Packet-Optical Integration: The Key to Evolving Towards Packet Enabled Agile Optical Networkds

Packet-Optical Integration: The Key to Evolving
Towards Packet-Enabled Agile Optical Networks

Vishal Sharma, Ph.D., Principal Technologist & Consultant, Metanoia, Inc., Mountain
View, CA 94041, USA. vsharma@metanoia-inc.com

Mark Allen, Ph.D., Director of Systems Engineering, Infinera Corporation, 169 Java
Drive, Sunnyvale, CA 94089, USA. mark.allen@infinera.com

Table of Contents

1 Introduction: The Carrier Cost-Capacity Crunch!.......................................................... 2

2 Major Solution Drivers: What is the Impetus? ................................................................ 2

3 Defining Characteristics of a Packet-Optical Solution ................................................... 4

4 Three Key Areas of Advancement: Photonic Sub-Systems, Systems, and Software ........ 4
4.1 ROADMs: Reconfigurable, Agile, and Gridless, & PICs......................................... 4
4.2 Packet-Optical Transport Systems (The New P-OTS!) -- Requirements,
Architectures and Trade-Offs .......................................................................................... 6
4.3 Photonic Control-Plane Software: Advances and Challenges.................................. 7

5 Open Issues and Carrier Concerns.................................................................................. 8

6 References ........................................................................................................................ 9

A Metanoia, Inc. Technology Paper Page 1 of 10

Metanoia, Inc., 888 Villa Street, Suite 500, Mountain View, CA 94041, USA. http://www.metanoia-inc.com
© 2011 Metanoia, Inc.

1 Introduction: The Carrier Cost-Capacity Crunch!
The operator's paradox, for the past several years now, has been that while there is an
explosion in data traffic volumes to the tune of 45-65% yearly, the corresponding revenue
growth is in the single digits at best. To bridge this gap between rising operating costs
(spurred by increased network capacity demands) and relatively flat revenues, providers
must assess how to better architect their networks -- from routers/switches to the optical
layer -- to reduce the transport-cost per bit, to conserve space and power, and to improve
network performance so as to lower the opex. (Indeed, statistics show that service
providers spend almost 5 opex dollars for each capex dollar! [1]). Furthermore, they must
optimize their networks to efficiently carry high growth services like Internet access,
packet traffic from 3G/4G mobile wireless networks, and video.
Achieving this efficiency entails a tighter integration between the packet and the
optical/photonic layers, since the photonic layer is the cheapest per-bit, per function, thus
motivating the packet-optical integration, we discuss in this paper.
We start by examining the defining characteristics of a packet-optical solution, and the
major solution drivers, and then focus on the architecture of 3 key components of the
solution -- wavelength transport and switching infrastructure, systems and ASICs, and
control- and management-plane software. Having discussed these, we outline some open
issues and key carrier concerns.

2 Major Solution Drivers: What is the Impetus?
Technological advances (such as cloud computing, remote diagnostics, multimedia
collaboration), bandwidth intensive applications (such as video services with HD, Carrier
Ethernet enterprise services, and remote data backup and disaster recovery), and fast
connection speeds (which, per Nielsen's Law (cf. Figure 1), double every 21 months) lead
today to a proliferation of data packets and drive the demand for a better networking
solution.
In addition, some key enterprise trends contribute to this traffic. For instance, almost 95%
of enterprise traffic is now Ethernet-based. Indeed, business Ethernet port demand was up
43% in 2008 alone. Further, almost 80% of traffic now leaves the enterprise (the reverse
of what it was just a little over a decade ago) implying a much greater load in the metro
and core [2].



