syn is L3 flow and syn/ack is L2 flow

MP18 — Tue, 06 Nov 2018 05:02:40 GMT

Can someone please explain me this in detail --

syn is L3 flow and syn/ack is L2 flow

can not undertsand this?

Re: syn is L3 flow and syn/ack is L2 flow

santonic — Tue, 06 Nov 2018 07:52:18 GMT

Good thing, cause it's wrong. It's all layer 4.

From Wiki:

Connection establishment

To establish a connection, TCP uses a three-way handshake. Before a client attempts to connect with a server, the server must first bind to and listen at a port to open it up for connections: this is called a passive open. Once the passive open is established, a client may initiate an active open. To establish a connection, the three-way (or 3-step) handshake occurs:

SYN: The active open is performed by the client sending a SYN to the server. The client sets the segment's sequence number to a random value A.
SYN-ACK: In response, the server replies with a SYN-ACK. The acknowledgment number is set to one more than the received sequence number i.e. A+1, and the sequence number that the server chooses for the packet is another random number, B.
ACK: Finally, the client sends an ACK back to the server. The sequence number is set to the received acknowledgement value i.e. A+1, and the acknowledgement number is set to one more than the received sequence number i.e. B+1.

At this point, both the client and server have received an acknowledgment of the connection. The steps 1, 2 establish the connection parameter (sequence number) for one direction and it is acknowledged. The steps 2, 3 establish the connection parameter (sequence number) for the other direction and it is acknowledged. With these, a full-duplex communication is established.

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syn is L3 flow and syn/ack is L2 flow

Re: syn is L3 flow and syn/ack is L2 flow