSecr value will generally be from the most
     recent Timestamp option that was received; however, there are
     exceptions that are explained below.