RTGWG Working Group Shankar Raman INTERNET-DRAFT Balaji Venkat Venkataswami Intended Status: Experimental RFC Gaurav Raina Expires: November 11, 2013 Vasan Srini IIT Madras May 10, 2013 Power Based Topologies in OSPF using LDP for label exchanges draft-mjsraman-rtgwg-ospf-ldp-power-topo-00 Abstract In this specification OSPF shortest path first computation is done based on power ratios (consumed-power to available-bandwidth OR available-bandwidth to available-bandwidth) assigned to links and nodes such as Broadcast-Multi-Access networks that form part of the topology in an area. When MPLS is deployed in the area (be it the backbone or non-backbone area) LDP can be used to distribute a disjoint set of labels for the power based topology. Flows some or all of those that traverse the area can then be mapped either to the regular shortest-path tree or the power based shortest-path tree. This document specifies the proposal to construct and maintain such a tree called the power based SPT. 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The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Shankar Raman et.al, Expires November 11, 2013 [Page 1] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 Copyright and License Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.0.1 Experimental results and their inferences . . . . . . . 8 2.1 Power Bias . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.1.1 Advertising Available POWER . . . . . . . . . . . . . . 8 2.2 ECMP links . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3 Dampening the side effects of constant change . . . . . . . 9 2.4 Calculating power shortest paths in an Area . . . . . . . . 9 2.4.1 Power profiles of Routers and Switches and SPF computation . . . . . . . . . . . . . . . . . . . . . . 10 2.4.1.3 Need to advertise both available power and consumed power . . . . . . . . . . . . . . . . . . . 14 2.4.2 Power to Available Bandwidth ratio in a TLV . . . . . . 14 2.4.3 LDP Capability Parameter TLV for Power-SPF based label exchanges . . . . . . . . . . . . . . . . . . . . . . . 16 2.4.4 When one peer says Power-SPF is fine but the other doesnt . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.4.5 Mapping flows to the Power based SPT . . . . . . . . . . 16 3 Security Considerations . . . . . . . . . . . . . . . . . . . . 17 4 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 17 5 References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.1 Normative References . . . . . . . . . . . . . . . . . . . 17 5.2 Informative References . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 Shankar Raman et.al, Expires November 11, 2013 [Page 2] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 1. Introduction Estimates of power consumption for the Internet predict a 300% increase, as access speeds increase from 10 Mbps to 100 Mbps [3], [8]. Access speeds are likely to increase as new video, voice and gaming devices get added to the Internet. Various approaches have been proposed to reduce the power consumption of the Internet such as designing low-power routers and switches, and optimizing the network topology using traffic engineering methods [2]. Typically both Campus networks and Service Provider networks face power saving challenges. It is even exacerbated in modern data centers. In this document we propose a scheme that will apply to all of these areas of interest. In a Interior Gateway Protocol like OSPF (Open Shortest Path First) the routes for networks and their specific next-hops are built from a tree with the router that is involved in the calculation being the root of the tree. Initially link-state database items are exchanged prior to this Shortest Path First computation. Once the database exchanges are complete then the weights assigned to links and Broadcast Multi-Access (BMA) nodes are used to find the shortest path from the said router to each destination advertised in the network (through these database exchanges). It is proposed in this document that the weights assigned to links and BMA nodes be determined by a ratio of consumed-power-to-available-bandwidth or available-power to- available bandwidth and be advertised along with the regular link and BMA node metrics. Thus an alter-ego of the regular topology with weights determined by the ratios mentioned are maintained. Once these are maintained in each router for its area the shortest path computation is done based on this power ratio based topology. When LDP is used to distribute MPLS labels by a router in an area, the router besides distributing its regular topology labels also distributes labels for the power-shortest path tree computed using the power ratios as link weights. This topology could be used to assign some or all of the flows (if all then the power based shortest-path tree becomes the default tree) passing through the area to the routers which are more power efficient. Power profiles of various routers is also discussed in this context in this document. 