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Hello, I have been tackling this mystery for
quite some time, and wonder if anyone can give
me an advise.I am pinging as shown below.(Intranet Network)
$ ping 10.84.81.81
PING 10.84.81.81 (10.84.81.81) 56(84) bytes of data.
64 bytes from 10.84.81.81: icmp_seq=0 ttl=128 time=1.44 msAnd when I change the packet size to 1459(1487)bytes - 1472(1500)bytes, the packet loss occurs.
ping -s 1459 10.84.81.81
PING 10.84.81.81 (10.84.81.81) 1459(1487) bytes of data.--- 10.84.81.81 ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 2999msIs there any reason for this? I had searched through webs but no luck.
There could be an MTU set on the router or it could be that the NIC can't handle that size packet. MTU is Maximum Transmission Unit.
I just checked mine and I start to lose it at 1473.
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Hello Guapo
Hmm,,, could this be a recieving side NIC which
can not handle that packet size? Or a Sender
side which can not handle it packet size.This mystery is starting to ick me all day
along. Thanks for your advise!
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I just tried to ping a different PC on my network, using 1473 and it responded. In my case it's the receiving side that can't handle the packet size.
0
Hello Guapo
Hmm,,, It seem for me that from the LINUX
Machine to Windows Machine, the ping fails
from a 1459(1487)bytes - 1472(1500)bytes.But from Windows Machine to a LINUX machine,
the above test sizes are okay.I had again searched through the webs but no
source had provided me the ideas or hint for
this matter. Probably not a big deal but this
mystery is killing me, I tell ya.
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I could be wrong ( which I probably am) but I believe that the windows nic doesnt support that kind of payload.
I also believe it has something to do with a icmp echo packet vs a tcp packet.
when data is transfered the mtu breaks up the packet.
I believe a echo packet doesnt support that? But I could be wrong
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As I said, my own testing shows that it's the receiving side that determines the success or failure. For me, it was the other way around. The FreeBSD box failed on the receiving side and the Windows box answered the higher ping.
I did all pings from and XP box.
XP to FreeBSD didn't answer a ping with 1473 or higher.XP to a Windows 2000 box had no problem.
I still think it's the NIC and not the OS that makes or breaks it.
0
uselessmitch-san, Guapo-san
Thanks for a wonderful Reply!
I am still trying to figure but the information
presented are great. I am currently checking if
the NIC model might have to with this.And also studying the ICMP role and such,,,
Hopefully I can clear up this mystery one day.
0
The MTU is the maximum packet size the unit can send or receive w/o fragmentation. If the receiver can't accept the packet size it make ignore it (older device) or send a response telling the sender to retransmit the portion of the packet that it couldn't read. As a rule most Internet devices default to an MTU of about 1473 so this is the maximum packet size you should transmit. As I said, modern devices *may* warn the sending device to reduce its MTU dynamically, and most new devices automatically comply. If you start losing packets mysteriously you may have to hunt and peck for an MTU that works.
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