Fujitsu PG-FCS103 Checksum Offload, Ieee 802.1p QoS Tagging, Large Send Offload, Jumbo Frames

Checksum Offload

Checksum Offload is a property of the Broadcom network adapters that allows the TCP/IP/UDP checksums for send and receive traffic to be calculated by the adapter hardware rather than by the host CPU. In high-traffic situations, this can allow a system to handle more connections more efficiently than if the host CPU were forced to calculate the checksums. This property is inherently a hardware property and would not benefit from a software-only implementation. An adapter that supports Checksum Offload advertises this capability to the operating system so that the checksum does not need to be calculated in the protocol stack. Checksum Offload is only supported for IPv4 at this time.

IEEE 802.1p QoS Tagging

The IEEE 802.1p standard includes a 3-bit field (supporting a maximum of 8 priority levels), which allows for traffic prioritization. The BASP intermediate driver does not support IEEE 802.1p QoS tagging.

Large Send Offload

Large Send Offload (LSO) is a feature provided by Broadcom network adapters that prevents an upper level protocol such as TCP from breaking a large data packet into a series of smaller packets with headers appended to them. The protocol stack need only generate a single header for a data packet as large as 64 KB, and the adapter hardware breaks the data buffer into appropriately-sized Ethernet frames with the correctly sequenced header (based on the single header originally provided).

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 this product. 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.

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