1.1 Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Shankar Raman et.al, Expires November 11, 2013 [Page 3] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 The proposal we make in this document indicates ways to solve the power reduction problem, by calculating a POWER metric whose importance is highlighted in the below mentioned sections. This POWER metric is obtained by including the factors such as power consumed by a linecard on a single chassis or multi-chassis router and consequently a port on that linecard by proportionally calculating power consumed for that port and hence for the link. The other factor that is taken into account is the Available Bandwidth on that port and hence on that link. 2. Methodology For each router / switch there exist linecards and each linecard has a set of ports or sometimes just one port of high capacity. This usually applies on routers and switches that are either single chassis or multi-chassis in their characterisation. By single chassis we mean that there exists a single chassis and slots for the Route Processor Card (one or more of these) typically upto to two of them, and one or more slots for linecards each having their respective characteristics such as number of ports (port density), type of such ports (SONET, ethernet, ATM etc..) usually depending on the link layer technology they support. Links are connections between ports on these linecards to other ports on linecards of other single chassis or multi-chassis system. A multi-chassis system is one that has multiple such chassis interconnceted amongst each other to form a single logical view of the system. Both single and multi-chassis have linecards and respective ports on these linecards. Multi-chassis typically have a switch fabric chassis which connects each of these chassis to each other or to chassis of other multi-chassis or single chassis systems. Shankar Raman et.al, Expires November 11, 2013 [Page 4] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 Consider the following topology... Router A Router B Router C +---+---+ +---+---+ +-------+ | | | | | | | | | |LC1|LC2| |LC1|LC2| |LC1|LC2| | | | | | | L11 | | | | P1| P1| | P1| P1|-------------- P1| P1|---+ | P2| P2|--+ | P2| P2| L12 | P2| P2| | | P3| P3| | L4 | P3| P3|-------------- P3| P3| | | P4| P4|--+----------- P4| P4| +---- P4| P4| | | P5| P5| | +----P5| P5--+ L5 | | P5| P5| | | | | | | | | | | | | | | | | | | +-|-+-|-+ |L3 | +---+---+ | | +---+-|-+ | L13 | | | +------------+-------+ | | | |L2 | L5 | | | | +----+------------+ | | | | | | | | | |L1 | | |L6 | | | | Router D | | Router E L12| | Router F | | +---+---+ | | +---+---+ | |+-------+ | | | | | |L2 | | | | | || | |L | | |LC1|LC2| | | |LC1|LC2| | ||LC1|LC2|1 | | | | | | | | | | | || | |4.. | +-| P1| P1---+ | | P1| P1|------+ || P1| P1|-> | | P2| P2| L7 +--- P2| P2| +--P2| P2|-> | | P3| P3|-------------- P3| P3| L10 | P3| P3|-> +----------| P4| P4| +---- P4| P4|-------------- P4| P4| | P5| P5| | +-- P5| P5| +----- P5| P5| | | | | | | | | | | | | | +-|-+---+ L8 | | +---+---+ L9 | +---+---+ +---------------+ +------------------+ Shankar Raman et.al, Expires November 11, 2013 [Page 5] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 The table of links between the various routers (which are assumed to be single chassis systems) is as follows... +--------+----------+-----------+-----------+-----------+----------+ | Links | Routers | LC <> LC | Port Conn.| Capacity |Available | | | | | | |Bandwidth | +--------+----------+-----------+-----------+-----------+----------+ | L1 | A <> D | LC1<>LC1 | P5<>P4 | 10G | 7.5 | | L2 | A <> D | LC2<>LC2 | P5<>P1 | 10G | 6.0 | | L3 | A <> D | LC2<>LC1 | P2<>P1 | 10G | 4.0 | | L4 | A <> B | LC2<>LC1 | P4<>P4 | 10G | 3.0 | | L5 | B <> C | LC1<>LC1 | P5<>P4 | 10G | 3.5 | | L6 | B <> E | LC1<>LC1 | P6<>P2 | 10G | 1.0 | | L7 | D <> E | LC2<>LC1 | P3<>P3 | 10G | 6.0 | | L8 | D <> E | LC1<>LC1 | P5<>P4 | 10G | 1.5 | | L9 | E <> F | LC1<>LC2 | P5<>P5 | 100G | 20.0 | | L10 | E <> F | LC2<>LC1 | P4<>P4 | 10G | 2.5 | | L11 | B <> C | LC2<>LC1 | P1<>P1 | 10G | 3.0 | | L12 | E <> C | LC2<>LC2 | P1<>P5 | 10G | 2.0 | | L13 | C <> F | LC2<>LC1 | P1<>P2 | 10G | 1.0 | | L14 | F <> OA | LC2<> | P1<> | | | | | | | | | | +--------+----------+-----------+-----------+------------+---------+ In the above topology assume all point-to-point links between the routers. For now we will deal with P2P links alone and not venture into Broadcast Multi-access links or Non-Broadcast Multi-access links etc.. It is suffice to show how the scheme works for P2P links and then move more specifically to other types of networks to demonstrate this method of calculating the power topology of the network in the figure. Each linecard consumes a certain amount of power and it is vendor dependent as to how the power consumed relates to the Available Bandwidth on any of the links to which the linecard connects to. It is possible that the