sharing the same ATM for internal and DMZ networks

[Jeffery.Gieser () minnesotamutual com]

I am working on my first network with an ATM backbone.  I have a Sidewinder
firewall with physical seperation of the internal network, external network,
and both DMZ networks.  Network Engineering wants to share our ATM pipe
between the internal network and both DMZ networks.  I know that, currently,
all traffic between any of the networks has to go through the Sidewinder and
I understand the security risks and advantages of the current setup.  I only
allow a few protocols through the firewall and I do not want to weaken
security from the DMZs to the internal network.  Is it safe to share the ATM
pipe in this type of setup?  Why? What additional security risks have I
created?  And finally, is there a good book on ATM and/or ATM security that I
can read to better understand this?  My e-mail addresses is
jeffery.gieser () minnesotamutual com.  Thanks.

Regards,
Jeffery Gieser