Figure 1 Neilsen’s Law of Internet Bandwidth: Predicted in 1998, shown
accurate and consistent for over a decade (From Jakob Neilsen’s Alertbox
http://www.useit.com/alertbox/980405.html )
Thus, a key impetus for carriers is to increase the effectiveness and efficiency of
transporting these packets over an optical transport network in the WAN environment.
Today, the IP/Ethernet packets are wrapped into SONET/SDH or G.709 TDM circuits,
and transported over wavelengths on an optical infrastructure. One disadvantage of this is
that when all switching occurs in a Layer 3 router/switch rather than judiciously
leveraging Layer 2 Ethernet or Layer “2.5” MPLS switching, the cost of the network
begins to increase. Consequently, control layer mechanisms, such as Multi-Protocol
Label Switching-Transport Profile, MPLS-TP (e.g. RFCs 5654, 5317, 5718, 5860; [3]),
or Provider-Backbone Bridging-Traffic Engineering, PBB-TE (IEEE 802.1Qay standard),
are becoming important. Plus, the transport of IP/Ethernet over optical infrastructure is
moving to sending native IP/Ethernet over wavelengths via WDM, which requires newer
packet-optical solutions.
The particular solution adopted will be dictated by a number of factors. For example, the
balance between the extent of connection-oriented (TDM) traffic and pure datagram
traffic, the existing capital investment in SONET/SDH ADMs, ROADMs, switches and
routers, the degree of equipment consolidation needed/desired to reduce opex, desire to
use the wavelengths better, the OAMP&T (operations, administration, maintenance,
performance and troubleshooting) provided by the deployed technologies, and whether
IP/MPLS expertise and transport expertise resides in a common team or in different parts
of the providers’ organization.



3 Defining Characteristics of a Packet-Optical Solution
So what are the key ingredients being looked upon by operators in a packet-optical
solution? It turns out that the following 4 elements are becoming table stakes:
i) Reconfigurable Optical Add/Drop Multiplexer (ROADM) infrastructure with support
for routing wavelengths at multi-degree junctions, as well as the simpler two degree
nodes [4].
ii) The ability to efficiently carry existing SONET/SDH services without compromising
support for high-growth packet and OTN traffic (see Optical Transport Network – ITU-T
G.709 for more discussion on OTN standards).
iii) Connection-oriented Layer 2 Ethernet switching and aggregation (for an exposition of
Optical Ethernet, consult our article in the Feb. 2010 issue of Photonic Tech. Briefs,
http://www.techbriefs.com/component/content/article/7146).
iv) Carrier-grade OAM -- merging what exists in the optical domain with what exists in
the packet domain to give an operator a comprehensive overall view of the network.
Thus, there is emerging a general industry consensus on the requirements of a Packet-
Optical Transport System (POTS). However, the jury is still out on how such a system is
finally realized, as we explain when discussing POTS in the section ahead.

4 Three Key Areas of Advancement: Photonic Sub-Systems, Systems, and
Software
The development of packet-optical solutions has involved advancements in 3 key areas:
wavelength-transport and switching infrastructure, systems and ASICs (such as Packet-
Optical Transport Systems), and control and management plane software for control
plane automation and management. In the following, we consider each of this one-by-
one.

4.1 ROADMs: Reconfigurable, Agile, and Gridless, & PICs
In this subsection, we focus on ROADMs and PICs, two key components of the
wavelength transport infrastructure.
Reconfigurable Optical Add-Drop Multiplexers (ROADMs) have played a key role in
moving the transport network toward greater agility/flexibility, by reducing the manual
intervention needed to setup new lightpaths. As a data point, as per Infonetics Research’s
ROADM Component tracking report, ROADM-based optical network revenue was the
fastest growing in the last couple years, with a 46% CAGR between 2005 and 2009,
while in the same period the overall optical equipment revenue grew only at 8% CAGR.
A ROADM is composed of a number of sub-systems such as a Wavelength Selective
Switches (WSSs), optical amplifiers, optical channel monitors, transponders, and control



and management software. A ROADM eliminates costly optical-to-electrical conversions
at intermediate nodes, by allowing wavelengths to pass intermediate nodes in the optical
domain.

