RE: UDP Question
- From: "David Farinic" <davidf@xxxxxxx>
- To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
- Date: Fri, 11 Feb 2005 20:24:14 +0100
>"Games use UDP because it doesn't require them to write their apps to
handle Winsock connection states, which are more difficult than simply
barfing packets."
Hmm I would opposite that. If they would just barf packets soon nobody
would be able connect to server as it would be overflowed.
Tcp/ip is much easier to code with. Almost everything is handled by it.
To make working/efficient UDP communication is much more difficult.
Think packet loss, data corruption/verification, delayed packets(
disordering- over jumping), pipe overflow etc... but all these
"troubles" gives you lower level data flow control which means new
features/options.
And ONE of them is ability to make time sensitive data transfers -
transfer where information has value only in certain time window. These
are applications with specific needs which tcp/ip as generic connection
oriented protocol can not offer.
0x56058's 2 Euro cents
________________________________
From: Jim Harrison [mailto:Jim@xxxxxxxxxxxx]
Sent: Friday, February 11, 2005 7:49 PM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: UDP Question
http://www.ISAserver.org
Just because you "see" it that way doesn't make it true.
Lots of folks think Elvis is alive and well; that doesn't make it true,
either.
Nothing about UDP makes it "time sensitive", regardless of how you want
to interpret it.
UDP is more efficient "on the wire" than TCP because there's no
connection state to maintain when sending packets, but this is offset by
the fact that the application is now required to handle all the packet
reassembly and ordering.
Where would you rather "waste" CPU cycles; in user or Kernel mode? TCP
packet reassembly operates in Kernel mode (more efficient), while UDP
packet reassembly operates in user mode (less efficient).
Yeh; I'll defer to games for my TCP/IP references - they're certainly
the defining force in the network world, yup-yup. Games use UDP because
it doesn't require them to write their apps to handle Winsock connection
states, which are more difficult than simply barfing packets. They also
prefer UDP because as you pointed out, it allows them to ignore packets
that arrive out of sequence. This is also true of PCAW.
________________________________
From: TRadtke@xxxxxxxxxxxx [mailto:TRadtke@xxxxxxxxxxxx]
Sent: Fri 2/11/2005 7:01 AM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: UDP Question
http://www.ISAserver.org <http://www.ISAserver.org>
So Jim, you'd use TCP for streaming video? I'd call that time
sensitive,
and if the packet is out of sequence, it's useless. No need for TCP
there.
How about online gaming? WoW, M59, etc, they all use UDP for data
transmission. Time sensitive. Didn't get it soon enough? Why bother
processing something that you don't even need to know about. Why use
TCP to
reconstruct the packet sequence when it's pointless. It wastes CPU
cycles
and network card buffers to hold out of sequence packets.
PCAnywhere uses UDP for data stream for the remote desktop. Time
sensitive?
Yes. Why in the hell would I want to see my mouse jump around the
screen
doing things that I did a few seconds ago?
If you even bothered to understand what I wrote, you'd see that you even
agreed with me that it's non-guaranteed delivery. Data that either is
there
or useless to me IS time sensitive. Just because your definition of
time
sensitive is different than mine does not make my fist post any less
valid
that your post.
-----Original Message-----
From: Jim Harrison [mailto:Jim@xxxxxxxxxxxx <mailto:Jim@xxxxxxxxxxxx> ]
Sent: Thursday, February 10, 2005 4:11 PM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: UDP Question
Some reading on basic TCP/IP is clearly in order...
"UDP is normally used for time sensitive information"?!? Where did you
get this? UDP in and of itself provides no delivery guarantees
whatsoever.
-----Original Message-----
From: TRadtke@xxxxxxxxxxxx [mailto:TRadtke@xxxxxxxxxxxx
<mailto:TRadtke@xxxxxxxxxxxx> ]
Sent: Thursday, February 10, 2005 1:41 PM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: UDP Question
http://www.ISAserver.org <http://www.ISAserver.org>
Well, UDP is normally used for time sensitive information. UDP delivery
is not guarantied at all. Most of the time it's used both ways if it's
being used since if I'm not getting your traffic, it really won't matter
if your not getting mine. For example, live video streams.
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