Subject: [NEXTEL-1] The Ten Hottest Technologies

From: Marcel <[email-masked]>
Date: Tue, 06 May 2003 22:59:39 -0400

The Ten Hottest Technologies

The mantra for 2003 is making more out of what you've got, and no place is that more true
than in telecom. Gone are the days when service providers deploy the latest and greatest
just
because it is the latest and greatest. While service provider capex has been the
headline-maker the last 18 months, reducing opex has now taken center stage.

Today's capex is being spent on technologies that extend the life and abilities of
existing
equipment and in some cases, help hot technologies of days past-such as VoIP and
ADSL-live up to their previously hyped potential. These technologies must slide seamlessly

into service provider networks, interoperate with back-office systems and, above all, save

money.

This year's technology picks are all about helping service providers maximize their
existing
investments while moving forward with next-gen services. In no particular order, the 10
Hottest Technologies for 2003 are:

Session Border Controllers
Wi-Fi n Virtual Private LAN Service
ADSL2/ADSL2+
Data over SONET
RF/Fiber Extension
Inventory Management
Coarse WDM
Next-gen Mobile Switching Centers
TDM over MPLS

Session Border Controllers: VoIP's Missing Link

While VoIP has become a cost-effective mechanism for transporting long-distance
voice traffic and PRI offload, the ability to provide native VoIP peering between
networks, which requires high levels of QoS, has been all but nonexistent. Emerging
to solve this problem are SCs (session controllers), also called SBCs (session border
controllers), to provide a demarcation point between two service providers' VoIP
networks, allowing them to manage signaling and control routing for VoIP traffic.

Operating in a carrier's existing signaling infrastructure (SIP, H.323), SBCs provide
Layer 5
routing and control to manage real-time traffic flows between IP networks and address
network security, signaling interoperability, call admission control, service quality,
CALEA
and session routing. As a complement to already-deployed carrier routers, SBCs sit at the
network edge and core to control connections between enterprise and service provider. In
addition, an SBC can provide session routing and service level call admission control to
ensure QoS and enforce carrier and end-customer policies.

When it comes to VoIP peering, there are three elements: IP-to-PTSN, PSTN-to-IP and
IP-to-IP. In an IP-to-PSTN deployment, calls begin at the enterprise as VoIP and are
converted to TDM via a customer-based gateway or a media gateway within a service
provider POP. On the PSTN-to-IP configuration, a call begins at the enterprise as TDM and
then is converted in the service provider's core as IP. In an IP-to-IP configuration,
originating
VoIP calls bypass the PSTN and peer to another service provider in a pure VoIP format.
Until now, traditional premises networking devices such as NAT (network address
translation) devices and firewalls were not designed to handle real-time voice traffic,
therefore
when a call is received it would be blocked by the firewall. A key function of the SBC is
to
open a pinhole to engage in authorized real-time communications sessions.

A number of emerging start-up and incumbent vendors are moving ahead with products,
including Acme Packet, Alcatel (via its Aravox acquisition), Jasomi, Netrake, Kagoor and
NexTone. Acme Packet, Alcatel and Kagoor call their products SBCs, while NexTone and
Netrake define theirs as SCs.

So besides becoming the latest telecom acronym, what's the buzz around SBCs and SCs?
Both will continue to gain value as enterprises continue to adopt hybrid IP/PBXs from
vendors such as Cisco, Avaya and Nortel, creating those so-called VoIP islands. As a
counterattack, providers such as WorldCom, Genuity, BellSouth and Verizon have launched
their own hosted-IP telephony services such as IP Centrex and managed PBX services.

"With SCs and SBCs, you are providing that demarcation line between the customer and the
network, or between networks, and we are starting to see the players get more specific,"
said
Chris Hartman, research director for Probe Research. "Some of the elements like being able

to control how many calls are in a session are not new, but are things you have to do to
make
packet look like the existing TDM world." -Sean Buckley

Wi-Fi: Up, Up and Away

What do a fast-food restaurant, a national bookseller, a computing giant and airports
have in common? They've all jumped on the Wi-Fi bandwagon. Limited until recently
to enterprise and home networking uses (with a few failed service provider
experiments), Wi-Fi is back in the spotlight. The difference this time is the major
support it's getting from some heavy hitters, including Intel, AT&T, IBM, and a slew
of smaller players. It also has a new market: wireless LAN hot spots in your favorite
hotel, the local airport, the town square and in places like Starbucks, McDonald's and
Borders Book Stores. According to the Wi-Fi Alliance, there are 2,000 to 3,000 hot spots
in
each the United States and Europe, and around 5,000 in Asia. Thousands more are promised
by year's end.

Wi-Fi, a.k.a. 802.11, comes in a few flavors, with more on the way-a veritable alphabet
soup
of options. The most widely deployed is 802.11b, which offers 11 Mbps data rates at 2.4
GHz. The issue: shared capacity means the more users, the slower the individual
connectivity.
802.11a, which operates in the 5 GHz spectrum at 54 Mbps, was supposed to overcome
this, but hasn't seen widespread support-perhaps because vendors are waiting for 802.11g
(54 Mbps at 2.4 GHz), expected to be ratified as a standard by the IEEE this summer and be

backward-compatible with 802.11b. The good news: The Wi-Fi Alliance is trying to do away
with the letters in an effort to simplify things for users and chip makers will likely put
all three
standards on the same silicon and allow equipment vendors to choose which to activate.

The computer industry is playing a very active role. Intel, for example, has set aside
$150
million to invest in Wi-Fi start-ups, including Cometa Networks, a joint venture with AT&T

and IBM that aims to set up 20,000 hot spots. Intel has also launched its Centrino chip,
which
includes a Pentium processor and built-in Wi-Fi antenna, and has announced deals with
McDonald's and Borders. The thinking: the more ubiquitous Wi-Fi is, the more users. The
more users, the more products sold.

The burning question for Wi-Fi recently has been security. Currently equipped with WEP
(wireless equivalent privacy) security mechanisms, Wi-Fi products will soon use WPA (Wi-Fi

protected access), a specification that offers advanced data encryption and user
authentication, which was largely missing in WEP. Next up: the 802.11i standard from which

WPA is derived.

WPA should be approved by the IEEE next month; approval for 802.11i, which will be called
WPA2 and be backward-compatible with WPA, is expected by Q3. The main pieces of the
802.11i draft not included in WPA are secure IBSS (independent basic service set), secure
fast hand-off, secure de-authentication and disassociation as well as enhanced encryption
protocols.

So what's next? Many predict Wi-Fi/2.5G/3G interoperability and the advent of centralized
LAN switches for controlling multiple access points in large Wi-Fi deployments. One
thing's
for sure: Wi-Fi's future is no longer up in the air. -Sue O'Keefe

VPLS: Another Choice for VPNs

It would seem that the concept of VPN is getting more and more amorphous or
perhaps there are just more options to consider. For example, MPLS technology
enables IP VPNs and, by tunneling data services such as ATM, frame relay or
Ethernet across an MPLS network, Layer 2 VPNs. Now add yet another
MPLS-based VPN technology--VPLS (Virtual Private LAN Service)-to the
choices.

The aim of VPLS is to provide customers a secure Ethernet service that interconnects
multiple
customer sites in a way that they appear to be on a single LAN even if the locations are
geographically dispersed. And in this sense, VPLS would seem to be a TLS (Transparent
LAN Service), although this term is so broadly used because, for example, it also applies
to
stacked VLANs, where a service provider affixes an 802.1 VLAN tag to a subscriber's
802.1Q VLAN tag. To further complicate matters, the Metro Ethernet Forum uses the term
Ethernet Private LAN Service to describe a multipoint Ethernet service, but the forum
doesn't
prescribe the enabling technology.

