User Manual

Rev 4.70

Mellanox Technologies

8.12 IPoIB SR-IOV over KVM

This feature is in Beta quality. For more details on how to configure IPoIB SR-IOV over KVM,

please contact Mellanox support.

8.13 Lossless TCP

8.13.1 Introduction

Inbound packets are stored in the data buffers. They are split into 'Lossy' and 'Lossless' according

to the priority field in the 802.1Q VLAN tag. In DSCP based PFC, all traffic is directed to the

'Lossless' buffer. Packets are taken out of the packet buffer in the same order they were stored,

and moved into processing, where a destination descriptor ring is selected. The packet is then

scattered into the appropriate memory buffer, pointed by the first free descriptor.

Figure 17: Lossless TCP

When the 'Lossless' packet buffer crosses the XOFF threshold, the adapter sends 802.3x pause

frames according to the port configuration: Global pause, or per-priority 802.1Qbb pause (PFC),

where only the priorities configured as 'Lossless' will be noted in the pause frame. Packets arriv-

ing while the buffer is full are dropped immediately.

During packet processing, if the selected descriptor ring has no free descriptors, two modes for

handling are available: