Synchronous Storage Replication Process

Hi,
I have a question regarding storage replication for synchronous mode. If I describe the process in detail having twin Data Centers called DC-A and DC-B we have:
1- The server in DC-A writes to the DC-A disk.
2-  Before the server in DC-A receives an ACK from the DC-A disk, this data is replicated to the other DC disk, DC-B Disk.
3-  To replicate the data to the other DC we will first ask to the other DC before passing through the DCI “are you ready to receive”?
4-  We will get the approval from DC-B that is ready
5-  Then DC-A will send the data through the DCI to arrive to DC-B.
6-  DC-B disk receives de data and then DC-B disk must send an ACK to DC-A Disk
7-  Once the ACK is received at DC-A disk, DC-A disk will then send the ACK to the server in DC-A which originated the write action.
My question is if step 3 and 4 sometimes are counted and sometimes not. I should counted or not? This decision is important for me because it affects by a factor of 2 the distance between the twin DCs.
Thank you very much for the help.
Regards,
J

Hi,
just to add more information. My doubt comes from the 2 Cisco live sessions about DCI.
On this session it says that we must count 4 times the traffic passing through the DCI in order to know the DCI Distance:
https://www.ciscolive.com/online/connect/sessionDetail.ww?SESSION_ID=6623&backBtn=true
On this other session it says that we must count only 2 times:
https://www.ciscolive.com/online/connect/sessionDetail.ww?SESSION_ID=7775&backBtn=true
Who is right then? because the impact is huge.
Thank you.
Regards,
J

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