Why the Ack number is bigger than the last Seq number? Why the Ack number is bigger than the last Seq number? ![enter image description here]( you see the Ack response for each two TCP packages. but there I have a question, you see the Ack response for `Seq=19997`, `Seq=22893` and `Seq=25789`. but the 3 Ack are not by add 1. `Seq:19997`->`Ack:21445`, `Seq:22893`->`Ack:24341`, `Seq:25789`->`Ack:27237`.

`ACK` is always bigger than the last `SEQ` number because `ACK` is the next expected value.

Let's assume I received a packet which has a sequence number zero `(SEQ=0)` and let's say that the size of the packet is `k` bytes. Then my ack will be the last sequence number `(0)+(k)+1`