OpenID Authentication 2.0 spec clarification - does assoc_type have default value

[Vlastimil Zíma]

Hello,

in OpenID specs 2.0 all request parameter are required unless opposite 
is said. Does it includes "openid.assoc_type" in association requests? 
It had default in specs 1.1, but it does not have one now.

What is proper response to request without assoc_type?

Parameters "openid.dh_modulus" and "openid.dh_gen" are not marked as 
optional as well, but they have default values mentioned in specification.

Can someone clarify this, please?

VZ