It is here that VPLS comes in because for the IETF and the MPLS Forum, VPLS is the
underlying technology for an Ethernet Private LAN Service. Thus, in a way, the two terms
Ethernet Private LAN Service and VPLS could be used interchangeably. "From a customer
perspective, the beauty of VPLS as a service is that it would look just like a Layer 2
switch
on their campus," notes Lindsay Newell, product marketing manager for TiMetra Networks,
a Mountain View, Calif., start-up that is building an MPLS-based router.

TiMetra, along with Riverstone Networks, has co-authored a proposal for an IETF standard
for VPLS. Because it offers an Ethernet handoff to customers, Riverstone believes that
VPLS
will prove popular not only with enterprises running IP on the LAN but, unlike IP VPNs,
also
with those using other Layer 3 protocols. As an access technology, Riverstone also sees
VPLS being favored by those carriers that support MPLS in the core as well as by carriers
that prefer to run Ethernet traffic over SONET, although the latter would rob a carrier of
the
benefits of statistical multiplexing. In any event, the case for VPLS comes down to this:
To
provide a multi-point Ethernet service a carrier don't necessarily have to build an
Ethernet
network. In addition to TiMetra and Riverstone, VPLS also has the backing of heavyweights
such as Cisco, Nortel and SBC. -Sam Masud

ADSL2/ADSL2+: Anatomy of a Standard

While the advent of the original ADSL standard certainly gave copper providers a
means to provide broadband data services, physical limitations such as distance have
prevented the technology from reaching its mass-market potential. To capitalize on
existing ADSL investments, the ITU-based ADSL2 standard and its counterpart,
ADSL2+, call for a number of improvements that provide increased reach and
power as well as add-on diagnostic features. Officially completed in July 2002,
ADSL2 is comprised of two standards: G.992.3 (G.dmt.bis) full-rate and G.992.4
(G.Lite.bis) splitterless.

ADSL2 boasts a number of improvements to the existing ADSL standard including increased
rate and reach, diagnostics, power enhancements, rate adaptation and bonding for higher
data
rates. ADSL2 also features channelized VoDSL (voice over DSL) and an all-digital mode for
transmitting ADSL in voice bandwidth.

Right on the heels of the ADSL2 standard is ADSL2+. In January, the ITU reached consent
to bring the ADSL2+ standard, known as G.992.5, to the ADSL2 family. ADSL2+ gives
providers the ability to increase downstream data rates up to 24 Mbps on phone lines
reaching 3,000 feet and 20 Mbps at 5,000 feet. To resolve crosstalk issues that often
hamper
data rates between the CO and RT (remote terminal), ADSL2+ utilizes tones between 1.1
MHz and 2.2 MHz by masking sub-1.1 MHz tones.

Within the ADSL2 and ADSL2+ standard are annexes or sets of specifications for certain
applications in each world region. Specifically, each of these annexes (A-L) specifies
subcarriers or tones and their respective transmission power for upstream and downstream.
Perhaps one of the most compelling annexes is annex L, a specification that has specific
enhancements for both ADSL2 and ADSL2+. Otherwise known as Reach Extended ADSL2
(RE-ADSL2), this annex, which is expected to reach ITU consent by October, enables an
ADSL2 link to incorporate a new power spectral density mask that can enable an additional
reach between 1,000 and 2,000 feet. For ADSL2+, Annex L provides an enhanced
upstream rate in a POTS environment.

As a testament to bringing ADSL2 to market, earlier this month seven silicon vendors
(Analog
Devices, Aware, Broadcom, Centillium, Infineon, Samsung Electronics and Texas
Instruments) gathered at University of New Hampshire's Interoperability Laboratory to
participate in the DSL Forum's ADSL2 "plugfest" interoperability event. Based on the DSL
Forum's internal proposed Draft 013 Interoperability Test Plan for ADSL2 plugfests, PD-013

provides a suite of basic PHY layer tests to ensure interoperability between multiple
ADSL2-based chips and systems. In May 2002, the ITU incorporated the DSL Forum's
TR-048 specification into the ADSL2 G.992.3 and G.992.4 standard recommendations.

