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Chapter 12
Value Added Services (VAS) Traffic Forwarding
Mirroring Exceptions
Since the decision to mirror is based on service classification, which can be done on the first payload or
after first few packets, the entire TCP handshake is not mirrored.
To save in performance on both sides, zero payload packets are also not mirrored. (note that this type of
packets have no real value for offline analysis).
SCE Connectivity
Traffic mirroring is implemented by sending the mirrored packets over a designated VLAN through a
predefined link of the SCE platform. The link that has been defined for traffic mirroring can be either
used exclusively for this purpose, or it can be one of the traffic ports, in which case the Tx capacity of
the link will be shared between the original egress traffic and the mirrored traffic.
The direction of the flow is preserved when mirrored, so traffic that is received on the subscriber
interface on either link is sent over a VLAN on the network interface over this predefined link. And
traffic that is received on the network interface on either link is sent over a VLAN on the subscriber
interface over this predefined link. The mirrored traffic does not return to the SCE platform.
Note
Enabling traffic mirroring is expected to impact the SCE performance due to the excessive processing
associated with it; the actual figure depending on the amount of the mirrored traffic. It is recommended
that you monitor SCE platform performance when enabling this capability
Figure 12-12
Figure 12-12
Subscribers
OL-7827-12
shows an SCE 2000 platform using a dedicated link for mirroring (link-1).
Traffic Mirroring on a Dedicated Link
Network
Network
Subscribers
Original Traffic
Mirrored Traffic
Traffic crosses the SCE
through link 1
Cisco SCE 2000 and SCE 1000 Software Configuration Guide
Intelligent Traffic Mirroring
Each server is located
on a separate vlan, to
allow load sharing
Mirrored Traffic leaves the SCE
through GBE ports 3 (subscriber)
and 4 (network) using predefined
VLANs
12-49
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