Optimizing Packet Mirroring Performance ! 179
Chapter 6: Packet Mirroring
Determine Traffic Loads
Using the previous assumptions, you can determine traffic loads for a given line
module:
Establish Resource Guidelines
Next, using the traffic loads that you determined for the line module, you can
establish guidelines for the amount of packet mirroring traffic for your router.
If you exceed these guidelines, regular (non-packet mirroring) packets from all
subscribers, including non-mirrored subscribers, will be dropped. If the fabric
bandwidth is not exceeded, then the performance penalties are contained within
the slot where the packet mirroring activity occurs. However, if the fabric bandwidth
is exceeded, traffic from other line modules might also be dropped.
! (A + 2X + Y) must be less than the maximum fabric bandwidth supported
from this line module.
! (2X + Y) must be less than 100Mbps (the enforced queue limit).
The 100 Mbps limit does not apply to the following line modules:
! GE-2 line module (ERX-310 router and ERX-1440 router)
! GE-HDE line module (ERX-310 router and ERX-1440 router)
! OC48 Frame APS I/O module (ERX-1440 router only)
! ES2 4G LM (E320 router)
! (B + X ) must be less than the maximum supported egress bandwidth.
! The number of mirrored interfaces per line module must be less than 1023 (the
configuration enforced for secure policy attachments).
! The number of interfaces mirrored per chassis must be less than 2400 (the
configuration enforced for secure policy attachments).
A = Load at ingress side of the line module
(B + X) = Load at egress side of the line module
(A + 2X + Y) = Load at ingress to fabric from the line module
NOTE: Packet mirroring can also affect the forwarding controller’s packet handling
performance.
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