[Linphone-users]valid from headers

[Yogesh]

Hi,
   I was trying to test linphone 0.9.1 with another UA1 which is rfc 
2543 compliant. The from header of the invite request from UA1 was as 
follows
   f:"1234"<sip:10.0.0.4>;xxxxxxxxxxxx

I wanted to know whether this is a valid from header ? If username is 
missing in the from url and display name is present then should we treat 
the display name as username ? Is this compliant with rfc 2543 or/and  
rfc 3261?

Thanks
Yogesh