Ping6 utility issue:-

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Re: Ping6 utility issue:-

In message <l2tfc485cbb1005030343qb2df7634u1a486e38531f833a <at> mail.gmail.com>, niviya vijayan writes:
> Hi All,
> 
> I am using linux os version 2.6.10 and i have an mtu configured 1500 .When i
> do a ping6 request  with size 1800 and DF bit set as yes, i could see a
> fragmentation happening eventhough DF bit is set. As per my understanding ,
> Ping6 request has to be dropped.Correct me if am wrong.Did anyone face
> this issue anytime before?
> 
> Looking forward to hear from you...
> 
> Regards,
> Niviya

Fragmentation and DF are not mutually exclusive.  DF says don't
fragment when forwarding.  When you are originating the packet
you are not forwarding.

Mark
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Re: Ping6 utility issue:-

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Re: Ping6 utility issue:-

On Mon, 3 May 2010, niviya vijayan wrote:

> Hi All,
>  
> I am using linux os version 2.6.10 and i have an mtu configured 1500 .When i do a ping6 request  with size
1800 and DF bit set as
> yes, i could see a fragmentation happening eventhough DF bit is set. As per my understanding , Ping6
request has to be
> dropped.Correct me if am wrong.Did anyone face this issue anytime before?

Can you send packet capture from originating and reciver side?

>  
> Looking forward to hear from you...
>  
> Regards,
> Niviya
> 
>

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Draft meeting minutes

All,
     A draft copy of the meeting minutes from Anaheim are available at
http://www.ietf.org/proceedings/10mar/minutes/6man.txt

Please review and let the chairs know of any corrections.  Many thanks
to Ed J. for taking minutes!

Regards,
Brian
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Re: Ping6 utility issue:-

* niviya vijayan | 2010-05-03 17:34:52 [+0530]:

>Hi Mark,
>
>Thanks for your reply. But for ipv6, fragmentation will happen at the host
>side.Intermediate routers will not do it and depending on the path MTU
>packets are fragmented at the initiator side. so while originating packets
>itself will do fragmentation.. Since the packets are sent with DF set as
>one, packets has to be dropped there itself.
>
>If I am wrong, Please give some more explanation.

With the -M option you actual disable the PMTUD mechanism, not IP
fragmentation at all. This means that no dynamic mechanism is involved, on the
contrary, the MTU size of the outgoing interface is used. Standard is to enable
path MTU discovery.

~3 month ago there where a interesting discussion on the netdev mailinglist,
maybe you should grep the netdev archive for some background information.

Cheers, Hagen

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Re: Ping6 utility issue:-

* Hagen Paul Pfeifer | 2010-05-03 20:46:24 [+0200]:

>* niviya vijayan | 2010-05-03 17:34:52 [+0530]:
>
>>Hi Mark,
>>
>>Thanks for your reply. But for ipv6, fragmentation will happen at the host
>>side.Intermediate routers will not do it and depending on the path MTU
>>packets are fragmented at the initiator side. so while originating packets
>>itself will do fragmentation.. Since the packets are sent with DF set as
>>one, packets has to be dropped there itself.
>>
>>If I am wrong, Please give some more explanation.

Small addendum: RFC 3542 specify a socket option (11.2.) called IPV6_DONTFRAG,
maybe this is the option you are searching for:

		This specification defines a mechanism to turn off the automatic
		inserting of a fragment header for UDP and raw sockets.  This can be
		enabled using the IPV6_DONTFRAG socket option.

Linux does *not* implement this option. 

Cheers, Hagen

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Re: Ping6 utility issue:-

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Re: I-D ACTION:draft-ietf-6man-dns-options-bis-00.txt

All,
     This draft is the result of the constructive discussion in Anaheim
on moving RFC 5006 (DNS option for RAs) to the standards track.  Please
review this document and provide feedback to the list.

Regards,
Brian

On 4/7/10 6:15 PM, Internet-Drafts <at> ietf.org wrote:
> A New Internet-Draft is available from the on-line Internet-Drafts 
> directories.
> This draft is a work item of the IPv6 Maintenance Working Group of the IETF.
> 
> 	Title		: IPv6 Router Advertisement Options for DNS Configuration RFC 5006-bis
> 
> 	Author(s)	: J. Jeong, L. Beloeil, S. Madanapalli, S. Park
> 	Filename	: draft-ietf-6man-dns-options-bis-00.txt
> 	Pages		: 16
> 	Date		: 2010-4-5
> 	
>    This document specifies IPv6 Router Advertisement options to allow
>    IPv6 routers to advertise a list of DNS recursive server addresses
>    and a DNS search list to IPv6 hosts.
> 
> 
> A URL for this Internet-Draft is:
> http://www.ietf.org/internet-drafts/draft-ietf-6man-dns-options-bis-00.txt
> 
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Re: Ping6 utility issue:-

Hagen Paul Pfeifer wrote:
> Small addendum: RFC 3542 specify a socket option (11.2.) called IPV6_DONTFRAG,
> maybe this is the option you are searching for:
> 
> 		This specification defines a mechanism to turn off the automatic
> 		inserting of a fragment header for UDP and raw sockets.  This can be
> 		enabled using the IPV6_DONTFRAG socket option.
> 
> 
> Linux does *not* implement this option. 

It will in 2.6.35 :)

http://marc.info/?l=linux-netdev&m=127205848417786&w=2

BTW, Linux-specific networking questions should be sent to
either linux-net <at> vger.kernel.org (general questions) or
netdev <at> vger.kernel.org (development).

-Brian
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