Chapter 6. Division of Labor

The Previous Chapter

The previous chapter provided an introduction to the five types of message transfer requests that can posted to and executed by a QP's SQ logic. It also introduced the single type of message transfer request that can be posted to and executed by a QP's RQ logic.

This Chapter

This chapter provides an introduction to the layers comprising the IBA stack that handles message transmission and reception. Those layers are:

• The ULP (Upper Layer Protocol). This is actually not part of the IBA stack. Rather, it is comprised of OS and application software that uses the stack to pass messages.

• The Verb Layer.

• The Transport Layer.

• The Network Layer.

• The Link Layer.

• The Physical Layer.

The Next Chapter

The next chapter defines how ports on channel adapters, switches, and routers are numbered. It then defines the Local ID (LID) address space, the purpose of the LID address, and the SM's assignment of a unique LID to each port. The SM may optionally assign a range of LID addresses to a port. This chapter defines how this is done as well as the value of assigning more than one address to a port. It describes how the QP indicates which of the local ports assigned LID addresses will be inserted into the LRH:SLID field when the QP sources a packet to the port for transmission. The concept of the SM's path database is introduced.