[c-nsp] Cisco Processing Regarding ICMP

[alaerte.vidali at nsn.com]

Thanks Paul,

I would like to find information about processing on 7609 under this
situation, from traffic coming from Internet, normally users downloading
files or watching videos. 
Because internal network design requirements, it is necessary decrease
internal MTU to slight lower than 1500 bytes, so I would like to know
how 7609 will handle high number (in the worst case, or attacks) of
packets with high MTU and DF bit set.

Br,
Alaerte 

-----Original Message-----
From: ext Paul Cosgrove [mailto:paul.cosgrove at heanet.ie] 
Sent: Saturday, May 10, 2008 9:53 PM
To: Vidali Alaerte (NSN - BR/Rio de Janeiro)
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Cisco Processing Regarding ICMP

Hi Alaerte,

This will be dependent on the hardware, traffic types, throughput and 
software version/configuration.   You may need to explain a little more 
in order to get an adequate answer to your question. 

Large numbers of packets from a handful of hosts running PMTUD may
require a smaller number of ICMP notifications than would be necessary
for a larger number of hosts sending less traffic.  The difference in
the MTUs, and the sizes of the incoming packets will also affect the
proportion of traffic which triggers notifications.  Similarly protocols
running on the router itself may require their packets to be fragmented.

Paul.

alaerte.vidali at nsn.com wrote:
>  Hi,
>
> Any document about how is the processing of a packet received on 
> interface A toward interface B, where interface B has lower MTU than 
> received packet and DF bit is set?
>
> (like description of the process)
>
> (considering CPU impact and if default limitation of ICMP generation 
> enough when the number of packets is very high)
>
> Thanks,
> Alaerte
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