To prepare your environment for Lync conferencing there are some key network optimization configurations you can perform:
Enable the required firewall ports to access the Lync Online conferencing servers.
Disable authentication for Lync Online audio and video traffic when an authenticating HTTP proxy is used.
Configure the network to allow User Datagram Protocol (UDP) traffic for better audio and video performance.
Modify internal routers and optimize internal network paths for audio and video traffic.
Filter traffic if required by the service provider’s service level agreement (SLA)