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4 Broadcom Gigabit Ethernet Teaming Services 125
E
Generic Trunking
Generic Trunking is a switch-assisted teaming mode and requires configuring ports at both ends of
the link: server interfaces and switch ports. This is often referred to as Cisco Fast EtherChannel or
Gigabit EtherChannel. In addition, generic trunking supports similar implementations by other
switch OEMs such as Extreme Networks Load Sharing and Bay Networks or IEEE 802.3ad Link
Aggregation static mode. In this mode, the team advertises one MAC Address and one IP Address
when the protocol stack responds to ARP Requests. In addition, each physical adapter in the team
uses the same team MAC address when transmitting frames. This is possible since the switch at the
other end of the link is aware of the teaming mode and will handle the use of a single MAC address
by every port in the team. The forwarding table in the switch will reflect the trunk as a single virtual
port.
In this teaming mode, the intermediate driver controls load balancing and failover for outgoing traffic
only, while incoming traffic is controlled by the switch firmware and hardware. As is the case for
Smart Load Balancing, the BASP intermediate driver uses the IP/TCP/UDP source and destination
addresses to load balance the transmit traffic from the server. Most switches implement an XOR
hashing of the source and destination MAC address.
4.3.3 Software Components
Teaming is implemented via an NDIS intermediate driver in the Windows Operating System
environment. This software component works with the miniport driver, the NDIS layer, and the
protocol stack to enable the teaming architecture (refer to "• Process for Selecting a Team Type"
(
Jpg.129)). The miniport driver controls the host LAN controller directly to enable functions such as
send, receive, and interrupt processing. The intermediate driver fits between the miniport driver and
the protocol layer multiplexing several miniport driver instances, and creating a virtual adapter that
looks like a single adapter to the NDIS layer. NDIS provides a set of library functions to enable the
communications between either miniport drivers or intermediate drivers and the protocol stack. The
protocol stack implements IP, IPX and ARP. A protocol address such as an IP address is assigned to
each miniport device instance, but when an Intermediate driver is installed, the protocol address is
assigned to the virtual team adapter and not to the individual miniport devices that make up the team.
The Broadcom supplied teaming support is provided by three individual software components that
work together and are supported as a package. When one component is upgraded, all the other
components must be upgraded to supported versions. "• Broadcom Teaming Software Component"
(
Jpg.126) describes the three software components and their associated files for supported operating
systems.