I did some searching on google and this is what I came up with :
It's probably not meant as a DOS attack but rather a scraper and/or comment spammer and/or referer spammer bot. It is probably a client hosted by Layeredtech. A lot of people seem to be having problems with this. See
this,
this,
this,
this and
this.
It would be best to block all layeredtech ip's in your firewall and send all the info to
abuse@layeredtech.com. But I'll doubt they'll do anything about it seeing all the stuff posted about them all over the net.