[AusNOG] network security Question

[Alex Samad - Yieldbroker]

Hi

Wondering what people do around 
1) letting through icmp

I like the idea of allowing icmp through, make network diagnosis a lot easier, but I don't want to be bomb.  
What sort of rate limiting do people think is acceptable?
What's acceptable from client to confirm connectivity?


2) blacklisting ip's

So I have (like a lot of others),  people port scanning look for open ports, what sort of levels do people actually do something about it ?

I asking as an end user, but I am also curious to know what providers do.

I have heard of companies blocking entire ranges, for example say china and/or Russia as they have no clients there. Do people do that, do ISP provide that service (can that be done through the auto black hole mechanism ?)


Alex