Cisco MDS 9000 Installation And Configuration Note page 10

Selecting Truncate Mode
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 .
Figure 4
NTM
ETM
STM
DTM
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
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
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
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.
Cisco MDS 9000 Family Port Analyzer Adapter Installation and Configuration Note
10
Ethernet Frames and the Four Truncate Modes
Ethernet Header
SOF-T/
14 bytes of
VSAN
(EDA + ESA + Type)
2 bytes
Ethernet Header
SOF-T/
14 bytes of
VSAN
(EDA + ESA + Type)
2 bytes
Ethernet Header SOF-T/
VSAN
14 bytes of
2 bytes
(EDA + ESA + Type)
Ethernet Header SOF-T/
14 bytes of
VSAN
(EDA + ESA + Type)
2 bytes
FC frame
Ethernet frame
Ethernet payload
FC Frame
0 - 2164 bytes
EOF-T
FC Frame
4 bytes
0-1496 bytes
FC Frame EOF-T
0-256 bytes 4 bytes
FC Frame
EOF-T
0-64 bytes
4 bytes
Figure 4.)
Figure 4.) Use this mode when you want more frames per second.
Figure 4.)
Enet
FC
EOF-T
CRC
CRC
4 bytes
4 bytes
4 bytes
Enet
CRC
4 bytes
Enet
CRC
4 bytes
Enet
CRC
4 bytes
OL-9077-01