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

UDS Security Definition Request

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.

CME Globex validates all required tags; the message is rejected if a required tag:

• is not included

• is empty

• contains spaces

• exceeds the character limit

UDS Security Definition

CME Globex sends the order entry iLink message in an acknowledgment response to a iLink message.

If the iLink Security Definition Request message is accepted, the CME Globex platform processes the combination in the iLink Security Definition Request message to generate a unique spread and sends an iLink Security Definition (tag 35-MsgType=d) message to the customer system with tag 323-SecurityResponseType = 2 (Accepted).

If the iLink Security Definition Request message is rejected, the iLink Security Definition message will contain tag 323-SecurityResponseType = 5 (Reject), tag 58-Text containing the reason for the reject, and tag 107-SecurityDesc containing the security description of the existing (identical) contract.