Subnet Administrator's Role

SA Location

The SA is typically a subset of the SM.

Description

The Subnet Administrator (SA) is a passive entity that provides an information database regarding the subnet's topology, device types, and device characteristics. The SA is, for the most, part passive in that it doesn't typically initiate access requests to other entities. Rather, it responds to database queries it receives from other entities.

The SA provides storage of and access to information of several types, some required, others optional:

• Information CAs require for operation in the subnet. This includes paths between CAs, event notification, etc. The SA is required to supply this type of information.

• Information that can't be recovered by subnet inspection after a power-on or an initialization event. This includes information required to allow off-line migration from one vendor's SM to another's. The SA is required to supply this type of information.

• Information useful to other management entities. Standby SMs may use this type of information to maintain sync with the Master SM. This includes subnet topology data, switch forwarding tables, etc. Whether or not the SA supplies this type of information is optional.

As an example, the SA may be interrogated by a software application to learn the various paths that may be taken to a target port and the DLID or DGID associated with each of these paths.

How Is a Query Sent to the SA?

The SA database elements are stored as a series of attributes. A database query is sent to the SA using a request GMP with its Class field = the SA class. The response is sent back as a response GMP.