Dell POWEREDGE M1000E - Manual (Page 371)

Ethernet Configuration Commands 371
15
Ethernet Configuration Commands
PowerConnect switches support a variety of configuration options to
optimize network operations. Features such as flow-control and jumbo frames
are supported along with a variety of commands to display traffic statistics as
well as limit the effects of network loops or other network issues.
Jumbo frame technology is employed in certain situations to reduce the task
load on a server CPU and to transmit large amounts of data efficiently.
Jumbo frames technology predominantly appears where certain applications
would benefit from using a larger frame size, e.g. Network File System (NFS).
The larger frame size eliminates some of the need for fragmentation, leading
to greater throughput. The increase in throughput is particularly valuable on
data center servers where the larger frame size increases efficiency of the
system and allows processing of more requests. The PowerConnect jumbo
frames feature extends the standard ethernet MTU (Max Frame Size) from
1518 (1522 with VLAN header) bytes to 9216 bytes. However, any device
connecting to the same broadcast domain should support the same or larger
MTU.
Flow control is a mechanism or protocol used to temporarily suspend
transmission of data to a device to avoid overloading the device receive path.
PowerConnect switching implements the flow control mechanism defined in
IEEE 802.3 Annexes 31A and 31B (formerly IEEE 802.3x). PowerConnect
switching is able to transmit a MAC Control frame containing the PAUSE
opcode to halt transmission by the device receiving the PAUSE frame
whenever internal congestion is detected by the switching fabric. Flow
control is enabled by default for all ports.
Storm control allows for rate limiting of specific types of packets through the
forwarding plane. The administrator can configure the absolute rate in
packets-per-second for the Storm control threshold. Each classified packet
type (broadcast, multicast, or unicast) can be enabled/disabled per port, and
the threshold level at which Storm-Control is active is also configurable per-
port and per-type (as a percentage of interface speed).
2CSPC4.XModular-SWUM200.book Page 371 Thursday, March 10, 2011 11:18 AM