sub encode {
    my $self = shift;
    my $href = $self->as_asn(); # builds a Convert::ASN1-parsable hash
    my $asn = $_asn->find( 'ILL-Request' ) or warn $_asn->error;
    my $pdu = $asn->encode( $href ) or warn $asn->error;
    return $pdu;
}