Very good ATM article with many ASND references zdnet.com
Inter@ctive WeekAugust 10, 1998
Core Switch Makers Ponder An
IP Future
Vendors start to identify strategies for
integrating Internet Protocol traffic into
core products
By Kathleen Cholewka
Technology Watch
The new service providers that aren't saddled to
legacy equipment like to talk about Internet Protocol
as the future of networking. But, at least for now,
they're making sure to deploy Asynchronous Transfer
Mode technology to offer services.
That's good news for the companies that make
Asynchronous Transfer Mode (ATM) core switches.
But even as these manufacturers rack up sales of
their ATM products, they are starting to develop
long-term plans to incorporate more Internet Protocol
(IP) technology into their product lines.
Level 3 Communications Inc., Qwest Communications
International Inc. and Williams Communications Inc.
are among the new service providers that have tested
and installed ATM switches as part of the core of
their fiber-based communications networks.
"As a wholesale provider, we need to take into
account the needs of carriers that have all types of
media in their networks," says Amy Reiber, senior
manager at Williams (www.wilcom.com), which uses
GX550 ATM switches from Ascend Communications
Inc. (www.ascend.com) in its network. "It's important
to use ATM because it offers quality of service," she
says. "There's also the ease of use it gives customers
who are connecting back into our network."
In many ways, these new carriers have no choice.
ATM is a proven technology that can handle different
forms of traffic effectively without delay. Its ability to
offer different qualities of service enables providers
to make service guarantees and offer differentiated
services with differentiated pricing -- something that
IP can't do just yet.
ATM's advantage on that front won't last forever,
however. "It's only a matter of time until IP is
perfected," says Niall Gallagher, senior manager at
Northern Telecom Inc. (www.nortel.com), a provider
of ATM core switches. "As IP networks get faster, the
issues of jitter and delay are going away."
As the performance gap between IP and ATM shrinks,
the debate over which technology to use will become
more intense. The big issue is whether investments
made now in ATM will look like the smart move five or
10 years from now.
"We've reached a funny stage," Gallagher says. "To
compete in offering IP services, providers have to
build ATM services."
The Big Switch
The coming together of the ATM and IP worlds has
equipment makers scrambling to articulate a
long-term strategy. Most manufacturers say they
expect the network's core to feature a mix of ATM
and IP -- although some aren't ready to say exactly
what that mix will be or how it will work.
"We're looking at IP very seriously right now, says
Joon Miller, director of product planning at Fujitsu
Network Communications. "We're looking to develop
an IP hybrid product. We're not sure whether we'll be
IP- or ATM-centric, but it has to be something in the
middle, like an IP router and ATM switch, to address
that market."
To date, however, Fujitsu (www.fnc.fujitsu.com) has
yet to announce an IP strategy for its core products.
Ascend continues to preach ATM. "Some vendors
would love you to believe that everything is going to
be IP," says Tim Krasky, vice president of marketing
for the core systems division at Ascend. "Well, SNA
[System Network Architecture] and frame relay and
voice are not IP. ATM is the best bet for those
multiple media types."
The key advantages of today's ATM core switches are
size and predictability. ATM core switches are big
and typically based on distributed processors with
high-speed interfaces and direct fiber connections.
They're built to carry large volumes of data at
incredibly fast speeds. And with voice migrating into
the core, the core itself becomes larger.
These monster switches do need some intelligence,
according to Krasky, such as being able to reroute
traffic automatically around a failed route through the
network via Switched Virtual Circuits. "There's no
market for stupid switches," Krasky says.
Some Of This, A Little Of That
Several ATM core switch makers say they will
develop terabit IP switch routers to accommodate IP
traffic in their networks. But those products won't
necessarily replace ATM at the network core, says
Fred Baker, chairman of the Internet Engineering
Task Force (www.ietf.org).
"It's a mix of engineering trade-offs," Baker says. "If
you need a muxed interface that can talk to
everything, then that'll be your choice. If you need a
point-to-point relationship between two routers, then
packet over SONET [Synchronous Optical Network] is
OK. They'll both have a place in the sun."
Baker notes that today's terabit products aren't ready
for heavy-duty core action. The segmentation and
reassembly chips that handle conversion between IP
and ATM formats aren't available at OC-48, or
2.4-gigabit-per-second speeds, he explains. "Until we
get a chip to handle framing at OC-48, we can't even
talk about terabit speeds," he says.
One knock against ATM is its high overhead when
compared with IP. With ATM, five bytes of every
53-byte cell is reserved for header information.
"Service providers say eliminating the cell tax could
pay for the line," Baker says. "There are costs and
benefits to each approach."
As the performance gap between IP and ATM shrinks,
the debate over which technology to use will become
more intense
Core Curriculum
Here's how key Asynchronous Transfer Mode (ATM)
core switch makers plan to handle Internet Protocol
(IP)
Vendor
ATM Core
Switch
IP Plans
Ascend
Communications Inc.
(www.ascend.com)
GX550 _---- Will develop terabit IP switch router
Cisco Systems Inc. (www.cisco.com)
BPX Sells TGX terabit switch router
Fore Systems Inc.
(www.fore.com)
ASX4000 Will develop hybrid ATM/IP core switch
Fujitsu Network
Comm.
(www.fnc.fujitsu.com)
FETEX-150 Will develop terabit IP switch router
NEC America Inc.
(www.nec.com)
ATOMNETM20 No IP plans announced
Newbridge Networks
Corp.
(www.newbridge.com)
MainStreetXpress
36190 Will develop hybrid ATM/IP core switch
(www.siemens.com) Same thing as NN
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