Visible to Intel only — GUID: nik1412473908593
Ixiasoft
Visible to Intel only — GUID: nik1412473908593
Ixiasoft
1.1.1. Protocol Overhead
An active link also transmits Data Link Layer Packets (DLLPs) and Physical Layer Packets (PLPs). The PLPs are four bytes or one dword and consist of SKP Ordered Sets. The DLLPs are two dwords and consist of the ACK/NAK and flow control DLLPs. The ACKs and flow control update DLLPs are transmitted in the opposite direction from the Transaction Layer Packet (TLP). If link is transmitting and receiving high bandwidth traffic, the DLLP activity can be significant. The DLLPs and PLPs reduce the effective bandwidth available for TLPs. The format of the TLP illustrates that the overhead if a TLP is seven dwords. The overhead is five dwords if the optional ECRC is not included.
The overhead includes the following fields:
- Start and End framing symbols
- A Sequence ID
- A TLP header that is three or four dwords long,
- The link cyclic redundancy check (LCRC).
The rest of the TLP contains 0–1024 dwords of data payload.