Quality of protection schemes with extended flexibility for improved energy efficiency

in transport networks (Invited paper)

J. López Vizcaíno1, 4, Y. Ye1, F. Jiménez2, R. Duque2, F. Musumeci3, M. Tornatore3,

P.M. Krummrich4, A. Pattavina3 1 Huawei Technologies Duesseldorf GmbH,Munich, Germany 2 Telefónica I+D, Madrid, Spain

3 CNIT and Politecnico di Milano, Milan, Italy 4 Technische Universitaet Dortmund, Dortmund, Germany

Abstract—In this paper we evaluate the potential of Quality of Protection (QoP) schemes to improve the energy efficiency in optical transport networks. Different levels of flexibility, both in the digital and optical domains, are considered for simulations over a nation-wide reference network model. Increasing power savings are achieved as long as the flexibility levels become higher, demonstrating the benefits of QoP deployments to accomplish power consumption reduction.

Keywords—protection schemes; quality of protection; energy efficiency; elastic optical networks; VLAN; ODU-Flex.

I. INTRODUCTION Telecommunication carriers are constantly deploying

higher capacity pipes within their innermost core networks. Extended service availability and resilience are seen as critical features that have to be considered on those networks.

On the other hand, end users are increasingly perceiving advanced telecommunication services as commodities, creating a high pressure on costs and making difficult the maintenance of acceptable profit margins. Resilience in optical core networks is usually provided by a dedicated protection 1+1 (DP 1+1) scheme, where data is first duplicated and then transmitted on two different link-disjoint paths. This requires the deployment of redundant transponders also for the protection path and, consequently, it duplicates their power consumption, as transponders have to be active on the working and protection paths.

Even though DP 1+1 offers highest reliability and shortest recovery time, it can exceed the resiliency needs in many situations. For this reason, some traffic demands can be served with a lower reliability, e.g., with dedicated 1:1 (DP 1:1) and shared protection (SP) strategies, or even without any degree of protection. With the DP 1:1 scheme, a unique transponder is used for both working and protection, i.e., the demand is protected by duplicating the optical signal generated by the transponder and transmitting it in both paths. Moreover, with the SP scheme, spectral resources can be reserved to protect a set of different demands as long as at most one of them needs to be recovered (this implies that they do not share any working resource).

In that sense, we have to consider that, on the one hand, protection resources can be available at other layers, e.g., at the

Internet Protocol/Multi-Protocol Label Switching (IP/MPLS) layer, making optical layer protection unnecessary; on the other hand, newly available coherent technologies will shorten the time needed for end-to-end lightpath establishment, fostering the use of “on-the-fly” restoration against static protection mechanisms.

Exploiting the heterogeneity of protection requirements requested by the clients would allow for a significant improvement on cost and power consumption. This can be done by following a differentiated quality of protection (Diff QoP) approach, whereby different resilience levels can be provided to optical tributary connections, depending on their survivability requirements and expenditures restrictions.

It has been previously shown that a significant reduction on blocking probability can be achieved by combining protection at different layers and by employing different protection schemes based on traffic classes [1, 2]. Also, the potential of Diff QoP architectures in terms of overall power efficiency has been preliminarily demonstrated in [3]. In this paper, we extend the analysis performed in [3], and consider the inclusion of intelligent packet-to-circuit mapping capabilities (e.g., through the ODU-FLEX (optical channel data unit flexible) technology) into the optical network nodes. The availability of these features will help deploying more flexible QoP schemes, consequently bringing additional advantages in terms of power efficiency.

The remainder of this paper is organized as follows. In Sec. II we describe the architecture considered in this study, with particular focus on the differentiated QoP schemes and their implementation by mapping traffic into different flexible-rate channels. In Sec. III we show the network topology as well as the characterization of traffic demands and their QoP. Finally, we show the obtained simulation results in Sec. IV and draw the conclusions of the paper in Sec. V.

II. NETWORK ARCHITECTURE The study will focus on corporate service deployments

exclusively involving optical transport infrastructure, i.e. optical virtual private network (VPN) services offered to enterprise customers. In such scenario, the deployment of a Diff QoP scheme involves the realization of three main tasks at the optical add/drop nodes to map a client traffic demand into

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an optical connection with a certain QoP level (see those three tasks depicted in Figs. 1, 2 and 3):

• Mapping of electronic traffic demands generated by physical logical ports (e.g., Ethernet ports) into low-hierarchy ODU containers.

