slapd bind method codes

Hi folks,

When clients bind with a provider and the provider's loglevel is set to stats, bind events show up frequently in the log. Often, some logged bind events have only a blank dn along with a "method" code. Here are two separate examples:

slapd[903]: conn=1021 op=0 BIND dn="" method=128

slapd[903]: conn=1020 op=0 BIND dn="" method=163

Two questions:

1.) What do these method codes mean? Perhaps there list somewhere that explains all possible method codes.

2.) When a method code is shown, as in the examples above, why is the value for the dn empty?

Thanks,

Jaap