An IS-IS routing domain is a network in which all the routers run the Integrated IS-IS routing protocol to support intradomain exchange of routing information. The network environment can be IP-only, ISO CLNP-only, or both. The IS-IS protocol was originally intended to support only CLNP. RFC 1195 adapts the original IS-IS specification (ISO 10589) to support IP, in what is referred to as Integrated IS-IS. The following implementation requirements are specified by RFC 1195:
Pure IP domains route only IP traffic but support forwarding and processing of OSI packets required for IS-IS operation.
Pure ISO domains carry only ISO traffic including those required for IS-IS operation.
A dual domain routes both IP and OSI CLNP traffic ...