Re: ISMS working group

Hi Ken,

The call home solution doesn't help with the problem of the _manager_ 
being behind a NAT.  It only applies to situations where the manager 
is at a fixed location on a globally-addressable network and the 
managed device is behind a NAT or firewall.

In those cases, the choices would be for the administrator to 
configure the NAT/firewall to admit his management traffic  so that 
the manager can establish a connection to the device, or for the 
device to perform a "call home" function so that the device can 
establish a connection to the manager.

BTW, the solution where you configure the NAT/firewall to admit the 
appropriate traffic could also be set-up to work properly when the 
manager is mobile and/or when the manager is gaining Internet access 
through a NAT.  "Call home" would not work in these situations.

The only cases that I can see where "call home" is a better solution are when:

(1) The NAT/firewall is not configurable to admit specific traffic, 
do static port mapping and/or to handle SSH tunneling.

(2) The NAT/firewall (nearest to the agent) is not under the 
administrative control of the people who want to do the management.

I'm not sure how often either of these cases really occurs on 
SNMP-managed networks in practice, but I think that is an interesting 
question.

Margaret

At 4:46 PM -0400 9/6/05, Ken Arnold wrote:
>Firewalls are a ubiquitous feature of my everyday life, as is NAT.
>My home is behind a NAT-ing firewall; my laptop has its own 
>firewall; every time I travel I rely on that firewall in hot spots 
>(such as starbucks); I run VirtualPC on my Mac, which has a firewall 
>and NAT translation; my parent's system is similar to mine: NAT-ing 
>firewall and on-system firewall for double protection (as are my 
>in-laws' and brothers' systems); my previous company had a NAT-ing 
>firewall for each ISP connection, and their product (a linux 
>cluster) had a firewall to protect itself from the customer's own 
>internal network.
>Many small network appliances have firewalls (sometimes NAT-ing 
>ones) that protect themselves the same way.  I could go on and on.
>
>Which means that any network solution -- let alone something as 
>potentially central as SNMP -- that ignores either NAT or firewall 
>-- is dead on arrival as far as I'm concerned, and as far as any IT 
>group I've ever seen is concerned.  If there are non-firewalled 
>networks of consequence anymore I am unaware of them.  Ignoring 
>these relegates any solution to theoretical situations or very small 
>in-home or in-group solutions.  Then someone else will have to 
>figure out some way to manage anything larger scale, which will be 
>able to also handle small scale and so will overwhelm the 
>non-firewalling, non-NAT-ing designs.  But only after such a 
>relatively impotent design confuses the world by adding yet one more 
>standard to chose from.
>
>Please get this right this time by including firewalls and NAT in 
>the solution space so it really *is* a solution.
>
>         Ken
>
>P.S.  Please also note that a non-firewalled SNMP creates some 
>pressure to bring down firewalls, to trade off SNMP for security.
>Things that pressure networks to be less secure are pretty 
>antisocial in our current security environment of zombie spam farms, 
>etc.

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