Ping doesn't like small packets.

Ping doesn't like small packets.

Post by Hugo van der Koo » Sun, 21 Jul 1996 04:00:00




Quote:>I noticed today that if you use the -s switch on ping, and set the size to
>less than 24 data bytes (total packet size < 32 bytes) you don't get your
>packet back.  It's not an ICMP or other such esoteric limitation, because
>the specific command I was trying to make work was:
>/bin/ping -s 1 -c 1 some.machine.domain

Well EtherNET has a physical limitation. The minimum packet size is 72
bytes including preamble or 64 bytes excluding preamble.

IP has a bare minimum of 24 bytes which does NOT include any ICMP
message. So It is propably another way of interpretating the value.
Linux considers the requirements for ethernet as well and the SGI
seems to fill up to the minimum required ethernet packet length.

Quote:>It worked on an SGI and on an MkLinux box, but not on a PC running kernel
>2.0.0.
>It might just be an old version of ping.  Where can I find the ping
>sources to recompile and test this theory?  Thanks!

It is propably not.

Hugo

 
 
 

Ping doesn't like small packets.

Post by Rhys Thury » Fri, 26 Jul 1996 04:00:00




: >I noticed today that if you use the -s switch on ping, and set the size to
: >less than 24 data bytes (total packet size < 32 bytes) you don't get your
: >packet back.  It's not an ICMP or other such esoteric limitation, because
: >the specific command I was trying to make work was:

: >/bin/ping -s 1 -c 1 some.machine.domain

: Well EtherNET has a physical limitation. The minimum packet size is 72
: bytes including preamble or 64 bytes excluding preamble.

: IP has a bare minimum of 24 bytes which does NOT include any ICMP
: message. So It is propably another way of interpretating the value.
: Linux considers the requirements for ethernet as well and the SGI
: seems to fill up to the minimum required ethernet packet length.

: >It worked on an SGI and on an MkLinux box, but not on a PC running kernel
: >2.0.0.
: >It might just be an old version of ping.  Where can I find the ping
: >sources to recompile and test this theory?  Thanks!

: It is propably not.

It *was* due to an older copy of ping.  That's why it worked in MkLinux.
The ping binary in there was built from more recent sources.

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