Addendum

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 using which a virtual machine (VM) can directly transfer information the memory
of another VM, thereby 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 the RoCE network and the normal IP network, called backend and front-end
network segments respectively, on two different networks, RRoCE enables the RoCE and the regular IP
networks to be combined and RoCE frames to be sent 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 at all times.
When an upgrade of the network nodes is performed in a planned manner, 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 occurs. You can enable the optimization mechanism for booting time of the ToR nodes that
experience a single point of failure to reduce the outage in traffic-handling operations to be less.
RoCE over a routed system is called RRoCE. RRoCE has IP headers. RRoCE is bursty and uses the entire
10 Gigabit Ethernet interface. Although RRoCE and normal data traffic are propagated in separate
network portions, it might also be necessary in certain topologies to combine both the RRoCE and data
traffic in a single network structure. RRoCE traffic is marked with dot1p priorities 3 and 4 (code points 011
and 100, respectively) and these queues are strict and lossless. DSCP code points are not tagged for
RRoCE. Both ECN and PFC are enabled for RRoCE traffic. For normal IP or data traffic that is not RRoCE-
enabled, the packets comprise TCP and UDP packets and they can be marked with DSCP code points.
Multicast is not supported in that network.
Preserving 802.1Q VLAN Tag Value for Lite Subinterfaces
This functionality is supported on the S6000 platform.
All the frames in a Layer 2 VLAN are identified using a tag defined in the IEEE 802.1Q standard to
determine the VLAN to which the frames or traffic are relevant or associated. Such frames are
encapsulated with the 802.1Q tags. If a single VLAN is configured in a network topology, all the traffic
packets contain the same do1q tag, which is the tag value of the 802.1Q header. If a VLAN is split into
multiple, different sub-VLANs, each VLAN is denoted by a unique 8021.Q tag to enable the nodes that
receive the traffic frames determine the VLAN for which the frames are destined.
Typically, a L3 physical interface processes only untagged or priority-tagged packets. The routing
decision is made based on the default L3 VLAN ID (4095) and routed packets are transmitted as untagged
packets. Tagged packets that are received on L3 physical interfaces are dropped. To enable the routing of
tagged packets, the port that receives such tagged packets needs to be configured as a switchport and
must be bound to a VLAN as a tagged member port.
A lite-subinterface is similar a normal L3 physical interface, except that additional provisioning is
performed to set the VLAN ID for encapsulation. This setting is mainly used for data-plane routing of
RRoCE packets.
A physical interface or a Layer 3 Port channel interface can be configured as a lite-subinterface. Once a
lite-subinterface is configured, only tagged IP packets with encapsulation VLAN are processed and
routed. All other data packets are discarded except the L2 and L3 control frames. It is not required for a
144
Flex Hash and Optimized Boot-Up