Lost of SQL Server connection

We have to pass through a firewall between our customer’s office and our work office. A group of users from our office are trying to connect to a SQL Server 7.0 on the customer’s side but continually get connection failed messages at different times. It’s a hit and miss type situation of when the lost connection will happen. It happens enough that no work can be accomplished. Is there any parameter settings that might help or something to look for when troubleshooting that might help resolve the problem. I did suggest that they try to the networking people to change their connection in the wiring closet. Any suggestions would be appreciated.