Highway communications networks get green light
Intelligent highway communications networks—ones that provide automated, integrated, and mission-critical communications based on IP/MPLS—are now the gold standard for highways agencies worldwide.
But what does this mean in practice? Well, for agencies like Highways England, they rely on these highway communications networks for connectivity between a myriad of vital applications including:
- Tolling systems
- Video protection systems
- Digital road signs
- Emergency communications systems
As a result, Highways England and other progressive agencies are able to provide on time, safe, and connected journeys for millions of travelers.
An intelligent transportation system
Underpinning an intelligent transportation system (ITS) solution is its highway communications network. The reliability and resiliency of such networks is essential to support mission critical applications so as to ensure safe journeys.
As shown in Figure 1, a highway communications network needs to support a wide range of ITS applications for traffic control, infrastructure, and drivers, as well as roadside workers.
The most commonly used ITS applications include:
- Closed circuit TV (CCTV)
- Corporate LAN/WAN
- Emergency telephone
- License plate recognition
- Mobile radio
- Public address
- Toll collection
- Traffic flow monitoring
- Traffic signal controller
- Variable message signage
- Weather station
Adding to the complexity, each application has particular bandwidth, quality of service (QoS), and availability, as well as latency requirements. That’s why the ideal communications infrastructure enables agencies to set parameters—critical, priority or best-effort—for each service and traffic type according to operational requirements.
Figure 1. Network architecture of communications infrastructure for highways agencies
Figure 2 illustrates how a highways communications network might take shape. To transport all traffic types effectively and reliably in real time, the 1-to-1 or 1-to-many network topology supports low jitter and delay.
Figure 2. Idealized MPLS-based highways communications infrastructure
You’ll also notice that the highway communications infrastructure includes 1 or more traffic control centers where operators gather and dispatch traffic information. Working in parallel is a network operations center where the network management subsystems provide key services including data services, voice services, video surveillance, and Internet access.
MPLS assures QoS and more
When it comes to ensuring QoS levels beyond best effort, traditional IP and Ethernet networks are often found wonting. They lack the ability to scale to support traffic and to optimize the use of network resources. Also, making matters worse, they are unable to react to network events quickly so as to guarantee end-to-end QoS per application.
This is where MPLS technology shines. A single IP/MPLS network has the robustness and predictability of a circuit-based network paired with high capacity and support for bursty traffic. And, for highways agencies, that’s just the beginning.
Offering a world of opportunities, MPLS-based intelligent communication networks:
- Are highly scalable and reliable with redundancy and fast reroute capabilities
- Allow for the deployment of new IP/Ethernet applications, as well as existing TDM-based applications
- Address a range of QoS and service level agreement requirements
- Optimize bandwidth usage through traffic engineering
- Have extensive OAM tools for troubleshooting and maintenance
The result? Agencies can set service parameters and multiple service levels for each service and traffic type, including voice, data and video. This MPLS-based network also supports low jitter and delay to handle all traffic types effectively and reliably, in real time.
The mission-critical communications imperative
When mission-critical services are mixed with less critical services operators again turn to unified IP/MPLS networks to assure QoS. That’s important because MPLS allows network operators to respect and deliver on the service level agreements (SLAs) of each application, as required. This ability to offer differentiated services means services are treated in priority sequence. So emergency services are priority 1.
What’s more, real-time analytics are a boon to everyone—travelers, traffic planners, and emergency services teams alike. They reduce congestion and accidents so that journeys are safer, as well as on time. But processing and transmission of real-time mission-critical information is bandwidth intensive. This service can only work on an ultra broadband network with traffic policies that dynamically allocate bandwidth according to the transportation agency priorities.
Plus, beyond video analytics, the network needs to support a multitude of services, including CCTV, driver information, road signs, tolls, field operations, and in-agency communications.
Looking again at Highways England, their traffic engineers at offer a case in point. Their ultra broadband network with real-time analytics allows them to manage lanes dynamically. By using highway shoulders they are able to relieve peak hour congestion or in the case of an accident an alternate passage.
