Christophe Charlier
email: charlier@gredeg.cnrs.fr

Mai-Anh Ngo
email: ngo@gredeg.cnrs.fr

Geographical indications outside the European Regulation on PGIs, and the rule of the free movement of goods: lessons from cases judged by the Court of Justice of the European Communities

Keywords: Geographical Indications, Intellectual property rights, Free movement of goods, European regulation JEL Classifications K11, K19

Several recent cases judged by the Court of Justice of the European Communities (the Court) have raised interesting issues related to the possibility for operators of food chains to use national quality signs to indicate territory of origin, which are different from the regulatory European 'Protected Geographical Indications'. The various attempts by

France (a list of quality signs), Germany ('Markenqualität aus deutschen Landen' sign) and Belgium ('Walloon' sign) have all been condemned as protectionist policies contradicting the free movement of goods in the European Market. These national quality signs can be seen as attempt to defend the viability of specific kinds of activities (involving small enterprises) in specific places (rural areas). These cases are a good illustration of the difficulties that a Member State of the European Communities (Member State) faces in trying to protect its traditional activities and/or rural areas in a way that is compatible with free markets. The paper analyses the recent court decisions underlining economic aspects such as information delivery and the cost of alternative protection mechanisms for these activities. We highlight in particular the collective trademarks and the kind of intellectual property right they form by the economic theory of clubs, and make some comparisons with protected geographical indications.

Introduction

Several recent cases judged by the Court of Justice of the European Communities (the Court) have raised interesting issues related to the possibility for Member States of the European Communities (Member States) to protect their various agricultural activities with the help of national quality signs to indicate territory of origin, as an alternative to the European labelling regulation . The European labels are known as Protected Geographical Indications (PGIs) and are a form of intellectual property (IP) rights protected by European Regulation 510/2006 (the European Regulation). 1 The various attempts made by France 2 (a list of broad quality signs such as 'Salaison d'Auvergne', 'Franche Comté', 'Savoie' etc.), Germany 3 ('Markenqualität aus deutschen Landen' sign) and Belgium 4 ('Walloon' sign), which relate to a class of products rather than one specific product, gave rise to the cases examined in this study. They were all condemned by the Court as protectionist policies contradicting the free movement of goods in the European Market.

These proposed national policies are aimed at providing information to consumers about product quality as well as defending the viability of specific kinds of activities (of small enterprises) in specific places (rural areas). Given the generality of the current proposed geographic labelling, it is fairly clear that protection of these activities was the motivation.

Thus, these cases are a good illustration of the difficulties faced by governments trying to make the protection of certain traditional activities compatible with free markets.

1 For a study on the expansion of PGIs see [START_REF] Barjolle | Some factors of success for "Origin labelled product" in agro-food supply chains in Europe: Market, internal resources and institutions[END_REF]. 3 Interestingly, supporting development of the rural economy is a declared aim of the European Regulation: along with providing consumers with information on quality, in the preamble to the European Regulation mention is made of rural economies with particular attention to lessfavoured areas -"the promotion of products having certain characteristics can be of considerable benefit to the rural economy, particularly in less-favoured or remote areas, by improving the incomes of farmers and by retaining the rural population in these areas." 5 This position is in line with the reform of the EU's Common Agricultural Policy which, as pointed out by [START_REF] Becker | European food quality policy: The importance of geographical indications, organic certification and food quality assurance schemes in European countries[END_REF], promotes rural development through improvement to food quality. The Court ruling condemning protective national policies, which clearly have the same aims, is therefore somewhat surprising and requires some explanation. At the same time, amassing various regulations, at different institutional levels, with identical objectives is questionable.

The aim of this paper is to present an analysis of these cases focusing on their legal and economic characteristics. Section II presents the cases and explores their legal aspects.

The fact that the geographical names which would be protected under the proposed national policies cannot be considered as IP (contrary to PGIs) is underlined as a cornerstone of the Court's decisions. Economic analysis of the cases considers the two aims of the policies being considered: delivery of information to consumers on the one hand, and protection of a certain kind of agricultural activity on the other hand. The information that geographical names would provide to consumers, especially in the case of PGIs, has been thoroughly analysed in the economics literature [START_REF] Auriol | Quality signaling through certification. Theory and an application to agricultural seed markets[END_REF] and [START_REF] Marette | Can quality certification lead to stable cartels?[END_REF]). But the idea of protection per se through the use of geographical labelling has not really been investigated although the fact that PGIs create non-tariff trade barriers [START_REF] Charlier | An analysis of the European Communities: Protection of trademarks and geographical indications for agricultural products and foodstuffs dispute[END_REF][START_REF] Charlier | An analysis of the European Communities: Protection of trademarks and geographical indications for agricultural products and foodstuffs dispute[END_REF][START_REF] Josling | The war on terroir: Geographical indications as a transatlantic trade conflict[END_REF] generating benefit as well as costs for a country has been pushed forward [START_REF] Anders | The benefits and costs of proliferation of geographical labelling for developing countries[END_REF]Caswell 2009, Evans andBlakeney 2006). The economic analysis of the cases developed in this article focuses on this protection per se aspect, interpreting the Court's decisions as a 'social choice' about admissible ways to protect activities (Section III). If PGIs are excluded for most of the products related to the cases analysed, and if the only protection of IP is acceptable, then other forms of IP will need to be found for these activities. 6 On this basis, Section III of the paper focuses on collective trademarks mentioning geographical indications. This form of IP is compared with that provided by PGIs and the results are used in Section IV to outline some of the implications for society of shifting protective labelling from a system of national policies to a collective trademark regime. The relation established in this paper between the IP rights of PGIs and public goods on the one hand, and between the IP rights of collective trademarks and club goods on the other hand, highlights a different aspect to the Court's decision than only the interest in maintaining the free movement of goods.

Presentation of the cases

The cases in this study have some common characteristics. First the parties are the same, in that the applicant is the Commission of the EC and the defendant is an EC Member State (France, Germany or Belgium). Second, the issue being judged is the same: national legal protection afforded by names or regional labels that explicitly (Salaisons d'Auvergne, Savoie, Franche Comté, Walloon label of quality…) include a geographical indication. Third, the judgement is the same. In every case, the national legal protection being applied for was found to violate the provisions of Article 28 EC stipulating that "Quantitative restrictions on imports and all measures having equivalent effect shall be prohibited between Member States". Finally, the Court, in every case, refused to consider that the different national legal protections might come under Article 30 EC, 7 which lists possible exceptions to Article 28 EC including "the protection of industrial and commercial property". This is the crux of the matter.