Figure 2 Conceptual Operation of a Wavelength Selective Switch
First generation ROADM's allowed a lightpath's direction to be changed, while it's
wavelength remained fixed. They were typically 2-dimensional nodes, that enabled ring
architectures. Subsequent ROADMs had higher degrees, of between 4-8, allowing for
mesh architectures.
Second generation ROADM's used tunable lasers and wavelength selective switches
(WSSs), thus, allowing both the direction and the wavelength of a lightpath to be
changed. WSS modules are the building blocks for ROADMs that can handle any
wavelength on any port (and so are known as 'colorless') and can connect signals flowing
in any direction on any port to any other port (hence 'directionless').
The next-generation of ROADMs will be gridless and contentionless. A contentionless
ROADM allows multiple copies of a given wavelength (coming from different
directions) to be dropped at a node, while a gridless ROADM has the capability to
accommodate wavelengths that do not fit on the ITU 50 GHz or 100 GHz grid, but will
utilize a flexgrid with a less rigid channel spacing (where some or all of the channels
could use more than the standard 50GHz bandwidth). This allows for variable channel
widths, enables operators to efficiently use spectrum to maximize fiber capacity. They
will also incorporate fast switching speeds to decrease latency, and superior optical
channel monitoring at the ROADM ports to better regulate signal power.
Photonic Integrated Circuits (PICs) have shown to be very effective in reducing the cost
(both Opex and Capex) of the DWDM systems deployed by operators [5]. For example,
Infinera’s PIC based transport system is the #1 most widely deployed DWDM system in
North America and includes a PIC-based Line Module with more than 100 optical
components (lasers, modulators, wavelength lockers, etc) integrated on a single
monolithic Indium Phosphide chip of approximately 5mm square. Next generation PICs



are now under development to incorporate more complex modulation schemes such as
QPSK and QAM, which are required to achieve 100Gbps per wavelength and higher and
achieve aggregate capacities of 500Gbps or 1Tbps per PIC, and more than 10Tbps per
fiber over long-haul networks.

4.2 Packet-Optical Transport Systems (The New P-OTS!) -- Requirements,
Architectures and Trade-Offs
Packet-optical transport systems/platforms (P-OTS or P-OTP) are a new class of
networking platforms that combine the functions and features of SONET/SDH/OTN
ADMs or cross-connects, Ethernet switching and aggregation systems, and
WDM/ROADM transport systems into either a single network element or a small set of
network elements.
The goal of a Packet-Optical Transport System is to combine the best features of all of
the legacy technologies – such as SONET/SDH, IP, ATM, and Ethernet. As a result, the
requirements can be thought of as drawing upon the features of each technology in the
following way:
i) From SONET/SDH: Resilience -- 50 ms recovery, path provisioning, and OAM (very
important for the operator)
ii) From ATM – Sophisticated Traffic Management and QoS as in ATM, including
traffic engineering and guaranteed QoS.
iii) From IP/Ethernet -- Very high efficiency from statistical multiplexing of
packets/frames, and packet-flow control that are key for multimedia traffic.
iv) Flexible grooming or the ability to efficiently map a rich service mix onto the
underlying transport layer by switching at the wavelength (lambda) level, sub-wavelength
(ODU) level, port (TDM or SONET/SDH) level, and sub-port/packet (Ethernet, MPLS)
level.
P-OTS architectures may be divided into three broad types:
i) IP-over-Glass or Layer 3 routers with integrated transponders connected to a DWDM
system. These rely on the router to perform the switching function and eliminate O-E-O
interfaces. Also, network architecture is simplified by eliminating SONET/SDH, thus
reducing Capex and Opex. Understandably, many carriers are cautious about this
approach because it burdens the Layer 3 IP routers with the additional responsibilities of
monitoring and managing an agile wavelength infrastructure – functions normally
performed by DWDM systems.
ii) Carrier Ethernet Switch Routers with Connection-Oriented Ethernet (COE;
controlled using PBB-TE or MPLS-TP) plus a DWDM layer. The goal here is to leverage



the low cost points of Ethernet, while getting the advantage of its traffic management and
traffic engineering capabilities.
iii) Packet-Optical devices combining SONET/SDH and IP/Ethernet
switching/aggregation with DWDM transport. They emphasize a modular architecture,
where sub-wavelength multiplexing and packet switching are done and traffic is groomed
onto DWDM transport. These systems permit router bypass of non-IP traffic (e.g. L2
traffic, TDM traffic, and transit traffic), and minimize wavelength requirements by
integrating SONET/SDH, MPLS, and OTN switching onto a single system.
The best alternative will depend on the existing and projected traffic mix (TDM to packet
balance in the operator's network), existing capital investment in network assets
(SONET/SDH ADMs, ROADMs, switches/routers), need for efficient utilization of
optical resources (wavelengths), and the carrier's operations model (i.e., whether the
IP/MPLS and transport teams are separate or common).
Packet Optical Transport System
Architectures