• Grooming of low hierarchy ODU containers into high hierarchy ODU containers.

• Mapping of high hierarchy ODU containers into optical transponders.

In order to realize a capacity-efficient service provisioning scheme, with multiple QoP levels, flexibility seems to be needed in these three tasks in order to configure an end-to-end connection (between a pair of customer physical/logical ports, e.g, 1 Gigabit Ethernet port), belonging to any specific QoP class, with a capacity range of sufficiently fine granularity.

In Fig.1, an example of client traffic mapping through traditional fixed ODU cards (with no flexibility) is shown. In the Figure, Client 1 requires 8 Gbit/s at QoP level 1 (DP 1+1) and 4 Gbit/s at QoP level 2 (DP 1:1), while Client 2 requires 6 Gbit/s at QoP level 1. As seen, an ODU-2 card (working at about 10 Gbit/s) is assigned to a set of Ethernet ports carrying 1GbE connection requests having the same QoP level (e.g., the two set of requests of Client 1 associated to QoP1 and QoP2, respectively, are mapped over two separated ODU-2 cards). Then, multiple ODU-2 cards with the same QoP can be further multiplexed into a higher hierarchy ODU-3 card (working at about 40Gbit/s) that feeds the transponder/s dedicated for the specific QoP.

As indicated in [3], the use of newly available optical transport network (OTN) matrices, with ODU-Flex capabilities at the reconfigurable optical add/drop multiplexer (ROADM), provides adequate levels of flexibility in the mapping process. In fact, tributary signals of some QoP class can be mapped to streams of ODU-Flex containers (with 1.25 Gbit/s capacity), multiplexed into a higher hierarchy ODU structure and switched to optical transponders assigned to this QoP. As a result, any physical client port in a ROADM tributary card could support an optical VPN connection with any resilience level, ranging from “unprotected” to DP 1+1. This is in clear contrast with the classical architectures based on fixed ODU-2/ODU-3/ODU-4 switching capabilities, which would be able to switch only a whole ODU-N structure, and enforce to rigidly assign all the physical ports in an ODU card to the same QoP.

The differences with an implementation based on ODU-Flex containers are shown in Fig. 2. In this case, the ODU cards are no longer rigidly assigned to a QoP level (e.g., the connection requests of Client 1, even though characterized by different QoP levels, can share the same ODU-flex cards), helping reduce ROADM resources and increasing flexibility on service provisioning.

Following the ODU-Flex approach, however, we still need to deploy a dedicated set of physical ports for every traffic demand with a certain destination and QoP level. In fact, in the current implementation with fixed-rate ODU mapping, a port has to be dedicated to every client signal with different destination (see Fig. 1).

Fig. 1. QoP implementation with classical ODU traffic mapping (2 different

QoP traffic classes, QoP1 and QoP2)

Fig. 2. QoP implementation with ODU-Flex traffic mapping.

Fig. 3. QoP implementation based on a ROADM architecture with basic

packet intelligence.

If we move to an ODU-Flex implementation (Fig. 2), we obtain some flexibility in the digital domain when mapping low to high hierarchy ODU containers, but we would still employ different ports for each client signal according to its destination and QoP class.

Furthermore, in this study we also consider a third scenario which adds some basic “packet intelligence” to the ROADM, as this is an emergent trend in the optical transport market. With “packet intelligence”, we mean that the node has packet-to-circuit mapping intelligence, which would make it possible

 

 

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to perform Virtual Local Area Network (VLAN) switching based on VLAN-tagging. In other words, signals generated by one client and having different destination and/or QoP can be combined together and use a single port. The node packet intelligence allows performing some differentiation based on VLAN-tagging, which would be in contrast to the implementations shown in Figs. 1 and 2. We also consider that digital switching remains at the OTN level and the added packet intelligence only serves for mapping purposes.

A simple VLAN-tagging scheme could be used by the network add/drop nodes to identify both destination and QoP requirements. As a consequence, a customer would deploy a single or a bundle of physical ports (aggregation group) whose aggregated capacity amounts to the total demand requirements for all the destinations (with a specific QoP) that need to be reached from a site. The use of per-VLAN shaping/limiting mechanisms at the customer equipment/transport node will also help improving the service performance and the control of the traffic injected into the network.