PGIs are recognized as IP rights by the World Trade Organization (WTO) TRIPS -Trade Related Aspects of Intellectual Property Rights -agreement. The Court, however, did not acknowledge the status of industrial and commercial property in relation to the names and regional labels being proposed, since they were not registered as PGIs under European Regulation 2081/928 on the protection of geographical indications (GIs). Furthermore, because these names and regional labels refer to classes of products rather than to single products, the Court deemed that they could not, in any case, be considered PGIs within the European framework. 7 Article 30 states that "The provisions of Articles 28 and 29 shall not preclude prohibitions or restrictions on imports, exports or goods in transit justified on grounds of public morality, public policy or public security; the protection of health and life of humans, animals or plants; the protection of national treasures possessing artistic, historic or archaeological value; or the protection of industrial and commercial property. Such prohibitions or restrictions shall not, however, constitute a means of arbitrary discrimination or a disguised restriction on trade between Member States".

What lesson can we draw from these cases? In the cases we analyse no harm in the form of economic or financial loss was directly at stake. The national legal protections being requested were attacked by the European Commission as such, because of their potential to discriminate on the grounds of nationality. The same reasoning and judgement was applied by the Court, which used the arguments of the European legal standard of free movement of goods between Member States, and only registered GIs could be considered as exceptions.

Outside the European regulatory framework on GIs, any national legal protection that mentions the geographic origin of a product or of a class of products will always be considered as interfering with the free movement of goods between Member States. In order to be considered an exception to the free movement of goods, a national legal protection in the form of a quality sign mentioning a geographic origin has to be in keeping with the European regulatory framework of regulation 2081/92, that is, it has to protect IP represented by a registered PGI. This position may seem odd. It can be seen as being in contradiction with the attempt of the European Union (EU) to promote the protection of GIs at the international level. In this context, the EU is generally considered a strong supporter of PGIs. 9 However, national legal protection for geographical origin labelling outside the European legal framework is a prime example of a threat of discrimination in favour of a country's own products. 10 The argument that it provides information for consumers (see section IV) is of secondary importance. In requiring that national protection afforded by geographic origin labelling complies with the European regulation on GI protection the Court is arguing from 9 See [START_REF] Charlier | An analysis of the European Communities: Protection of trademarks and geographical indications for agricultural products and foodstuffs dispute[END_REF], Evans and Blakeney (2006) and [START_REF] Josling | The war on terroir: Geographical indications as a transatlantic trade conflict[END_REF].

10 At the international level the European Commission strongly supports its model of protection of geographical indications. [START_REF] Charlier | An analysis of the European Communities: Protection of trademarks and geographical indications for agricultural products and foodstuffs dispute[END_REF] showed how the European wish of unilateral harmonization of the international systems of protection of geographical indications on the European model contradicts National Treatment and has produced the international dispute over GIs arbitrated by the WTO.

the point of view that it is IP rights, rather than quality per se, that is the subject of legal protection.

In order to comment on the substantive aspects of the Court's decisions, this reference to registered PGIs needs to be explored further. A PGI in European Regulation is the inclusion of the name of a region in the labelling of an agricultural product or a foodstuff that meets all of three requirements (Article 2.1 of the European Regulation): (i) the product originates from that region; (ii) the product possesses "a specific quality, reputation or other characteristics attributable to that geographical origin"; (iii) the "production and/or processing and/or preparation" of the product take place in that region. To be eligible for a PGI, an agricultural product or foodstuff must comply with a product specification form (Article 4 of the European Regulation). This document has also to identify the authorities or bodies that should verify compliance with the product specification. In addition to its definition there are two other features that are important and highlight the 'nature' of the IP right of a PGI. First, only groups (any association of producers or processors working with the same agricultural product or foodstuff, irrespective of its legal form or composition) are entitled to apply for registration (Article 5.1 of the European Regulation). Second, a name registered under the European Regulation may be used by any operator marketing an agricultural product or food stuff conforming to the corresponding specification (Article 8.1 of the European Regulation).

These two characteristics allow us to draw a parallel between the definition of the nature of the IP right of a PGI implicitly used by the European regulator, and public goods theory. The first characteristic shows that the IP of a PGI is 'non rivalrous'. If the agricultural good corresponding to a PGI is individually exploited, the IP of a PGI concerns a group of producers. The second characteristic shows that the IP of a PGI is 'non excludable'. As soon as an operator conforms to the product specification of a PGI, he can use this PGI without being able to prevent another operator whose products conform to the product specification from also using it. As a consequence, in a given area the number of operators marketing an agricultural product or foodstuff corresponding to a PGI cannot be limited. This clearly shows that the property rights represented by a PGI cannot be appropriated by an operator even if he is the only one marketing the corresponding product. These two properties (non-rivalry and non-excludability) of the IP of a PGI attributable to Articles 5.1 and 8.1 of the European Regulation show that in the spirit of the European regulator the IP right of a PGI is a public good. 11 This interpretation, furthermore, is perfectly in line with the idea expressed in the European Regulation (in its Article 2) according to which the quality of the agricultural product or foodstuff is essentially (or exclusively) due to its geographical origin, that is, to human and natural factors historically constructed by a society, inherited and therefore escaping the strict operator ability condition. An operator marketing a PGI benefits from the pre-existing reputation of the PGI, and cannot be considered its creator. The difference with a privately owned trademark (i.e. with a privately owned IP right) is here very clear. The reputation of a trademark is constructed and maintained by its owner. In line with this, a trademark owner can lose his property right if he ceases to exploit his trademark or if he ceases to defend it. A PGI, however, 'never dies': a PGI may be discontinued for many years if a product stops being produced but will be revived as soon as an operator starts to produce a good that conforms to the product specification for that PGI. This property of permanence underlines the independence of the IP right of a PGI, from the operators' actions.

11 [START_REF] Langinier | Agricultural production clubs: Viability and welfare implications[END_REF] have suggested that PGIs can be seen as 'club goods'. For that, they consider that producers are free to decide the size of the club representing a PGI. This idea is however in contradiction with the non-excludability property underlined here.

The main consequence for our analysis of the Court's judgements of this interpretation of the nature of the IP rights of PGIs which underlines their public good dimension is straightforward. In awarding costs to the different Member States involved in these cases, the Court explicitly stated that the names and regional labels being judged were not IP rights, unlike the case of PGIs. If operators want to seek IP within a different format, other possibilities can be explored such as individually owned or collective trademarks. However, whatever form is considered, the dimension of a public good will not be reached. The properties of 'non-rivalry' and 'non-excludability' are assigned to PGIs by the European Regulation and are not the consequences of material properties, as is the case with a conventional public good. It is the consequence of the expression of an implicit social choice that gives these properties to the intellectual protection bestowed by PGIs. This choice supports the intangible properties of PGIs, of inheritance and timelessness.

These remarks raise a series of questions. Should we limit a specific legal protection related to origin labelling, for IP that can be considered as public goods? What are the consequences (both private and social) of using trademarks to afford legal protection of IP rights through some form of geographic labelling? Would this option be 'economically' feasible? Could collective trademarks be considered as having a public good dimension? If not, what are the consequences? We try to answer these questions and examine any consequences in the next two sections.

Collective trademarks and PGIs

A brief history of the agricultural products that were protected under national legal protection schemes shows that some are now protected by PGIs and some are protected under quality signs such as the French 'Label Rouge'.12 These protections are not at issue for all the products to which they relate. Some regional labels have turned into collective trademarks. 13In order to get a complete picture of the consequences of the Court ruling we need to consider the possibility to protect a geographic name with a collective trademark.

A trademark can be owned by an individual or by a legal entity representing a group of operators. The latter occurs when a specific agricultural product is produced by several small operators for whom the financial burden of owning a trademark on their own would be too great. Operating as a group eases for example the advertising costs involved in building and maintaining trademark reputation. However, it does imply some coordination costs. We focus on this form of protection since it is a good illustration of the context that has likely created the need for the national legal protections condemned by the Court in the cases described in this paper. The trademarks owned by legal entities are known as 'marques collectives de certification' in France and 'collective trademarks' within the Office for Harmonization in the Internal Market (OHIM) at European level. 14 In this paper, we do not distinguish between types and refer to them as 'collective trademarks' throughout.

Collective trademarks and PGIs have several common points. First, both are IP rights.

Second, a collective trademark such as the French 'marque collective de certification' 15 is defined in terms of the origin of the product, and this is the case for other types of collective trademarks. Third, as in the case of a PGI, only a group is entitled to register a collective trademark, and product specification, which is an important aspect of PGIs in the European Regulation, is also imperative for a collective trademark, and is now called 'rule' in the collective trademark scheme. Finally, the idea that an operator can use the relevant collective trademark as soon as he complies with the requirements of the 'rule' also applies to certain forms of collective trademarks. 16A collective trademark, therefore, implies non-rivalry and non-excludability. Can we therefore assume a public good dimension in the IP rights bestowed by a collective trademark as in the case of a PGI? The answer is no. To become a PGI, a GI has to apply for registration.

The European Commission in evaluating whether to accept or reject the application considers two things. The first is a series of points (Article 5.3 of the European Regulation) relating to the legitimacy of GI in reference to the particular product: e.g. the definition of the product, the definition of the geographical area, the link between the product and the geographical environment and, "where appropriate, the specific elements of the product description or production method justifying the link". The second (Article 7 of the European Regulation) involves examining the objections (if any) to the proposed registration (e.g., a conflict with a generic name or an existing trademark, etc.), the admissibility of these objections, and, where necessary, taking decisions on these aspects. The application procedure in the case of trademarks (and therefore "collective trademarks") is less cumbersome under national 15 'Cochon de Bretagne' is an example. 12 regulations or the OHIM directives at European level. Qualification for a collective trademark is based on certain general attributes (novelty of the trademark, product with individual characteristics, a denomination that is not contrary to public policy, etc.) and the guidelines in the OHIM concerning its proceedings focus on objections (the trademark shall be justifiable in the preceding sense and not conflict with existing trademarks) rather than on the authenticity of the geographical indication per se. Thus, demonstrating the existence of a link between quality of the good and the natural and human environment of its origin is not compulsory within the 'rule' document of a collective trademark, which allows greater latitude to applicants for collective trademarks.

This greater latitude can be exploited by a group of producers in order to obtain a rule for a collective trademark that is more restrictive than the product specification in a PGI. A group of producers can limit access by other producers by including constraints relating to the production area and production technique, all of which will contribute to increasing profits.

This clearly shows that the IP of a collective trademark is 'congestible', and does not have the dimensions of a pure public good where, ideally, such congestion cannot appear. In other words, the IP of a trademark encompasses some characteristics that are halfway between a purely public good (non-rival and non-excludable) and a purely private good (rival and excludable) to obtain a club good attributes (non rival, non excludable and congestible). What are the consequences for the cases under scrutiny? We deal with these below.

Analysis of the cases

The key words in the Court's decisions were the same: preservation of the 'free movement of goods' between Member States. Does this guarantee the maximum wellbeing of society? We consider this question looking first at informational problems and, second, with the help of the relationship established between the IP of a PGI and a public good on the one hand, and the IP of collective trademarks and club goods on the other hand.

Provision for the free movement of goods, competition and information

The rule bestowing free movement of goods between Member States has normative roots. It is seen as a necessary condition for competition in markets. From that perspective, the Court's decisions clearly consider the national legal protections afforded by names and regional labels in these cases as policies implying or favouring withdrawn attitudes by domestic consumers towards national products. Favouring this kind of behaviour with a national policy is seen as equivalent to an implicit entry barrier and is banned. However, names and regional labels can also be quality signs which give information to consumers in the context of asymmetric information. A number of theoretical results point to the utility of public intervention in such contexts, since without such signalling, the market for high quality goods could collapse. The case of 'credence goods', 17 that is goods for which consumers cannot determine the qualityeither before or after purchase, is particularly sensitive. Geographical origin is typically a credence attribute. Signalling this origin to consumers where demand for this attribute exists, is thus essential. The information provided transforms a credence good into a 'search good', that is, a good where consumers can check the quality before they purchase. Without 17 See [START_REF] Nelson | Information and consumer behaviour[END_REF].

signalling, the variety of goods available on the market would diminish, decreasing the wellbeing of society.

Signalling of credence attributes, however, is something of a puzzle [START_REF] Auriol | Quality signaling through certification. Theory and an application to agricultural seed markets[END_REF]. Because these attributes can never be experienced by consumers, signalling through price or producer's reputation is not very effective. Certification of credence attributes provides a way to transmit missing information to consumers. As a consequence, this is an important aspect of the national legal protections provided by the names and regional labels in the cases analysed. In making certification available, these national policies can be seen as organizing information delivery and would therefore be useful from a wellbeing maximization perspective. At the same time, however, such policies simultaneously protect producers from competition giving them a market power that increases their surplus, but generating fewer exchanges than the optimum. As a result, the legal protection of geographical origin would be justified if the net effect on society is positive, which is something that has to be evaluated, case-by-case, as shown in the economics literature.

In order to characterize this situation, [START_REF] Marette | Can quality certification lead to stable cartels?[END_REF] consider a case where producers of high quality goods (with high quality understood as a credence attribute) bear higher cost of production than producers of low quality goods, but can certificate the high quality and create a cartel, which has the power to reduce the quantities available in the market so as to increase price. Controlling the quantities of high quality goods supplied to the market creates incentives for producers to differentiate their production with high quality goods. Certification allows consumers to choose the quality they want, and therefore increases their surplus. In cases where the certification cost is high, Marette and Crespi show that, if the product differentiation allowed by quality certification is sufficiently high, the positive effects of certification are bigger than the negative one of increased market power for producers. This idea that a sufficiently high product differentiation is necessary to make national protective policies and quality certification welfare improving, was also found by [START_REF] Zago | Labelling policies in food market: Private incentives, public intervention, and welfare effects[END_REF].

