Next Gen SONET/SDH

Legacy Transport Networks

SONET and its international equivalent, SDH have been the trusted technologies used in transport networks worldwide for many years. SONET and SDH were developed to standardize optical network transmission at a time when the vast majority of communications traffic was circuit-switched-based voice content carried through TDM-based DS1/3 and E1/3 pipes. The stunning growth of the Internet, the demand for WAN data communications and the increasing excitement over Ethernet transport services in the MAN and WAN space have dramatically changed the makeup of transport networks. Data traffic has surpassed traditional voice traffic as the dominate content on optical networks.

Legacy SONET/SDH uses STS-1 containers (51.84Mbps) to carry traffic. This is perfectly suitable for circuit-switched voice traffic, but data traffic is asynchronous with bursty characteristics and and cannot be efficiently transmitted over legacy SONET/SDH networks. For example, transmitting a GbE signal (1.25Gbps) over traditional SONET/SDH networks requires an STS-48C (2.488Gbps) container. Fifty-percent of the bandwidth is unused.

Diagram

Competition from cable and satellite content providers and broadband internet have fundamentally changed how network operators compete, eroding traditional voice revenue. Forward-thinking service providers are actively looking for new revenue opportunities with triple-play solutions and Ethernet services. However, traditional SONET/SDH is not well suited for Ethernet traffic.

Next Generation Transport Networks

Next Gen SONET delivers the required additional flexibility. Considering the global investment in SONET/SDH and knowledge of and trust in the technology, a solution based on enhanced or next-generation SONET/SDH resonates with service providers.

Next Gen SONET/SDH employs VC, LCAS and GFP technologies.

• Virtual Concatenation (VC or VCAT) is a method of creating a single SONET payload out of two or more associated payloads that are transported through a network independently. VC can maximize bandwidth utilization of SONET payloads by “right sizing” existing channels.
• GFP (Generic Framing Procedure) maps higher order protocols onto SONET. GFP provides rules for payload-specific mapping on various network topologies.
• LCAS (Link Capacity Adjustment Scheme) allows for dynamic provisioning of bandwidth using VC. With LCAS, the network does not need to be shut down and data is not lost during the re-provisioning of bandwidth.

These new technologies create many new testing challenges. For example, the diverse routing process inherent in VC creates differential delays—that is, time differences between the arrivals of different paths at the receiving end of the network, as shown in the diagram. The ramifications of these delays can be significant, especially on delay sensitive services such as video and storage.

Anue SONET/SDH Network Delay Emulators help organizations that are developing and deploying Next Gen SONET solutions by generating two types of delay: signal delay and path-layer delay.

• A Signal Delay Emulator is like a programmable spool of fiber; delays can be injected in bit-level increments up to 750ms.
• A Path Delay Emulator is like multiple programmable spools of fiber; delays can be injected in individual segments of data of various sizes within a SONET signal by up to 320ms of differential delay.

With these Next Gen SONET emulation solutions, users can simulate the transmission delays and path jitter that will be encountered by diversely-routed members of a VC group.

Change in network content and competitive pressures have fueled the need to develop Next Gen SONET technologies to efficiently deliver new revenue-generating services over existing optical networks. Before deploying these new technologies, however, it is critical to evaluate the effects on services using GFP or running through a VC/LCAS environment. Anue WAN emulators can help you do this!

With a scalable, cost-effective solution for many of the challenges faced by developers of Next Gen SONET network equipment and systems, Anue Systems is leading the way in Next Gen SONET testing. Designing, building and testing Next Gen SONET products, including VC/LCAS solutions, require WAN emulation tools such as those from Anue Systems with targeted delay emulation and impairment functionality.

For more information on Next Gen SONET: Testing Delays in Optical Networks