You might be interested in how Kerberos uses ASN.1, with extension messages having a field that describes whether understanding the extension is required (this is important if extension covers information that might change the result of authorization operation, for example)
If I add a field to the message I expect the new binaries to read the messages serialized by the old binaries and vice versa.
Obviously the old binaries are not expected to understand the added field but they should not break when handed the upgraded message.