On Aug 7, 2009, at 2:59 PM, Christopher Morrow wrote:
On Wed, Aug 5, 2009 at 5:07 PM, Margaret
Wasserman<m...@sandstorm.net> wrote:
On Aug 5, 2009, at 3:55 PM, Christopher Morrow wrote:
This I don't recall at all... I think part of my question is we
(as a
group) are assuming that the reasons for requiring ipv6 udp
checksums
as stated +10 years ago are still valid, I don't see data supporting
that fact.
There are some classic papers on this topic. The most recent I
could find
is from 2000:
If by 'classic' you mean 'not relevant to today's networking
technologies', sure.
http://conferences.sigcomm.org/sigcomm/2000/conf/abstract/9-1.htm
This study captured data on:
1) a web crawl server on a 10mb hub
2) a dorm on a broadcast 10base2 network
3) 2 locations that don't give enough information about the
connections/tech used
The dataset analyzed is not relevant to today's networking
connectivity or technologies. Looking very quickly at a small set of
data I have access to (servers serving web content to the internet
users):
32,945,810,591 packets received, 0 dropped due to bad checksum (ip
header checksum)
1,004,728,008 datagrams received, 0 bad checksum, 15886 with no
checksum (udp datagram stats)
Just polling the routers here, I see a similar scenario, e.g.,
4,166,900,871 packets 0 dropped due to bad checksum
However, this is over good clean fiber links. What I would worry about
are RF links, such as 802.11 or P2P microwaves. These generally have
link layer redundancy / checksums, etc., which I think are pretty good
at detecting corrupted packets, but
it might not be wise to rely on that.
I wonder if we could dig up similar numbers for the IETF 802.11
network. I will make inquiries.
Regards
Marshall
(collected from some unix hosts, via netstat -s or netstat -s -p udp
output)
Given this set of data I don't think that having a checksum matters
for UDP or IP-header on today's internet, since there are zero errors
out of ~34B packets.
-chris
In a quick re-read of this paper, I didn't see anything that is
obviously
dated about it. So, I'd assume its error rates and analysis are
still
pertinent, unless there is a more recent study that says otherwise.
Margaret
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