NY Times: Multimedia Transmissions Drive Net Toward Gridlock
nytimes.com
By SARA ROBINSON
When a computer sending conventional data encounters congestion, it
significantly slows its own transmission rate, but a computer sending
streaming data will reduce the flow only slightly. So if streaming traffic
competes with conventional traffic for the same congested strip of
roadway, the streaming traffic, like some VIP motorcade, assumes the
right of way and lets all other data traffic pile up. ...
***
By its very nature, streaming media has to flow continuously to the user's
computer, so it cannot follow the same traffic rules as conventional data.
But even so, it is possible for packets of streaming data to interact civilly
with other traffic on the Internet. The reason they do not, Jacobson said,
is that streaming media providers have no incentive to comply with traffic
rules.
Today, he said, "if Real Networks is polite and Microsoft isn't, then Real
looks crummy."
Even elbowing all other data aside, today's streaming media produces a
very low quality of entertainment most of the time.
Much of that lack of quality today is a result of slow modems at the
user's end. In three to five years, when cable modems and souped-up
digital telephone lines are expected to be common, most Internet users
may be listening to live Webcasts or playing high-quality radio on their
computers. In 10 years, movies and commercial television might very
well be carried over Internet channels. ...
***
Jacobson's proposal, developed with Ms. Floyd in 1989 and only now
being tested in Cisco routers, uses a kind of virtual penalty box. When
the router experiences congestion, it takes a random sample of its traffic.
If a certain host computer is overrepresented in that sample, its packets
are placed at the end of the line.
This creates the right incentive structure, he said, because the Internet
service providers do not have to persuade Real Networks or any other
company to obey the rules. Rather, he says, "The customers do instead,
because the quality" of their audio and video "gets really crummy."
All the best,
Michael |
