Source vs destination
In all the interviews I've seen/heard with people in the government who understand the topic they're talking about - ie Malcolm Turnbull - what they want is user/network/ip address/device/times. So you had IP address X on your mobile on Monday and you've had IP address Y on your home machine for the last 3 weeks. That's about it.
If they break a terror site or something like that and they spot a login from an Australian IP address, they get a warrant to find out who had that IP address at that time. NO traffic info is needed, NO destination info is needed. And they don't want any of it. They just want to be able to map an IP address/time pair to a person.
And the process for getting that info is already in place. It requires warrants and it already exists. Under warrant they can get much more information than that but Telcos/ISPs are not required to collect that info BEFORE the warrant. But all comms must be interceptable.
This push is apparently just to ensure that the info above (RADIUS data effectively) is kept for a nominated period. ISPs already collect this information in some form or another and keep it for some time (for billing) which might be very short or very long.
But I know Turnbull has been quite clear - they do not want ANY traffic information kept unless post a legal intercept order.