Endace DAG 3.7G Series, Руководство пользователя

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EDM01-07: DAG 3.7G Card User Guide
Version 7: May 2006 14 ©2005
Detecting Packet Losses
Once the buffer fills, any new packets arriving will be discarded by the DAG
card until some data is read out of the buffer to create free space.
You can detect any such losses by observing the Loss Counter
(lctr
field)
of the Extensible Record Format [ERF]. See Chapter 6: Data Formats later
in this User Guide for more information on the Endace ERF.
Increasing Buffer Size
You can increase the size of the host PC buffer to enable it to cope with
bursts of high traffic load on the network link.
By default the
dagmem
driver reserves 32MB of memory per DAG card in the
system. However if you are capturing at OC-12/STM-4 (622Mbps) rates or
above, you may require a larger buffer.
For Linux/BSD, please refer to the
Linux FreeBSD Software Installation
Guide, which is shipped on the installation CD with the DAG3.7T card, for
further information on increasing buffer size.
For Windows the upper limit is 32MB. This is usually sufficient, however if
you do need to increase the amount of reserved memory please contact
Endace customer support at support@endace.com for more information
The
dsize
option sets the amount of memory used per DAG card in the
system.
Note: For 32-bit Linux kernels, the value of
dsize
multiplied by the
number of DAG cards in the system must be less than the amount of
physical memory installed, as well as less than 890MB.
Packet
Transmission
The firmware included with the DAG 3.7G card allows the DAG to transmit
as well as receive packets, however the DAG does not appear as a network
interface to the operating system.
The following information describes the DAG 3.7G capabilities for
transmitting and receiving packets.
Process Description
Explicit packet
transmission.
The DAG will not respond to ARP, ping, or router
discovery protocols. It will only transmit packets
explicitly provided by the user.
This capability allows the DAG card to be used as a
simple traffic load generator.
The DAG can also be used to retransmit previously
recorded packet traces. The packet trace will be
transmitted at 100% line rate, the packet timing of the
original trace file is not reproduced.