ECC==error checking and correction. UDP does neither. That is why it is termed "unreliable."

http://www.tech-faq.com/udp.shtml :

"When we say that UDP is unreliable, we mean that UDP does not provide mechanisms for error detection and error correction between the source and the destination. Because of this, UDP utilized bandwidth more efficiently than TCP."

According to rfc 768 (User Datagram Protocol http://www.faqs.org/rfcs/rfc768.html ) the checksum "gives protection against misrouted datagrams." It is for the header only (sip,dip,protocol,header length). Not to insure data integrity.

--p



-----Original Message-----
From: firewall-wizards-bounces@listserv.icsalabs.com
[mailto:firewall-wizards-bounces@listserv.icsalabs.com]On Behalf Of Paul
D. Robertson
Sent: Thursday, March 13, 2008 12:43 PM
To: Firewall Wizards Security Mailing List
Subject: Re: [fw-wiz] syslog and network management


On Mon, 3 Mar 2008, Darden, Patrick S. wrote:

> UDP is a LOT faster than TCP. No ECC so it uses less cpu, less memory,
> and has less of a memory footprint. If you were dropping a lot of UDP,
> then TCP would not help at all--you would receive less, just more
> reliably.


First, Cisco routers drop UDP on overlaod before they drop TCP, so if your
log server isn't on the same subnet, that may mean TCP is a better choice
if you're getting flooded.

Second, it depends on your buffers with TCP, but at least you'd know on
the receiving end that you're dropping packets. With buffer tuning, you
may be able to withstand flooding the log server and catching up again.

Third, I'm pretty sure the RFCs say that UDP must default to checksumming
packets.


Paul
-----------------------------------------------------------------------------
Paul D. Robertson "My statements in this message are personal opinions
paul@compuwar.net which may have no basis whatsoever in fact."
http://www.fluiditgroup.com/blog/pdr/
Art: http://PaulDRobertson.imagekind.com/

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