数字数据网DDN定义为OSI模型的（）。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='30251' and id < 2447166 and id<>'2447166' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='30251' and id > 2447166 and id<>'2447166' order by id asc limit 5