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To create a UDS, a client systems must be able to process the following iLink 2.X message types:



Security Definition Request (tag 35-MsgType=c)

Submitted to CME Globex by customer system to request
creation of user-defined spread.

Security Definition - Accept or Reject (tag 35-MsgType=d)

Sent to customer system by CME Globex upon acceptance or rejection
of Security Definition Request message.

Business Level Reject (tag 35-MsgType=j)

Sent by CME Globex to reject messages at the FIX session level
(e.g., messages with missing or invalid FIX tags) where the message cannot be processed.


CME Group customers use the iLink Security Definition Request (tag 35-MsgType=c) message to create a spread on the CME Globex platform. The iLink Security Definition Request message requires a repeating group of user-populated tags for instruments included in the spread.



If an iLink Security Definition Request (tag 35-MsgType=c) is rejected as "Contract is invalid" due to an existing, identical spread instrument definition sent in tag 107-SecurityDesc. It is strongly recommended that the client system reload all market data Security Definition (tag 35-MsgType=d) messages from the Replay channel.