After a user and an agent connect and a co-browsing session begins, several things start synchronizing.
One of the advantages of this approach is that it allows for co-browsing to start at any time. For example, a user can initiate a co-browsing session while in the middle of filling out a long form. This approach also eliminates the need to worry about cookies and session timeouts on the agent side. In other words, the agent can co-browse on any site, and the co-browsing won't create a session on that site for the agent or store cookies in the agent's browser. All of these things are done on the user's side, who started the co-browsing.
The following diagram illustrates the detailed communication between the parties mentioned above.