Along with the silicon vendors, DLC/DSLAM vendors such as Alcatel, UTStarcom, Lucent,
Calix, Net to Net, XAVI and Next Level claim to be ready to integrate ADSL2/ADSL2+
elements as silicon becomes available. More importantly, as carriers migrate to ADSL2 and
ADSL2+ as demand dictates, they won't need a forklift upgrade.

For operators like Bell Canada, the fact that ADSL2 and ADSL2+ systems are
backward-compatible with their existing base is key. "As new equipment comes in we will
adapt to ADSL2. However, we still have 1 million-plus embedded ADSL modems so we're
not sure when we will have a critical mass to turn on the ADSL2 features," said Jean
Huppé,
Bell Canada's director of access technology. "For ADSL2+, a similar thing will happen as
we
will eventually buy new cards and modems that will be ADSL2+ ready. In our case, if we go
with VDSL, which may cover 80 percent to 90 percent of the population, I see ADSL2+ as
complementary to the remaining 10 percent to 20 percent." -Sean Buckley

Data over SONET: The Next Generation

Nearly half a decade ago, Cerent (which was acquired by Cisco) pioneered a new
type of network equipment. And while Cerent quite possibly never used the term
MSPP (multi-service provisioning platform) to describe its box, that is now the
popular label that's used to describe next-gen SONET products from a number of
other vendors including Alcatel, Fujitsu and Nortel. Broadly speaking, these devices
combine ADMs (add-drop multiplexers) that support multiple SONET rings
operating at different speeds with a cross-connect capability.

Now vendors are bringing to market a new generation of SONET-based products (Does the
label next, next-gen SONET sound right here?) designed to ensure that the vast, embedded
SONET infrastructure can be evolved to handle all sorts of data services. So we'll admit
to
coining a term by picking Data-over-SONET as a hot technology that encompasses a handful
of techniques that would make SONET a more flexible technology for transporting and
switching data traffic.

Platforms from established vendors such as Tellabs (via its acquisition of Ocular
Networks) as
well as start-ups such as Polaris Networks and Turin Networks have taken the lead to
implement some or all of the standards, or emerging standards, that enable better use of
SONET bandwidth for data services. One of the techniques these platforms support is VCat
(virtual concatenation), which, more simply put, enables the gluing together of several
STS-1
or VT1.5 pipes so there is minimum wastage of a SONET network's bandwidth. For
example, this enables two GigE links to be carried inside an OC-48 channel and still leave
six
STS-1s available for other traffic, as opposed to taking up an entire OC-48. Or, to use
another example, a 10-Mbps Ethernet link could be transported inside seven VT1.5s.
Perhaps what sets these new platforms apart from earlier MSPPs is the ability to
transport,
switch and groom (the latter ensures that trunks between any two points are filled to
capacity)
traffic at the more granular VT1.5 level instead of just at the STS level.

A new feature that makes VCat even more effective is LCAS (link capacity adjustment
scheme). LCAS enables a network operator to right-size-either up or down in bandwidth-on
the fly by, for example, adding another VT1.5 if the traffic demands without disrupting
traffic.
While almost all of the new transport switches have the VT1.5 cross-connect and grooming
capability, the LCAS feature is something that many only now are in the process of
incorporating. Both VCat and LCAS are being driven by GFP (generic framing procedure),
which, like its ANSI equivalent X.86, is a method for mapping data services to SONET.
Although the initial impetus for GFP was for transporting Ethernet over SONET networks,
GPF can also be used for other data services such as Ficon, Escon, Fibre Channel and even
extended ATM and frame relay. Thus in addition to making use of the existing
infrastructure,
Data-over-SONET also leverages carriers' investment in Telcordia OSSs. -Sam Masud

RF Distribution: Maintaining the Connection

How many times has a wireless call dropped when you enter a shopping mall, tunnel
or office building? With the onset of data and business applications, the ability to
provide seamless coverage is essential. Acquiring additional spectrum and building
new base stations can be difficult and expensive, so carriers need more effective
methods to handle this problem. One answer could be the advent of in-building and
wide area RF distribution solutions, which transmit RF signals over Cat 5, coax or
optical fiber.