Figure 3 shows an example of QoP solution based on a ROADM architecture with basic packet intelligence. In this case, a client interface is logically divided by means of VLAN-tagging. Traffic demands at each of the VLANs are mapped to some number of ODU-Flex containers, which are further multiplexed to a higher order ODU structure feeding a transponder assigned for a specific destination and QoP. With this scheme, a destination/QoP is no longer tied to a physical port, helping reduce the number of Ethernet ports and ODU cards and making efficient use of lower energy consumption (per transmitted bit) high capacity ports.

The abovementioned scheme allows relevant power savings with respect to an architecture with no packet functionalities at the ROADM nodes, as the number of Ethernet ports and ODU cards would be highly reduced.

Another important contribution to the energy consumption of such network architecture is provided by the optical transponders. Recently traditional single line rate transponders are being evolved towards more flexible optical transponders able to dynamically adjust their line rate [4]. The use of such elastic and sliceable bit-rate variable transponders (BVTs) would enable an efficient use of optical resources and,

consequently, would justify a Diff QoP implementation in the practice. This can be better understood by the following reasoning:

1) Current single rate transponders: Whenever the add/drop nodes are equipped with currently available single rate transponders there could be not enough demand for one or several QoP to justify deploying dedicated transponders. As a possible way through this problem, it could be decided to provide QoP levels higher than requested when this avoids the installation of a new dedicated transponder:

• A transponder assigned to SP could be used for unprotected services.

• A transponder with dual line connection for DP 1:1 (line protection) services could be used for unprotected or services protected by SP.

• Every transponder of the pair assigned for DP 1+1 protection (transponder and line protection) could be used for services requiring lower QoP (DP 1:1, SP) or even for unprotected services.

A pre-emption mechanism would help ensure that higher QoP connections are prioritized, so that transponder resources consumed by the lower classes can be released and freed for higher QoP classes.

Although pre-emption alleviates the need of installing extra low-filled transponders, the constantly increasing capacity offered by coherent technologies remains a barrier for efficient QoP deployments. Potentially unefficient situations, such as a generalized DP 1+1 resilience scheme for most of the connections added/dropped at a node, could become commonplace even when the majority of connections require low levels of resiliency.

2) BVT: Whenever the add/drop nodes are equipped with elastic and sliceable BVTs (capable of adjusting the transmission rate by software configuration), the amount of resources to be assigned to specific QoP connections between end-points (derived from the number of optical carriers and modulation format) can be flexibly selected. As a result, several QoP classes can be deployed with a limited number of

Fig. 4. Implementation of the different protection schemes with BVT and ODU-Flex containers: a) Best-effort traffic; b) SP; c) DP 1:1; d) DP 1+1.

c)

a)

d)

b)

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physical transponders, which can be considered as virtually divided into several logical low-capacity transponders, each serving a different destination/QoP aggregate demand. Figure 4 shows how the sliceable BVTs can be used for the protection types considered in this paper.

As shown in Fig. 4, sliceable BVT transponders are fed by digital streams composed by concatenated ODU-Flex “digital channels”, each with a capacity multiple of 1.25 Gbps. The BVTs are logically divided into a number of logical transponders generating multicarrier structures of different capacities. Digital channels aggregate demands belonging to specific QoPs, e.g. one channel could aggregate a capacity of 4x1.25 Gbit/s = 5 Gbit/s of Best-effort (BE) demands, while another channel can aggregate 6x1.25 Gbit/s = 7.5 Gbit/s of DP 1:1 demands.

In the BVTs, a digital channel (QoP) is mapped to a logical transponder with a multicarrier structure of N optical carriers and a specific modulation format. This optical structure provides a capacity that is adjusted to the digital channel. In this way, we are providing a fine granularity both at the data and at the optical layer, making use of (logical) digital channels and (logical) optical transponders of similar capacities.

In the simplified ROADM diagrams, “Y” connections between transponders and wavelength selective switches (WSS) allow to define any potential QoP. Blocking a multicarrier structure (in our case a block of N frequency slot of 12.5 GHz) at one of the two WSS implies that the service is assigned a QoP of BE (unprotected and unrestorable) or SP, the distinction (BE or SP) being made by proper configuration in the optical management system, which will indicate to the end-point nodes if a recovery action must be performed or not upon a failure event. For these two cases there is a one to one relation between a digital channel and a logical transponder.

