From FIXwiki

FIX Message StreamAssignmentReport (MsgType=CD)

MsgType	FIX Specification	First introduced	Deprecated
MsgType=CD	PreTrade messages - MarketData	FIX.5.0SP1

The StreamAssignmentReport message is in response to the StreamAssignmentRequest message. It provides information back to the aggregator as to which clients to assign to receive which price stream based on requested CCY pair. This message can be sent unsolicited to the Aggregator from the Price Maker.

Message Contents By FIX Version

Notes

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Don't forget to refer to the FPL Discussion Groups to back up anything you write.
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Links from FIXwiki pages to relevant discussions on the FPL site are very valuable.

For example if you were writing a clarification on how to specify the "quantity" of an order in FIX, you might add the
following relevant link, http://www.fixprotocol.org/discuss/read/f5014573, to back up your points.