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By Kimberly
Caisse
Network World,
12/24/01
Today's Ethernet is mature, fast and flexible enough to
support data links to metropolitan- and wide-area networks. To hear Ethernet's
proponents talk, the LAN favorite is muscling onto the wide-area scene tornado-fast.
But its detractors point out that it's not ready to displace existing high-speed
services such as frame relay and ATM altogether. Ethernet's limited availability
and lack of several important functions, such as failover protection and multiprotocol
support, are its weaknesses.
Still, Ethernet shows enormous potential. At speeds that
range from 1M to 1G bit/sec, it's as fast as frame or ATM, and companies can
select a speed anywhere in that range.
Acts Retirement-Life Communities in West Point, Pa., replaced
10 of its frame relay links with Ethernet from Yipes Communications, with
seven sites remaining on its previous WorldCom frame relay network because
Yipes doesn't offer service to them, says Dan Brindell, director of network
engineering at the organization. When using frame exclusively, he set most
of the sites, located in four East Coast states, at 256K-bit/sec Committed
Information Rate (CIR). Some of the larger sites got 384K-bit/sec CIR,
Brindell says.
"The most exciting part of [our] Ethernet service
is the ability to purchase the amount of bandwidth we need in increments of
1M bit/sec," Brindell says, adding that his company purchased 3M, 5M
or 9M bit/sec, depending on what each of its locations needed. "Contrast
that to traditional carrier offerings where you get a choice of T-1 [1.5M
bit/sec] or T-3 [45M bit/sec], and nothing in between."
Nothing may be an exaggeration, but certainly frame and
ATM lock customers into set amounts of bandwidth. Frame port speed starts
at 56K bit/sec, and can increase in 64K-bit/sec increments until a customer
reaches 45M bit/sec. To go beyond 45M bit/sec, a customer must buy more frame
ports. ATM supports transmission speeds of 1.5M, 25M, 100M, 155M, 622M, 2.5G
or 10G bit/sec.
And bit for bit, Ethernet costs less, too.
Sean Curry, chief network engineer at Calpine in Houston, moved
to Yipes from AT&T's ATM service to link three offices
in a Houston MAN. Originally, the energy company's Houston
office multiplexed two T-1 lines to provide 3M bit/sec
of bandwidth for its link to an ATM cloud, with a T-3
line to provide access from the core. Calpine also had
a 1M-bit/sec CIR on a permanent virtual circuit running
between the main office and the core network, he says.
Today, Calpine's Ethernet service provides two 200M-bit/sec
MAN links, two 20M-bit/sec MAN links and one 10M-bit/sec Internet connection
at its Houston office, Curry says. Calpine plans to install the same connections
at a facility in San Jose. The company also wants to install a 100M-bit/sec
cross-country link in the next six months.
"I'd say on average for the same bandwidth, I paid
AT&T 10 times what I pay Yipes," Curry says.
Brindell agrees that Ethernet is a bargain. Compared with
its frame relay network, Acts Retirement-Life Communities is now "getting
more than 10 times the bandwidth for about a 20% increase in monthly fees,"
he says. "The Ethernet MAN is a good fit for midsize companies like Acts
Retirement-Life Communities. Larger companies typically already have T-3s.
Midsize companies like us can't cost-justify a T-3 but we need more than a
T-1."
Yet to even consider Optical Ethernet, a company must
be in a large metropolitan area. Providers such as Yipes, Cogent Communications
and Telseon are only present in the top 20 U.S. cities. Start-up GiantLoop
Network, which builds customized networks for large companies, has customers
in 10 cities in the U.S. and one overseas.
Qwest Communications and AT&T, the first of the established
carriers to announce Optical Ethernet services, have even more limited locales.
In May 2001, Qwest began offering its Dedicated Internet Access over Ethernet
service in seven major cities, including Dallas and Washington, D.C. By December,
the service was available in more than 20 markets, a Qwest spokesperson says.
AT&T launched controlled introductions of its Optical
Ethernet services in September. While service providers can tap into the service
in 100 metropolitan areas, enterprise users can only get it in New York and
San Francisco.
Availability aside, some users wouldn't choose Ethernet
even if they could. Terry Korus, product service manager at Bemis, a packaging
manufacturer in Minneapolis, simply says he is satisfied with his company's
frame relay service from AT&T.
T-1s easily satisfy bandwidth requirements at Bemis' three
sites in Minneapolis, Korus says. Bemis' corporate headquarters connects to
the two other sites via point-to-point T-1 connections. The corporate site
has two AT&T Integrated Network Connection Service (INCS) ports, which
let speeds vary dynamically based on the amount of voice traffic present at
any given time. "I get more than a T-1 out of a single T-1" with
INCS, he says.
