Subject: question about checksum calculation of PIM for IPv6

From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Wed, 27 Oct 1999 01:52:23 +0900

In RFC 2362 and draft-ietf-pim-v2-sm-00, there is description about
the checksum field of PIM packets;

        Checksum
             The checksum is the 16-bit one's complement of the one's
             complement sum of the entire PIM message, (excluding the
             data portion in the Register message).  For computing the
             checksum, the checksum field is zeroed.

i.e. the checksum is calculated without a pseudo-IP header.  Should
this be applied to IPv6 as well as to IPv4? As far as I know, all
upper layer checksums for IPv6 (including ICMPv6 and OSPFv6) are
calculated with an IPv6 pseudo-header, mainly because IPv6 does not
have an IP layer checksum. IMO, the checksum for PIMv6 should obey the
same rule for the same reason.

I've read draft-ietf-pim-ipv6-01 as well, but have not seen any
specification about the checksum calculation. I'd like to know PIM
specialists' opinion.

Thanks in advance,

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					[email-masked]

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From: Steve Deering <[email-masked]>
Date: Tue, 26 Oct 1999 12:03:56 -0700

At 1:52 AM +0900 10/27/99, JINMEI Tatuya / 
>same rule for the same reason.

Including a pseudo-header in an upper-layer checksum is necessary only
for those higher-layer protocols that depend on the contents of some
IP-layer fields for their own correct operation.  For example, TCP uses
the addresses from the IP header as part of the identity of TCP connection
state, and uses the IP length field to determine the size of the TCP
payload.  An upper-layer protocol that had no dependencies on any IP
header fields would not need to use a pseudo-header.  (I don't know,
off hand, whether or not PIMv6 is such a protocol.)

Steve

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From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Wed, 27 Oct 1999 10:25:10 +0900

>>>>> On Tue, 26 Oct 1999 12:03:56 -0700, 
>>>>> Steve Deering <[email-masked]> said:

> off hand, whether or not PIMv6 is such a protocol.)

PIM uses, for example, the value of the source address field of the
IP(4 or 6) header to recognize PIM neighbors. The source adress is
also used in order to elect the Designated Router. There is no
different in these point between PIMv4 and PIMv6.

					JINMEI, Tatuya