Networks - msndevs/protocol-docs GitHub Wiki
According to MSNPiki, MSNP12 introduced the concept of "contact types" or "network IDs"
These are hardcoded numbers.
MSNP14?
This one is copied from MSNPiki, which doesn't specify what version it applies to - I'm guessing it corresponds to MSNP14 due to the yahoo support:
1Windows Live2Office Communicator4Telephone8MNI (Mobile Network Interop, used by Vodafone)16SMTP (Jaguire, Japanese mobile interop)32Yahoo
MSNP22
Added 13, "ConnectUser", no idea what it is.
1Windows Live2Office Communicator4Telephone8"Mobile Network" (see MNI above)13ConnectUser16SMTP32Yahoo
MSNP24
Replaced 8 with skype. Added 19 and 20.
19 is the identifier of a Thread which in fact is a non-persitent groupchat known from Skype.
1Windows Live2Email3Alias4Telephone5Domain6Sink7Contact8Skype9Circle10TemporaryGroup11Cid12AppId13ConnectUser14ConnectNetworks16SMTP17LiveIdSink18Multicast19Thread20"Short Circuit"?21OneToOneText22GroupText28Bot32Yahoo33PubSubTopic34PubSubSubscriber35WnsSid