Some security conscious customers choose deliberately lock-down their networks to prevent unwanted or unnecessary outbound connections towards the internet. It's also quite common to see free or public WiFi services that are similar. But some choose to block outbound UDP connections entirely and may even require traffic to be relayed via a proxy server as part of their security policies. There are many reasons customer may choose to do this, some of which are regulatory other for simplicity. In these more restrictive scenarios MS Lync 2013 / Skype for Business clients cannot send outbound UDP (or access is limited to HTTP & HTTPS only) resulting in federated calls towards Lifesize Cloud failing.
This idea or feature request suggests adding support for TCP media within the Lifesize Cloud platform, so inbound calls from Microsoft Lync 2013 and/or Skype for Business clients from these networks are possible. Adding support for TCP media will allow the Lync/SfB client to either establish: a TCP session from the client to Lifesize Cloud; or relay its traffic via the MS Edge server (on TCP 443) then onto Lifesize Cloud.
Both permutations should give the Lync / SfB client a much greater chance of successfully establishing an A/V media connection to Lifesize cloud from the restrictive network environment.