Tools for building deterministic transport networks

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Military bases and defense installations, as well as other governmental organizations, support a wide variety of service applications. These range from basic internet connectivity to highly secure, time-sensitive, mission-critical applications. Considered on their own, these would drive divergent network architectures. However, for operational efficiency reasons, there is an ever-increasing need for network convergence.

It is vital that a converged network can meet the packet loss and delay performance requirements for each application. A converged network should also be able to isolate various traffic types from one another so that non-mission-critical traffic does not impede critical traffic. To achieve this, networks need to be deterministic, i.e., highly flexible to support various traffic types, with assurances that packets arrive and arrive on time.

Three important tools deliver deterministic transport and isolate mission-critical traffic from other traffic on a converged transport network – OTN, MPLS-TP, and FlexE.

Optical Transport Network (OTN)

OTN is an ITU-U standard for optical transport and is ideal for providing high-bandwidth deterministic transport. The OTN network transports client signals transparently, making it ideal to transport a wide variety of services and applications. OTN uses time division multiplexing (TDM) to map these client signals into fixed size containers that are multiplexed and groomed into defined transport timeslots. The size of these containers starts at 1.25Gb/s and grows in increments of 1.25Gb/s up to 100Gb/s and beyond.

The use of TDM means OTN transport is inherently deterministic. Seeing that there is no use of shared packet switches, queues, or buffers, OTN provides the complete service isolation required for mission-critical services. In addition, as optical encryption operates at the lowest layer possible, it can be used to secure the MAC and IP address spaces as well as the traffic.

Multiprotocol Label Switching Transport Profile (MPLS-TP)

IP Multiprotocol Label Switching (IP/MPLS) provides converged packet transport for multiple services and applications, each of which will generate IP packets or Ethernet frames at different rates. However, traditional IP/MPLS is not suitable for mission-critical services because packet loss and packet delay are based on long-term statistical averages rather than being deterministic. MPLS-TP is used to provide a finer granularity of deterministic transport.

The ITU Telecommunication Standardization Sector (ITU-T) and Internet Engineering Task Force (IETF) standards organizations introduced MPLS-TP to provide deterministic MPLS that delivers:

• Bi-directional transport to ensure identical latency in forward and reverse traffic flow directions.
• OAM (Operations, Administration, and Monitoring) functions to provide robust fault and performance management.
• Protection switching in 50ms or less.
• Centralized management to provide deterministic control of the network rather than the traditional control plane used by IP/MPLS. This centralized management ensures network links never become oversubscribed and that new MPLS-TP tunnels can only be added if there are enough network resources.

FlexE, G.mtn

Flex Ethernet (FlexE), an Optical Internetworking Forum (OIF) standard, is used to extend traditional Ethernet. FlexE uses TDM to map 5Gb/s time slots into conventional 100GE and 200GE Ethernet circuits. IP traffic and Ethernet frames for each service transported are carried independently in each time slot.

The ITU-T standard “G.mtn” is an emerging choice for deterministic networking. G.mtn takes the transport layer provided by FlexE and adds OAM and 50ms automatic protection switching to become a deterministic networking technology. G.mtn is unique in that it can multiplex Layer 2 and Layer 3 VPN traffic into individual time slots, providing deterministic behavior and isolation for a bundle of VPNs.

These 5Gb/s timeslots act very much like OTN containers; the bandwidth is fixed and there’s complete isolation between traffic in different time slots.  Network equipment implementations can forward G.mtn time slots through a node using a special low-latency path that does not process and queue IP/Ethernet traffic.  This results in a unique, low-latency, near-zero packet loss capability essential to mission-critical military applications.

Takeaways

Network planners face complex challenges when designing and implementing optical networks. A deterministic network structure optimizes the cost of network implementation while meeting the demanding needs of highly variable traffic types ranging from routine to highly secure.

ECI, now part of Ribbon, has extensive experience in deploying deterministic transport solutions to support mission-critical applications worldwide. Ribbon’s technologies provide custom solutions specifically tailored to the needs of some of the largest enterprises and governmental entities in the world. Learn more about ECI, Ribbon, and our solutions by visiting rbbn.com; optical network solutions specific to the defense industry can be found here.

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