RTGWG Working Group Shankar Raman Internet-Draft Balaji Venkat Venkataswami Intended Status: Experimental RFC Gaurav Raina Expires: February 2013 I.I.T, Madras August 4, 2012 Building power shortest inter-Area TE LSPs using pre-computed paths draft-mjsraman-rtgwg-intra-as-psp-te-leak-02 Abstract In this paper, we propose a framework to reduce the aggregate power consumption of an Autonomous System (AS) using a collaborative approach between areas within an AS. We identify the low-power paths within non-backbone areas and then use Traffic Engineering (TE) techniques to route the packets along the stitched paths from non- backbone areas / backbone area to other non-backbone areas. Such low- power paths can be identified by using the power-to-available- bandwidth (PWR) ratio as an additional constraint in the Constrained Shortest Path First (CSPF) algorithm. For routing the data traffic through these low-power paths, the Inter-Area Traffic Engineered Label Switched Path (TE-LSP) that spans multiple areas can be used. Extensions to the Interior Gateway Protocols like OSPF and IS-IS that support TE extensions can be used to disseminate information about low-power paths in the respective areas (backbone or non-backbone) that minimize the PWR ratio metric on the links within the areas and between the areas thereby creating a collaborative approach to reduce the power consumption. The feasibility of our approaches is illustrated by applying our algorithm to an AS with a backbone area and several non-backbone areas. The techniques proposed in this paper for the Inter-Area power reduced paths require a few modifications to the existing features of the IGPs supporting TE extensions. The proposed techniques can be extended to other levels of Internet hierarchy, such as Inter-AS paths, through suitable modifications as in [11]. When link state routing protocols like OSPF or ISIS are used to discover TE topology, there is the limitation that traffic engineered paths can be set up only when the head and tail end of the label switched path are in the same area. There are solutions to overcome this limitation either using offline Path Computation Engine (PCE) that attach to multiple areas and know the topology of all areas. This document proposes an alternative approach that does not require any centralized PCE and uses selective leaking of low-power TE path information from one area into other areas. Shankar Raman et.al Expires February 2013 [Page 1] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." 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 Copyright and License Notice Copyright (c) 2012 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 . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1 Low-power routers and switches . . . . . . . . . . . . . . . 4 1.2 Power reduction using routing and traffic engineering . . . 4 2. Methodology of the proposal . . . . . . . . . . . . . . . . . 6 2.1 ABR Operation . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 TE Path Head-end Operation . . . . . . . . . . . . . . . . . 10 Shankar Raman et.al Expires February 2013 [Page 2] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 2.3 Suppression of Frequent updates owing to fluctuation in power and bandwidth . . . . . . . . . . . . . . . . . . . . 12 2.4 Advantages . . . . . . . . . . . . . . . . . . . . . . . . . 12 3 Security Considerations . . . . . . . . . . . . . . . . . . . . 14 4 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 14 5 References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.1 Normative References . . . . . . . . . . . . . . . . . . . 14 5.2 Informative References . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Shankar Raman et.al Expires February 2013 [Page 3] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 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]. 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]. 1.1 Low-power routers and switches Low-power router and switch design aim at reducing the power consumed by hardware architectural components such as transmission link, lookup tables and memory. In [4] it is shown that the router's link power consumption can vary by 20 Watts between idle and traffic scenarios. Hence the authors suggest having more line cards and running them to capacity: operating the router at full throughput will lead to less power per bit, and hence larger packet lengths will consume lower power. The two important components in routers that have received attention for high power consumption are buffers and TCAMs. Buffers are built using dynamic RAM (DRAM) or static RAM (SRAM). SRAMs are limited in size and consume more power, but have low access times. Guido [1] states that a 40Gb/s line card would require more than 300 SRAM chips and consume 2:5kW. DRAM access times prevent them from being used on high speed line cards. Sometimes the buffering of packets in DRAM is done at the back end, while SRAM is used at the front end for fast data access. But these schemes cannot scale with increasing line speeds. Some variants of TCAMs have been proposed for increasing line speeds and for reduced power consumption [7]. 