As its name implies, the RF/Fiber distribution approach takes RF signals and converts them

into optical signals and back to transmit to remote antenna units within a building or a
remote
location in the wide area. In an in-building application, fiber or coax would be run
through the
riser and delivered via distributed antennas. Vendors in this space all have a slightly
different
take on this. For example, ADC's Digivance transmits signals in an all-digital format from

within and between buildings over multimode fiber or single mode fiber utilizing DWDM.
Andrew's InCell system is an analog-based, single mode fiber optical distributed antenna
system that works both in conjunction with an operator's base station or can serve as a
complement to off-air repeaters to provide coverage in buildings or airports.

Not everyone is following the RF/Fiber approach, however, other vendors have opted for
either a passive coax distributed antenna system (InnerWireless, Spotwave and Andrew's
passive DAS) Cat 5-only (Radio Frame) or a hybrid Cat 5/6, multimode fiber (LGC
Wireless).

Hand in hand with in-building is wide area RF/fiber distribution where signals are
converted to
an optical signal over long distances and back to RF at a remote location. Andrew's
EOCell,
newcomer Celerica's 500 System, LGC's MetroCell and ADC's LRCS (Long Range
Coverage Solution) can help enhance wide area coverage and capacity in areas such as
tunnels and highways. Another important application is base station hoteling, where a
carrier
can centralize base station equipment and deploy antennas into the necessary coverage
areas.
To bolster wide-area links, ADC, for example, has partnered with FSO (free space optics)
vendors such as fSONA and LightPointe to enable a carrier to create connections where
fiber
is limited. Celerica, which has also incorporated FSO into its system, says it can be used
to
extend links between base stations and antennas. -Sean Buckley

Inventory Management: A Real-world View

Service Provider A is a Tier 2 carrier in Chapter 11 bankruptcy. Service Provider B
is a stable international carrier rolling out a host of new services. What do they have
in common? They both need to know what physical and logical assets they have and
how to use them to the best of their abilities. Although it seems ironic that a bankrupt
carrier would want to spend more money, to successfully emerge from bankruptcy it
needs to get a better grip on its complete asset inventory to determine what is worth
keeping and what is not. "Bankrupt companies are telling us that their No. 1 priority is
finding
out what they have and where it is," says Mark Mortensen, chief marketing officer at
Granite
Systems.

Coined NRM (network resource management) by analyst group RHK, inventory
management has moved to a whole new level. It's no secret: service providers' back offices

are a mess; different departments within a service provider keep records in different
ways, so
engineering's view of the network isn't the same as billing's and finance's isn't the same
as
customer care's. The new breed of NRM systems track and maintain information, eliminating
the need for duplicate data entry, and track more carefully the impact of changes in the
network. "It's not just tracking assets, it's understanding when a problem is reported
where
the problem is and who it affects," says Larry Goldman, program director for RHK's OSS
program. "It's when your customers ask for a service, knowing what's available to provide
that service. It's knowing where to put more equipment to meet demand."

One huge piece of NRM coming into focus is auto discovery, or finding out about network
equipment whose existence was previously unknown and determining what connections and
services are running in the network. While most IP, ATM and frame relay equipment can be
auto-discovered, most DWDM and SONET/SDH equipment can't, because inventory
systems need address information to find the node or a gateway node. "Auto discovery is
very, very hard," Goldman says. "You can't discover everything, but what you can discover
can be very valuable." Newer, more intelligent network elements have a lot more ability to
be
discovered, he says.

The hardest part in getting the NRM market off the ground may be a service provider's
internal struggles among departments and, once those are settled, understanding that the
best
solutions may not be built internally. Goldman points to Sprint and Level 3 as examples of

providers that have made early moves to get their NRM under control. He says others will
follow; indeed, RHK predicts that by 2005, providers will spend $1.3 billion on NRM
solutions. Leading the way for vendors are a host of smaller companies, including Granite
Systems, Cramer Systems, MetaSolv, Micromuse and CoManage, while most of the larger
vendors have opted for an OEM route. -Sue O'Keefe

CWDM: A Metro Dream?

We'll admit we glossed over CWDM (coarse WDM) technology when it started to
make an appearance three years ago. But in the red-hot telecom market of the time,
attention was focused on DWDM systems that could shoot lots of colors of light
over increasingly long distances. The expectation was that systems that supported
2.5-Gbps channels would soon give way to gear delivering 10-Gbps
wavelengths-and the race was on to build systems which could provide 40-Gbps
channels. But that was then, and in the new reality of today CWDM technology might be the
appropriate counterpoint-and even a complementary technology-to DWDM in the metro
network.

Although deployment of CWDM remains thin, the technology promises to provide bandwidth
at a price point that is well below that for metro DWDM equipment, something that should
appeal to carriers keeping tight control of their capex.

While a Yugo-vs.-Lexus comparison would be unfair, the simple facts are that CWDM
systems are cheaper because they use cheaper lasers that don't have to tightly control the
light
and because they're intended to operate over shorter distances (typically 40 km to 80 km).

The downside-which, in fact, is really their value proposition-is that they provide from
two to
16 wavelengths at prices that won't break the bank.

Like their metro DWDM counterpart, CWDM systems from different vendors might be
designed to support point-to-point, linear add/drop, ring and mesh topologies. Likewise,
some systems may provide only 2.5 Gbps channels, while some other systems, such as those
from Germany-based Microsens and Meriton Networks, an Ottawa start-up that integrates
transmission and switching in a single platform, offer a hybrid solution that supports
both 2.5-
and 10-Gbps wavelengths. In addition to these two vendors, CWDM gear today is available
from a number of established vendors including Advanced Fibre Communications, Ciena,
LuxN and Nortel, with Tellabs promising a CWDM solution late this year.

Although built for the access network, depending upon their capacity/distance
requirements,
some carriers might choose to deploy CWDM in the metro core. The big benefit of CWDM
is that it offers a low-cost way for carriers to meet the transport needs of enterprise
customers
by supporting multiple protocols on the same fiber.

And this exactly is what Progress Telecom did when earlier this year it announced that had

begun delivering a wavelength service to Blue Cross and Blue Shield of North Carolina.
Although Progress Telecom is largely a carrier's carrier operating its own fiber network
from
Miami to New York, it's using Ciena's metro DWDM gear to support Blue Cross and Blue
Shield of North Carolina's GigE and Fibre Channel connectivity needs between various sites

in the Raleigh-Durham area. But Progress is also in the process of installing Ciena's CWDM

system as an economical way to deliver wavelength services at the very edge of the
network.

While the established carriers haven't rolled out CWDM gear as aggressively as vendors
might have hoped, some say that they'll give the CWDM market a boost when they see
carriers such as Progress Telecom lighting up fiber for customers. Meanwhile, Progress
Telecom notes that the economics of CWDM might give it reason to look beyond its carrier
customers to the large enterprise market. -Sam Masud

Next-Gen MSCs: Wireless Takes IP Baby Steps

Like the wireline network, the wireless network's journey to packet will not take
place overnight. A key enabler of this migration will be the advent of the next-gen
MSC (mobile switching center), which also promises opex savings. Similar to the
wireline world, where carriers have utilized next-gen Class 4 switches to offload
Internet data and trunking applications onto low-cost VoIP links, such a model
appears to be gaining traction in the wireless world as well.

Taking on this opportunity is a host of start-up and existing vendors, all of which come
from
different angles. On one hand, Winphoria purpose-built its WMS-5000 platform to leverage a

disaggregated architecture that separates bearer and control functions. Meanwhile,
Santera,
Sonus, Tekelec and Telica have added new functionalities to their existing softswitch
platforms
to support wireless applications. Applying the knowledge it has gained in the Class 4 VoIP

market, Sonus recently launched its SMARRT wireless solution that leverage its existing
Insignus softswitch and GSX switch. In a similar manner, Telica now offers a suite of
wireless
applications on its existing Plexus 9000 switch, while Santera's broadband office exchange

provides both tandem and wireless access to the PSTN. Spatial Wireless' distributed MSC
Atrium integrates its call server and element management system with Santera's Media
Gateway.