Optical devices combining CESRs (Carrier-Ethernet Switch Layer 3 Routers with
-- SONET/SDH Routers) with COE integrated transponders
-- Ethernet swtiching/aggregation Combined with a separate WDM (IPoDWDM)
-- WDM transport layer E.g. Cisco CRS-1, GSR 12000,
E.g. Fujitsu Flashwave 9500 E.g. Tellabs 8800, Juniper 960 MX Juniper T-Series

Figure 3 Packet-Optical Transport Systems (P-OTS): Architectures in use
today

4.3 Photonic Control-Plane Software: Advances and Challenges
The data plane, comprising flexible ROADMs and packet-optical transport systems, must
be complemented by a highly integrated management and control plane that spans the
packet, TDM, and optical domains. This control plane software is critical for future agile
optical networks, and is largely lacking in today's networks.
The control plane, which uses routing and signaling to setup the connections between
nodes, coupled with an efficient management plane is essential to orchestrate the
operations of the data plane.
Developments in the control plane are occurring within the IETF, which has developed
the GMPLS control plane that is now being refined to include wavelength switched
optical network (WSON) requirements. This will allow the control plane to have
simplified knowledge of the optical parameters (such as chromatic dispersion and
polarization mode dispersion) and simple rules that can be used to decide whether an
optical path is adequate or requires signal regeneration.



The ITU-T has developed control plane requirements and architecture, under the
umbrella of ASON (Automatically Switched Optical Networks). The GMPLS/ASON
control plane comprises a common part and a technology-specific part to include
technologies such as SONET/SDH, OTN, wavelengths, and MPLS-TP.By combining
electrical and optical switching and an integrated control plane, the operators will be able
to continually optimize their networks, and devolve them to the lowest-cost and most
power-efficient solutions. This approach can provide lowest TCO, the flexibility to adapt
to any service mix, and provide carrier-class performance across the network.
The User-to-Network Interface (UNI) and the External Network- to-Network Interface
(E-NNI) implementations, based on the ITU-T, OIF and MEF standards could prove
very useful for carriers. The UNI standards should enable operators to have packet
switching devices that can signal the agile optical network, and request wavelength
services for certain duration over a specific path and with a defined level of protection.
E-NNI implementations will enable Wavelength Networks to share topology and
availability information in a way to facilitate service deployment across multi-vendor
(and possibly even multi-carrier networks) in an end-to-end manner. The (OIF) is one
body focused on facilitating trials and agreements in this area.

5 Open Issues and Carrier Concerns
Even as advancements in packet-optical integration continue to be made, challenges
remain before a fully agile optical network is a reality.
An important consideration is providing the control plane with knowledge of the optical
impairments, and enabling routing transparently between vendors. This is because it is
very difficult to identify all the optical parameters in a compact way to be used in an
inter-vendor setting. Another challenge is inter-layer management, both across the
different layers (optical, TDM, and packets) and across diverse vendor gear.
Similarly, handling increasing customer application rates, say 1, 10 or 40 Gb/s on 100
Gb/s infrastructure, will require the use of OTN (G.709) multiplexing and electrical
switching, plus control plane support.
Other important operator concerns include network management costs, which are
significant. Thus, advanced management software that integrates with operator OSS/BSS
systems is key. Some operators, such as BT, have deployed dedicated devices for
surveillance and diagnostics, and have developed SDK’s or API’s that enable new
equipment to “speak” to any component of their OSS systems, and simplifies software
development that occurs as a result of introduction of new hardware platforms. In
addition to investing in significant in-house OSS development efforts, operators,
including Verizon, AT&T and Qwest, have frequently leveraged third-party certifications
or integrators like Telcordia’s OSMINE process to ensure that any potential vendor
solution will work with the carriers existing management systems.



