 | 1 | initial version |
The brown line represents the (cumulative) ACK from the receiver side. The red lines represent the SACK blocks in the DUP-ACKs.
When frame 132 and 133 are received, there is a missing segment in between. This generated a DUP-ACK where the cumulative ACK (brown line at the bottom) is raised to ACK the reception of the data segment in frame 132. But sinde there is data missing in between, the data segment in frame 133 is SACKed which is visible in the red line. The gap between the brown line and the bottom of the red line is the missing data:
Frame 216 fills the gap between the cumulative ACK and the left edge (LE) of the SACK block, this results in an ACK that now includes the newly received data segment as well as the previously received data segments. This is shown by the (cumulative) ACK being increased, represented by the brown line being raised:
