WDM deals unplug circuit-based telecom
By Loring Wirbel, Posted: 11:45 p.m., EST, 6/5/98
eet.com
ATLANTA - On the eve of the Supercomm
'98 show, the circuit-oriented Public Switched
Telephone Network is rapidly coming to
resemble an endangered species. A flurry of
unexpected announcements in the past week
underlined an industry-wide push to
packet-switched local and long-distance public
networks based on
wavelength-division-multiplexing optical
technology.
The shift to WDM is driving both business and
technical agendas, as evidenced by two recent
mergers and a new harmony between the
once-warring advocates of asynchronous
transfer mode (ATM) and the Internet Protocol.
The common bond of photonic WDM brought a
different tenor to the ATM Year '98 conference
this past week, where Cisco Systems Inc.'s "IP
Loves ATM" slogan became the central theme
for a show in which physical-layer optoelectronic
transport proved more important than
transport-layer flavors.
Telephony's new interest in WDM was
exemplified by Tellabs Inc.'s offer to acquire
high-flying WDM specialist Ciena Corp.
(Linthicum, Md.) for $6.9 billion in stock.
Tellabs (Lisle, Ill.), a telephony circuit-switching specialist, has lacked ATM or broadband
switches in its product portfolio. A Ciena
acquisition thus would fit Tellabs' strategy for the
packet-based future.
In a move mirroring the Ciena deal, Alcatel
Alsthom (Paris) Thursday morning announced its
pending acquisition of DSC Communications
Inc. (Dallas) in a $4.4 billion stock deal. Alcatel
has a strong suite of ATM switching and WDM
muxing products; DSC is known primarily for
circuit-switching systems and digital-loop-carrier
transmission equipment. While DSC has lagged
in some central-office markets because of
sluggish marketing efforts in broadband packet
data, one analyst said that Alcatel could gain a
base of traditional transmission products, along
with customers for its advanced
packet-switching and optical multiplexing
technology. DSC will become part of Alcatel's
network systems division.
Sprint Corp.'s announcement that it will largely
abandon its current circuit-switched
long-distance backbone in favor of a
multiservice, packet-switched backbone
network edged the public switched telephone
network closer toward irrelevancy. Sprint plans
later this year to roll out an end-to-end
packet-based network based on ATM switches
and WDM systems, with services charged per
bit, rather than per minute.
But, analysts noted, the plan was scant on
details. And Hank Zannini, vice president of
business development at tera-router vendor
Avici Systems Inc., said that "it seems backward
to build a packet-switched infrastructure on
circuit-switched hardware."
Schizophrenia
The outlook for ATM seemed schizophrenic in
light of the WDM activity surrounding ATM
Year '98. On the one hand, high order rates for
WAN-access equipment have made ATM a
belated hit in certain market segments. On the
other, the ease with which networks can move
from ATM switching to core IP switching to
IP-over-Sonet to ATM-over-WDM makes
signaling and transport protocols a secondary
matter.
As a result, attendance at ATM Year '98 was
down amid evidence of the switching topology's
success, and next year the show will be
rechristened "Broadband Year '99" in deference
to the trend.
"A factor to watch is the emergence of a Sonet
link layer as an interface in its own right," said
Michael Grady, president and chief executive of
tera-router startup Argon Networks Inc. "The
interface between WDM and other services is
just a raw-bits issue. The mere existence of
WDM doesn't favor packet-over-Sonet or
ATM. WDM will simply be an underlying layer
in a services realm where ATM and IP continue
to coexist."
But that means telecom-equipment OEMs,
router manufacturers and broadband-switch
developers must control WDM interfaces to
switching equipment. That imperative led
Northern Telecom to make a 20 percent
investment in Avici, so that Nortel WDM muxers
could be embedded into Avici's multiprocessing
router.
And it led Tellabs to make an unprecedented
offer for the influential Ciena, taking a $2 hit in its own share price as a result.
Still up for debate is whether silicon integration
favors a particular architectural direction in
making packet-overlay networks
primary-telecom networks. Gordon Stitt,
president of Gigabit Ethernet specialist Extreme
Networks Inc., said ATM switching was made
irrelevant when silicon acceleration was applied
to ultrafast routers, since that let routers move
packets at high Sonet rates without requiring
higher-layer switching protocols.
But Robert Sansom, cofounder and vice
president of Fore Systems Inc., said he believes
"Moore's Law serves us all equally well,"
propelling integration trends in single-chip
systems for ATM switching, WDM muxing and
ultrafast routing.
One point on which ATM Year '98 achieved
virtual consensus was that carriers no longer look
for specific architectures but instead seek to
provide service differentiation as transparently as
possible to customers. That seems to favor
ATM, at least for now, since methods of
assigning services to virtual channels and
applying Quality of Service parameters to service
streams is far more mature in ATM than in IP's
Differentiated Services model.
That puts some wrinkles in the process of selling
ATM architectures to carriers. Two years ago,
ATM was still pitched as a data-oriented
network that could handle voice and video. But
ever since Qwest Communications International
Inc. and Level 3 Communications Inc. began
touting cheap voice phone calls over an
IP-switching backbone, small carriers have been
interested in using fast packet switches to enable
voice channels.
Mohammad Raza, director of marketing for the
ATM business unit at General DataComm Inc.
(Middlebury, Conn.), said his company's Apex
switch had been sold primarily for data services
until the advent of the Voice Services Module for
the switch, which General DataComm designed
from a core bank of 60 digital signal processors.
The module lets carriers provision a mix of voice
channels based on ADPCM or ACELP
compression algorithms, or even enable ATM
voice using AAL-1 services.
As a result, several carriers are purchasing ATM
switches to provide packet-switched voice now,
with an eventual expansion to data services.
Irrelevant niches
Zannini of Avici does not believe the traditional
voice networks of long-distance carriers and
local-exchange carriers will fall apart
immediately, but he thinks they will become
irrelevant niches as more data, voice and video
traffic is carried over IP and ATM switched
networks. Avici is less bullish on ATM, he said,
because its design engineers found that when
QoS algorithms developed for ATM are
retargeted into ASICs for IP networks, the need
for ATM layers all but disappears.
Whether ATM or IP remains the protocol of
choice when WDM is added as a common
lower layer for services, Zannini said, the impact
will be profound. "We are now in a position
similar to where Intel was with the 4004
processor architecture 25 years ago," he said.
"Thanks to WDM, within three years, achieving
a terabit per second on a single fiber will become
commonplace."
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