Support for this mod is provided in the Zero duplicate forum.
Release thread : [Mixed] Zero Duplicate V 0.2.2.

index.php?c=xx => cat-title-cxx.html

viewforum.php?t=xx => forum-title-fxx.html

viewforum.php?t=xx&start=xx => forum-title-fxx-yy.html

viewtopic.php?t=xx => topicxx.html

viewtopic.php?t=xx&view=prev/next => topicxx.html

viewtopic.php?t=xx&start=xx => topicxx-yy.html

viewtopic.php?p=xx => topicxx.html or topicxx-yy.html if required

profile.php?mode=viewprofile&u=xx => memberxx.html
Wrong titles will be HTTP 301 redirected (all cases) :

miss-spelled-title => correct-title

Will get rid of SIDs and mark Vars in URLs for guests :

topicxx.html?sid=SID => topicxx.html
forum-title-fxx.html?mark=fids => forum-title-fxx.html

Will check $start consistency :

Example with 25 topics per pages :
forum-title-fxx-32.html => forum-title-fxx-25.html

Will by default HTTP 301 redirect index.php :

http://www.phpbb-seo.com/en/index.php => http://www.phpbb-seo.com/en/

Will automatically follow the eventual settings in the phpBB SEO mod rewrite like :
example.com/phpBB/ => example.com/phpBB/index.html

As HTTP 301 are to be used with caution, the downloads are only available for registered users.
This mods makes HTTP redirecting very easy and you should not change all your URLs every other day.
Do not hesitate to ask for support when first installing.