said topology of routers come from one vendor or from multiple vendors. It is assumed that the algorithm proposed will have the power consumed by a linecard available as a readable value in terms of W or kW or whichever measurable metric that is provided by the vendor. It is possible that some of the Linecards are more capable than the others. Consider that Router A is a more capable router with more powerful linecards with higher port density. This is not shown in the figure, but assume so. LC1, LC2 on Router A could be consuming more power than the other Linecards on other routers. The main reason could be that LC1 and LC2 may have higher port density or higher Shankar Raman et.al, Expires November 11, 2013 [Page 6] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 speed ports than the other routers. In order to calculate the power consumed on a link by a linecard it is important that we normalize the power as power consumed per port. Here the ports are normalized to lowest common denominator. If all links in the topology have 10G port capacity then the power calculated should be in terms power consumed per 10G port. Assuming we have done this normalization we go on to calculate the POWER metric for each of the ports involved in a link which is derived as follows... POWER metric = Power consumed per XG (normalized bandwidth) port for a given ------------------------------------------------- Port on a LC Available Bandwidth on that port Assume link L1. The ports concerned are both 10G and the ports are P5 on Router A and P4 on Router D. For calculating the POWER metric for a link which we will call PWRLINK we calculate the POWER metric for each side of the link and average the two to get PWRLINK. So PWRLINK for L1 = POWER for P5 on LC1 + Power for P4 on LC1 on Router A on Router D ============================================ 2 The above can also be weighted if there is a multi-capacity port on one side of the link and not on the other. A multi-capacity link is one which provides multiple bandwidth capabilities such (1G/10G/100G) for example but auto-negotiates with other end to provide a lesser than highest capacity service. The PWRLINK metrices once calculated are flooded in already defined OSPF-TE-LSA as an adapted TE-metric and is typically flooded as a link characteristic. It is important to note that the denominator for POWER metric is Available Bandwidth on that port. The Available Bandwidth is measured in terms of intervals and not as discrete quantities. This is in order not to flood PWRLINK metrics into the OSPF area in LSAs very frequently as Bandwidth may constantly change. The same applies to POWER metric as well. Once the LSAs have been flooded the Routers run regular SPF on the graph of the topology with PWRLINKs assigned to the links and calculate the PWRLINK based paths which consume the least power. The shortest power paths based on this topology can be used for forwarding high bandwidth streams and to optimally use power within the area. Shankar Raman et.al, Expires November 11, 2013 [Page 7] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 The Available Bandwidth column shows the Available bandwidth of the link corresponding to the row and column intersection. This figure is used as the numerator in the POWER metric computation for that port. 2.0.1 Experimental results and their inferences The first experiments were carried out with Available Utilization since only 10G and 100G ports were considered. This baselines the metric to 10G ports and proportionality thereof. But in reality the actual Available Bandwidth needs to be considered for real world experiments. Hence this draft has been adapted to reflect the Available Bandwidth to be taken as the denominator of the formula thereof. Dividing the Power consumed or Available Power by the Available Bandwidth gives a better picture of how much power cost per Gb is consumed and normalizes the metric amongst links of varying bandwidth. Please refer to the section on Power Profiles where the different decisions in the SPF computation are described. 2.1 Power Bias Assume in the figure that there exist Routers A and D and that there is a bias on the link L1 in such a way that Router D computes a POWER metric of 10 and the Router D computes a POWER metric of 2 on the ports P5 and P4 respectively. Now the PWRLINK would be 6 for that link L1. Thus even if one side is excessively power guzzling then the PWRLINK moves up and thus is less preferred in the CSPF algorithm and path computation based on the Power topology. If there is no bias and both the sides of the link are optimal in their power usage then the metric stays low even if more streams are sent on it. This is the main objective that is set out for router and switch manufacturers in the single chassis and multi-chassis world, in that they are incentivised to manufacture linecards that are not power hungry even if the number of packets flowing through them is high and thus the Bandwidth Available is also reasonably on the higher side compared to other routers. For those manufacturers who set a high power value for even minimal traffic, the vendors that dont would win out in the end. 2.1.1 Advertising Available POWER Please see section 2.4.1 for more information on why Available POWER plays a crucial role in determining the choice of routers based on Shankar Raman et.al, Expires November 11, 2013 [Page 8] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 the Power metric. 