28 January 2021

Swedish STANAG-5066 client-application... (2)

(just a little update to the previous post) A further confirmation of the role of the STANAG-5066 DTS (Data Transfer Sublayer) in the duplication of D_PDUs  comes from the examination of the S5066 frames produced by the dissector that I'm still writing (Figure 1).
As said previously, C_PDU segment offset in the duplicated D_PDUs does not change and thus the same data segment is processed two times and then sent into two distinct frames (#85 and #86 in this example). In this regard, it's interesting to notice the valuse of the EOT field. The field End Of Tansmission (EOT) contains a binary number expressing the number of half (1/2) second intervals remaining in the current transmission from the beginning of the current D_PDU. Once an EOT is sent, the EOT in each subsequent D_PDU in that transmission contains a consistent calculation of the EOT, that is, monotonically decreasing in half-second (0.5 second) intervals (calculations by the transmitting node is rounded up to the nearest half-second interval). As you may see, the flow control updates the EOT value.

Fig. 1


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