This is the great thing about magic numbers. They offer a thin veneer of authority and the possibility of enabling easy policing. In many respects, it a real pity that rules based on numbers pulled out of the air like this have such a completely arbitrary basis. Life would be much easier.
So where does the magic number 53 come from? Why is this anycast policy only going to give an address block to those who wish to anycast services on port 53? If I ran http on port 53, could I get an allocation under this policy? Why not? Note that when this was discussed in the past, it was pointed out that some people had done some actual experiments and discovered that many protocols which seem to be not-anycastable, are able to be anycast in practice due to the stability of the net. RIPE should not be making arbitrary limits on what people can do. Yes, let's have a policy to give out address blocks to people who can show that they are running (or intend to run) real anycast services. Let's not restrict what those services are. If we are concerned about too many requests coming in, then let's place an arbitrary numerical limit for now, which can be removed later. In the case of anycast, the relevant thing to count for an arbitrary limit, is the number of separate geographical locations. Two is sufficient from a technical point of view, but given that RIPE policy can change to meet changing needs, it seems to me that it is not unreasonable to place a larger limit, perhaps 4, perhaps 5. --Michael Dillon