On Tue, 2012-02-28 at 07:56 -0600, Jack Coats wrote:

>   In my experience, TCP/IP seems to have about 10% overhead,

I think the overhead depends greatly on the packet size.  TCP/IP
overhead can be as high as 98% if your app is streaming packets that
each contain 1 byte of actual data [given a header of 52 bytes] and that
doesn't even include ack/nack traffic or session setup/tear-down.  [Hey,
I've seen it happen].

If the application is stupid it can be staggeringly inefficient.

And as you pass network boundaries [routers, firewalls, proxies, ...]
typically the real cost comes from packet count more than absolute
bandwidth [although of course, that will catch up to you at some point].

Make sure some kind of nagle / coalescing is happening on the sender to
get larger units of work sent over the network.

>  but if there are packets from other sources going over the same link,
> if trying to put over about 10% of the total bandwidth down a link
> collisions start causing slow down.
> TCP/IP is a great protocol,  but designed for a 'not so busy' network
> IMHO.  It works great if you are over provisioned.

Nah, IPv4 kind of sucks.  IPv6 is far more streamlined and removes a
great deal of the pointless header processing required for IPv4.  But
that is another topic....

> (I got into this with our network guru when I worked at a bank.  We
> had branches with T1 links, we had about 1/3 cut off for VOIP, and the
> rest was TCP/IP.  Doing backups remotely over the TCP/IP link were
> excruciatingly slow, and we tracked down about 98% of the bits before
> I was satisfied.  There is a lot of various overhead related things
> that go down the protocol stream that all 'add value' but also get in
> the way, IMHO.)


-- 
System & Network Administrator [ LPI & NCLA ]
<http://www.whitemiceconsulting.com>
OpenGroupware Developer <http://www.opengroupware.us>
Adam Tauno Williams

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