Chapter 31. Discovery

The Previous Chapter

The previous chapter described all of the issues related to multiple SMs in the same subnet. Specifically, it covered:

• Issues that are outside the scope of the specification.

• Multi-vendor SM failover is not supported.

• A subnet can have more than one SM.

• How the SM issues requests (using SMPs).

• An introduction to the SM states.

• Standby SMs monitor the Master SM's heartbeat.

• The purpose of SM Control Packets and how they are issued.

• When there are multiple Master SMs.

• A detailed description of the SM states.

This Chapter

This chapter provides a detailed description of how the SM discovers devices during startup, as well as how it issues attribute accesses to devices that have not yet been assigned LID addresses. It covers:

• Who performs discovery?

• How packets are normally routed (when all devices have already been assigned LIDs).

• Packet routing during discovery (before LIDs have been assigned).

• Accessing device attributes when the path to the device is only partially configured.

The Next Chapter

The next chapter provides a detailed description of the General Services Interface (QP1). It is provided at this point in the book because the SA is accessed via the GSI and the next chapter covers the SA. Specifically, this chapter covers the following:

• The GSMs, GSAs, and GSIs.

• How to prepare an HCA GSI for use.

• The required versus optional GSAs.

• The SA and the GSI.

• GMPs use a VL buffer determined by the GMP's SL value.

• GMPs can transit routers.

• QP1 is a controlled-access QP.

• QP1's P_Key insertion and checking.

• Additional reference material.