DescriptionIdentifier for Trading Session Can be used to represent a specific market trading session (e.g. "PRE-OPEN", "CROSS_2", "AFTER-HOURS", "TOSTNET", "TOSTNET2", etc). To specify good for session where session spans more than one calendar day, use TimeInForce = Day in conjunction with TradingSessionID. Values should be bi-laterally agreed to between counterparties. Firms may register Trading Session values on the FIX website (presently a document maintained within "ECN and Exchanges" working group section).