With Shared Ethernet Adapters
on the Virtual I/O Server logical
partition, virtual Ethernet adapters on client logical partitions
can send and receive outside network traffic.
A Shared Ethernet Adapter is
a Virtual I/O Server component
that bridges a physical Ethernet adapter and one or more virtual Ethernet
adapters:
- The real adapter can be a physical Ethernet adapter, a Link Aggregation or EtherChannel
device, or a Logical Host Ethernet Adapter .
The real adapter cannot be another Shared Ethernet Adapter or a VLAN
pseudo-device.
- The virtual Ethernet adapter must be a virtual I/O Ethernet adapter.
It cannot be any other type of device or adapter.
Using a Shared Ethernet Adapter,
logical partitions on the virtual network can share access to
the physical network and communicate with stand-alone servers and
logical partitions on other systems. The Shared Ethernet Adapter eliminates
the need for each client logical partition to a dedicated physical
adapter to connect to the external network.
A Shared Ethernet Adapter provides
access by connecting the internal VLANs with the VLANs on the external
switches. Using this connection, logical partitions can share the
IP subnet with stand-alone systems and other external logical partitions.
The Shared Ethernet Adapter forwards
outbound packets received from a virtual Ethernet adapter to the external
network and forwards inbound packets to the appropriate client logical
partition over the virtual Ethernet link to that logical partition.
The Shared Ethernet Adapter processes
packets at layer 2, so the original MAC address and VLAN tags of the
packet are visible to other systems on the physical network.
The
Shared Ethernet Adapter has
a bandwidth apportioning feature, also known as
Virtual I/O Server quality of
service (QoS). QoS allows the
Virtual I/O Server to give a higher
priority to some types of packets. In accordance with the IEEE 801.q
specification,
Virtual I/O Server administrators
can instruct the
Shared Ethernet Adapter to
inspect bridged VLAN-tagged traffic for the VLAN priority field in
the VLAN header. The 3-bit VLAN priority field allows each individual
packet to be prioritized with a value from 0 to 7 to distinguish more
important traffic from less important traffic. More important traffic
is sent preferentially and uses more
Virtual I/O Server bandwidth than
less important traffic.
Note: To use this feature, when the Virtual I/O Server Trunk Virtual
Ethernet Adapter is configured on an HMC, the adapter must be configured
with additional VLAN IDs because only the traffic on these VLAN IDs
is delivered to the Virtual I/O Server with
a VLAN tag. Untagged traffic is always treated as though it belonged
to the default priority class that is, as if it had a priority value
of 0.
Depending on the VLAN priority values found in the VLAN headers,
packets are prioritized as follows.
Table 1. VLAN traffic priority
values and relative importancePriority value and importance |
1 (Most important)
2
0 (Default)
3
4
5
6
7 (Least important)
|
The
Virtual I/O Server administrator
can use QoS by setting the
Shared Ethernet Adapter qos_mode
attribute to either strict or loose mode. The default is disabled
mode. The following definitions describe these modes:
- disabled mode
- This is the default mode. VLAN traffic is not inspected for the
priority field. An example follows:
chdev -dev <SEA device name> -attr qos_mode=disabled
- strict mode
- More important traffic is bridged over less important traffic.
This mode provides better performance and more bandwidth to more important
traffic; however, it can result in substantial delays for less important
traffic. An example follows:
chdev -dev <SEA device name> -attr qos_mode=strict
- loose mode
- A cap is placed on each priority level so that after a number
of bytes is sent for each priority level, the following level is serviced.
This method ensures that all packets are eventually sent. More important
traffic is given less bandwidth with this mode than with strict mode;
however, the caps in loose mode are such that more bytes are sent
for the more important traffic, so it still gets more bandwidth than
less important traffic. An example follows:
chdev -dev <SEA device name> -attr qos_mode=loose
Note: In either strict or loose mode, because the Shared Ethernet Adapter uses several
threads to bridge traffic, it is still possible for less important
traffic from one thread to be sent before more important traffic of
another thread.
In SEA, QoS is provided per SEA thread. By default,
SEA runs in thread mode with seven threads. When SEA receives traffic,
it routes the traffic to a thread, based on source and destination
information. If the QoS mode is enabled, it further queues the traffic,
based on its priority, to the appropriate priority queue associated
with the selected thread. Queued traffic for a particular thread is
serviced in the order of higher to lower priority. All threads handle
all priorities.
Note: SEA QoS does not assure bandwidth for a particular
priority.
The effect of SEA QoS can be seen when there is enough
traffic to keep all SEA threads busy, such that when a SEA thread
is scheduled to run, it has enough higher priority traffic to service
before it can get to the lower priority traffic. SEA QoS is not effective
when the traffic pattern is such that the higher and lower priority
traffic is spread across different threads.
GARP VLAN Registration Protocol
Shared Ethernet Adapters, in Virtual I/O Server version 1.4
or later, support GARP VLAN Registration Protocol (GVRP), which is
based on Generic Attribute Registration Protocol (GARP). GVRP allows
for the dynamic registration of VLANs over networks, which can reduce
the number of errors in the configuration of a large network. By propagating
registration across the network through the transmission of Bridge
Protocol Data Units (BPDUs), devices on the network have accurate
knowledge of the bridged VLANs configured on the network.
When
GVRP is enabled, communication travels one way, from the Shared Ethernet Adapter to the switch.
The Shared Ethernet Adapter notifies
the switch which VLANs can communicate with the network. The Shared Ethernet Adapter does not
configure VLANs to communicate with the network based on information
received from the switch. Rather, the configuration of VLANs that
communicate with the network is statically determined by the virtual
Ethernet adapter configuration settings.
Host Ethernet Adapter or Integrated
Virtual Ethernet
With Virtual I/O Server version 1.4,
you can assign a logical host Ethernet port, of a logical host Ethernet
adapter (LHEA), which is sometimes referred to as Integrated Virtual
Ethernet, as the real adapter of a Shared Ethernet Adapter. The logical
host Ethernet port is associated with a physical port on the Host Ethernet Adapter. The Shared Ethernet Adapter uses the
standard device driver interfaces provided by the Virtual I/O Server to communicate
with the Host Ethernet Adapter.
To
use a Shared Ethernet Adapter with
a Host Ethernet Adapter,
the following requirements must be met:
- The logical host Ethernet port must be the only port assigned
to the physical port on the Host Ethernet Adapter. No other
ports of the LHEA can be assigned to the physical port on the Host Ethernet Adapter.
- The LHEA on the Virtual I/O Server logical
partition must be set to promiscuous mode. (In an Integrated Virtualization Manager environment,
the mode is set to promiscuous by default.) Promiscuous
mode allows the LHEA (on the Virtual I/O Server) to receive
all unicast, multicast, and broadcast network traffic from the physical
network.
Recommendations
Consider using Shared Ethernet Adapters on the Virtual I/O Server in the following
situations:
- When the capacity or the bandwidth requirement of the individual
logical partition is inconsistent or is less than the total bandwidth
of a physical Ethernet adapter. Logical partitions that use the full
bandwidth or capacity of a physical Ethernet adapter should use dedicated
Ethernet adapters.
- If you plan to migrate a client logical partition
from one system to another.
Consider assigning a Shared Ethernet Adapter to a Logical
Host Ethernet port when the number of Ethernet adapters that you need
is more than the number of ports available on the LHEA, or you anticipate
that your needs will grow beyond that number. If the number of Ethernet
adapters that you need is fewer than or equal to the number of ports
available on the LHEA, and you do not anticipate needing more ports
in the future, you can use the ports of the LHEA for network connectivity
rather than the Shared Ethernet Adapter.