xmlrpc in smsbox

Hello,

I want to use xml rpc as source of a smsbox.

(I would rather use SOAP, but I'm afraid that I have to develop that 
part myself later)

Some research learned me that I have to use the following format:

<?xml version="1.0" 
encoding="utf-8"?><methodCall><methodName>sms.send</methodName><params><param 
name="x">value</param><param name="y">value</param>...</params></methodCall>

where param name can be one of:
'username'
'password'
'to'
'from'
'account'
'smsc'
'udh'
'dlrmask'
'dlrurl'


What I do not understand is: What is the meaning of udh, dlrmask and dlrurl?
Where do I put the message?

thanks in advance,
Jaap