With the ever increasing demand for data services and broadband services,
operators are now feeling the heat to upgrade their network to incorporate new
services. The 3G applications and growing hunger for bandwidth demands better
Problems and solutions
- Move towards single NMS: Service providers are deploying different
flavors of transmission products. The products deployed are not only different
in terms of technology but also with respect to different vendors. So, the
option is to opt for a mix-and-match approach and move forward. On technology
the focus was earlier on SDH and DWDM but presently it is tilted towards Metro
Ethernet, CWDM, AON, MSPP, and others.
Even on vendor selection, service providers are opting for multiple vendors.
This makes networks more cumbersome and complicated. So, service providers are
now looking for a single network management system that will take care of
network management system of all the transmission products deployed in a service
provider network. All this is not easy, as service providers are looking for the
- Performance management, need of the hour: With bandwidth
prices dropping every year, and resource cost increasing, service providers have
a very difficult task to check opex to retain their competitiveness. To become
competitive, service providers are looking at an opportunity to leverage
performance management software to reduce operational expenditure thereby
increase network reliability. All this is being done through close monitoring of
managing fault, performance, and the availability of networks across
To be successful, service providers should focus on: proactive performance
management for automating threshold behavior and managing network restoration;
flexible management of point-to-point architectures for flexibility and
resiliency, creating QoS thresholds for premium customers; dynamic bandwidth
reporting for event driven service delivery; leveraging open standards and
interfaces for maximum interoperability in hybrid network; understanding
convergence issues in diverse network topologies; and real time reporting for
managing network resources.
- Increased redundancy: Service providers are now looking at
increased redundancy as it is a necessity in broadband networks. Redundancy is
increased through RPR (resilient packet ring). Earlier it was deployed in
datacom but presently it is now also available in SDH also.
- Increased flexibility: Multiservice provisioning platform (MSPP)
gives service providers increased flexibility in terms of offering all kinds of
services be it basic Ethernet, Fast Ethernet, or Gigabit Ethernet. So all
datacomm features which were earlier present in a network are being incorporated
in conventional SDH system. Storage solutions are also being incorporated in SDH
- One-stop solution: Service providers are looking for a single
vendor who can take care of core and edge, and also provide infrastructure in
different verticals like enterprise, residential and SMB segment. It should also
take care of the last mile rollout be it: cable, DSL, wireless, and Ethernet.
Vendors should focus from telco's perspective and should also provide
infrastructure for the CATV industry.
- Integrating optical technologies: Despite the benefits
integrating optical control plane with the existing system is a major challenge
for the organizations. Such integration issues are a major roadblock in the
older networks, as they had not taken the optical network elements while
designing their networks. In any case putting in a new system without disrupting
the normal operations is always on top of CIOs/CTOs mind.
There is a need to have some kind of interface or software to communicate the
network performance log to the existing network control system and management
systems. The idea is to exploit the benefits of new optical technologies as well
as keep the inherent qualities of the existing system. Apart from technology
integration, people manning these systems have to be educated and trained to
absorb the optical components.
- SDH/SONET: Synchronous digital hierarchy (SDH) and synchronous
optical network (SONET) refer to a group of fiber-optic transmission rates that
can transport digital signals of different capacities. SDH has provided
transmission networks with a vendor-independent and sophisticated signal
structure that has a rich feature set. This has resulted in new network
applications, the deployment of new equipment in new network topologies, and
management by operations systems of much greater power than previously seen in
It was widely accepted that the new multiplexing method should be synchronous
and based not on bit interleaving as was the PDH, but on byte interleaving, as
are the multiplexing structures from 64 kbps to the primary rates of 1,544 kbps
(1.5 Mbps) and 2,048 kbps (2 Mbps). By these means the new multiplexing method
was to give a similar level of switching flexibility both above and below the
primary rates (though most SDH products do not implement flexibility below
In brief, SONET defines optical carrier (OC) levels and electrically
equivalent synchronous transport signals (STSs) for the fiber-optic—based
transmission hierarchy. SONET, a fiber optic transmission system for high-speed
digital traffic, is a North American standard. SONET is widely used in carrier
networks to aggregate lower speed T1 and T3 lines and transport their traffic on
self-healing ring architectures that have advanced network management and
restoration capabilities. SONET is an intelligent system that provides advanced
network management and a standard optical interface.
- Multi-protocol label switching (MPLS): A major thrust area
for the service providers has been MPLS as a packet-based technology. It uses
label switching to forward data through the network.
MPLS-based networks separate routing and forwarding in IP networks making
data transfer easy and fast. The constraint-based routing gives it an edge in
terms of traffic engineering and is well suited for VPNs.
