>> Does anybody know if the X6724 and X6728 SFP cards have head >> of line blocking issues ? > you mean if multiple ports share a port-asic like the 6548-GE- > TX? I don't think so. They don't. They *are* ~48:40 over-subscribed, however. (48 ports to 40 Gbps backplane, minus a bit of overhead) -A