2.2 ECMP links It is possible that multiple links would have the same PWRLINK metric after a computation cycle. In such a case load-balancing techniques can be used to keep the ECMP links in a steady state with respect to each other. Depending on the Available Bandwidth thereafter it is possible that the ECMP links may no longer be Equal cost but UCMP or Unequal Cost Paths. 2.3 Dampening the side effects of constant change It is recommended in this draft that the implementation of the proposal be adaptive, infrequent in computation to the extent possible without sacrificing adapting to the dynamism and also reduce any frequent oscillations. It SHOULD be specified that intervals of Available bandwidth and Consumed-Power or Available-Power be used instead of discrete values in arriving at the power ratios. This will dampen any frequent SPF computation for the power based topology. Even if intervals are used dampening fluctuations should be in place to prevent frequent re-computation of the SPF tree. 2.4 Calculating power shortest paths in an Area Assume the following topology where A,B,C etc.. are routers and corresponding labelled edges with weights are the links. These weights are the current values of the PWRLINK attribute that has been flooded in the LSAs through the Area concerned. Assume B is the ABR for Area 1 and the routers A and C are the Area 0 core routers. The rest of the routers are assumed to be in Area 1. Once the power topology of the Area 1 has been calculated as shown below with the PWRLINK attributes being assigned to the links, Power based shortest path first (SPF) computation can be run on the routers say. The SPF algorithm does its computation for the power topology which is characterized in terms of the PWRLINK attributes along with other attributes to construct a power shortest path tree from the router performing the computation to all the destinations in the area. Calculations for the power based topology are done on ABRs, ASBRs and area core routers. Shankar Raman et.al, Expires November 11, 2013 [Page 9] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 0.5 (C) +----------------+ 0.5| / | | / | 0.05 V/ 0.1 0.03 0.2 V (A)--->(B)--->(D)--->(G)--->(H) | | | | 0.5| | 0.1 | V V +----------->(E)--->(X) 0.5 0.3 The power based SPT on router B would look like as shown below. The regular SPT may be divergent from this picture. 0.5 (C) +................+ 0.5| . . | . . 0.05 V. 0.1 0.03 0.2 V (A)--->(B)...>(D)...>(G)----->(H) . | . . 0.5| . 0.1 . V V +...........>(E)--->(X) 0.5 0.3 2.4.1 Power profiles of Routers and Switches and SPF computation It has been experimented and from several sources found that there exist routers which have different power profiles. The power profile of a router is the curve of power consumption to available bandwidth. Mentioned below are a few of these prominent ones that have to be taken into consideration. The power based SPF computation follows the procedures specified below when confronted with two or more routers that have reachability to destinations in its calculation for the power based shortest path tree. The first profile that we will consider is the flattening curve. The power consumed to available bandwidth curve takes the shape of a steep one initially and then tapers off to a plateau. The point at which it begins to give a delta-C (delta in Power Consumed) to delta- B (Available Bandwidth exhausted) is the inflection point that tapers off to a plateau. Here the delta-C/delta-B begins to slow down or decrease rapidly. The more the traffic that is added onto the device the lesser it draws power. Shankar Raman et.al, Expires November 11, 2013 [Page 10] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 ^ | P | . o | . w | . e | . r | . | . c | . o | . n | . s | . u.| . ------------------------------------> | Available Bandwidth exhausted The second profile that we will consider is the exponential curve. The power consumed to available bandwidth curve takes the shape of an ever increasing steep curve as shown below. Here the delta-C/delta-B begins to increase as more traffic is thrown onto it as the Available bandwidth exhausted increases. This power curve beyond a point is intolerable with respect to power guzzling. ^ | P | . o | . w | . e | . r | . | . c | . o | . n | . s | . u.