Subject: Re: [BEHAVE] translator generating packet too big ICMP errors

From: Xing Li <[email-masked]>
Date: Mon, 02 Nov 2009 22:25:16 +0800

marcelo bagnulo braun 写道:
> Hi,
>
> After reading the stateless translation draft, i couldn't find that 
> the translator should generate ICMP error packet too big messages, in 
> case it needs to drop an IPv4 packet with teh DF flag set with larger 
> MTU than the one available in the IPv6 side or when it receives an 
> IPv6 packet wihtout the fragment header that doesn't fit in the IPv4 MTU.
>
> Did i miss that or it isn't there? If it isn't there, should we 
> include it?

It is there (but not presented directly) in the xlate draft, it reads

2. Translating from IPv4 to IPv6

When the IPv4 node performs path MTU discovery (by setting the DF bit
in the header) the path MTU discovery can operate end-to-end, i.e.,
across the translator. In this case either IPv4 or IPv6 routers
might send back ICMP "packet too big" messages to the sender.

or we can make it more clear

2. Translating from IPv4 to IPv6

When the IPv4 node performs path MTU discovery (by setting the DF bit
in the header) the path MTU discovery can operate end-to-end, i.e.,
across the translator. In this case either IPv4 or IPv6 routers 
（including translator）
might send back ICMP "packet too big" messages to the sender.

And in

2.1. Translating IPv4 Headers into IPv6 Headers

We may add

If the DF bit is set and the MTU of the next-hop interface is less than 
or equal to the
total length value of the IPv4 header minus 20, Send ICMP (packet too
big) to IPv4 source address. Otherwise,

What do you think?

regards,

xing

>
> Regards, marcelo
>
> _______________________________________________
> Behave mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/behave
>
>

---

From: marcelo bagnulo braun <[email-masked]>
Date: Mon, 02 Nov 2009 15:30:11 +0100

> or we can make it more clear
i think this is not very clear, especially since the translator is not a 
common router

> might send back ICMP "packet too big" messages to the sender.
I think we shoudl include somehting along these lines.
Actually, i think it should state that the translator MUST behave as a 
normal router in this aspect i.e. it must send an ICMP packet too big 
error in the same conditions that a normal router would.

would that make sense?

Regards, marcelo

> If the DF bit is set and the MTU of the next-hop interface is less 
> than or equal to the

---

From: Xing Li <[email-masked]>
Date: Mon, 02 Nov 2009 22:37:04 +0800

marcelo bagnulo braun 写道:
>>> the translator should generate ICMP error packet too big messages, 
>>> in case it needs to drop an IPv4 packet with teh DF flag set with 
>>> larger MTU than the one available in the IPv6 side or when it 
>>> receives an IPv6 packet wihtout the fragment header that doesn't fit 
>>> in the IPv4 MTU.
>>>
> i think this is not very clear, especially since the translator is not 
> a common router
>
>>

I agree.

xing