SPD VIOLATION.

Narrative

DURING DSCNT INBOUND TO CROSS THE DRIVR FIX AT 10000 FT; ATC ADVISED ME TO MAINTAIN 320 KTS. THIS WAS AN INCREASE OF 20 KTS ABOVE MY NORMAL DSCNT SPD OF 300 KTS. I COMPLIED; BUT WHEN I LEVELED OFF AT THE DRIVR INTXN; AT 10000 FT; I BEGAN TO SLOW TO 250 KTS. THIS APPARENTLY CAUSED A BACKUP OF TFC BEHIND ME AND CHICAGO ATC WANTED TO KNOW WHY I HAD SLOWED. I ADVISED THAT I HAD SLOWED IN PREPARATION FOR THE NEXT XING RESTR AND THAT MY UNDERSTANDING OF THE CLRNC WAS TO MAINTAIN 320 KTS IN THE DSCNT - NOT UNTIL ADVISED BY ATC. APPARENTLY ATC IS OF THE OTHER OPINION. I OFFERED AND DID INCREASE MY SPD AGAIN; BUT STILL GOT CHEWED OUT BY THE CURRENT CTLR AND WAS THEN TOLD TO SWITCH BACK TO THE PRIOR CTLR WHO ALSO CHEWED ME OUT. I DON'T FEEL THAT I WAS ADVISED TO MAINTAIN 320 KTS UNTIL ADVISED AND MY FO AGREES WITH ME. WHILE WE WERE DSNDING TO 10000 FT; WE ACTUALLY DISCUSSED THE SPD TO PROGRAM AT THE DRIVR INTXN. I DID CALL AND DISCUSS THE SIT WITH AN ATC SUPVR AT ZAU AND EXPLAINED MY POS. HE WAS RECEPTIVE. I FEEL THE SPD INSTRUCTIONS WERE NOT CLR.