[j-nsp] If you are going to set egress-shaping-overhead on a TRIO based MX, READ THIS

[Christopher E. Brown]

So, TRIO cards have ability to set a overhead offset for their shapers.

By default the offset is +24 bytes to account for preamble, frame start
and FCS.

This is a good thing, as the shapers now match actual L1 rates.

You can change this if needed if what you actually need to do is set
target rate for a service operation at a different layer.  For example,
if using the shapers for rate control of MEF compliant services over a
STAGged last mile you might set it to -24, offsetting preample, frame
start and the STAG, only counting the full L2 fram including FCS.


Important note...

The setting is per PIC, but changing the setting for any PIC on a TRIO
resets the whole FPC.

More important note...

While you can make the change to any or all of the PICs on a FPC, if you
make the change on _all FPCs_ in the box at the same time the system
will never come back without resetting the FPCs manually a second time.

Found this out the hard way, and retested on a second system, same results.

Doing the change one FPC at a time (waiting for the FPC to come back and
start forwarding before doing the next) seems to work fine, on my third
system using that method and have not had to fall back to out of band modem.

-- 
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Christopher E. Brown   <chris.brown at acsalaska.net>   desk (907) 550-8393
                                                     cell (907) 632-8492
IP Engineer - ACS
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