3Com 4007, Implementation Manual, Page: 587 / 684

QoS Controls 587
Specifying TCP Drop
Control
The TCP drop control option lets you create a control for packets used to
establish TCP connections. This control affects QoS Flow Classifiers that
have TCP traffic going from
source IP addresses to destination IP
addresses.
TCP drop control does not function with nonflow classifiers or UDP. It is
only available for flow classifiers that include TCP.
Figure 67 illustrates how TCP handshaking works between the source
and destination to establish a connection. By dropping only the
initial TCP
packet used to establish TCP connections (those packets containing a
signature of SYN=1, ACK=0), you can establish one-way TCP flow
filtering.
Figure 67 TCP Handshaking
SYN=1, ACK=0
SYN=1, ACK=1
SYN=0, ACK=1
Source
Destination
3 - Way TCP Handshake