But this is not a total start-up play; Ericsson, Lucent and RAD Data Communications have
their own platforms. RAD recently launched its Vmux-2100 Voice Trunking Gateway, a
compact compressed voice solution for MSC-to-MSC interconnectivity. Lucent, which owns
a large part of the wireless market, has its own wireless softswitch. Since most wireless
operators are preoccupied with their various air interface migrations, the adoption of an
all
IP-based wireless network is not the first thing on their minds. Nonetheless, there are
practical
applications such as wireless gateway MSCs for transit/tandem, wireless backhaul and long
distance in current 2G and 2.5G networks. Along with opex savings, a next-gen MSC gives
operators a chance to offer new IP-based services.

With the traditional inter-MSC connections tying up legacy ports and reliance on PSTN
interconnections, a wireless gateway MSC can save an operator's roaming costs by routing
PSTN calls directly to the mobile subscriber's serving MSC without touching the home MSC.

As a regional wireless transit switch, the MSC allows carriers to break their reliance on
multiple inter-machine trunks while reducing MSC routing translations. On the
long-distance
side, a carrier can bypass TDM facilities by offloading long-distance traffic onto its own
IP
network. Finally, when providers are ready, platforms can move with emerging 3GPP release
5 where voice calls are converted into IP.

"Right now, it's a 'taking baby steps' approach for operators," said Peter Jarich, senior
analyst
for wireless infrastructure at Current Analysis. "If you look at the latest vendor
offerings, the
focus is really on opex with the notion that somewhere down the road we are providing some

great tools to move to next-gen MSCs and IP. But right now the focus is on saving money in

terms of backhaul and transport." -Sean Buckley

TDM over MPLS: A Tale of Two Camps

There's a strong push to make MPLS the converged network that supports all kinds
of Layer 2 services as well as provides IP VPNs. The Martini draft, which the
industry has embraced, already defines a way to tunnel frame relay, ATM, Ethernet,
PPP and HDLC services across an MPLS network. Now there's an effort underway
to come up with a standard for running TDM services over MPLS.

Although the lead for this in the IETF has been taken up by Andrew Malis, president and
chairman of the MPLS Forum as well as chief technologist for start-up Vivace Networks, a
number of industry players including Corrigent Systems, Laurel Networks and Lucent are
also
behind the effort. Strictly speaking, the proposed standard doesn't specify supporting TDM

services over MPLS; rather it says that the circuit emulation could be done over a variety
of
packet-switched networks.

There are, moreover, two sometimes-overlapping camps behind this concept. While the Malis
Draft talks about doing SONET emulation over packet networks, there's a parallel effort
for
supporting low-speed services, specifically DS3s and DS1s, across packet networks.

For instance, Corrigent and IC vendor Litchfield Communications back both efforts.
However, the proposed SONET-over-packet standard does not exclude running
lower-speed services over a packet/MPLS network per se because the VT1.5 channels
inside an STS-1 frame could be carrying DS1 signals. Corrigent, which makes a packet
ADM that supports the transport of SONET (as well as Ethernet) traffic across an
MPLS-over-RPR network, notes that SONET-over-packet also would provide carriers a
cross-connect capability at no additional cost by enabling the routing of STS-1s to their
destination.

Of the two efforts, circuit emulation of SONET over packet-switched networks is expected
to become an IETF standard sooner-mostly likely by year's end-than the effort for
supporting
low-speed services over packet networks. Indeed, it's quite possible that there may be
more
than one RFC for the lower-speed services. The work on these specs is being done in the
IETF's PWE3 (pseudo-wire edge-to-edge emulation) working group, which is the same
group under whose aegis the Martini Draft for Layer 2 VPNs was developed. -Sam Masud

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