ACR ON PROFILE DSCNT AND CLRED FOR APCH HAS TCASII RA TO CLB. TFC SIGHTED.

Narrative

WHILE ON THE CIVET PROFILE DSCNT INTO LAX; SOCAL APCH CTL CLRED US TO FLY THE ILS RWY 25L AFTER PASSING ARNES. WE DID JUST THAT. DURING OUR DSCNT ON GS THROUGH 9000 FT WE RECEIVED A TCASII ALERT FROM AN ACFT AT OUR 10-11 O'CLOCK LOW WHICH WE HAD ACQUIRED VISUALLY. AT THE SAME MOMENT SOCAL ASKED US TO CONFIRM OUR ALT. I STATED THAT WE WERE DSNDING THROUGH 9000 FT. WE THEN RECEIVED A TCASII WARNING AND CLB COMMAND; AS SOCAL TOLD US THAT HE HAD RESTRICTED US TO 9500 FT BECAUSE THERE WAS VFR TFC XING UNDERNEATH US AT 8500 FT. THE CAPT INITIATED THE CLB IN RESPONSE TO THE TCASII AT APPROX 8700 FT. AT NO TIME DID THE CAPT OR I HEAR OR ACKNOWLEDGE THE 9500 FT ALT RESTR. SOCAL SAID THAT WE DID ACKNOWLEDGE. DURING THIS ENTIRE CHAIN OF EVENTS SOCAL WAS SATURATED WITH RADIO TFC; WITH NUMEROUS STEPPED ON RADIO XMISSIONS. WE HEARD SOCAL GIVE NUMEROUS TA'S TO NUMEROUS ACFT; BUT AT NO TIME; AFTER WE WERE CLRED FOR THE APCH; DID WE HEAR OUR CALL SIGN; UNTIL HE REQUESTED US TO VERIFY OUR ALT. DURING HVY TFC PERIODS INTO LAX; SOCAL NEEDS TO BE DIVIDED INTO MORE SECTORS TO REDUCE CTLR WORKLOAD. ONE CTLR IS HANDLING ENTIRELY TOO MUCH TFC. I COULD HAVE AIDED THE CTLR BY QUESTIONING THE TFC SINCE I HAD SPOTTED THE ACFT PRIOR TO THE TCASII ALERT. WHY WAS VFR TFC ALLOWED TO CROSS OUR FLT PATH AT GS ALT WHILE WE WERE ESTABLISHED ON (AND CLRED FOR) AN INST APCH?