headset works only as OSS, why not as alsa?

[H.S.]

Hello,

On Ubuntu 8.10 if I plug in a USB headset (Logitech), it works only if I
choose its OSS entry in Preferences->Sound and not if I select the alsa
entry (the headset creates both OSS and alsa enteries).

So, what is the significance of OSS in ubuntu and why do we need it? Can
it be removed in favor of alsa?

Thanks.

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