I have reviewed this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG. These comments were written primarily for the benefit of the security area directors. Document editors and WG chairs should treat these comments just like any other last call comments. The document does not explicitly discuss the use-cases for multi instance IS-IS. Is this intended to be used a security mechanism for isolation? The document should provide some guidance here. If the mechanism is intended as an isolation mechanism for security then I think more guidance is appropriate. For example, in this case shouldn't each instance have its own authentication configuration? If it is not intended as a security mechanism then the document probably say so.