FIX 4.2 vs FIX 4.4
FIX protocol has evolved over time; it’s now more than a decade it’s started by Fidelity and Solomon Brothers. FIX connectivity is the most popular connectivity solution exists for trading whether its equities, futures, options or fixed income or even foreign exchange (FX). FIX protocol has dominated the market and become as standard solution for any market or broker which is trying to develop connectivity with market within a short period of time because of complexity of native exchange api and lack of support FIX protocol come as handy.
To develop fix connectivity you need to agree upon which FIX protocol version are you going to follow , since many fix protocol version exists e.g. FIX4.0, FIX4.1, FIX4.2 and FIX4.4 even more newer version are available but most firm use FIX 4.2 as there preferred FIX connectivity solution or you can say still most widely used version is FIX 4.2 , many firms , clients , hedge funds , pension funds still use it for online trading but even after launch of more advance version it still remains the popular one. On advance side FIX 4.4 is getting popularity.
In this short discussion I am highlighting some of the difference between FIX 4.2 and FIX 4.4. Two most popular FIX protocol versions you can check FIX specification for more detail and some other difference which exits. FIX specification are available on http://www.fixprotocol.org you can download pdf version of these specification and can look before developing your FIX connectivity.
There are many differences between these two versions of fix protocol, some of them I am highlighting here.
1) There was tag called ExecTransType (tag 20) which was there in FIX 4.2 and now merged to ExecType tag 150 into FIX4.4, this tag used to define the nature of execution received from the exchange or broker.
2) Replaced the use of the QuantityType (tag 465) field with new QtyType (tag 854) which contains a re-organized/consolidated set of values.
3) Removed various Settlement Instructions-related fields.
4) Added "Quote Response" to list of messages for which Quote Status Report message is the appropriate response.
Establishing FIX connectivity is challenging if it involves custom fix tags, these are the tags which are not defined by FIX protocol but used by many firm or between client and broker for carrying some extra information which is agreed upon that. FIX protocol allows you to define custom FIX tags for your FIX connectivity until and unless they are not conflicting with any other FIX tags. Generally firms use tag above 10000 or 5000 to define this custom FIX tags.
There are many other changes which are available in the release notes of fix 4.4 http://www.fixprotocol.org, I will add some more as I come to know which is used in day trading more often.
I have documented my discussion on my FIX protocol tutorial series, please check for more information on different areas of FIX protocol and FIX connectivity e.g FIX Session management , FIX application management or FIX Interview questions.
FIX Protocol Tutorial 2: Basics of FIX Protocol and FIX Engine