client behavior - cname vs A record

[Jonathan de Boyne Pollard]

WC> What ttl value will be honored? 

By the caching proxy DNS server: Both.

WC> In other words, will the client re-request name 
WC> resolution when the cname or A record ttl is reached?

Different DNS client libraries, and different applications using those
libraries, behave differently.  Some (indeed, most) DNS Client libraries have
no caching, and each request from the application for query resolution results
in a query datagram being sent to the proxy DNS server.  Some applications
only employ the DNS Client library to perform a name->address mapping once,
and hang onto the result for grim death thereafter.