General network considerations – Dell Broadcom NetXtreme Family of Adapters User Manual
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Broadcom Teaming Services: Broadcom NetXtreme II® Network Adapter User Guide
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TCP Offload Engine (TOE)
The TCP/IP protocol suite is used to provide transport services for a wide range of applications for the Internet, LAN, and for
file transfer. Without the TCP Offload Engine, the TCP/IP protocol suite runs on the host CPU, consuming a very high
percentage of its resources and leaving little resources for the applications. With the use of the Broadcom NetXtreme II
adapter, the TCP/IP processing can be moved to hardware, freeing the CPU for more important tasks such as application
processing.
The Broadcom NetXtreme II adapter's TOE functionality allows simultaneous operation of up to 1024 fully offloaded TCP
connections for 1-Gbps network adapters and 1880 fully offloaded TCP connections for 10-Gbps network adapters. The TOE
support on the adapter significantly reduces the host CPU utilization while preserving the implementation of the operating
system stack.
Jumbo Frames
The use of jumbo frames was originally proposed by Alteon Networks, Inc. in 1998 and increased the maximum size of an
Ethernet frame to a maximum size of 9000 bytes. Though never formally adopted by the IEEE 802.3 Working Group, support
for jumbo frames has been implemented in Broadcom NetXtreme II adapters. The BASP intermediate driver supports jumbo
frames, provided that all of the physical adapters in the team also support jumbo frames and the same size is set on all
adapters in the team.
IEEE 802.1Q VLANs
In 1998, the IEEE approved the 802.3ac standard, which defines frame format extensions to support Virtual Bridged Local
Area Network tagging on Ethernet networks as specified in the IEEE 802.1Q specification. The VLAN protocol permits insertion
of a tag into an Ethernet frame to identify the VLAN to which a frame belongs. If present, the 4-byte VLAN tag is inserted into
the Ethernet frame between the source MAC address and the length/type field. The first 2-bytes of the VLAN tag consist of
the IEEE 802.1Q tag type, whereas the second 2 bytes include a user priority field and the VLAN identifier (VID). Virtual LANs
(VLANs) allow the user to split the physical LAN into logical subparts. Each defined VLAN behaves as its own separate
network, with its traffic and broadcasts isolated from the others, thus increasing bandwidth efficiency within each logical
group. VLANs also enable the administrator to enforce appropriate security and quality of service (QoS) policies. The BASP
supports the creation of 64 VLANs per team or adapter: 63 tagged and 1 untagged. The operating system and system
resources, however, limit the actual number of VLANs. VLAN support is provided according to IEEE 802.1Q and is supported in
a teaming environment as well as on a single adapter. Note that VLANs are supported only with homogeneous teaming and
not in a multivendor teaming environment. The BASP intermediate driver supports VLAN tagging. One or more VLANs may be
bound to a single instance of the intermediate driver.
Wake On LAN
Wake on LAN (WOL) is a feature that allows a system to be awakened from a sleep state by the arrival of a specific packet
over the Ethernet interface. Because a Virtual Adapter is implemented as a software only device, it lacks the hardware
features to implement Wake on LAN and cannot be enabled to wake the system from a sleeping state via the Virtual Adapter.
The physical adapters, however, support this property, even when the adapter is part of a team.
Preboot Execution Environment
The Preboot Execution Environment (PXE) allows a system to boot from an operating system image over the network. By
definition, PXE is invoked before an operating system is loaded, so there is no opportunity for the BASP intermediate driver to
load and enable a team. As a result, teaming is not supported as a PXE client, though a physical adapter that participates in a
team when the operating system is loaded may be used as a PXE client. Whereas a teamed adapter cannot be used as a PXE
client, it can be used for a PXE server, which provides operating system images to PXE clients using a combination of
Dynamic Host Control Protocol (DHCP) and the Trivial File Transfer Protocol (TFTP). Both of these protocols operate over IP
and are supported by all teaming modes.
General Network Considerations
Teaming with Microsoft Virtual Server 2005