6.7

Table Of Contents
Lossless Layer 3 Network
RoCE v2 requires that lossless data transfer is preserved at layer 3 routing devices. To enable the
transfer of layer 2 PFC lossless priorities across layer 3 routers, configure the router to map the received
priority setting of a packet to the corresponding Differentiated Serviced Code Point (DSCP) QoS setting
that operates at layer 3. The transferred RDMA packets are marked with layer 3 DSCP, layer 2 Priority
Code Points (PCP) or with both. Routers use either DSCP or PCP to extract priority information from the
packet. In case PCP is used, the packet must be VLAN-tagged and the router must copy the PCP bits of
the tag and forward them to the next network. If the packet is marked with DSCP, the router must keep
the DSCP bits unchanged.
Like RoCE v1, RoCE v2 must run on a PFC priority-enabled VLAN.
Note Do not team RoCE NICs, if you intend to use RDMA on those NICs.
For vendor-specific configuration information, refer to the official documentation of the respective device
or switch vendor.
Jumbo Frames
Jumbo frames let ESXi hosts send larger frames out onto the physical network. The network must support
jumbo frames end-to-end that includes physical network adapters, physical switches, and storage
devices.
Before enabling jumbo frames, check with your hardware vendor to ensure that your physical network
adapter supports jumbo frames.
You can enable jumbo frames on a vSphere distributed switch or vSphere standard switch by changing
the maximum transmission unit (MTU) to a value greater than 1500 bytes. 9000 bytes is the maximum
frame size that you can configure.
Enable Jumbo Frames on a vSphere Distributed Switch
Enable jumbo frames for the entire traffic that passes through a vSphere Distributed Switch.
Procedure
1 In the vSphere Web Client, navigate to the distributed switch.
2 On the Configure tab, expand Settings and select Properties.
3 Click Edit.
4 Click Advanced and set the MTU property to a value greater than 1500 bytes.
You cannot set the MTU size to a value greater than 9000 bytes.
5 Click OK.
vSphere Networking
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