| . ------------------------------------> | Available Bandwidth exhausted Shankar Raman et.al, Expires November 11, 2013 [Page 11] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 The third profile that we will consider is a linear curve. In other words just a straight line. Here delta-C/delta-B is a constant. ^ | P | . o | . w | . e | . r | . | . c | . o | . n | . s | . u.| . ------------------------------------> | Available Bandwidth exhausted 2.4.1.1 Concave and Convex power curves Given that there are 3 kinds of major profiles in the router power consumption, what line would we like to pick. This is an important point when choosing the metric to pick the low power paths. (a) If the confrontation is between 2 first profile routers the lower of the 2 would be considered as shown below. The lower curve offers better power savings for each GB of bandwidth transported. ^ | P | . o | . w | . . e | . . r | . . | . . c | . . o | . . n | . . s | . . u.| . ------------------------------------> | Available Bandwidth exhausted Shankar Raman et.al, Expires November 11, 2013 [Page 12] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 (b) If the confrontation is between 2 second profile routers the upper curve offers more power savings per GB of bandwidth. ^ | P | . . o | . . w | . . e | . . r | . . | . . c | . . o | . . n | . . s | . u.| . ------------------------------------> | Available Bandwidth exhausted (c) When the confrontation is between a first profile curve and a second profile curve, it would be optimal to pick (as shown below) the lower of the curves because it gives us lesser power consumed for every GB of traffic routed / switched. Here the exponential curve is the one that offers lesser amount of power consumed per GB of traffic is chosen. But when it gets to a point that the two curves intersect it would be more optimal to pick the tapering curve. Thus at the meeting point of the 2 curves the exponential curve becomes more costly and the tapering one gives us more GB for the power buck. Thus this switchover from one curve to the other (in other words from the exponential curve to the tapering one) does the trick in terms of finding an optimal solution. Shankar Raman et.al, Expires November 11, 2013 [Page 13] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 ^ . | . P | . . o | (*) w | . . e | . . r | . . | . . c | . . o | . . n | . . s | . . u.| .. ------------------------------------> | Available Bandwidth exhausted (*) Metric switchover point from Consumed Power to Available Power. 2.4.1.3 Need to advertise both available power and consumed power Thus the above sections have shown that both the available power and the consumed power MUST be advertised so that case (c) can be deciphered and the switchover of the curves be done and the appropriate router be chosen for the rest of the bandwidth to be switched over to. Thus there will exist Consumed-Power to Available Bandwidth ratio and the Available Power to Available Bandwidth ratio. Both the ratios are computed and the lower value chosen. The Available Power can be judged from the calibration process such as the one carried out by independent test organizations as in [12]. An example of their calibration is referred to in [12]. Here given below is the formula for calculating the Available Power to Available Bandwidth ratio also called the Available POWER metric. Available POWER metric = Available Power consumed per XG (normalized bandwidth) port for a given ---------------------------------- Port on a LC Available Bandwidth on that port 2.4.2 Power to Available Bandwidth ratio in a TLV As per [RFC3630] the Link TLV can be used to carry this power to available Bandwidth ratio with an additional sub-TLV of the link TLV. The sub-type number 11 is recommended to be defined for this purpose. Shankar Raman et.al, Expires November 11, 2013 [Page 14] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 [RFC 3630] states in section 2.2.1 and we QUOTE ... 2.2.1 Link TLV The Link TLV describes a single link. It is constructed of a set of sub-TLVs. There are no ordering requirements for the sub-TLVs. Only one Link TLV shall be carried in each LSA, allowing for fine granularity changes in topology. The Link TLV is type 2, and the length is variable. The following sub-TLVs of the Link TLV are defined: 1 - Link type (1 octet) 2 - Link ID (4 octets) 3 - Local interface IP address (4 octets) 4 - Remote interface IP address (4 octets) 5 - Traffic engineering metric (4 octets) 6 - Maximum bandwidth (4 octets) 7 - Maximum reservable bandwidth (4 octets) 8 - Unreserved bandwidth (32 octets) 9 - Administrative group (4 octets) 10 - Power-to-Multicast-replication-capacity (4 octets) 11 - Consumed-Power-to-Available-Bandwidth (4 octets) 12 - Available-Power-to-Available-Bandwidth (4 octets) This memo defines sub-Types 1 through 9. See the IANA Considerations in [RFC3630] section for allocation of new sub-Types. The Link Type and Link ID sub-TLVs are mandatory, i.e., must appear exactly once. All other sub-TLVs defined here may occur at most once. These restrictions need not