Zago and Pick also show that in a situation characterized by a high fixed certification cost and a large difference between the marginal costs of a high quality product and a low quality product, protecting geographical indications can reduce the wellbeing of society. In a different setting, [START_REF] Moschini | Geographical indications and the competitive provision of quality in the agricultural markets[END_REF] consider the case of a competitive market for a GI-certified good. In that context they show that the need for certification involving fixed costs creates increasing returns to scale at the industry level, so that the competitive equilibrium cannot be Pareto efficient. Under-provision of the GI-certified good appears as a consequence.

Furthermore, since in that competitive setting the producers have no market power, they do not take advantage of the GI protection, whereas consumers do.

These results in the economics literature on GI protections can be used to qualify the reference to free movement of goods used in the analysed Court decisions. They show effectively that protecting GIs can be defended even when it has an effect on competition in the market, since GIs furnish valuable information to consumers. The results of [START_REF] Moschini | Geographical indications and the competitive provision of quality in the agricultural markets[END_REF] go further. Maintaining the hypothesis of competitive market and pointing out that the fixed certification cost creates a distortion to the first best equilibrium, the authors show that the protection of GI as a form of intellectual property alone is not sufficient to ensure an optimal provision of GI-certified goods. A government aiming at restoring the Pareto efficiency should therefore consider additional form of support to GIs. These results underline the need for protection and permit to understand why, as soon as the national quality signs under scrutiny have been condemned by the Court, other forms of protection have been sought after. Compared to this, the conclusions of the analysis considering imperfect competition form a contrast. They stress that protection of GIs should not be considered automatic and evaluations needs to be made case by case, taking account especially of certification cost, degree of differentiation between quality levels and differences in marginal costs of production. The specificity of a large part of the agricultural products initially protected by the disallowed national policies was not strong, the labelling referring to classes of products rather single products. In our view, therefore, for many products, an analysis of information provided by such labelling would support the Court's decisions.

The IP right of a collective trademark as a club good

The producers whose national protection was disallowed by the Court, could gain protection for their products under the trademark scheme as outlined in Section III. Collective trademarks are of particular interest here. They can include the geographical origin of the product and they constitute a way of sharing out the cost of managing a brand image. This latter is especially significant for small businesses. The feasibility of this strategy and whether, compared to the protection provided by a national regulation, this strategy has an effect on the wellbeing of society are questions that need to be addressed. Finding the answers to these questions would enable a better appreciation of the consequences of the Court decisions. We consider first the latitude offered to operators in the elaboration of the 'rule' of a collective trademark and second the cost of the protection mode.

As described in section III, one of the main consequences of resorting to a collective trademark rather than a PGI for protection of activities, is the latitude given to operators in setting the rules defining a collective trademark. Groups of producers are allowed to enforce restrictive dispositions in order to limit access by other producers in order to increase their profits. Not only can there be limitations imposed on the legitimate production area, but also only certain techniques may be considered eligible. There are consequences from these practices. [START_REF] Lence | Collective marketing arrangements for geographically differentiated agricultural products: Welfare impacts and policy implications[END_REF] for instance compare the different legal forms of production organization allowing the supply of high quality products to be controlled (in order to make them more profitable for producers). These include limiting the cultivated surface area, or implementing restrictions on the production process, or a combination of both. [START_REF] Lence | Collective marketing arrangements for geographically differentiated agricultural products: Welfare impacts and policy implications[END_REF] show that these various modes of organization of supply impact differently on the total surplus for society. A regulation that would favour restrictions on the production process without any other form of limitation could provide incentives for producers to choose production techniques that were more restrictive than necessary, to obtain high quality goods. This situation would impose an unnecessary social cost as a consequence. In considering only the free movement of goods in order to rule against the national protection of names and regional labels ignores these kinds of effects. However, if producers seek protection under a collective trademark these effects could be significant. Another way to consider the Court's ruling therefore would be to make reference to collective trademarks as an alternative mode of protection for the particular activities and look at the costs of this protection.

The organization of the supply of goods that have a common specificity (here names or regional labels), but are produced by different operators implies costs. These costs are different from the operating costs borne by individual operators. They concern specifically the coordination required among producers and the costs involved in promoting a trademark: product specification establishment, maintaining brand reputation, etc. These 'collective trademark costs' are shared by the producers and should be regarded as the costs of creating the value of the IP right of the trademark. The theory of club goods initiated by [START_REF] Buchanan | An economic theory of clubs[END_REF] shows that comparing the costs per person in a club with the benefits per person, enables the optimal size of the club to be determined. 18Under the disallowed national protections or under a PGI regime these cost of coordination are small compared to what they could be within a collective trademark scheme: the denominations can easily be defended, the regulatory labels act as quality signs whereas a collective trademark requires that its 'rule' be specified, its brand image established and defended, etc.). Banning the legal national protections by names and regional labels creates a negative external shock on the activities involved. If collective trademarks are chosen as the alternative mode of protection, the operators' coordination framework has to be reinvented and its cost supported. The increase in coordination costs affects the optimal size of the producers' club. However, the effect is not systematic and depends on the shape of the cost function. This is illustrated in figure 1.

FIGURE 1 19

In this figure,   X s B , is the benefit per person of the producers' club membership for a given level X of reputation created/defended for their collective trademark. This benefit first increases with the size s of the group and then decreases. The decrease is due to congestion, whereas the increase can be explained by positive externalities: for a given level of reputation of a collective trademark the increase in the number of producers in the group reinforces the presence of the trademark in the market so that the benefit per person increases (until 19 Derived from J. M. [START_REF] Buchanan | An economic theory of clubs[END_REF]. The curves are representing the following functions:

  3 4 1 , 2     s s X s B ,   s R X s C 1 , , 0  ,   s R X s C 3 , , 1  and   1 , 0 1 3 , , ~s R X s C 
and the three different optimal sizes are calculated with these functions : ̃ 2,24, 2,36 and 2,78.

Benefits, Costs

1 size , , , , , , , congestion occurs)
. The curves   0 , , R X s C and   1 , , R X s C and   1 , , ~R X s C
stand for the cost of the club per person, for a given reputation of the collective trademark X , under different protective regimes 0 R and 1 R . The optimal size for the producer group is calculated maximizing the difference between benefit and cost. 20 The curve   If the optimal size of the producers club increases following a shift in protection mode, as in the first scenario, it is important to ensure that a sufficient number of producers exists.

Obtaining an optimum number in remote rural areas that probably were the target of the disallowed national legal protections might be difficult. Situations could arise in which a club cannot emerge because of an insufficient number of producers to cope with a significant increase in costs.

If, as in the second scenario, the optimal size of the producers club decreases following the shift in the protection mode, fewer producers will be protected. The unprotected ones may disappear or be in less favourable positions. As a consequence, the protected producers will have stronger market power. In that case, a decrease in the quantity of the good produced would therefore affect the wellbeing of the society. These effects of the Court's decision on both the number of producers protected and on the quantity of high quality goods supplied, highlight other aspects of the problem than the mere free movement of good. No systematic conclusions can be drawn; a case by case approach is the only possible approach to assessing their existence and magnitude.

