Google Networking Best Practices for Large Deployments - Manual (Page 21)

Network Configuration 21
Google Protocols
Google Apps services are mostly web-based or API-based. The table below shows common
Google Apps services, and the protocol used for each. As shown in the table, the datagrams
that Google Apps uses are almost always TCP-based, except as noted.
Google Talk Voice and Video and Google+ Hangouts
Google Talk Voice and Video
During a voice or video call, the Google Talk Voice and Video plug-in attempts to establish a
connection from the caller to the callee (for details,
see Google Talk Developer
Documentation ). The plug-in attempts different protocols and transport methods, depending
on the network connection at the time of the call.
Google Talk Voice and Video attempts to make a connection using any of the following
protocols and connection endpoints, in the following order of preference
1. Direct UDP connection between caller and callee, using STUN, on random ports.
2. UDP connection between caller and callee with NAT-table traversal, using STUN, on
random ports.
3. UDP connection between caller and callee through a Google Relay server, using STUN,
on random ports. (This connection works for symmetric NAT.)
4. Direct TCP connection between caller and callee.
5. TCP connection between caller and callee through a Google Relay server.
6. SSL over TCP connection between caller and callee through a Google Relay server, on
port 443.
Application Protocol Port
Mail, Calendar, Docs, Sites TCP 443
Google Apps Sync for Microsoft Office TCP 443
Google Apps Connector for BlackBerry
Enterprise Server TCP 443
Google Talk (Web) TCP 443
Google Talk (Desktop Client) TCP (XMPP) 5222 or 443
Google Talk (Voice and Video) Special; see
below Special; see
below
Google+ Hangouts Special; see
below Special; see
below
Google Apps Migration for Microsoft
Exchange TCP (API) 443
Google Apps Migration for Lotus Notes TCP (API) 443