Whenever both WSS remain “open” (at some port) for a multicarrier structure, the service will be either DP 1:1 or DP 1+1. In the first case, there is a one to one relation between the digital channel and the logical transponder, that is further connected through a “Y” connection to both WSSs, providing redundant connectivity in the network. This means that the logical transponder signal is duplicated and sent over two different transmission lines. In the second case, for the DP 1+1, the digital channel is duplicated and sent to a pair of physical transponders. The multicarrier structure assigned to DP 1+1 QoP is then sent, from every transponder, to both of the WSS cards. One of the WSS will block the signal coming from one of the transponders, while the other WSS will block the signal from the peer transponder. This means that the digital channel is sent from two independent physical transponders and over two different transmission lines. As seen, this is by far the most robust protection scheme, as both transponder and transmission line are fully protected. It also gives much more flexibility, as, in contrast to DP 1:1, the two optical signals can be assigned a different frequency slot, simplifying the service provisioning and reducing the blocking probability.

III. PROBLEM DESCRIPTION

A. Network scenario As already introduced, the new QoP architectures with

extended flexibility will be applied to optical VPN services, offered to enterprise customers for the connection between their sites and headquarters locations. We will assume that the service can be offered nation-wide by means of transparent lightpaths between add/drop nodes.

In particular, the evaluation has been carried out using the Spanish core network model provided by Telefónica I+D for the studies within the ICT STRONGEST project [5]. The network model comprises 5 regional domains interconnected by a national domain, and composed of 150 nodes and 319 bi-directional links as depicted in Fig. 5.

Different QoP classes can be offered to the customers depending on their protection requirements. More specifically, four different classes have been defined, as presented in Table I, ranging from maximum protection (C1 with maximum protection) to unprotected services (C4 with best-effort protection).

In [3], traffic demands between nodes were defined at an aggregated level (for each QoP class towards every destination), since the power consumption of tributary interfaces was not included in the analysis. For the studies in this paper, the same traffic demands have been considered, but a detailed service model containing individual customer demands for every pair destination/QoP has been defined. The following considerations apply:

1. Nodes exchanging traffic: The optical VPN service will be offered only at a subset of the optical ROADMs with enough demand of high performance corporate services. This subset is composed of 47 nodes that are distributed across the network regions according to the service demands.

2. Number of connections per customer and site: For every VPN customer, a different number of inter-site connections is assigned, using a random distribution with uniform probability and min/max values between 3 and 20. The number of sites will vary between 4 and 40. The geographical add/drop locations for the customer VPN sites (4 to 40) are also selected randomly and with uniform probability.

3. Single QoP class per connection: We assume that every optical connection of a VPN customer belongs to a single QoP class. As an example, if site “x”, site “y” and site “z” belong to VPN customer “1”, if site “x” to site “y” traffic has a QoP C1 (DP 1+1), site “x” to site “z” might have a QoP C4 (best-effort protection).

The total number of customers has been fixed to 100 for all the scenarios. For each of the origin/destination optical pairs (add/drop nodes connecting customer sites), traffic demands will be distributed randomly (with uniform probability) among the customers with presence in the pair nodes.

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TABLE I. DESCRIPTION OF QOP CLASSES [3]

QoP Class Description

C1-Maximum Protection DP 1+1, duplicate transponder(s), fastest recovery.

C2-High protection DP 1:1, single transponder(s) for working path.

C3-Medium protection SP, single transponder(s) for working path.

C4-Unprotected Best-effort (BE).

TABLE II. TRAFFIC SCENARIOS [3]

Traffic Scenario

C1 (%) C2 (%) C3 (%) C4 (%)

S1 41 27 19 13 S2 19 13 41 27 S3 25 25 25 25

Furthermore, the distribution of the traffic classes and the total traffic will determine the degree of differentiation that can be finally applied to the network. In this manner, in order to evaluate the possible power consumption savings under different conditions, the study has been carried out for four different traffic loads (i.e. starting from an initial overall traffic of 1.56 Tb/s for 2012 and scaled by factors of 5, 10 and 15), and considering three possible scenarios with different distributions of traffic classes (see Table II).

B. Mapping of client traffic at the tributary side and computation of power consumption with port and VLAN association. For every customer, the number of physical ports required

to deploy its optical VPN infrastructure is computed following both a physical port to destination/QoP (Fig. 2) and a logical VLAN to destination/QoP strategy (Fig. 3), as explained in Section II.

A rule for the traffic to physical port mapping has been adopted for a trade-off between complexity, performance, fiber usage, capital expenditures and power consumption:

• Whenever the demand for a destination/QoP is below or equal to 3 Gbit/s, individual GbE ports will be used for the connection among customers and add/drop node.

