The network firewall controls certain types of connections between SLAC buildings and the Internet.
Details are here:
For the majority of people, these controls are totally fine! You can ssh and ping from the outside to machines in SLAC buildings and essentially all the usual outgoing traffic is permitted.
However, some developers who write programs which access resources on the Internet via non-standard protocols, or those who access SLAC resources using non-standard applications from external locations, may need to get additional applications or ports onto the approved list.
If you are concerned, please discuss this with your facility point of contact and allow for some addtional time in setting up computers on the building networks.