Conclusion

The relation established in this paper between the IP rights of PGIs and public goods on the one hand, and between the IP rights of collective trademarks and club goods on the other hand, has some implications for the rulings made by the Court on several cases concerning legal national protection afforded to geographical names and labels that do not comply with the European Regulation on PGIs. Some of the results from this analysis uphold the Court's decisions; others provide reasons for different judgements. For example, stressing the implicit dimension of public good in the IP rights of a PGI adds emphasis to the Court's reasoning feasibility of such a producer group and the impact on the quantities produced should thus be addressed.

An analysis that would focus on maximizing society's well-being would therefore give weight to the amount of information provided to consumers, the latitude allowed to producers to limit their production and the feasibility of a producers club. Case-by-case studies would be necessary and the results would most probably be different in each case. The invariability of the approach chosen by the Court along the different cases and the correspondence in its conclusions underline the primacy given by the Court to the free movement of goods over any other criteria.

  2 C-6/02. Commission of the European Communities v French Republic. [2007] ECR I-164. 3 ECJ Case C-325/00 Commission of the European Communities v Federal Republic of Germany. [2002] ECR I-9977. 4 . ECJ C-255/03 Commission of the European Communities v Kingdom of Belgium [2007] ECR I-5567.

  under the condemned national protection for regional names and labels. With this cost the optimal size is  under a collective trademark for two different scenarios.Both scenarios consider that exchanging the initial national protection for protection by a collective trademark raises the cost per person. In the first scenario, the new cost function This increase in the club's size allows the higher costs to be shared among a larger number of producers. In the second scenario, the new This decrease in the club size moderates the increased costs of coordination. The relevance of these scenarios has to be evaluated case by case because they imply completely different social difficulties.

Council Regulation (EC) No 510/2006 of 20March 2006 on the protection of geographical indications and designations of origin for agricultural products and foodstuffs. Official Journal of the European Union, L 93/12, 31.3.2006. Point (2) of the preamble.

This can be seen as a branding strategy choice. See[START_REF] Argawal | Emerging issues for geographical indications branding strategies[END_REF].

Now European Regulation 510/2006.

Saucisson sec d'Auvergne was protected under the regional label "Auvergne" and was awarded the French quality sign 'Label Rouge'.

This is the case for example for the label 'Savoie', http://www.marque-savoie.com/ (visited 10 November 2008). The trademark 'Ardennes de France' is another example, http://www.ardennes-defrance.com/association/ardennes-de-france.html (visited 10 November 2008).

14[START_REF] Ibele | The nature and function of Geographical Indications in Law[END_REF] and[START_REF] Schuler | Protecting 'single-origin coffee' within the global coffee market: the role of geographical indications and trademarks[END_REF] compares PGIs with certification and collective marks found in the US Trademark Act.

This is true for 'marques collectives de certification' in particular.

See Glazer et al. (1997) and[START_REF] Sandler | The economic theory of clubs: An evaluative survey[END_REF] for a survey.

This optimal size is obtained where the derivatives of the benefit and cost functions are equal.

considering that PGIs should be considered as an exception to the rule of free movement of goods. However, when we consider the rulings of the Court in terms of their potential effects on the well-being of society, we can show that the capacity of the condemned national legal protection to provide information to consumers should not be ignored and should be evaluated case by case. From this point of view, we would argue that the effects of choosing alternative protection modes, such as collective trademarks, in the wake of the Court's decisions should also be considered.

Evaluation of the capacity of national legal protection for geographical names and labels to provide information highlights the issue of product differentiation. The generality of the names and labels at stake in the cases considered and the fact that they address classes of products rather than individual goods would suggest that an examination of the information provided by the names and labels would add force to the Court's rulings. The consideration of alternative protection modes, such as collective trademarks, is far more delicate. First, such consideration highlights the motives of protection of rural economies, in many cases constituted of small producers without the capacity to efficiently develop individual trademarks in order to signal the quality of their products. Protecting such rural economies was probably the real aim of the original national policies. Second, such consideration draws attention to collective trademarks making reference to geographical origin, as substitutes for PGIs. The property of a club good given to this form of IP in this article underlines the importance of the congestion phenomenon. An optimal size for the producer group protected under a collective trademark can be determined in order to manage congestion and coordination cost. The optimal size of the producer group can be different from the number of producers initially protected under the disallowed national policies. The question of the


Frédéric Giroire
email: frederic.giroire@inria.fr

Joanna Moulierac
email: joanna.moulierac@inria.fr

Khoa Truong
email: truongkhoa.phan@inria.fr

Phan

Frédéric Roudaut
email: frederic.roudaut@orange.com

Minimization of Network Power Consumption with Redundancy Elimination

Keywords: Green networking, Energy-efficient routing, Algorithm

Recently, energy-aware routing has gained increasing popularity in the networking research community. The idea is that traffic demands are aggregated over a subset of the network links, allowing other links to be turned off to save energy. In this paper, we propose GreenREa new energy-aware routing model with the support of the new technique of data redundancy elimination (RE). This technique, enabled within the routers, can identify and remove repeated content from network transfers. Hence, capacity of network links are virtually increased and more traffic demands can be aggregated. Based on our real experiments on Orange Labs platform, we show that performing RE consumes some energy. Thus, while preserving connectivity and QoS, it is important to identify at which routers to enable RE and which links to turn off so that the power consumption of the network is minimized. We model the problem as an Integer Linear Program and propose a greedy heuristic algorithm. Simulations on several network topologies show that GreenRE can gain further 30% of energy savings in comparison with the traditional energy-aware routing model.

Introduction

Some recent studies [START_REF] Chabarek | Power Awareness in Network Design and Routing[END_REF] [START_REF] Mahadevan | A Power Benchmarking Framework for Network Devices[END_REF] exhibit that the traffic load of routers only has small influence on their energy consumption. Instead, the dominating factor is the number of active elements on routers such as ports, line cards, base chassis, etc. Therefore, in order to minimize energy consumption, fewer network elements should be used while preserving connectivity and QoS. Intuitively, it is possible to have multiple paths between a pair of source-destination on the network. When traffic load on links is low, we can aggregate the traffic into fewer links so that the other links do not need to carry any traffic. Routers then can turn off idle links (or precisely, two ports on the two routers at the ends of the link) for energy reduction. Although today's routers cannot turn off the ports and bring them back to active state quickly, we believe that this advance will come in near future, especially if it offers big energy savings.

In general, link capacity is the main constraint when aggregating traffic flows to a subset of links. In this work, we use an assumption that routers can eliminate redundant data traffic and hence virtually increase capacity of the links. As a result, more traffic flows can be aggregated and more links can be turned off to save energy. Although routers nowadays cannot remove repeated content from network transfers, we notice that there is WAN Optimization Controller (WOC) -a commercial device used in enterprises or small ISPs to eliminate traffic redundancy [START_REF]BlueCoat: WAN Optimization[END_REF] [10][14]. In order to identify the power consumption directly induced by RE, we perform real experiments on the WOCs. Because the principle idea of routers performing RE is similar to that of the WOC (section 2.2), we believe that when a router eliminates traffic redundancy, it also consumes more energy than usual. Therefore, in order to evaluate the global power consumption of the network, we should consider both the number of active links and the number of routers that perform RE. In summary, the contributions of this work are the following:

-We do real experiments to show power consumption of a WOC.

