Re: [VRRP] RFC5798 - clarification on checksum calculation

[Tomoyuki Sahara <[e-mail]>]

Hi,

On Thu, Mar 29, 2012 at 4:29 PM, Hermin Anggawijaya
<[e-mail]> wrote:
> Would someone be able to help clarifying RFC5798 Sec. 5.2.8 on
> checksum for me please...
>
> It says that
>
>  "The checksum is the 16-bit one's complement of the one's complement
>   sum of the entire VRRP message starting with the version field and a
>   "pseudo-header" as defined in Section 8.1 of [RFC2460].  The next
>   header field in the "pseudo-header" should be set to 112 (decimal)
>   for VRRP.  For computing the checksum, the checksum field is set to
>   zero.  See RFC1071 for more detail [RFC1071]."
>
> My interpretation of the above clause is, for IPv4 VRRP the checksum would be
> defined as:
>
> "The checksum is the 16-bit one's complement of the one's complement
>  sum of the entire VRRP message starting with the version field"
>
> as per RFC 3768, instead of involving "pseudo header" (as defined in
> Section 8.1 of [RFC2460]).

My understanding is only reference text ("as defined in Section 8.1 of
[RFC2460]") is irrelevant for IPv4.  Our implementation calculates checksum
including pseudo header as for TCP/UDP/DCCP.

> If my interpretation is correct, would it be useful to change the text to
> reflect specific checksum detail for IPv4 ?

My interpretation is different from yours but clarification should be
very useful.
It's vital for interoperable implementations of VRRPv3/IPv4.


Thanks,
Tomoyuki