[Snort-users] Snort inline latency

Ian Bowers iggdawg at ...11827...
Mon May 7 10:48:15 EDT 2012


Apologies if I misunderstood your purpose.  The setup I suggested was only
to calculate the difference in latency for when snort is placed inline vs
snort removed from the path.  This would be useful for determining if your
inline snort setup is in fact a source of latency.

Are you trying to determine if snort itself is a hinderance, if the
physical device you've placed inline is a hinderance, or if it is something
else?

Regards
-Ian

On Mon, May 7, 2012 at 10:10 AM, Abdelmonaim Mokadem <
abdelmonaim.mokadem at ...13827...> wrote:

>  Hi,****
>
> Thanks for the reply.****
>
> I’m not sure that putting my snort into a VLAN is gonna bring me different
> results from what I actually have…****
>
> Can you explain what would putting my IPS into a VLAN change ?****
>
> As I understand it, it would only isolate the tests, but I think it won’t
> change the latency nor help calculate it..****
>
> My big problem here is to understand why my latency is so high (nearly 200
> milliseconds with clean traffic, even without snort inline activated
> results remain unsatisfactory) and to know if my way to calculate this
> latency is the right one.****
>
> Regards,****
>
> Abdelmonaim Mokadem.****
>
> ** **
>
> *From:* Ian Bowers [mailto:iggdawg at ...11827...]
> *Sent:* Friday, May 04, 2012 4:19 PM
> *To:* Abdelmonaim Mokadem
> *Cc:* snort-users at lists.sourceforge.net
> *Subject:* Re: [Snort-users] Snort inline latency****
>
> ** **
>
> If you have a VLAN capable switch, use VLANs to place the snort sensor
> inline.  run your tests, calculate latency.  Then use VLANs to take the
> sensor out of line.  repeat tests.  Do this a couple times to make sure you
> have consistent results.   I use this technique all the time in my lab to
> toss test appliances or VMs in the path of traffic without having to mess
> around with cables like.  IE:****
>
> ** **
>
> Snort inline:****
>
> Server --- VLAN 102 ---- snort --- VLAN 103 --- router --- client****
>
> ** **
>
> Snort removed:****
>
> Server --- VLAN 102 --- router --- client****
>
>    VLAN 104 --- snort --- VLAN 104****
>
> ** **
>
> inline, both sides of snort are on different VLANs, and act as if they're
> on their own little switches.  The switchports are access ports so the end
> devices don't see the VLAN tags.  In the second scenario, snort sits in its
> own little penalty box on VLAN 104 where the two sensor ports don't talk to
> anyone.  the router and the server are both on VLAN 102 at this point and
> can communicate directly.  I'm assuming a router is involved but it doesn't
> have to be.   just eliminate the router and put the client in its place,
> works the same.  I pick random VLANs in the 100s for most examples to
> discourage people from using native VLANs by mistake since that may break
> the scanario.****
>
> ** **
>
> ** **
>
> Example switch config if you're using Cisco gear:****
>
> ** **
>
> INLINE:****
>
> vlan 102****
>
>  name servernet_inside****
>
> vlan 103****
>
>  name servernet_outside****
>
> ** **
>
> interface FastEthernet0/4****
>
>  description Server access port****
>
>  switchport access vlan 102****
>
>  switchport mode access****
>
> !****
>
> interface FastEthernet0/5****
>
>  description Snort HOME_NET port****
>
>  switchport access vlan 102****
>
>  switchport mode access****
>
> !****
>
> interface FastEthernet0/6****
>
>  description Snort EXTERNAL_NET port****
>
>  switchport access vlan 103****
>
>  switchport mode access****
>
> !****
>
> interface FastEthernet0/7****
>
>  description Router access port****
>
>  switchport access vlan 103****
>
>  switchport mode access****
>
> ** **
>
> ** **
>
> REMOVED:****
>
> ** **
>
> vlan 102****
>
>  name servernet_inside****
>
> vlan 104****
>
>  name on_deck****
>
> ** **
>
> interface FastEthernet0/4****
>
>  description Server access port****
>
>  switchport access vlan 102****
>
>  switchport mode access****
>
> !****
>
> interface FastEthernet0/5****
>
>  description Snort HOME_NET port****
>
>  switchport access vlan 104****
>
>  switchport mode access****
>
> !****
>
> interface FastEthernet0/6****
>
>  description Snort EXTERNAL_NET port****
>
>  switchport access vlan 104****
>
>  switchport mode access****
>
> !****
>
> interface FastEthernet0/7****
>
>  description Router access port****
>
>  switchport access vlan 102****
>
>  switchport mode access****
>
> ** **
>
> ** **
>
> Regards,****
>
> -Ian****
>
> ** **
>
> On Fri, May 4, 2012 at 3:35 PM, Abdelmonaim Mokadem <
> abdelmonaim.mokadem at ...13827...> wrote:****
>
> Hi all,****
>
> I am currently trying to calculate my snort inline latency.****
>
> I have 2 hosts : one running snort inline and the other one which inject
> pcaps (a bridge is set to send back packets from the snort host machine to
> the injection one).****
>
> I use tcpdump to sniff packets at the emission and at the reception from
> my injection host and (I match only ACK packets with a little program) then
> calculate the difference between the timestamps (emission and reception),
> but unfortunately my results are really bad…****
>
> Can anyone tell me if I’m doing right? Or does anyone know what is the
> best way to calculate snort inline latency?****
>
> Thanks,****
>
> AM.****
>
>  ****
>
>  ****
>
>
>
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