apply to future sub-TLVs. Unrecognized sub-TLVs are ignored. Various values below use the (32 bit) IEEE Floating Point format. For quick reference, this format is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |S| Exponent | Fraction | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ S is the sign, Exponent is the exponent base 2 in "excess 127" notation, and Fraction is the mantissa - 1, with an implied binary point in front of it. Thus, the above represents the value: Shankar Raman et.al, Expires November 11, 2013 [Page 15] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 (-1)**(S) * 2**(Exponent-127) * (1 + Fraction) It is proposed that we use the Power-to-Available-Bandwidth ratio as a 32 bit IEEE floating Point format field for the purpose of this document. 2.4.3 LDP Capability Parameter TLV for Power-SPF based label exchanges As per [5561] a capability parameter TLV can be exchanged at the initialization time or when the administrator fo the network turns on the feature later on. On turning on this feature, the power based shortest-path computation is done and labels exchanged for prefixes through regular LDP operation. The set of labels used for this power based shortest-path tree is disjoint from the label space used for regular IPoMPLS LDP and other features enabled. 2.4.4 When one peer says Power-SPF is fine but the other doesnt All the peers should advertise this capability. In other words all of the routers in the area should be involved in disseminating power SPT based labels. 2.4.5 Mapping flows to the Power based SPT It is possible to map FECs (Forwarding Equivalence classes) some or all of them to the power based SPT. This offers flexibility to the admin to map certain set of large flows to the least power consuming routers in the topology thus getting the best bang for the bit as far as power is concerned. Shankar Raman et.al, Expires November 11, 2013 [Page 16] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 3 Security Considerations No additional security considerations are required other than the existing mechanisms available for securing LDP exchanges. 4 IANA Considerations New requirements are required from IANA for a new type in the Link TLV in order to carry the PWRLINK metric as well. This is needed for both Consumed Power Ratio and Available Power Ratio. A new code-point for the Capability Parameter TLV needs to be assigned for indicating that a router supports power based SPT and label space thereof. 5 References 5.1 Normative References 5.2 Informative References [5561] Thomas et.al, LDP Capabilities, July 2009, [1] G. Appenzeller, Sizing router buffers, Doctoral Thesis, Department of Electrical Engineering, Stanford University, 2005. [2] A. P. Bianzino, C. Chaudet, D. Rossi and J. L. Rougier, A survey of green networking research, IEEE Communications and Surveys Tutorials, preprint. [3] J. Baliga, K. Hinton and R. S. Tucker, Energy consumption of the internet, Proc. of joint international conference on optical internet, June 2007, pp. 1-3. [4] J. Chabarek, J. Sommers, P. Barford, C. Estan, D. Tsiang and S. Wright, Power awareness in network design and routing, Proc. of the IEEE INFOCOM 2008, April 2008, pp. 457-465. [5] B. Venkat et.al, Constructing disjoint and partially disjoint InterAS TE-LSPs, USPTO Patent 7751318, Cisco Systems, 2010. [6] M. Xia et. al., Greening the optical backbone network: A traffic engineering approach, IEEE ICC Proceedings, May 2010, pp. Shankar Raman et.al, Expires November 11, 2013 [Page 17] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 1-5. [7] W. Lu and S. Sahni, Low-power TCAMs for very large forwarding tables, IEEE/ACM Transactions on Computer Networks, June 2010, vol. 18, no. 3, pp. 948-959. [8] B. Zhang, Routing Area Open Meeting, Proceedings of the IETF 81, Quebec, Canada, July 2011. [9] M.J.S Raman, V.Balaji Venkat, G.Raina, Reducing Power consumption using the Border Gateway Protocol, IARIA conferences ENERGY 2012. [10] A.Cianfrani et al., An OSPF enhancement for energy saving in IP Networks, IEEE INFOCOM 2011 Workshop on Green Communications and Networking [12] http://www.juniper.net/us/en/local/pdf/validation-reports/eantc- mx-marketing-report.pdf, September 2009. Authors' Addresses Shankar Raman Department of Computer Science and Engineering, IIT Madras Chennai - 600036 TamilNadu India. EMail: mjsraman@cse.iitm.ac.in Balaji Venkat Venkataswami Department of Electrical Engineering IIT Madras Chennai - 600036 TamilNadu India. EMail: balajivenkat299@gmail.com Shankar Raman et.al, Expires November 11, 2013 [Page 18] INTERNET DRAFT Power based Topologies using LDP and OSPF May 10, 2013 Prof.Gaurav Raina Department of Electrical Engineering IIT Madras Chennai - 600036 TamilNadu India. EMail: gaurav@ee.iitm.ac.in Vasan Srini Department of Computer Science and Engineering IIT Madras Chennai - 600036 TamilNadu India. EMail: vasan.vs@gmail.com Shankar Raman et.al, Expires November 11, 2013 [Page 19]