This operation sends a string value in a header block that is unknown to the nodes in the message path, and a string value in an "echoOk" header block. The message is relayed via an intermediary to the ultimate destination (configuration based static routing is used, no routing header entry is present). The target of the unknown header block is a role that is supported only by the intermediary. The "echoOk" header block is targeted at the ultimate receiver. MustUnderstand is "1".
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