Subject: IPv6 header's Payload Length field

From: Grigoriy Klyuchnikov <[email-masked]>
Date: Tue, 30 Apr 2002 00:38:22 +0400 (MSD)

Hello,

I have some questions about the behaviour of an implementation in cases
when the IPv6 header's Payload Length + size of IPv6 header isn't equal the size
of the real recieved data.

RFC 2460 say:

"4.7 No Next Header

   The value 59 in the Next Header field of an IPv6 header or any
   extension header indicates that there is nothing following that
   header.  If the Payload Length field of the IPv6 header indicates the
   presence of octets past the end of a header whose Next Header field
   contains 59, those octets must be ignored, and passed on unchanged if
   the packet is forwarded."

1) What must an implementation do in the case if the Payload Length field
of the IPv6 header indicates the of octets past the end of the upper layer
packet? Must it generate ICMP Parameter Problem message in this case or
pass superfluous data unchanged (in end-point case and in router case)? 
Is it implementation depended? 

2) If IPv6 header's Payload Length is zero, but the size of the real recieved
data is longer then size of the IPv6 header (40 bytes). Is it an error? 
Or an implementation may pass superfluous data unchanged to the
destination.

3) If IPv6 header's Payload Length > 0, but the size of the real recieved
data is longer then IPv6 header's Payload Length + size of IPv6 header.
May an implementation pass superfluous data unchanged?

4) If IPv6 header's Payload Length + size of IPv6 header is longer then 
size of the real recieved data. Is it an error case or implementation depended?

Thanks.

Regards,
Grigory Klyuchnikov, System Engineer, 
Institute for System Programming 
Russian Academy of Sciences

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