With the development of Metro OTN, carriers can now
efficiently map GE into the new ODU0 container operating at 1.25G – right sized
for GE. The GE may be mapped in a bit and timing transparent manner for private
line service, or may be MAC terminated for managed service delivery. Figure 6
illustrates that in comparison to 1st generation OTN, Metro OTN will double the
efficiency of GE transport.
Figure 6
also illustrates how the new variable rate ODUflex container drives efficiency
gains for other common metro access clients. Take for instance 3G-SDI. In 1st
Generation OTN equipment, this video client was at best 30% efficient when
transported using a 10G ODU2 signal. ODUflex enables a container to be assigned
that closely matches the client rate. ODUflex can also be used to transport
subrate 10GE signals, which has the power to open up new private line service options
for enterprises and revenue streams for carriers, while at the same time
allowing the carrier to efficiently use its fiber resources. Furthermore, each
ODU container contains all of the OAM flexibility that OTN is known for.
The new ODU0 and ODUflex containers are also switchable.
Let’s explore the final aspect of Metro OTN: the support for flexible, granular
and distributed OTN switching.
Flexible, Granular and Distributed OTN Switching
The vast majority of access services are sub-10G, with GE
the access currency of choice for broadband and enterprise access. At the same
time, the metro network is generally built around 10G wavelengths, with carriers
preparing for broad
deployment of 40 and 100G wavelengths in the metro. As a result, the gap
between client rate and wavelength bandwidth is increasing.
In recognition of this trend, early OTN deployments were
based on muxponders which multiplex client signals into a single outgoing OTU2,
OTU3, or OTU4 as shown in figure 5.
Muxponder based compact metro access solutions are ideal for
aggregation of mobile, broadband, and enterprise services, and are a growing
trend among equipment vendors and carriers alike. In a fiber-rich access
network, muxponders can cost-effectively provide bit and timing transparent
mapping of SONET/SDH, Ethernet, SAN, and Video into grey or colored OTN
signals.
However, when used in multi-slot / multi-wavelength systems
deeper in the metro and the core, muxponders and transponders can lead to
inefficient wavelength utilization as a full wavelength must be assigned
regardless of the total client bandwidth. Client Add / Drop and Continue is
also hindered by the inflexible nature of Muxponder/Transponder architectures.
Only clients that are physically connected to a particular board can be mapped
into that boards specific outgoing wavelength. This leads to a more complicated
service provisioning and management model. For example, if a client needs be
moved from one muxponder to another (in order to be transmitted on a different
wavelength), human intervention is required. This inflexibility leads to
increased OPEX for the carrier.
Metro OTN addresses these challenges through the deployment
of OTN switching systems.
In comparison to muxponders, the benefits of OTN switching
include:
- Efficient grooming of any sub-wavelength client
onto any outgoing lambda,
- Maximum wavelength utilization
- The ability to switch an ODU from any outgoing
line interface to any outgoing line interface
- The ability deploy remote management,
eliminating the need for manual patching,
- Separation of client and line optic interfaces,
which enables a carrier to deploy 100G wavelengths as traffic dictates
Unlike SONET/SDH, OTN imposes no limitations on switching
granularity. All ODUs may be switched between any ingress and egress line card
through a cell, TDM, or off-the-shelf packet fabric using the new OIF OTN over
Packet Fabric format.
The deployment of an OTN switching system in the metro is a
critical requirement if carriers are to achieve the most efficient use of their
network resources at the lowest possible OPEX.
Silicon Impact of Metro OTN
Just as the metro transport evolution is driving new
requirements for OTN equipment vendors, Metro OTN also drives new requirements
for silicon vendors. No longer is a simple implementation of G.709 sufficient. The
following fundamental features are also required:
- Any-Service, Any-Port, Any-Rate SERDES and
mappers in order to deliver true
multiservice capabilities,
- High density deeply channelized OTN framing, mapping,
and ODU0/ODUflex granular switching,
- High Density SONET/SDH framing, mapping and
switching to enable carriers to transition from SONET/SDH to OTN without
stranding their legacy network,
- Onboard Carrier Ethernet PCS and MACs with
integrated packet timing capabilities in order to address the requirements of
mobile backhaul in the age of LTE,
- Packet and OTN fabric interfaces to enable both
packet and OTN switching applications,
- Ability to address OTN, packet and lambda
switched deployments with the same device
These features enable the equipment vendor to address all
present and future requirements imposed by Metro OTN while minimizing total
cost of ownership.
Summary
PMC-Sierra has introduced a new family of OTN products that
uniquely delivers on the requirements of Metro OTN enabling OEMs to deliver a
new class of transport equipment upon which carriers can build their next
generation Metro transport networks which are:
- Multi-service, with seamless transport of Ethernet, Storage, Video,
SONET/SDH, and Private Line
- Scalable with the rapid growth in packet traffic
- Switchable, providing fine-grain sub-lambda grooming
- Efficient, especially for the transport of packet centric services
- Compatible with the core network, providing end-to-end
Access-Metro-Core continuity for flexibility, protection and management.
With this new class of equipment, carriers can achieve reduction
in OPEX and CAPEX necessary to enable
profitable scalability to support the upcoming 4x growth in network
traffic.
About the Author
As a Product Line Manager in PMC-Sierra’s Communication Products Division, Scott Wakelin has helped define some of the industry’s most successful communication semiconductor solutions including PMC’s HyPHY, TEMUX, and FREEDM product families. Currently focused on packet-optical transport solutions, Mr. Wakelin has over 12 years of experience delivering OTN, SONET/SDH, and Ethernet products to market. Mr. Wakelin holds a Master of Applied Science degree in network infrastructure and security.
About the Company
PMC (Nasdaq: PMCS) is the semiconductor innovator transforming networks that connect, move and store big data. Building on a track record of technology leadership, the company is driving innovation across storage, optical and mobile networks. PMC's highly integrated solutions increase performance and enable next-generation services to accelerate the network transformation. For more information visit www.pmcs.com.