prop. 159 relay and peer test versions

i2p2www/spec/proposals/159-ssu2.rst

@@ -2313,6 +2313,21 @@ The following mechanisms may assist in achieving these goals:
 These possible mechanisms may increase the processing time and latency of
 the Relay or Peer Test functions. All effects must be evaluated.
 
+Cross-version relaying and peer testing should also be supported if possible.
+This will facilitate a gradual transition from SSU 1 to SSU 2.
+The possible version combinations are:
+
+=========   ===========   =============   =============
+Alice/Bob   Bob/Charlie   Alice/Charlie   Supported
+=========   ===========   =============   =============
+1           1             2               no, use 1/1/1
+1           2             1               yes?
+1           2             2               no, use 1/2/1
+2           1             2               yes?
+2           2             1               no, use 2/2/2
+2           2             2               yes
+=========   ===========   =============   =============
+