size of sasl auth

[Petre Agenbag]

Hi
I don't know if this is a stupid question, but it's been asked of me, 

The sysadmin of another ISp wanted to know "how big is the
authentication" on my server.
It runs cyrus & sendmail and I use SASL for authentication.
I guess what they want is the packet size or "overhead" in the
connection to authenticate.
Is this obtainable?
Thanks