An IA identifier subfield is constructed as an IKsubfld. This RFC does not define this subfield's contents for the symmetric key management case. Any prospective IAs which are to issue symmetric keys for use in conjunction with this RFC must coordinate assignment of IA identifiers in a manner (centralized or hierarchic) which assures uniqueness.
For the asymmetric key management case, the IA identifier subfield will be formed from the ASN.1 BER representation of the distinguished name of the issuing organization or organizational unit. The distinguished encoding rules specified in Clause 8.7 of Recommendation X.509 ("X.509 DER") are to be employed in generating this representation. The encoded binary result will be represented for inclusion in a transmitted header using the procedure defined in Section 4.3.2.4 of this RFC.