-We define and model the problem using Integer Linear Programing (ILP).

-We propose and evaluate a greedy heuristic algorithm that can be used for large-scale networks. -By simulation, we present energy savings on real network topologies. In addition, we discuss the impact of GreenRE on route length (or delay also).

The rest of this paper is structured as follows. We summarize related works in Section 2. In Section 3, we model GreenRE using ILP, then propose a greedy heuristic algorithm. Simulation results are presented in Section 4. We have discussion in Section 5 and finally, we conclude the work in Section 6.

Related Works

Reduction of Energy Consumption

Measurement of energy consumptions. Several empirical measurements showed that energy consumption of network devices is largely independent of their load [6][12]. In addition, many experiments show that the power consumption depends on the number of active ports on routers [START_REF] Mahadevan | A Power Benchmarking Framework for Network Devices[END_REF]. Hence, explicitly turn off unused ports can reduce power consumption of routers.

Energy minimization. The work on energy consumption of the Internet has been first evoked as a hypothetical working direction in [START_REF] Gupta | Greening of The Internet[END_REF]. Recently (2008present), researchers have started to massively invest their efforts in this research area [START_REF] Bianzino | A Survey of Green Networking Research[END_REF]. The authors in [START_REF] Chiaraviglio | Minimizing ISP Network Energy Cost: Formulation and Solutions[END_REF] modeled the problem using ILP and showed how much energy can be saved on different network topologies. In [START_REF] Giroire | Minimizing Routing Energy Consumption: from Theoretical to Practical Results[END_REF], the authors proved that there is no polynomial-time constant factor approximation algorithm for this problem. Then they give theoretical bounds for specific network topologies and present heuristics to find solution close to the optimal one.

Reduction of Traffic Load

Internet traffic exhibits large amount of redundancy when different users access the same or similar contents. Therefore, several works the patterns of previously sent data are stored in database of the WOCs at both sending and receiving sides. The technique used to synchronize the databases at peering WOCs can be found in [START_REF] Grevers | Application Acceleration and WAN Optimization Fundamentals[END_REF]. Whenever the WOC at the sending side notices the same data pattern coming from the sending hosts, it sends a small signature instead of the original data (called encoding process). The receiving WOC then recovers the original data by looking up the signature in its database (called decoding process). Because signatures are only a few bytes in size, sending signatures instead of actual data gives significant bandwidth savings.

Recently, the success of WOC deployment has motivated researchers to explore the benefits of deploying RE in routers across the entire Internet [START_REF] Anand | Packet Caches on Routers: the Implications of Universal Redundant Traffic Elimination[END_REF][2][3] [START_REF] Song | Redundancy-Aware Routing with Limited Resources[END_REF]. The core techniques used here are similar to those used by the WOC: each router on the network has a local cache to store previously sent data which then is used to encode and decode data packets. Obviously, there are two key challenges that hinder the deployment of RE on routers. First, a significant number of memory accesses and heavy computation are required during various stages of RE. Second, a large amount of memory is required for the local cache at routers. However, Anand et al. [START_REF] Anand | SmartRE: an Architecture for Coordinated Network-wide Redundancy Elimination[END_REF] have introduced SmartRE which considers these challenges in the design. The authors show that on the desktop 2.4 GHz CPU with 1 GB RAM used for storing caches, the prototype can work at 2.2 Gbps for encoding and at 10 Gbps for decoding packets. Moreover, they believe that higher throughput can be attained if the prototype is implemented in hardware. Hence, the key limitations can be overcome and this technology should come in future's routers, especially if it offers significant bandwidth savings. Several real traffic traces have been collected from many networks such as at 11 corporate enterprises in US [START_REF] Anand | Redundancy in Network Traffic: Findings and Implications[END_REF], at a large university in US [START_REF] Anand | Packet Caches on Routers: the Implications of Universal Redundant Traffic Elimination[END_REF] and at 5 sites of a large corporate network in North America [START_REF] Song | Redundancy-Aware Routing with Limited Resources[END_REF]. The authors in [START_REF] Anand | Packet Caches on Routers: the Implications of Universal Redundant Traffic Elimination[END_REF][2] [START_REF] Song | Redundancy-Aware Routing with Limited Resources[END_REF] conclude that up to 50% of the traffic load can be reduced with RE support.

In this work, we propose GreenRE -the first model of energy-aware routing with RE support. We show that RE, which was initially designed for bandwidth savings, is also a potential technique to reduce power consumption of the Internet.

Energy-aware Routing with RE

Traditional energy-aware routing model (without RE) has been presented as a multicommodity integral flow problem with the objective of minimizing the number of links [START_REF] Giroire | Minimizing Routing Energy Consumption: from Theoretical to Practical Results[END_REF]. Our GreenRE model can be modeled in a similar way. However, when performing RE, routers consume some additional energy (section 4.1). Thus both the active links and the RE-routers (routers that perform RE) should be considered in the objective function. We model a network topology as an undirected weighted graph G = (V, E), where the weight C uv represents the capacity of an edge (u, v) ∈ E. We represent a set of demands by D = {D st > 0; (s, t) ∈ V × V, s ̸ = t} where D st denotes the amount of bandwidth required for a demand from s to t. A feasible routing of the demands is an assignment for each D st ∈ D a path in G such that the total amount of demands through an edge (u, v) ∈ E does not exceed the capacity C uv . We present in Fig. 2 a example to show the efficiency of using RE-routers in energy-aware routing. The objective is to find a routing solution for the two demands D 0,5 and D 10,15 (both with traffic volume requirement of 10) so that it satisfies the link capacity constraint and minimize power consumption of the network. As shown in Fig. 2a, the routing solution without RE-router requires 10 active links, then we can turn off 7 links and save 41% of energy consumption of the network. Meanwhile, when routers 6 and 9 are RE-routers, and assume that 50% of the traffic is redundant, then we have a better solution in which 57% of energy is saved (Fig. 2b). Moreover, if the two demands increase traffic volume to 20, there is no feasible routing solution without RE-router. But it is possible to find a solution if we have RE-routers at 0, 5, 10 and 15. Energy-aware routing problems are known to be NP-hard [START_REF] Chiaraviglio | Minimizing ISP Network Energy Cost: Formulation and Solutions[END_REF][9], hence we first define and model the problem using Integer Linear Program (ILP), then we present a greedy heuristic algorithm for large scale networks.

