SMT Frame Classes and Types

SMT frames are used for peer-to-peer (station-to-station) management. They are divided into classes, which define the function of the frame. Each class is then divided into up to three types, which define whether the frame is an announcement (information only), a request for service, or a response to a request. Refer to the ANSI/FDDI Station Management (SMT) X3.299 R7.3 Specification for a detailed description of SMT frames and their functions.

The pf_smtmon(1M) or nf_smtmon(1M) utility is used to monitor the following SMT frame classes:

NIF (Neighbor Information Frames)

These are the most common frames displayed when you run pf_smtmon(1M) or nf_smtmon(1M). As the name suggests, they carry information about a neighboring station (for example, address, description, state, MAC capabilities) and are used as keep-alive notifications that a station is still attached to the ring and functioning. An NIF frame can be an announcement, a request, or a response.

SIF (Status Information Frames)

These frames carry more detailed information about a station. SIF configuration frames describe the station configuration (for example, number of ports, number of MAC entities, connection policy). SIF operation frames describe the current status of the station. A SIF frame can be either a request or a response.

ECF (Echo Frames)

These frames are equivalent to ICMP ping packets and are used to test connectivity between stations. An ECF frame can be either a request or a response.

RDF (Request Denied Frame)

These frames are used to indicate that the request is rejected. If an SMT agent (such as the SunNet Manager proxy agent delivered with SunFDDI) receives an unsupported or unrecognized request, it issues an RDF frame to indicate that the request is rejected. An RDF frame is always a response.

ESF (Extended Service Frame)

These frames are implementation dependent. An ESF frame can be an announcement, a request, or a response.

PMF (Parameter Management Frame)

These frames are used to access remote station attributes. The Parameter Management Protocol supports both get (display) and set (modify) functions. However, the pf_smtmon(1M) or nf_smtmon(1M) utility can display only PMF_get frames. A PMF_get frame can be either a request or a response.