[Techtalk] 2nd networking question

BUNTER MATTHEW Matthew.Bunter at renaultvi.com
Mon Sep 2 12:11:00 EST 2002


--- Reçu de       VITEUR.BUNTERMA 04 72 96 57 77             02/09/02 12.11       ------------------------------------------------------------------------------

Date: Fri, 30 Aug 2002 16:57:45 +0200
Subject: Re: [Techtalk] 2nd networking question

Matt,

In your original message, you said "it doesnt work".

What did you mean by this? What errors are you getting?

Maybe youre running into issues with the DF flag, or the machine youre pinging is dropping packets larger than x , or
dropping fragmented ping packets, or or or

Need more info.

Hamster

_______________________________________________
Techtalk mailing list
Techtalk at linuxchix.org
http://mailman.linuxchix.org/mailman/listinfo/techtalk

All,

Sorry I wasn't being clear. Friday late afternoon problems at work while I was trying to understand this issue.

We are testing the newtork response times between Lyon in France and Gothenborg in Sweden. One of the Swedish network team
said to send a large packet to get an accurate response time when pinging a machine in Sweden. He suggested 1500 bytes as the
packet size.

So I did :
----------------------------------------------
[root at mylinuxbox root]# ping -s 1500 systema
PING systema.renaultvi.fr (12.34.56.78) from 23.45.67.89 : 1500(1528) bytes of
data.

--- systema.renaultvi.fr ping statistics ---
4 packets transmitted, 0 received, 100% loss, time 3014ms
----------------------------------------------

So this tells me that when specifying 1500 bytes in reality one gets 1528 (I understand this part). I tried other sizes and
found the max was 1472 which actually gives 1500 bytes.

So if the MTU is the maximum size that a packet can be before fragmentation then this is the limiting factor. What I don't
understand (now) is why ping (ICMP) cannot be fragmented, and why I didn't get any response when setting the packet size
above 1500 bytes.

Rgs,

Matt

---- 02/09/02 12.11 ---- Envoyé à      -------------------------------------------------------------------------------------------------------------------------
  -> TECHTALK(a)LINUXCHIX.ORG



More information about the Techtalk mailing list