• Whenever the demand lies between 3 and 20 Gbit/s, then 10GbE and GbE ports are allowed, but the number of GbE ports must be below three. As an example, 12 Gbit/s would be implemented with one 10GbE port and two GbE ports, while 13 Gbit/s would need two 10GbE ports.

• For a demand between 20 Gbit/s and 80 Gbit/s, only 10GbE and 40GbE ports will be used, with the restriction that the number of 10GbE ports must be below three.

• Above 80 Gbit/s, 100GbE, 40GbE and 10GbE ports can be used, with the restriction that the total number

of ports must be below or equal to three. This rule can always be applied as the maximum customer demand for any destination/QoP, in the scenario with highest overall traffic, is below 300 Gbit/s.

Once the total number of ports of each type for every of the customers has been obtained, the power consumption share of the tributary interfaces (between customer and optical node port) can be calculated. The power consumption model in [6] will be used for reference.

C. Mapping of traffic at the line side and computation of power consumption for the different network technologies. As mentioned before, traffic grooming of the client signals

is assumed to be performed by ODU-Flex containers with 1.25 Gbit/s capacity, which permits to fit any client rate into any higher level ODUk of OTN. Client signals aimed to the same destination node can be groomed together if the protection requirements of each of the individual clients can be satisfied. Thus, if the capacity of the higher classes is not fully utilized, some clients requiring lower protection could be temporarily provided with better protection for “free” in order to achieve a better utilization of network resources (i.e. spectral resources are already reserved and WDM transponders consume constant power independent of the actual load).

Conventional Wavelength Division Multiplexing (WDM) networks and an elastic OFDM-based network have been considered for the operation at the line side. The WDM approaches assume up to 80 wavelengths within the 50 GHz ITU-T grid in the C-band with rates of 10 Gbit/s, 40 Gbit/s, and 100 Gbit/s, and reaches of 3200, 2200, and 1880 km [8], respectively. Moreover, two different strategies are taken into account: A single line rate (SLR) of 40 and 100 Gbit/s, and a mixed line rate (MLR) approach, combining the transmission of three line rates in a single fiber (10/40/100 Gbit/s). In the latter approach, the C-band is divided into two bands separated by a guard band of 200 GHz to minimize the nonlinear cross-talk between adjacent channels of different transmission technologies: 1) for 10 Gbit/s (On-off keying) transmission, and 2) for both 40 and 100 Gbit/s, which are based on quadrature phase shift keying (QPSK) modulation format.

Fig. 5. Network Scenario-Spanish core network model from TID [5].

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On the other hand, the elastic OFDM-based network assumes a frequency slot of 12.5 GHz and a single polarization transmission resulting in different subcarrier capacities and transparent reaches [7], which are presented in Table III). Additionally, a bilateral guard band with the size of a frequency slot (25 GHz in total per each channel) has been considered to separate adjacent channels.

The evaluation of the power savings at the line side is based on a comparison of the power savings that can be obtained with the adoption of a Diff QoP scheme with respect to the widely used DP 1+1 one (overall aggregated demand is protected without any differentiation).

The total power consumption at the line side is obtained by the contributions of three network elements: transponders, optical amplifiers and ROADMs. The power consumption values for WDM transponders are 34, 98 and 351 W for 10, 40 and 100 Gbit/s transponders, respectively [9]. The elastic approach uses BVTs (coherent optical-OFDM) whose power consumption depends on the number of subcarriers and modulation format. The power consumption for the transmission and reception of a single subcarrier is presented in Table III for the different modulation formats [7]. The Erbium Doped Fiber Amplifiers (EDFAs) are assumed to consume 30 W per direction with an overhead of 140 W per node location [9], and the power consumption of an ROADM is assumed to depend on the node degree (N) and the Add/Drop degree (α) as follows: (𝑁 ∗ 85 +𝛼 ∗ 100 + 150)  [𝑊], where 150W is the overhead [9].

TABLE III. POWER CONSUMPTION AND TRANSPARENT REACH VALUES OF A CO-OFDM TRANSPONDER FOR DIFFERENT MODULATION FORMATS

The methodology used in this study for the routing and resource allocation in the elastic OFDM-based and WDM SLR/MLR networks, is based on heuristic algorithm, described in more detail in [3].

IV. SIMULATION RESULTS

A. Power Savings at the tributary side. Figure 6 displays the number of physical ports (customer

and network side) that need to be installed for each of the overall demand values with the following strategies:

• Port association: there is an association between physical port and destination QoP (i.e. no packet intelligence at the ROADM, as shown in Fig. 2).

