Cisco MDS 9000

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10
Cisco MDS 9000 Family Port Analyzer Adapter Installation and Configuration Note
OL-9077-01
Selecting Truncate Mode
Figure 4 Ethernet Frames and the Four Truncate Modes
In ETM, the adapter truncates a Fibre Channel frame to a maximum payload of 1496 bytes on the
Ethernet side. Fibre Channel frames larger than 1496 bytes will be truncated. The Fibre Channel payload
transmitted is 1472 bytes. (See Figure 4.)
Shallow Truncate Mode (STM)
STM provides less payload than ETM but more frames per second. In STM, the adapter truncates the
Fibre Channel frame to 256 bytes. (See Figure 4.) Use this mode when you want more frames per second.
Deep Truncate Mode (DTM) for Most Frames per Second
As a default, the adapter comes configured in DTM mode and 1-Gbps Fibre Channel speed. This mode
should be used when you want the most frames per second. DTM provides less payload than STM but
more frames per second.
In DTM, the adapter truncates the Fibre Channel frame to 64 bytes. The total packet length including the
Ethernet header and trailer is 88 bytes. (See Figure 4.)
Management Mode (MNM) for Troubleshooting
MNM mode should be used only when troubleshooting the PAA. In this mode, the adapter will not accept
any Fibre Channel frames.
NTM
ETM
STM
DTM
SOF-T/
2 bytes
VSAN
SOF-T/
2 bytes
VSAN
SOF-T/
2 bytes
VSAN
SOF-T/
2 bytes
VSAN
Ethernet Header
(EDA + ESA + Type)
14 bytes of
Ethernet Header
(EDA + ESA + Type)
14 bytes of
Ethernet Header
(EDA + ESA + Type)
14 bytes of
Ethernet Header
(EDA + ESA + Type)
14 bytes of
FC Frame
0 - 2164 bytes
FC Frame
0-1496 bytes
FC Frame
0-256 bytes
FC Frame
0-64 bytes
EOF-T
4 bytes
EOF-T
4 bytes
EOF-T
4 bytes
FC
4 bytes
CRC
EOF-T
4 bytes
Enet
4 bytes
CRC
Enet
4 bytes
CRC
Enet
4 bytes
CRC
Enet
4 bytes
CRC
FC frame
Ethernet frame
Ethernet payload
85765