White Paper

The Value of OTN for Network

Convergence and IP/Ethernet Migration

TODAY, NETWORK OPERATORS ARE FORCED TO CONVERGE

THEIR NETWORKS in order to reduce Operational Expenses (OPEX),

and also to eliminate unnecessary additional Capital Expenditures

(CAPEX) on multiple parallel networks. Every network operator is

attempting to solve the convergence problem of providing the

greatest number of services on the least amount of infrastructure. In

order to drive faster returns on investments, traditional telecom

carriers are trying to integrate residential broadband services,

advanced enterprise data connectivity services and video into

existing voice networks; cable operators are trying to add VoIP and

commercial services to video and cable modem services.

At the same time, there is a massive migration from traditional

SONET/SDH-   and   PDH-based   TDM   services   to   IP/Ethernet-

based   services, including Voice, Video, Internet Access and

Layer-2   Business   Services.   Operators   are   facing   difficult

challenges implementing network convergence while minimizing

risk, and converting to all IP/Ethernet-based services without

stranding investments.

Ciena's CN 4200

"

FlexSelect

"

Advanced Services Platform is based

on the ITU G.709 OTN (Optical Transport Network) standard as a

vehicle to enable convergence, and for providing a common and

SONET/SDH-like operational model for network administration,

performance monitoring and fault isolation, without altering the

individual services. Using OTN, multiple networks and services such

as legacy SONET/SDH, Ethernet, Storage protocols and Video can

all be combined onto a common infrastructure. Most importantly,

unlike SONET/SDH, OTN is the only transport layer in the industry

that can carry a full 10 Gigabit Ethernet (GbE) LAN PHY from

IP/Ethernet switches and routers at full bandwidth. With the rapid

migration towards IP/Ethernet-based infrastructure, OTN becomes

the transport layer of choice for network operators.

Ciena's CN 4200 is based upon the architecture defined in ITU

recommendations G.709, G.798 and G.8251. It offers transparent

wavelength and sub-wavelength services transport and add/drop

capabilities that provide service bit-stream transparency, as well as

service timing transparency. The CN 4200's unique FlexSelect

architecture provides the capability to switch (cross-connect) full 2.5

Gb/s   wavelength   services   or   sub-wavelength   services   at   a

granularity of 155 Mb/s. Sub-wavelength service channels are

supported via non-contiguous concatenation of 155 Mb/s timeslots,

with 16 timeslots per 2.5 Gb/s wavelength for simple high-density,

multi-service aggregation (see Figure 1).

However, the key differentiating value proposition of the FlexSelect

platform is that these services are not fixed and defined in hardware.

Rather, the services are fully software-programmable on one and the

same line card, so that protocols, connectivity and functionality can

be remotely reprogrammed as services or customers change.

Per-port programmablility is how the CN 4200 provides investment

protections for network operators as they migrate from a largely

TDM-focused network to an all-IP/Ethernet network.

Figure 1. Multiservice aggregation using OTN