• VLAN association: traffic mapping to destination/QoP is based on logical connections over the physical ports (VLAN-tagging, as shown in Fig. 3).

As shown, the VLAN association strategy will allow for significant savings in terms of number of ports at the client

side, around the 90%. This is explained by the possibility of grooming several client signals into high capacity line cards enabled by the VLAN differentiation possibility. For instance, this can be observed for the lowest traffic value (1.56 Tb/s), where a port association will require the installation of a big number of 1GbE ports, whereas with VLAN tagging it would be possible to replace the majority of those cards by a smaller number of 10GbE and 40GbE. This strategy can bring relevant savings in cost, but also in power consumption.

Fig. 6. Number of ports for the different traffic scenarios with port association and VLAN association.

Fig. 7. Power consumption [kW] with port and VLAN association for the different traffic demand conditions.

The power consumption at the tributary side with port and VLAN association are presented in Fig. 7, for the different traffic demands. As shown, the total power consumption could be nearly halved by using VLAN association.

Modulation Format

Subcarrier Capacity (Gbit/s)

Power Consumption

(W)

Transparent reach (km)

BPSK 12.5 112.374 4000 QPSK 25 133.416 2000 8QAM 37.5 154.457 1000

16QAM 50 175.498 500 32QAM 62.5 196.539 250 64QAM 75 217.581 125

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B. Overall power savings including both line side and tributary side.

In addition to the power consumption reduction brought by VLAN association at the tributary side (presented in previous section), applying a Diff QoP scheme at the line side can help improving further the energy savings, as shown in [3]. This section aims at presenting the overall power consumption savings that could be achieved by combining the two mentioned strategies with respect to the current networks in which a port is commonly dedicated to every client at the tributary side, and DP 1+1 is the predominant protection scheme at the line side.

The overall power savings are numerically presented on Table IV for the different traffic scenarios and network technologies, and in a graphical manner in Fig. 8.

In addition to the significant power reduction that can be achieved at the line side [3], the VLAN association brings further savings with respect to the conventional port association. These additional savings at the tributary side can be up to 7%.

The results show that the degree of power savings will depend on the network technology, total traffic, and distribution of traffic classes. Even though power savings can be obtained for all the different traffic conditions, these can be more significant at high traffic load. This is explained by the fact that, at low traffic load, a bigger number of traffic demands with lower protection requirements (C2, C3 and C4) are “upgraded” to C1 in order to get a better utilization of the resources, thus resulting in an overall power consumption closer to that of the conventional DP 1+1 scheme.

TABLE IV. OVERALL POWER SAVINGS OF A DIFF QOP SCHEME AT THE LINE SIDE + VLAN ASSOCIATION AT THE TRIBUTARY SIDE VS. DP 1+1 AT THE LINE

SIDE AND PORT ASSOCIATION AT THE TRIBUTARY SIDE.

Fig. 8. Power savings [%] of a network implementing a QoP scheme and VLAN differentiation with respect to a network with DP 1+1 scheme at the line side and port differentation at the client side. Results are presented for the three possible traffic scenarios (Table II) and the different traffic load values.

However, as traffic increases further, it would be possible to apply more differentiation to a higher fraction of the total traffic (i.e. more lightpaths will be protected by less power consuming schemes such as DP 1:1, SP, or best-effort protection). Regarding the different traffic scenarios, higher energy savings can be achieved in S2 and S3, as there are more customers requiring lower protection levels which allows for the application of more energy-efficient protection schemes.

V. CONCLUSION Exploiting the different and heterogeneous protection

requirements of the customers by a Quality of Protection scheme has been evaluated as a strategy to improve the energy efficiency in optical transport networks. More specifically, significant power savings can be obtained by the application of a differentiated QoP scheme at the line side, and the introduction of “packet intelligence” at the node by means of VLAN tagging at the tributary side.

Results on fixed-grid WDM and elastic OFDM-based networks have shown the potential of these strategies to achieve power consumption reduction in a nation-wide network under different traffic conditions. These power savings can be up to 24% with respect to a network implementing both a conventional DP 1+1 and the common association of a connection to a specific tributary port at the client side.

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ACKNOWLEDGMENT The research leading to these results has received funding

from the European Community's Seventh Framework Programme under grant agreement n. 257740, TREND project, n. 258644, CHRON project, and n. 317999, IDEALIST project.

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