Internet's Congestion Makes Streaming Iffy
(03/02/98; 7:11 p.m. EST)
By Jeff Caruso and Kate Gerwig, InternetWeek
Stormy weather on the Internet could put the kibosh on streaming audio and video applications.
Walt Disney got an unsettling glimpse of the public
Internet's limitations while demonstrating a new multicast
service recently. The network access point (NAP) Mae
West "went crazy" during one demonstration, said Scott
Watson, chief computer scientist at Disney. The
demonstration lost 50 percent of its packets, then settled
back down to an acceptable 5 percent packet loss.
"We expect thunderstorms on the Internet," Watson said.
Even though the multicast-enabled MBone is an
experimental part of the Internet, Disney's experience
highlights the problems of getting time-sensitive data
through congestion points.
Worse, conditions will likely deteriorate further as more
companies use broadcast services for multimedia training
and content providers blast preview clips at moviegoers.
And handling the increased traffic load promises to be a
multidisciplinary exercise. Providers have to deploy more
fiber faster. Vendors must develop gigabit routers. In
addition, ISPs must expedite their deployment.
Additionally, ISP networks need to be multicast-enabled to
send real-time audio, video, and data across the Internet
once rather than using numerous individual unicast
streams, as is the case today. And ISPs must work out a
way to bill and compensate each other for carrying each
other's multicast traffic. Such efforts are just getting under
way.
Not A Sure Thing
Although MCI is dramatically increasing its backbone
capacity, it still might not be enough to keep up with the
traffic loads. MCI has backbone connections of 1.2 gigabits
per second and will upgrade to 2.4 Gbps by the end of the
year, said Vint Cerf, senior vice president of Internet
architecture and engineering at MCI. But what comes next is
still a mystery.
"I'm not just believing in miracles -- I'm relying on them,"
Cerf said. "Up to now, we've been lucky. We can throw
bandwidth at it and hope to stay ahead of demand."
The Internet is already congested, particularly at the public
NAPs, where providers exchange traffic. Several of the
biggest ISPs are already exchanging traffic privately to get
around the NAPs.
But even private peering arrangements can't eliminate
congestion coming from increasing volumes of
high-bandwidth content, which includes audio and video,
software downloads, and streaming content coming from
push applications.
"The Internet as we know it today is being overwhelmed by
increasing data streams. We have a bandwidth congestion
problem," said Martin Hall, chief technology officer of
Stardust Technologies and co-chair of the IP Multicast
Initiative (IPMI). Hall sees multicasting as just one of many
solutions to the problem.
Satellites To The Rescue
Satellite vendors could help with the bandwidth crunch.
Rather than keeping the Internet predominantly terrestrial,
several satellite companies working with the IPMI want to
bring content into specific ISP backbones, even into home
and business networks. Satellite downlinks could also
circumvent the crowded NAPs.
Streaming technology has the potential to overtax public and
private peering points if it is sent using unicast rather than
multicast technology, according to Alan Taffel, Uunet's vice
president of marketing.
Multicast may wipe out the redundant network load that
occurs with unicast streams, but when the one-to-many
multicast stream spreads throughout a network, it could
cause congestion during its transmission, depending on
the size of the stream, Taffel said.
Of course, raw bandwidth isn't the only issue. There's the
absence of quality-of-service controls in the Internet to give
real-time traffic priority.
Plus, there are bugs plaguing many of the multicasting
routers that are part of the MBone, one of the few
multicast-enabled portions of the Internet. Although they
have been fixed in the latest releases of the routing
software, the onus is on individual ISPs to upgrade their
routers' software.
And the question ISPs are grappling with is: Who pays for all
this, and how?
No pricing model exists to reimburse providers for carrying
one another's multicast traffic across their networks. To that
end, the IPMI is concentrating on coming up with billing and
metering solutions for ISPs this year, Hall said.
"Pricing multicast is very non-intuitive because there's no
correlation between the number of recipients and the cost
for network services," Uunet's Taffel said.
Billing Inconsistencies
Unicast streams can be billed using a traditional Internet
usage-based model. But multicasting requires a different
mind-set. For example, AudioNet of Dallas shares a
percentage of its revenue with the ISP that carry its
streaming content, a formula more familiar in the broadcast
industry.
Billing and pricing questions are the main reasons GTE
Internetworking hasn't rolled out a commercial multicast
service, even though its network has been
multicast-enabled from the beginning, according to GTE
Internetworking CTO John Curran.
"My concern is a multicast content provider can send a
small amount of data, but it crosses every network link,
whereas a unicast stream passes only one path," Curran
said. "There may be only one listener in Montana clicking on
that multicast stream, and we're dragging half a T1's worth
of traffic for one listener. Who should pay for that? I know by
default the ISP pays for it."
When it launched its multicast service in October, Fairfax,
Va.-based Uunet chose a pricing model based on the
network resources being used, which is a function of the
size of the stream used to send one multicast stream and
the cost of sending unicast streams to 500 people. |
