Subject: (ngtrans) MTU of Shipworm

From: Zhang Qingjun <[email-masked]>
Date: Tue, 26 Mar 2002 10:50:29 -0800

Hi all:
This is Zhang Qingjun. Engineer of Institute for Communications Research 
(ICR), Singapore.
During the use of my shipworm virtual device, I found that sometimes the 
1280 MTU is not enough.
Our project is based on Mobile IPv6 and hence most of our traffic have 
normal mobile-IP header inside. Now we are using icecast as server and xmms 
as client. The phenomenon is when the shipworm's MTU is 1280, sometimes the 
shipworm server will send back "too big" ICMP6 packets to the icecast 
server and the icecast server stops sending packets. It seems that the 
sender cannot repack packets into new MTU. After I increase the MTU of 
shipworm device to 1500, then everything works well.
So I think that MTU 1280 may be not enough and suggest to increase it somehow.

Regards

Qingjun

---

From: "Christian Huitema" <[email-masked]>
Date: Mon, 25 Mar 2002 19:11:16 -0800

> as client. The phenomenon is when the shipworm's MTU is 1280,
sometimes
> the

While I agree that we could increment the MTU limit in Teredo, it seems
that the problem is caused by your server rather than by Teredo itself.
There are other media that have a limited MTU -- PPPoE comes to mind. If
Icecast cannot work within the legal MTU of 1280 bytes, then it is
probably broken, and needs to be fixed.

-- Christian Huitema

---

From: Zhang Qingjun <[email-masked]>
Date: Tue, 26 Mar 2002 12:53:17 -0800

Hi:
I agree with you that it's caused because the icecast server failed to send 
a smaller packet.
It seems to me that the icecast may have a minimal packet size which should 
be less than 1280. But if add some extra headers, then the minimal size 
maybe larger than 1280.

Regards

Qingjun