Finally, modularity of the system makes the challenge of integration for an operator much
easier. This modularity comes in multiple forms--as universal switch fabrics and the
ability to mix-and-match linecards (from all TDM to all packets and everything in
between), or as modularity of the associated software with the ability to selectively turn
on or off specific features.

6 References
[1] Michael Kennedy, “Sizing-Up The Approaches,” Presentation, Network
Strategy Partners, Fierce Telecom: Packet-Optical Networking Platforms
Webinar, July 14, 2010.
[2] Matt Rossi, “Enterprise Bandwidth Consumption,” Presentation, Zayo
Enterprise Networks, Fierce Telecom: Making the 100 Gb/s Connection
Webinar, July 21, 2010.
[3] Internet Engineering Task Force IETF, “MPLS-TP Standard,” WikiPage,
http://wiki.tools.ietf.org/misc/mpls-tp/wiki/drafts, Accessed 12/29/2010.
[4] Steven Gringeri, Bert Basch, Vishnu Shukla et al, “Flexible Architectures
for Optical Transport Nodes and Networks,” IEEE Comm. Mag., Vol. 48,
Issue 9, July 2010, pp. 40-50.
[5] Mark Allen, Chris Lou, Serge Melle, Vijay Vusirikala, “Digital Optical
Networks Using Photonic Integrated Circuits Address the Challenge of
Reconfigurable Optical Networks,” IEEE Comm. Mag. Vol. 44, Issue 12, Dec.
2007, pp. 2-11.

***********************************
About Metanoia, Inc.

Metanoia, Inc. is a niche Bay-area consultancy that, since 2001, has been helping players across
the full telecom ecosystem (chip and semiconductor vendors, system vendors, operators and
carriers, technology houses, and software/planning tool vendors) solve complex problems in the
telecom space. Our contributions have spanned the strategy for, and the analysis, design, and
architecture of, systems, networks, and services, to the optimization of the equipment and
networks deploying them.

Our contributions have allowed a marquee list of client companies (ranging from fast-paced
innovative startups and international leaders, to giants and technology leaders in the US Fortune
1000) across 4 continents accelerate technology design and development or network design and
deployment, speed-up time-to-market, slash learning cycles, master complex technologies, and
enhance customer-interaction and revenues, yielding benefits many times their investments in
our services.

In short, we have been Powering Leadership Through InnovationTM! To learn more about how
we can help you, please contact us at experts@metanoia-inc.com or at +1-888-641-0082, and we
will be delighted to collaborate on efficiently solving your problem, and enhancing savings and
revenue for you.



About Infinera, Inc.

Infinera (Nasdaq: INFN) provides Digital Optical Networking systems to telecommunications
carriers worldwide, and counts itself among the world’s most innovative developers of optical
networking systems. Founded in 2001, Infinera developed the industry's first large-scale photonic
integrated circuit (PIC), which dramatically increases the performance of optical networking by
putting 50 optical components on a single chip smaller than a human fingernail, and with ten
times the data rate of the lasers used in conventional optical systems.
With one of the most successful technology IPOs of recent years, Infinera has developed and
brought to the market innovations at every level of optical system design. At a time when the
Internet has entered an exciting new growth phase, Infinera gathered a broad array of skills and
talents and put them to work to deliver the future of optical networking. Lead by Infinera's
founders, all major figures in the optical systems and components business, Infinera's
engineering team consists of more than 300 engineers in the U.S. and India, with expertise in
photonics, optical components, ASIC design, system design and software design.
Its innovations have helped it win market share leadership among major US and global networks,
accounting for more than 40% of the shipments of 10Gb/s long-haul DWDM ports worldwide,
according to the Dell'Oro Group.

Infinera's systems are unique in their use of a breakthrough semiconductor technology: the
photonic integrated circuit (PIC). Infinera's systems and PIC technology are designed to provide
customers with simpler and more flexible engineering and operations, faster time-to-service, and
the ability to rapidly deliver differentiated services without reengineering their optical
infrastructure. For more information, please visit http://www.infinera.com/.



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