Firewall Wizards mailing list archives
Re: syslog and network management
From: Chuck Swiger <chuck () codefab com>
Date: Thu, 13 Mar 2008 11:28:30 -0700
On Mar 13, 2008, at 10:33 AM, Roel Jonkman wrote:
UDP checksum is optional, if the checksum field is 0, there is no checksum.
Agreed-- from RFC 768 page 2: "Checksum is the 16-bit one's complement of the one's complement sum of a pseudo header of information from the IP header, the UDP header, and the data, padded with zero octets at the end (if necessary) to make a multiple of two octets. [ ... ] If the computed checksum is zero, it is transmitted as all ones (the equivalent in one's complement arithmetic). An all zero transmitted checksum value means that the transmitter generated no checksum (for debugging or for higher level protocols that don't care)." I have a stratum-2 NTP server (well, I run several, actually, but lets pick one :) which gets lots of UDP traffic [1] from a wide variety of different platforms. The "netstat -s" data looks like: udp: 60392051 datagrams received 0 with incomplete header 0 with bad data length field 1071 with bad checksum 25653 with no checksum ...which seems to be about 0.04% frequency of no checksum being set for UDP traffic. -- -Chuck [1]: ~5 GB/month or about 5 requests per second. _______________________________________________ firewall-wizards mailing list firewall-wizards () listserv icsalabs com https://listserv.icsalabs.com/mailman/listinfo/firewall-wizards
Current thread:
- Re: syslog and network management david (Mar 01)
- <Possible follow-ups>
- Re: syslog and network management david (Mar 01)
- Re: syslog and network management Darden, Patrick S. (Mar 10)
- Re: syslog and network management david (Mar 13)
- Re: syslog and network management Paul D. Robertson (Mar 13)
- Re: syslog and network management Darden, Patrick S. (Mar 16)
- Re: syslog and network management Darden, Patrick S. (Mar 10)
- Re: syslog and network management Roel Jonkman (Mar 13)
- Re: syslog and network management Paul D. Robertson (Mar 13)
- Re: syslog and network management Chuck Swiger (Mar 13)