If you have a big company with engineers in many time zones, you need to establish some rules for realtime communication. I will not address email or phone/video calls as a solution, because email is too asynchronous (you don't stare at your email waiting for responses) and phone calls are too synchronous (calls are either scheduled or disruptive, and always blocking). Chat, however, performs well both ways.
To put it simply, all employees must run the same chat client. I suggest Skype or Hipchat. It's easier for an engineer to use Skype than it is for a designer to use IRC. Something is broken if these employees can't chat with each other. No matter the client, two features are essential: persistent group chats and offline messaging. Google Talk fails at persistent group chats, IRC fails at offline messaging.
When a company gets big enough, it's impossible to know everyone's name. Therefore,
Employees must be discoverable:
- Every team in the company should have a corresponding group chat. The names of these chatrooms should match team names to maintain discoverability.
- Every person must have profile details filled in so that their display name is simply their first and last name. Nicknames are useless to new employees.
One of the luxuries of having all employees under one roof is the ability to glance across the room to see if someone is at their desk. It makes communication decisions instantaneous. To preserve this, even across continents...
Availability must be predictable:
- If you're at work, you're online.
- Every person must enable "Set my status to Away after 10 minutes of inactivity" or a similar option. The 10 minutes is flexible as long as everyone in the company uses the same value. Employees must be able to reliably glance at the chat client to see who is active.
Open channels don't necessarily mean increased interruptions. This scheme is about reducing latency, not increasing the quantity of conversations taking place.