InfiniBand Network Architecture

Every Packet Contains a BTH

Refer to Figure 1-4 on this page and Figure 1-5 on this page. In addition to the LRH and, possibly, the GRH, every packet contains a Base Transport Header (BTH). Among other things, the BTH contains:

• The Opcode field identifies the type of request or response packet.

• The DestQP field identifies the destination QP within the remote CA. The destination QP is responsible for handling the incoming packet. QPs are described in the chapter entitled, “QP: Message Transfer Mechanism” on page 31.

• The PSN field contains the packet's 24-bit Packet Sequence Number. The PSN is inserted into a transfer request packet by the initiator and is checked for correctness by the recipient. This permits the recipient to detect missing packets. ...