There is no reason to go anywhere else to get all the information you need to Identify Friend or Foe (IFF) in the F-15. It is very simple.
1. Visual Identification - get close enough to see which's country's markings are on the plane. (And have the knowledge of which countries are enemies)
or
2. Radar Identification - Look at the symbol of the unlocked radar return on the radar MFD. Flat rectangles are enemy and dots are friendly. If there is a vertical row of flat rectangles, that means that the plane is jamming and you CANNOT tell if that plane is friendly or enemy. See below for examples of each.
Some of you may be saying, "But what about TWS mode? The symbols are the same in TWS mode."
And I will answer, "No, they are not the same. They are harder to see, but the rectangles and dots are still there."
If you use any of the autolock modes of the F-15 radar, you will not see the radar return symbols to establish that the plane you are attempting to lock is enemy or friendly. Once a plane is locked, the F-15 will NOT give you any information about whether the plane that is locked is friend or foe except for one possible exception: NCTR
NCTR, which stands for Non-Cooperative Target Recognition, will tell you which type of aircraft you have locked, but it won't tell you if it is friend or foe. But if you take the time to read the briefing and gather any useful information you can find BEFORE you enter the mission, you MIGHT be able to use the NCTR to identify friend or foe. To do this, you must know if there are any plane types that are ONLY on one coalition. For example, if you KNOW that there are no Su-33s on your coalition and you see this on your radar MFD:
...then you know that the plane you have locked is an enemy.
As a side note, if you notice the NCTR picture, that situation is a VERY BAD time to fire a 120 at that Su-33. If you don't understand why, just ask.
Another side note, if you see that there is a friendly plane on your radar, there are very few good reasons to lock it. And all the good reasons to lock it require you to be in communication with it. So, unless that friendly knows you are about to lock him (and tells you that it is OK), DON'T LOCK ANY FRIENDLIES.