Most telecommunications players may be skeptical about
whether routers can deliver toll-quality voice services in IP format, but a growing list
of providers inside and outside of cable think they can.
British Telecommunications plc has contracted with Nortel
Networks to supply a national Internet-protocol telephony and data communications system
in Spain, starting with service launches over 12 metro regional nodes in the first quarter
of next year.
Almost as ambitious, Canada's Le Groupe Vidéotron Ltée is
deploying a router-based system supplied by Cisco Systems Inc. to support IP-voice
services across 2.1 million households in Quebec next year. That effort starts with a
2,000-home trial in the quarter ahead.
Those operators are pursuing different network-architecture
strategies with variations in voice-provisioning and call-control systems. But they share
a reliance on new routers that use the same protocol base to deliver service quality on a
par with that of switched-voice circuits.
The new router design taps the benefits of two protocols --
"Differentiated Services" (Diff-Serve) and "Multi-Protocol Label
Switching" (MPLS) -- assuring that different systems will eventually interoperate
after suppliers upgrade software to final specifications.
These emerging standards are stable enough that Nortel can
implement much of the Diff-Serve and MPLS processing in microprogrammable ASICs
(application-specific integrated circuits), eliminating delays and jitter caused by
extensive processing in software, said Ed Jasho, group manager for IP infrastructure at
Mark Bakies, manager of voice solutions for Cisco's
cable-business unit, made it clear that there was an important role for MPLS and
Diff-Serve in the cable model.
"DOCSIS [Data Over Cable Service Interface
Specification] only takes care of that part of the IP network that operates across the HFC
[hybrid fiber-coaxial] plant, which means that you have to have a means of setting
precedents for bits and controlling traffic flows at the metropolitan level and in the
interface with backbone networks," Bakies said.
"Our 'Versalar' edge and core routers have been
developed specifically for the carrier networks to provide redundancy in hardware and the
other requirements that are needed to deliver 'five-9s' [99.999 percent] reliability in an
IP-only environment," Jasho said. "By moving most of the IP-forwarding
capabilities into ASICs, we've reduced latency to 100 microseconds or less, compared with
the few milliseconds that has been the industry norm."
Diff-Serve and MPLS are linchpins to service quality in IP
routing. Diff-Serve identifies traffic flows. MPLS is applied on a systemswide basis,
using labels assigned at layer three to create "label-switched paths," which
gives carriers a way to maximize efficiency across the network along assigned priorities.
BT has no doubt that it can take on established carriers
using the all-IP approach, European director Pat Gallagher said. "The new network
will enable BT to adapt rapidly to future developments and offer new services more quickly
and economically than in-country competitors, and it will ensure that our Spanish
customers receive the most advanced communications in the world," he added.
Initially, BT will offer residential and business customers
a range of advanced IP-telephony services, including direct and indirect dial facilities
and virtual-private-network applications. From there, BT will extend its service range
into value-added and other new multimedia services, Gallagher said.
The 12 nodes to be activated in the start-up phase will
extend network reach to several million potential customers, he added.
Confidence in IP-based infrastructure runs against the
grain of a growing list of players pursuing packetization of voice services in the year
ahead, including MSOs AT&T Broadband & Internet Services, MediaOne Group Inc. and
Cox Communications Inc., which are pursuing proprietary "constant-bit-rate"
Other carriers tapping digital-subscriber-line platforms
are turning to multiline voice-over-ATM (asynchronous transfer mode). Sprint Corp., for
example, is moving to VoATM for its ION (Interactive On-Demand Network) service rollouts
next year after an initial foray into voice-over-IP, figuring that IP service quality
won't match that of ATM for another year or two.
"MPLS begins to emulate the connection-oriented world,
but IP isn't there yet," Sprint director of advanced-technology development Ed
Thurman said. "As IP takes on the functionalities of ATM, we'll be in a position to
As ION's lead vendor, Cisco sees the question of whether or
not IP routing is ready to support voice as more a matter of who's asking the question,
product manager for xDSL marketing David Lively said.
"IP also has the [service-quality] mechanisms to
support voice," he said. "It's just a different way of thinking than ATM, and
not everyone is ready to take that step."
Lively added: "The demand for voice transport directly
over ATM is driven mostly by efficiency and carrier comfort level. For many of the new
CLECs [competitive local-exchange carriers] that want to offer local voice services over
DSL, they see ATM as the easy route."
But, he warned, "The efficiency of ATM today comes at
a price. Voice transport over ATM is limited to the WAN [wide-area network], and it does
not integrate as well as VoIP with IP phones, network-based PBXs [private branch
exchanges], unified messaging and many other IP-based voice services that we haven't even
Bakies noted that cable has less need to worry about router
support, insofar as the capabilities provided by Diff-Serve and MPLS outside of the cable
"cloud" are handled effectively by the specifications established for
PacketCable, which include features of version 1.1 of DOCSIS. "The way we're doing
[service quality] in the Vidéotron network is an enhancement to DOCSIS 1.0," he
Helping the router-based telephony cause is the emergence
of terabit routers, which are designed to aggregate all forms of IP traffic across the
backbone at speeds high enough to allow carriers to fully exploit the carrying capacity of
"IP voice isn't a volume-traffic factor driving
terabit router deployments," Avici Systems Inc. vice president of product management
Peter Chadwick said. "But deployment of terabit routers will provide carriers with an
opportunity to add IP-voice traffic at practically no cost, which has important
implications for making IP telephony a competitive force in the local telecommunications
Avici is supplying terabit routers for testing by various
carriers -- including MCI WorldCom Inc., Deutsche Telekom A.G. and GST Telecommunications
Inc. -- with plans to begin delivering product for commercial deployment in the second
The system is designed to scale from single modules
operating at 2.5 gigabits per second to an array of multiple modules seamlessly
interconnected to deliver aggregate throughput of up to 5.6 terabits per second.
Terabit routing will also play a fundamental role in
expanding the efficiency of the cable industry's play in IP telephony, noted Dee Dee Nye,
vice president of the cable-communications group at Lucent Technologies, which is
supplying IP-voice equipment for a trial by Comcast Corp. in Union, N.J.
Once the "zone-to-zone" specifications for cable
IP telephony are established in version 1.1 of the PacketCable standard, due in March,
cable companies will be able to interconnect IP-voice services directly across IP
backbones, avoiding the intervening steps of converting signals to ATM or switched-circuit
formats, she added.
"We see a big role in IP telephony for the terabit
routers we'll be bringing to market through Nexabit [Networks]," Nye said. "Our
customers believe the ability to operate end-to-end in IP across each other's networks
will give them a significant advantage over their competitors."