WCCP flows during Lead WAE Failure

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Mar 1st, 2010
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We are actually planning a large scale WAAS solution. We found many descriptions how  the WCCP flows is protected in redundant design against a WAE failure. We learnt that the Lead WAE is necessary to redirect the WCCP flow to the remaining WAEs. Our question is what will happen when the Lead WAE fails. How will the WAE farm recover the WCCP flows. 

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Zach Seils Mon, 03/01/2010 - 07:48
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Hi Peter,

The lead WAE is responsible for instructing all of the WCCP-enabled routers/switches how traffic should be distributed across the cluster of WAE devices.  It does this by communictaing an assignment table of buckets/masks.  The lead WAE does not actually handle the flows, they are redirected directly from the router/switch to the target WAE.

In the event that the lead WAE fails, another WAE in the service group takes over the lead role and updates the assignment for all of the routers/switches.



PETER GEHRMANN Mon, 03/01/2010 - 09:40
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Hi Zach,

thanks for your quick response. The answer clearifies the role of the Lead WAE. But one issue is still not clear for me. When the new Lead WAE takes over will the buckets be assigned as before or may active flows switch from one WAE to another.



Zach Seils Mon, 03/01/2010 - 09:44
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Whenever there is a change in the service group membership, there is no guarantee that the buckets will be reassigned the same way.  However, in the event that they aren't, the WCCP Flow Protection feature will ensure that the WAE that was originally handling the flow will receive it.



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