- Dense wavelength division multiplexing (DWDM): It enables a
single optical fiber to simultaneously carry multiple traffic-bearing signals,
thereby increasing the capacity of fiber many times over. DWDM systems can
support more than 150 wavelengths, each carrying up to 10 Gbps. Such systems
provide more than a terabit per second of transmission on one optical strand.
SDH and DWDM are complimentary in nature with DWDM at the backbone and SDH at
- Coarse wavelength division multiplexing (CWDM): It's an
older WDM technology and is emerging as a low cost alternative to DWDM
especially in metro network access and enterprise applications. As they need to
serve smaller bandwidth applications than DWDM systems, CWDM systems are
characterized by wider channel spacing than DWDM optical networks.
The frequency separation between each individual color of light on the actual
fiber is significantly further apart, which allows the system designers to use
lasers that have looser tolerances on spectral width and thermal drift,
therefore less expensive.
- Optical Ethernet: Two alternative architectures based on the
successful fusion of optical and Ethernet technologies-collectively referred
to as Optical Ethernet-have recently emerged to address the shortcomings of
legacy SONET/SDH in today's metro networks.
Purposely built for data transport, Ethernet over fiber and next generation
SONET/SDH-based metropolitan-area networks (MANs) combine the familiarity and
ubiquity of Ethernet networking with the speed of optical transport to overcome
capacity bottlenecks and alleviate opex and capex constraints.
Optical Ethernet is the technology that extends Ethernet beyond the
local-area network (LAN) and into MANs and wide-area networks (WANs). While
Ethernet LANs are almost exclusively used within the enterprise, optical
Ethernet technology can be used as a service provider offering. Optical Ethernet
supports the delivery of a full suite of carrier class Ethernet services up to 1
Gbps. It also provides for integrated optical transport, switching, and
statistical multiplexing to help reduce the number of devices and capital
expenses in the MAN. Finally, optical Ethernet provides bandwidth-on-demand
- Automatically switched optical network/intelligent optical
network (ASON/ION): As networks become more data centric and rising volume
of traffic forces service providers create high bandwidth networks, there is a
need to provide traffic-engineered services to the service platforms.
Automatically Switched Optical Networks (ASON) fulfills this requirement of
providing fast services to the platforms.
By adding intelligence to the networks, they are being made smarter and
various processes being automated. A possible first step is to upgrade the
network management systems with more sophisticated provisioning capabilities.
Such a centralized approach to intelligent networking, however, has limitations
of both functionality and scalability.
The alternative approach, which is being widely endorsed by the industry, is
to distribute intelligence to every network element and link the elements at the
control plane level so that they communicate and provide bottom-up data and
functions for management.
The network becomes the database of record rather than the management system.
This is the approach being embodied now in industry standards efforts such as
the ITU-T's G.8080 (formerly G.ason) standards, the IETF's GMPLS
specifications and the OIF's Optical UNI or user-network interface.
High bandwidth optical networks are being designed by telecommunications
providers to provide traffic-engineered services to the service platforms like
routers, ATM switches. Automatically Switched Optical Networks (ASON) is a
concept that is being discussed to provide quick service activation to the
service platforms in a data-centric network reliably.
- Multi-service provisioning platforms (MSPPs): A major problem
for the service providers is to provide data and voice services across
dissimilar networks. Multi-Service Provisioning Platforms promises to solve this
challenge and allows the service provider to consolidate the number of systems
required to provide intelligent optical access.
An MSPP enables add-drop multiplexing, digital cross-connecting, voice
trunking, Ethernet switching, ATM switching, IP routing, and DWDM transport
among other things.
- Reconfigurable optical add/drop multiplexers (ROADM): With
reconfigurable optical add/drop multiplexers additional network capacity can be
added without going in for any major upgrade. The best part of ROADM is that it
works wherever there is additional services are required without interrupting
The scalability feature of ROADM is expected to assist third generation of
WDM systems for metro and long haul networks. ROADM-based WDM equipments are
expected to be a serious challenger to SDH/SONET systems.
Challenges for Metro Service Providers
Challenges for Metro Service Providers
Service breadth where the providers must be able to offer a variety of
offerings like IP, Frame Relay, Ethernet, ATM etc. with flexibility for new
services without heavy additional cost. Service delivery where the network is
optimized for changing access requirements with easy and quick provisioning.
Service awareness where requirements as QoS, class of service, protection
levels take higher precedence. Scalability where the network capacity should be
able to scale much higher than the capital costs for upgrades.
Network reliability where the capability of a SONET network must be
maintained with regard to protection and restoration. Co-existence with existing
infrastructure to carry voice as well as data traffic as well as interfacing
with existing infrastructure.
Topological flexibility where the equipment must be able to support different
physical topologies thereby supporting flexible application traffic flows.
Reduction in operational and network costs since the metro network is driven
by central office access and transmission equipment costs. Newer equipment must
offer increased functionality and performance without proportional cost