[smokeping-users] Re: Biggest fping size

[Edinilson J. Santos]

You are correct. Simulating a fping via shell I can see that the biggest 
value is 4096, as you can see below:

fping -b 7300 -C 5 172.16.254.150
172.16.254.150 : [0], 4096 bytes, 79.3 ms (79.3 avg, 0% loss)
172.16.254.150 : [1], 4096 bytes, 96.6 ms (87.9 avg, 0% loss)
172.16.254.150 : [2], 4096 bytes, 121 ms (99.1 avg, 0% loss)
172.16.254.150 : [3], 4096 bytes, 82.8 ms (95.0 avg, 0% loss)
172.16.254.150 : [4], 4096 bytes, 156 ms (107 avg, 0% loss)

fping -b 8096 -C 5 172.16.254.150
172.16.254.150 : [1], 4096 bytes, 96.1 ms (96.1 avg, 50% loss)
172.16.254.150 : [2], 4096 bytes, 77.4 ms (86.8 avg, 33% loss)
172.16.254.150 : [3], 4096 bytes, 129 ms (101 avg, 25% loss)
172.16.254.150 : [4], 4096 bytes, 134 ms (109 avg, 20% loss)

I'm using a FreeBSD 6.0 and pinging machines in an ethernet segment.
I don't know exactly if this is an OS limitation or fping limitation because 
ping works correctly, as you can see below:

ping -s 8096 -c 5 172.16.254.150
PING 172.16.254.150 (172.16.254.150): 8096 data bytes
8104 bytes from 172.16.254.150: icmp_seq=0 ttl=255 time=69.757 ms
8104 bytes from 172.16.254.150: icmp_seq=1 ttl=255 time=71.283 ms
8104 bytes from 172.16.254.150: icmp_seq=2 ttl=255 time=79.959 ms
8104 bytes from 172.16.254.150: icmp_seq=3 ttl=255 time=75.632 ms
8104 bytes from 172.16.254.150: icmp_seq=4 ttl=255 time=85.651 ms


Thanks.

Edinilson
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----- Original Message ----- 
From: <hkclark at gmail.com>
To: "Edinilson J. Santos" <edinilson at atinet.com.br>
Sent: Tuesday, March 21, 2006 11:16 PM
Subject: Re: [smokeping-users] Biggest fping size


On 3/20/06, Edinilson J. Santos <edinilson at atinet.com.br> wrote:
> I'm trying to use fping with packetsize ABOVE 7300 without success (for
> example, packetsize = 8192).
> Graphs simply returns nothing.
>
> Any idea?
>
> Thanks
>
> Edinilson

Hi Edinilson,

Different systems limit what the max supported ping value is.  Note
that both the max on the SmokePing server and the destination being
pinged can limit the max size.  But, assuming that you are pinging
over an Ethernet network (that isn't doing jumbo frames on and
end-to-end basis), you will effectively be limited to an fping payload
size (I'm assuming fping here) of 1472 bytes (with 8 bytes of ICMP and
20 bytes of IP that gets you to 1500 bytes, the max non-jumbo Ethernet
payload size).  Most systems support something bigger than this, but
they just fragment the payload across multiple frames of maximum 1500
bytes.

Regards,
H


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