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Understanding duplicate packets
Chapter 15: Gen3 Capture Card 347
Supported time
stamps for
reordering
Arista
cPacket
Gigamon
GigaSMART
Gigamon H-Series
IXIA Anue
NetScaler
Network
Instruments
PacketPortal PDG
VSS Monitoring
VSS Monitoring w/
Port
Supported time
synchronization
methods
Description
Sync capture
drivers with
Windows system
clock during
Observer launch
Each time Observer starts, the capture card drivers are
synchronized with the Windows system clock one time.
Sync capture
drivers with
Windows system
clock at scheduled
times
Observer can synchronize the capture card drivers with the
Windows system clock at scheduled times. These options include
daily or weekly synchronizations at a specific time of day, plus
an option to synchronize if the time difference exceeds a set
number of seconds only.
Sync Windows
system clock to
internal capture
card time
The Windows system clock is kept synchronized with the
internal clock of the capture card. If selected, this option can
greatly reduce clock drift.
Understanding duplicate packets
Duplicate packets lower the statistical accuracy of analysis, increase network link
saturation, and can interfere with tools. Packet deduplication removes duplicate
packets and helps you avoid those situations.
A duplicate packet is any packet that is identical to another packet. The
packet header is inspected and all fields must be identical for it to be a duplicate.
However, there are some situations where the header has been modified slightly
during the packet's journey. These situations require some fine-tuning of the
deduplication settings to ignore those fields that were modified before the
duplicate packet is received.