How Does Collaboration Content Sharing Work?

The Web Conferencing Conference Service is responsible for managing collaboration content sharing in conferences. This service is installed on all Lync Front End servers. When whiteboards and polls are shared during a meeting, the content is created and stored in the Lync Server File Store defined for the pool of the conference organizer. This content is then distributed to conference participants over HTTPS. Internal and external users connect to the web service URLs defined in topology. For external users, this traffic travels through the reverse proxy solution deployed.

When a presenter decides to share a whiteboard or poll, the presenter uploads the content to the conference using the Persistent Shared Object Model (PSOM) protocol. This protocol is a Microsoft proprietary protocol that has been used in web conferencing since OCS 2007 and the Live Meeting products. In addition to the initial content upload, any modifications of a whiteboard are submitted using the PSOM protocol. See the diagram in Figure 19.3 for the content upload and download process in a web conferencing scenario.

Figure 19.3. Content upload over PSOM and download over HTTPS.

In Figure 19.3, client 1 is a presenter in the conference who is sharing a whiteboard. The details of the whiteboard sharing process are described below:

1. Client 1 sends a PSOM upload request to the web conferencing service.

2. After the conferencing service validates the request, the client sends the actual whiteboard content to the service.

3. The Web Conferencing Service saves the content to the Lync file store defined for that pool. This content is created in a subfolder specific to the organizer and the conference.

4. The Web Conferencing Service then sends the presenter and participants a download URL and key to be used when making the HTTPS download request. This request is sent to the Lync clients over PSOM.

5. Each client then sends an HTTPS request to the Lync Web Services for the content.

6. The Lync Web Services requests the content from the file store, and delivers this to each user over HTTPS.

In Lync Server 2013, if archiving is enabled, any content including whiteboards and polls that are uploaded to a meeting will be archived. If Exchange Server integration is enabled, this content will be archived in to the Exchange Server data store.

Lync Server 2013 collaboration content sharing does not have a major network bandwidth impact on many organizations. The data that is sent and received during meetings is often very small. However, organizations that are expecting a heavy usage of this functionality should consider the read and write impact on the file servers that will be maintaining the Lync file store. Table 19.8 is provided by Microsoft for file activity capacity planning for Content Collaboration sessions.

Table 19.8. Lync Server 2013 Content Collaboration Upload and Download Rates