And in Oshgosh, Wis., where Bemis built its own T-3 MAN
between 10 sites, Ethernet service isn't available. Speeds between the sites
vary from 1.5M to 45M bit/sec. While Korus keeps an eye on Optical Ethernet
and other MAN services, such as upgrades in SONET, Bemis is not in dire need
of them.
"It's fair to say a good portion of industry can
sit back and watch the shake out" in the MAN, Korus advises.
Multipoint and counterpoint
Technologically, Ethernet has some maturing to do. It
lacks the multiprotocol support, point-to-multipoint capabilities, high reliability
and rapid failure detection needed by large companies with older, mission-critical
applications.
Ethernet lends itself to companies that move "a lot
of packetized IP data," says Martin Capurro, director of Dedicated Internet
product management at Qwest. "What it's not really suited for just yet
is nonpacketized information that's still a large portion of your voice communications
and some of your legacy data protocols like SNA or X.25," he says.
That's one reason why GiantLoop designs customer networks
to run various protocols, such as Enterprise Systems Connection, Fiber Connection
and SONET over a dense wavelength division multiplexing infrastructure, says
Jon Olstik, vice president of marketing and strategy. "The amount of
[Ethernet] bandwidth being generated by our customers is very small relative
to the multiprotocol requirements that we're seeing," he says.
And although Ethernet is an inexpensive way to establish
point-to-point connections, many large companies with remote offices need
multipoint capability. "It takes sophisticated algorithms to find new
paths through, say, a mesh network," says Jennifer Nisenoff, data product
manager in AT&T's local data services group. "I don't think the [Ethernet]
switches are there yet."
But Ethernet MAN users shrug off these failings. A meshed
network probably wouldn't provide Acts Retirement with "useful redundancy
if it ran over the same physical facilities," Brindell says. "I'm
looking for redundancy to avoid outages from cable cuts, equipment failures
and the like."
Besides, Brindell adds, Acts Retirement's frame service
was, and still is, point-to-point. "I don't consider that to be a serious
limitation," he says.
Calpine has three point-to-point Ethernet links that form
a triangle between its Houston offices, Curry says. But Calpine could move
to point-to-multipoint service, if it wanted, through a virtual LAN. The Ethernet
switches "run 802.1Q trunking already, so having multiple points of a
customer network appear in the same VLAN tag should be right up [Yipes'] alley,"
he says.
Point-to-multipoint support will probably happen when
Ethernet switches become more prevalent in MANs and WANs and more sophisticated
network operating and management systems are developed, Nisenoff says. And
that's in the works. The IEEE's Ethernet in the First Mile working group is
in the early stages of developing standards for point-to-multipoint fiber
links as well as point-to-point copper and fiber links, says Howard Frazier,
president of Dominet Systems and working group chairman.
Frame and ATM fight back
Ethernet may be older than frame or ATM, but its failure
detection and response rate (typically called failover) and reliability rates
fall short for some high-end applications such as voice and database mirroring.
Since their inceptions 10 years ago as WAN and MAN technologies, frame relay
and ATM have been perfected to meet these higher service levels.
Frame and ATM provide things such as 99.999% reliability,
failure detection and response rates of up to 50 msec, low latency and quality
of service (QoS). Ethernet offers 99.995% reliability and failover times between
3 and 30 seconds.
"Some of the newer technologies may reach the point
where they can be on the same par as frame, but frame has these key attributes
in the marketplace today," says Tim Halpin, vice president and treasurer
of the Frame Relay Forum.
The same can be said about ATM services. "The customer
who wants data, voice, video and videoconferencing" can get it with ATM,
says Rick Townsend, president of the ATM Forum. But customers with a lot of
data traffic may not need the QoS or timing features in ATM. "For them,
a bandwidth-centric [service] like Ethernet is a perfectly viable choice,"
he says.
Just as Ethernet is evolving to meet the needs of metropolitan
customers, work is under way to make frame and ATM more useful to existing
customers.
IP VPNs are being added to frame networks so companies
can reduce the communications costs of their remote offices. AT&T's IP
VPN service, which runs IP-over-frame, lets remote offices of its frame customers
tap into a VPN through dial-up, Ethernet or whatever type of connection the
remote office dictates. These customers can use "all the existing assets
of their frame equipment to create an IP VPN," Halpin says.
Meanwhile, several start-ups are busy trying to make ATM
bandwidth more flexible. Companies such as Gotham Networks, Equipe Communications
and WaveSmith Networks are developing next-generation ATM equipment that lets
bandwidth be metered, says Michael Howard, principal analyst at Infonetics
Research. Ultimately, this could invigorate ATM. "If you look at the
metropolitan area, even though there is more data traffic than voice traffic,
most of the revenue being generated is by voice traffic," Howard says.
With the competition in pricing and technology that Ethernet
MAN services are sparking, no matter how the battle progresses, user companies
have already won.
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