Re: Multicast Packet Delay

I'm afraid you don't really understand how UDP/IP works.
When you send it a datagram it tries to stuff the entire data
into the network. The UDP layer has no buffering - it passes
all data immediately to IP. IP has no buffering either - it chops
the packets and stuffs them into the datalink layer (Ethernet).
There's a buffer here of course, but you can easily overflow
it with big enough packets. Anything that doesn't fit is silently
dropped on the floor. Fortunatley for you, the maximum datagram
size is under 64K and it typically fits into the datalink buffer -
if there's nothing else there. Now, whatever fragments you
succeeded in pushing into the Ethernet driver's buffer will
eventually make it to the other end and into the IP layer.
They will be waiting for the dropped segments to arrive,
but these never will, since they were dropped before reaching
the datalink layer. Hence your present troubles. While thinking
about performance, you managed to kill it outright. A very good
rule of thumb is to avoid IP fragmentation at all costs. For example
the TCP protocol takes special care to determine the minimum
MTU of all network it traverses in order to avoid fragmenting
its IP packets. Other TCP algorithms deal with network congestion
to avoid having packets being dropped by intermediate routers.
Just giving you a hint...

--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@xxxxxxxx
MVP VC FAQ: http://www.mvps.org/vcfaq
=====================================

"walls1500" <walls1500@xxxxxxxxx> wrote in message
news:1141857639.092233.311720@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Thanks Alexander for your idea. In my domain, I need to send anywhere
from 1500bytes up to 1,000,000,000 bytes. I'm afraid that if I drop my
packet size down too far, it would kill the performance, and in this
domain, performance is absolutely critical. I may try that though,
just to see if I can get around this problem.

Thanks again!



.

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