Re: Question about latency

On Fri, 1 Oct 2010, in the Usenet newsgroup comp.os.linux.networking, in article
<9d7adea4-9acf-4502-82e9-ab7b3cbeab36@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Industrial One wrote:

NOTE: Posting from groups.google.com (or some web-forums) dramatically
reduces the chance of your post being seen. Find a real news server.

FIOS has a higher ping than cable? Y'all can't be serious... I thought
FIOS was way faster?

Not sure where you determined we're talking about FIOS, but also not
sure why you would think it to be faster than radio or copper.

Based on everything I heard on this thread, I get that the shortest
possible ping halfway around the world is 88 ms since signals at most
travel 75% of Einsteins/s,

Try again - 11000 miles (or 17600 km) at the speed of light is going
to be about 68 msec, or about 97 msec in copper or fiber. That's the
time it takes to go "out" - but a "ping" also includes a reply, so
the time is going to be double that (about 194 msec) plus any delays
in the repeaters/routers and the delay at the far end responding to
the interrogatory packet.

but commonly would be double that due to the way UDP works to make
sure you are connected

0768 User Datagram Protocol. J. Postel. August 1980. (Format: TXT=5896
bytes) (Also STD0006) (Status: STANDARD)

0791 Internet Protocol. J. Postel. September 1981. (Format: TXT=97779
bytes) (Obsoletes RFC0760) (Updated by RFC1349) (Also STD0005)
(Status: STANDARD)

0793 Transmission Control Protocol. J. Postel. September 1981.
(Format: TXT=172710 bytes) (Updated by RFC1122, RFC3168) (Also
STD0007) (Status: STANDARD)

UDP is connectionless - but to know that the message did get through
you have to wait for a reply. Compare that to TCP. Use that search
engine to find RFC0768 et.al.

and twice again because it doesn't travel in a completely straight
line due to the bounces it has to make.

Just like the air lines, there isn't a plane leaving from your
house going to every other house in the world. You gotta go to the
airport, change planes one or more times en-route, and then catch a
cab from the airport at the far end. All those distances add up,
never mind the fares.

Does this mean that I'd have to be on crack to look forward to
latency-free real time online gaming in the future?

Be glad you aren't using satellite links - no matter what the distance
on earth, it's at least one round trip out to satellites orbiting
22700 miles out at a minimum 238.8 msec per, and maybe double that if
the reply also goes by satellite. Half second pings are not unheard
of, especially to a ship or plane out of sight of land.

Old guy
.

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