Optimal solution -Integer Linear Program (ILP)

For each link (u, v) ∈ E , we use a binary variable x uv to determine if the link is used or not. We consider a simplified architecture where each line card on router has one network interface. Therefore, when a link (u, v) is used (x uv = 1), the two network interfaces at router u and router v are enabled, and the power consumption of this link (called P L uv ) is the sum of power consumption of the two interfaces at router u and router v. We note f st uv be the flow on edge (u, v) corresponding to the demand D st flowing from u to v. We use an assumption that all routers on the network can perform RE, however they can disable RE when unused to save energy. Then, we define a binary variable w u which is equal to 1 if router u perform RE (called RE-router and it consumes additional P N u Watts). We also use a redundancy factor γ to represent amount of data that can be eliminated by the RE-routers. We differentiate the usual flow f st uv from the RE-flow f r st uv (the redundant data has been removed), on link (u, v) for a demand (s, t) and f r st uv = f st uv /γ. When a flow enters a RE-router u, it can happen:

-If the flow is RE-flow, the router u can decode it to usual flow or do nothing (just forward the RE-flow). -If the flow is usual flow, the router u can perform RE for this flow or just forward it.

The Objective Function of the ILP is to find a routing solution that minimizes the total power consumption of the network: min

[ P L uv ∑ (uv)∈E x uv + P N u ∑ u∈V w u ] subject to: "Flow conservation constraint": ∀u, v ∈ V , N (u) -neighbors of u ∑ v∈N (u) f st vu - ∑ v∈N (u) f st uv +γ ( ∑ v∈N (u) f r st vu - ∑ v∈N (u) f r st uv ) =    -D st if u = s, D st if u = t, 0 otherwise. (1)
"Capacity constraint":

∀(u, v) ∈ E, C uv -capacity of link (u, v) ∑ (s,t)∈D ( f st uv + f st vu + f r st uv + f r st vu ) ≤ x uv C uv (2) "RE-router ": ∀u, v ∈ V , M.w u ≥ ∑ v∈N (u) ( f r st uv -f r st vu ) (3a) M.w u ≥ ∑ v∈N (u) ( f r st vu -f r st uv ) (3b)
Equation ( 1) states the flow conservation constraint and we differentiate between RE-flows and usual flows. Constraint (2) forces the link load to be smaller than the link capacity. Like some existing works [START_REF] Chiaraviglio | Minimizing ISP Network Energy Cost: Formulation and Solutions[END_REF][9], we consider a simplified model where link load is the total volume of all the flows passing through this link. In addition, to accommodate traffic bursts, we should limit the maximum utilization over any links in the network. For instance, the capacity using in equation ( 2) would be set to αC uv where α = 50%. The constraints (3a) and (3b) (where M is a big constant number) are to make sure when the router u disables RE (w u = 0), the difference between the sum of the RE-flows that enter and leave router u is equal to zero.

Heuristic solution

The heuristic algorithm, in the first step, tries to find a routing solution for all demands so that it minimizes the number of active links. Because all routers on the network are assumed to be RE-routers, we virtually decrease volume of all the traffic demands to Dr st = D st /γ. Then for the second step, based on the routing found in the previous step, we try to disable RE on as many routers as possible to save energy. Starting with the Algorithm 1, we compute a feasible routing for the REdemands. Initially, all links on the network are set up with the same metric w e which is equal to the total number of demands. We compute the shortest path for each demand with the metric w e on links. Then, the links that have carried the shortest path is updated with metric: w e = w e -1. Using this metric in the shortest path, we implicitly set high priority to reuse links that have already been selected. Then, the Algorithm 2 -Step 1 is used to remove in priority links that are less loaded. C e /R e is used as the load on a link where R e is the residual capacity on link e when previous demands have been routed. In Step 2, we use the routing solution found in the Step 1 as the input of the algorithm. Then, we consider all the traffic demands as normal demands without RE. Hence, some links can be congested because the total traffic volume of demands may exceed the link capacity. The heuristic we use in Step 2 is based on following observations: when performing RE for D 0,11 on router 1 and 10, the amount of traffic passing all the congested links (links (1, 3), (8, 9) and (9, 10)) is also reduced. Then, the heuristic in step 2 decides to perform RE for this flow first. Assume that the redundancy factor γ = 2, then the links (8, 9) and (9, 10) are still congested. After removing Dr 0,11 , the available capacity of links (8, 9) and (9, 10) are 5 and 10, respectively. Applying the same rule, the next demand to perform RE is D 7,11 . Then, there is no congested link on the network since the link (9, 10) is also released from congestion. Finally, only the routers 1, 8 and 10 are needed to enable RE. In summary, the algorithm will perform RE for the flows that passes through most of the congested links first.

(b) End Points Congestion: in Fig. 3b and Fig. 3c, the demand (0,6) has traffic volume of 10 and the number on links indicates link capacity. Therefore, the two links (0, 1) and (4, 5) are congested. Hence, a naive solution is to enable RE at the two end-point routers of each congested link as shown in Fig. 3b. However, a better solution with less RE-routers should be to enable RE only at the starting (router 0) and ending point (router 5) of all the congested links (Fig. 3c). In summary, the algorithm will look for the longest congested part of the flow to enable RE-routers.

Experiments and Simulation Results

Energy Consumption with WOC

Several results of bandwidth savings using WOC can be found in [START_REF] Grevers | Application Acceleration and WAN Optimization Fundamentals[END_REF]. We have also performed experiments on the network platform of the project Network Boost at Orange Labs 1 . We installed two WOCs, each at the access links of the two sites (let's call site A and site B). These two sites are connected via a backbone composed of 4 routers. We setup FTP connections for uploading files from site A to site B. As shown in Fig. 4a, power consumption of the WOC The results show that the WOC consumes around 30 Watts on average (Fig. 4b). Therefore, for sake of simplicity, we use an average value of power consumption (30 Watts) to represent additional cost for the router to perform RE. 1 The full figure of the test-bed can be found in [START_REF] Khoa | Minimization of Network Power Consumption with WAN Optimization[END_REF]

Simulation Results with GreenRE

We studied ten classical real network topologies extracted from SNDLib [START_REF] Sndlib | [END_REF].

Because CPLEX [8] takes several hours to find an optimal solution even for the smallest network (Atlanta network), we force CPLEX to stop after two hours of execution. According to the results of the works mentioned in Section 2.2, we use a redundancy factor γ = 2 for all the simulations. We present in Fig. 5 results for Atlanta network topology -optimal solutions without RE-routers (OPT-Green) given by [START_REF] Giroire | Minimizing Routing Energy Consumption: from Theoretical to Practical Results[END_REF], ILP results (within two hours) with RE-routers (ILP-GreenRE), heuristic with RE-routers (H-GreenRE) and shortest path routing with RErouters (SP-RE) given by [START_REF] Anand | Packet Caches on Routers: the Implications of Universal Redundant Traffic Elimination[END_REF]. For worst-case scenario and for comparison with previous work [START_REF] Giroire | Minimizing Routing Energy Consumption: from Theoretical to Practical Results[END_REF], all links are set up with the same capacity C and the demands are all-to-all (one router has to send traffic to all remaining routers on the network) with the same traffic volume D for each demand. The x-axis in Fig. 5 Low even with λ = λ min . Recall that routing with RE-routers is possible even with λ < λ min meanwhile no feasible solution is found without RE-router. When λ is large enough, it is not necessary to have RE-routers on the network, hence both the solutions (with and without RE-router) converge to almost the same value of gaining in energy consumption.

