Consider the 3-way handshaking protocol for TCP connection establishment. Let the three packets exchanged during the connection establishment be denoted as P1, P2, and P3, in order. Which of the following option(s) is/are TRUE with respect to TCP header flags that are set in the packets?

In the standard TCP 3-way handshake for establishing a connection between a client and a server:

1. First Packet ($P_1$) [Client $\to$ Server]: The client sends a segment with the synchronize flag set to initiate the connection.

   $$\text{SYN} = 1,\quad \text{ACK} = 0$$

   Hence, Option (D) is TRUE.

2. Second Packet ($P_2$) [Server $\to$ Client]: The server acknowledges the client's sequence number and synchronizes its own sequence number.

   $$\text{SYN} = 1,\quad \text{ACK} = 1$$

   Hence, Option (B) is TRUE and Option (C) is FALSE.

3. Third Packet ($P_3$) [Client $\to$ Server]: The client acknowledges the server's sequence number.

   $$\text{SYN} = 0,\quad \text{ACK} = 1$$

   Hence, Option (A) is FALSE.

Therefore, the correct options are B and D.