Cisco MDS 9000 Installation And Configuration Note page 9

S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m .
Table 3
Average Size of the FC Frame
512 bytes
256 bytes (worst case to obtain
maximum data)
The truncate modes can be hot switched (no power off is necessary). However, if you configure a new
speed setting (for example, changing the Fibre Channel port speed from 2 Gbps to 1 Gbps), the adapter
must be power cycled for the new setting to take effect. Power cycling consists of unplugging the adapter
wall plug, waiting for four seconds or more, and then plugging it back in and powering on.
No Truncate Mode (NTM) for Ethernet Encapsulation
In NTM, Fibre Channel frames are encapsulated into Ethernet frames without any modification to the
payload (the full 2164 bytes are transmitted). Ethernet devices must support jumbo frames for this mode
to work; otherwise, the Ethernet MAC may not work properly for the frames larger than the maximum
Ethernet size. Jumbo frames are Ethernet frames greater than 1520 bytes. (See
Ethernet Truncate Mode (ETM) for Maximum Payload
This mode is appropriate when jumbo frames are not supported by the Ethernet devices. In that case, this
mode provides the maximum amount of Fibre Channel payload within a single Ethernet frame.
OL-9077-01
Selecting the Truncate Mode to Achieve No Dropped Frames (continued)
Fibre Channel to Ethernet Speed
1 Gbps to
1 Gbps
NTM, ETM,
STM, or DTM
NTM, ETM,
STM, or DTM
Cisco MDS 9000 Family Port Analyzer Adapter Installation and Configuration Note
1 Gbps to 2 Gbps to
100 Mbps 1 Gbps
Frames may DTM or STM
be dropped.
Frames may DTM
be dropped.
Selecting Truncate Mode
2 Gbps to
100 Mbps
Frames may be
dropped.
Frames may be
dropped.
Figure 4.)
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