Discussion

We propose in this paper the GreenRE model with an assumption that all routers on the network can perform RE. However, this model can be extended to support incremental deployment of RE on routers across the Internet. For instance, we have presented in [START_REF] Khoa | Minimization of Network Power Consumption with WAN Optimization[END_REF] the models that work for the two following cases:

-Only a subset of routers on the network can perform RE. Hence, the model should utilize these RE-routers and find a routing solution so that power consumption of the network is minimized. -Given a network topology and a maximum number of RE-routers, the model should find where to place these RE-routers and the corresponding routing solution to minimize network power consumption.

Conclusion

To the best of our knowledge, GreenRE is the first work which considers RE as a complementary help for energy aware routing. We formally define the model using Integer Linear Programming and propose a greedy heuristic algorithm. The simulations on several network topologies show a significant gain in energy savings. Moreover, in comparison with the traditional energy-aware routing, GreenRE works better especially when the traffic load on the network is high. We also prove by simulations that the heuristic algorithm works well and approximates to the solutions given by the ILP. As part of future work, we will carry on more simulations with real trace redundancy factor on links and real traffic demands. We will also consider the impacts of GreenRE on the network such as network fault tolerance. Moreover, we plan to develop a distributed algorithm for GreenRE.

[ 1 ]Fig. 1 .

 11 Fig. 1. Reduction of end-to-end link load using WOC

Fig. 2 .

 2 Fig. 2. Feasible routing solution (a) without RE-router and (b) with RE-routers

Algorithm 1 :

 1 Finding a feasible routing Input: An undirected weighted graph G = (V, E) where each edge e has a capacity C e , a residual capacity R e , an initial metric w e and a set of demands Dr st ∈ D. ∀e ∈ E, Re = Ce, we = total number of demands Sort the demands in random order while Drst has no assigned route do compute the shortest path SPst with the metric (we) assign the routing SPst to the demand Drst ∀e ∈ SPst, Re = Re -Drst, we = we -1 end return the routing (if it exists) assigned to the demands in D

( a )Fig. 3 .

 a3 Fig. 3. Congested links and RE-routers

Fig. 4a .Fig. 4 .

 4a4 Fig. 4a. With concurrent FTP sessions Fig. 4b. With increasing size of uploaded files

Algorithm 2 :

 2 Input: An undirected weighted graph G = (V, E) where each edge e ∈ E has a capacity C e and a residual capacity R e

	Step 1 -Removing less loaded links:
	while edges can be removed do
	remove the edge e that has not been chosen and has smallest value Ce/Re
	compute a feasible routing with the Algorithm 1
	if no feasible routing exists, put e back to G
	end
	return the feasible routing if it exists.
	Step 2 -Enabling set of RE-routers:
	Consider normal demands (without RE) and routing solution in Step 1
	while network is congested do
	find demands to perform RE first (details later in part (a))
	enable set of RE-routers using end points congestion (details later in part
	(b))
	end

Table 1 .

 1 Note that in the simulations, λ has the same value and it represents the traffic load on the network. Large value of λ means that the link capacity is much larger than the required bandwidth of traffic demands or we can say the traffic load on the network is low. The power consumption of a link and of a RE-router used in the simulations are 200 Watts[START_REF] Chiaraviglio | Minimizing ISP Network Energy Cost: Formulation and Solutions[END_REF] and 30 Watts (section 4.1), respectively. Power consumption of a network with RE-routers are calculated as [(the number of active links) ⋆ 200+ (the number of RE-routers) ⋆ 30]. Without considering energy-aware routing and without RE-router, all the links on the network are used. Hence, the power consumption is computed as [(the number of links) ⋆ 200]. The difference between these two values of power consumption represents how much energy can be saved. As shown in Fig.5, without RE-router (OPT-Green), there is no feasible routing solution and hence, no energy is saved if λ < 38. When λ increases, links have more bandwidth to aggregate traffic, hence the solutions with and without RE-Gain of energy consumption (in %)

		40
		35
		30
	energy savings (%)	15 20 25	H-GreenRE ILP-GreenRE OPT-Green SP-RE
		10
		5
		0
			104	96	88	80	72	64	56	48	40	32	24
			traffic			capacity/demand ratio			High traffic

Fig. 5. Simulation results for Atlanta network represents the capacity/demand ratio (λ = C/D).

Acknowledgment

This work has been done in collaboration with Network Boost Project (Orange Labs) and partly funded by the ANR DIMAGREEN. The authors would like to thank Didier Leroy (Orange Labs), Yaning Liu and David Coudert (Project Mascotte) for their advices and support.

router converge to the same amount of energy savings. In general, the heuristic with RE-routers works well and approximate to the results of ILP. In addition, we also consider shortest path routing with RE-routers given by [START_REF] Anand | Packet Caches on Routers: the Implications of Universal Redundant Traffic Elimination[END_REF]. The results show that: without considering energy-aware routing, there is no energy saving even if all the routers have enabled RE. We present in Fig. 6a the number of (a) (b) RE-routers used by the heuristic and by the ILP. When λ increases, it is not necessary to have many RE-routers because the links have enough capacity for traffic aggregation. As shown in Fig. 6a, in general, the number of RE-routers is reduced when λ increases. However, there are some points where the number of RE-routers increases. It is because at these points, having more RE-routers allows to turn off more links and hence, reducing the global power consumption of the network. We compare average route length (which also gives an idea of the delay) between the heuristic algorithm (H-GreenRE) and the shortest path routing with RE (SP-RE) in Fig. 6b. As we can see, when turning off links on the network, we save energy but the traffic demands need to route on longer paths. When λ increases, more traffic demands can be aggregated to a small number of links, resulting in longer routing paths. However, when this ratio is large enough, the routing solutions do not change much, and hence the average route length seems to be unchanged. Because SP-RE does not aggregate traffic, the route length is shorter than those in H-GreenRE.

We present in Table 1 energy gain for ten classical network topologies extracted from SNDLib [START_REF] Sndlib | [END_REF]. Because these networks are too large to launch ILP, we compare heuristic results of H-GreenRE and H-Green (the heuristic without RE-router given by [START_REF] Giroire | Minimizing Routing Energy Consumption: from Theoretical to Practical Results[END_REF]). We use λ min be the smallest value of capacity/demand ratio that allows to find a feasible route for all the demands without RE (found in [START_REF] Giroire | Minimizing Routing Energy Consumption: from Theoretical to Practical Results[END_REF]). In the simulations, a range of λ = {λ min , 2λ min , 3λ min } is used to represent high, medium and low traffic load on the network. As shown in Table 1, with RE-routers, it starts to save a large amount of energy (in average 32.77%)