Dell Networking S6000 Uživatelský manuál stáhnout pdf (Strana 337)

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While the above change will ensure that at least one path to each destination gets into the FIB as quickly

as possible, it does prevent additional paths from being used even if they are available. This downside has

been deemed to be acceptable.

RDMA Over Converged Ethernet (RoCE) Overview

This functionality is supported on the S6000 platform.

Remote direct memory access (RDMA) reduces both CPU cycles and latency. RDMA over converged

Ethernet (RoCE) implements IB over Ethernet. RRoCE sends InfiniBand (IB) packets over IP. IB supports

input and output connectivity for the internet infrastructure. InfiniBand enables the expansion of network

topologies over large geographical boundaries and the creation of next-generation I/O interconnect

standards in servers. Although the endpoints or the destination servers generate such RRoCE packets,

from the switch's perspective, RRoCE is processed as an IP packet.

RRoCE packets are received and transmitted on specific interfaces called lite-subinterfaces. These

interfaces are similar to the normal Layer 3 physical interfaces except for the extra provisioning that they

offer to enable the VLAN ID for encapsulation.

You can configure a physical interface or a Layer 3 Port Channel interface as a lite subinterface. When

you configure a lite subinterface, only tagged IP packets with VLAN encapsulation are processed and

routed. All other data packets are discarded.

To provide lossless service for RRoCE, the QoS service policy must be configured in the ingress and

egress directions on lite subinterfaces.

A normal Layer 3 physical interface processes only untagged packets and makes routing decisions based

on the default Layer 3 VLAN ID (4095).

To enable routing of RRoCE packets, the VLAN ID is mapped to the default VLAN ID of 4095 using VLAN

translation. After the VLAN translation, the RRoCE packets are processed in the same way as normal IP

packets that a Layer 3 interface receives and routes in the egress direction. At the egress interface, the

VLAN ID is appended to the packet and transmitted out of the interface as a tagged packet with the

dot1Q value preserved.

RDMA is a technology that a virtual machine (VM) uses to directly transfer information to the memory of

another VM, thus enabling VMs to be connected to storage networks. With RoCE, RDMA enables data to

be forwarded without passing through the CPU and the main memory path of TCP/IP. In a deployment

that contains both the RoCE network and the normal IP network on two different networks, RRoCE

combines the RoCE and the IP networks and sends the RoCE frames over the IP network. This method of

transmission, called RRoCE, results in the encapsulation of RoCE packets to IP packets.

When a storage area network (SAN) is connected over an IP network, the following conditions must be

satisfied:

• Faster Connectivity: QoS for RRoCE enables faster and lossless nature of disk input and output

services.

• Lossless connectivity: VMs require the connectivity to the storage network to be lossless always.

When a planned upgrade of the network nodes happens, especially with top-of-rack (ToR) nodes

where there is a single point of failure for the VMs, disk I/O operations are expected to occur in 20

seconds. If disk in not accessible in 20 seconds, unexpected and undefined behavior of the VMs

Flex Hash and Optimized Boot-Up

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