Legacy services migration
At the same time, TDM, SDH, and PDH are costly to maintain and they can’t support new real-time applications. And, making matters more pressing, they are also nearing end of service or end of life. But unplugging these legacy networks isn’t always an option. For example, retention of existing tolling and road sign applications running on legacy networks often makes sense.
The answer of course is to smoothly migrate these legacy networks to a converged MPLS-based highway communications network. Fortunately, this transition to a multiservice MPLS network won’t leave legacy applications in the cold. Rather, the MPLS network supports TDM traffic with psedudowire services so the agency can determine when the time is right to migrate existing services to IP.
Advanced MPLS capabilities
Highways agencies should also be aware of several advanced capabilities that can be enabled by MPLS technologies. For instance there’s non-stop routing, non-stop services and fast reroute (FRR). And then there’s provisioning VPNs based on Virtual Leased Line, Virtual Private LAN Service (VPLS), and IP VPNs.
An MPLS-based network enables virtualization of a single network infrastructure to support different services and traffic types. In practice this means 1 service can be carried across 1 VPN while the traffic of different services is securely separated in their own private networks.
Again, in the case of mission-critical applications, the service-aware MPLS infrastructure permits the agency to offer services with guaranteed bandwidth to meet peak requirements. At the same time, the service router enables IP routing and switching, to support real-time Layer 2 and Layer 3 applications.
IP-based video surveillance
For highway agencies still using traditional IP networks, managing video traffic can be a challenge. For instance, adding CCTV traffic onto an IP network can adversely impact all services on the network. This makes it doubly important for highway agencies to select a network that is prepared for video traffic. They should specify a reliable, ”always-on” network that can handle multiple high-quality video streams while accommodating converged voice and data traffic.
With video streams from a single IP camera already at 4 Mb/s, an intelligent highways communications network needs to handle current traffic while anticipating significant future bandwidth increases. On top of that, the converged network needs to guarantee concurrent delivery of mission-critical CCTV traffic alongside critical data and voice traffic.
High availability through unique MPLS features
High availability is essential for mission-critical highways communications networks and again on this front MPLS excels. An advanced IP/MPLS network assures fast path restoration and network reconvergence within 50 ms. This level of network resiliency is achieved by the end-to-end restoration capabilities of the MPLS FRR feature which minimizes service interruption is during a network failure.
Going even further, end-to-end standby MPLS paths are provisioned to protect the network against node or interconnection failures. Plus, MPLS offers the flexibility to provision hot or cold-standby paths to protect an active path.
In particular, the Nokia IP/MPLS implementation includes the unique additional high availability features of non-stop routing and non-stop services supported by our service router portfolio. For highways agencies, the 2 most important operations-related benefits are availability and reliability:
- Non-stop routing ensures that a control card failure has no service impact. Label Distribution Protocol adjacencies, sessions, and databases remain intact if there is a switchover.
- Non-stop service ensures that VPLS and IP VPN services are not affected when there is a control fabric module switchover.
Hierarchical QoS and service-based queuing
An intelligent highways communications network implementation of hierarchical QoS (H-QoS) is service-aware. This allows lower priority traffic to ”burst” to fill available bandwidth when higher priority applications go idle.
Typical routers offer QoS levels per port with either strict priority or weighted fair queuing. In contrast, the Nokia IP/MPLS network implements service-based queuing. This approach sees that each logical port (virtual LAN or a virtual circuit) within a physical port has a dedicated queue.
The Nokia network also supports queues and QoS for traffic classes within the logical port, and provides each service with committed information rate and peak information rate type guarantees.
As an added incentive for highways agencies, adoption of MPLS technology paves the way for future ITS. That matters because automated cars, intelligent roads that communicate with drivers and passengers, and roadside smart grids are already in development with numerous trials underway. Moreover, vehicle-to-vehicle and vehicle-to-infrastructure communications are just around the corner.
Our authors look forward to your questions and comments.