Bandwidth needed for DNS server?

[Dragoncrest]

	Hi again all.  Looking to go into the next stage of our move to Linux by 
implementing an internal authoritative DNS server.  I only expect to hold 
zones for 4 different domains on it for now, so I'm not expecting much from 
it, but I'm curious how much bandwidth usage to plan for.  Right now our 
ISP does all our DNS, but I'd like to take it in house if possible so we 
have direct control over it.  If all our TTL's are set to 24 hours, what 
could I expect to see as far as an increase in bandwidth usage by doing 
this?  I'd like to be able to plan how and where I'm going to implement 
this so as to have the least impact on our network.