It turns out to be simpler and more efficient to ship the request when it arrives to the node that has the ticket than to struggle to ship the ticket in advance to all the nodes that may receive the request.
The modern network Front End device can be easily programmed with a small amount of knowledge of CAS protocol to route each request to the server that can best handle it. If that is not possible with your network administrators, then the CushyFrontEndFilter does the same thing less efficiently than programming the Front End but more efficiently than running Ehcache or similar ticket replication mechanisms without the Filter.
Front End Background
Any cluster of Web Servers requires some sort of Front End device to screen and forward network traffic. Ten years ago this was a computer with some fairly simple programming. Common strategies for distributing requests:
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So teaching a Front End about CAS protocol is not that big a deal. Commercial sites do this all the time, but they don't run CAS. Universities probably spend less time optimizing eCommerce applications and so they may not normally think about Front End devices this way.
Routing the CAS Protocol
First, however, we need to understand the format of CAS ticketids because that is where the routing information comes from:
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