best ids placement?

["SB CH" <chulmin2 () hotmail com>]

Hello, all.

I have read this document, subject is "Using Snort For a Distributed 
Intrusion Detection System" at 
http://www.sans.org/rr/paper.php?id=352

according to this document, the proper placement say like this 

The first example of the remote sensor placement is if you have a 
high-speed connection
to the Internet. You will want to monitor traffic coming from and going to 
that connection. The
best way to achieve this would be to place a hub between the border router 
and your firewall.
                                                ~~~~~~~~~
dummy hub placement between router and firewall or main switch like this?

                 router 
                    |
IDS ---------HUB 
                    |
                 Switch 


but another document say like this.
due to the limitation of shared media, this cannont be used if the 
connection between the switch and router is a full-duplex connection, as 
collisions will degrade the throughput.
and due to the limitation of shared media, it will increase the number of 
collisions impaction the flow of traffic between the router and switch.

What's the true and how did you set ids placement  and what is the best?
using taps? or span port? or hub?



Thjanks for your opinions.

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