1.2 Power reduction using routing and traffic engineering At the Internet level, creating a topology that allows route adaptation, capacity scaling and power-aware service rate tuning, will reduce power consumption. In [8] the author has proposed a technique to traffic engineer the data packets in such a way that the link capacity between routers is optimized. Links which are not utilized are moved to the idle state. Power consumption can be reduced by trading off performance related measures like latency. For Shankar Raman et.al Expires February 2013 [Page 4] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 example, power savings while switching from 1 Gbps to 100 Mbps is approximately 4 W and from 100 Mbps to 10 Mbps around 0:1 Watts. Hence instead of operating at 1 Gbps the link speed could be reduced to a lower bandwidth under certain conditions for reduced power consumption. Multi layer traffic engineering based methods make use of parameters such as resource usage, bandwidth, throughput and QoS measures, for power reduction. In [6] an approach for reducing Intra-AS power consumption for optical networks that uses Djikstra's shortest path algorithm is proposed. The input to this method assumes the existence of a network topology using which an auxiliary graph is constructed. Power optimization is done on the auxiliary graph and traffic is routed through the low-power links. However, the algorithm expects the topology to be available for getting the auxiliary graph. This topology is easy to obtain for Intra-AS scenario, but by using a centralized PCE (Path Computation Element) as in a hierarchical PCE approach. Here for each area a PCE is assigned and each such PCE calculates the path from a head-end router to a tail-end router, both falling within the same area. When TE paths have to be stitched across several areas then the hierarchical PCE which may be one level up from the respective area PCEs is contacted for such a stitching. In our approach, we propose a collaborative approach by the respective areas in calculating low-power paths that result in power reduction within an AS. This document proposes an alternative approach that does not require any centralized PCE and uses selective leaking of low-power TE path information from one area into other areas. The core of most ISP ASes use the Multi-Protocol Label Switching (MPLS) technology. MPLS label switched paths that traverse multiple areas carry traffic from a head-end to a tail-end that can be situated in different areas within the AS. The AS uses the Interior Gateway Protocol (IGP) for exchanging routing related information. The topology of one area is not revealed to the other in OSPF-TE and IS-IS-TE. The CSPF algorithm as proposed here is run on a specific area with the available power-to-bandwidth (PWR) ratio as a constraint, to determine "k" (where k is a suitable number) low-power-paths from the head-end to the tail-end within the same area. The low-cost power paths that minimize the PWR ratio can be exchanged among the collaborating areas using IGP-TE TLVs that we propose in this document. Explicit routing using RSVP-TE (for signalling) then can be achieved between the head-end and the tail-end routers traversing multiple areas through these low-power paths connecting the head-end and tail-end using the Inter-Area Traffic Engineered Label Switched Path (TE-LSP) that span multiple areas. Shankar Raman et.al Expires February 2013 [Page 5] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 2. Methodology of the proposal There are three known solutions to inter-area TE (a) hop expansion at area boundaries where the head end can only choose the path to area boundary rather than right to tail end, (b) centralized PCE is attached to all areas and is aware of entire topology, and (c) path stitching by designating ABRs acting as BGP route reflectors. It is of course possible to build out low-power paths through the above techniques but they suffer limitations such as not knowing for certain whether the path exists a-priori. This document proposes a technique where a-priori low-power paths are pre-computed in the various areas and are leaked into other areas so that provisioning these paths is done much more quicker than is otherwise possible. Assume {N} as the set of nodes in a network running link state routing protocol and {N' } be the set of nodes that are known to be the endpoints of the traffic engineered paths. The topology {N, E} has been divided into hierarchical areas with backbone area as the second level that connects first level of all non-backbone areas. We assume the network runs either OSPF-TE or ISIS-TE for establishing TE paths. The set of nodes {N'} can be situated in any non-backbone area or the backbone area. Nodes in {N'} may become aware of being potential endpoints through offline configuration. Once the nodes in {N'} become aware of being TE endpoints, they advertise themselves in a special TLV in TE link state information. We would term this "TE Endpoint TLV". In OSPF, they would advertise a newly defined TLV in TE LSA and in ISIS, they would advertise a newly defined TLV in TE LSP. Apart from nodes in {N'} the area border routers or ABRs advertise another newly defined TLV that we would term as "Area Border TLV". 2.1 ABR Operation Apart from standard OSPF/ISIS ABR functions, each ABR should discover the TE endpoints in every area attached to it. Assume for an ABR, let the set discovered be {Ai, Nj}. The ABR should compute k-power- shortest-paths to every element in {Ai, Nj} based on the constraints applicable to the network. The constraint applied here is the minimization of the PWR ratio which is defined as follows. Shankar Raman et.al Expires February 2013 [Page 6] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 For a given router that is either an ABR or a core router within an area (be it backbone or non-backbone), all egress links that can be potentially be used as a link towards a TE endpoint are identified. The link / links that have the maximum of the available bandwidth at that instant in time are identified. The maximum available bandwidth so identified is used in the following equation to determine the PWR ratio. PWR = (Power Consumed by the router) DIVIDED BY (Maximum bandwidth of all links that are potentially leading to a TE endpoint). In other words PWR = POWER-CONSUMED / MAX BANDWIDTH OF EGRESS LINKS The power consumed by each router may fluctuate over short time intervals. In order to dampen these fluctuations which can cause unnecessary updates, power can be measured when falling within intervals of suitable size (say a range of values). This is as opposed to measuring power as a discrete quantity. This method of power measurement reduces the frequency of triggered updates from the routers due to power change. This PWR metric is then assigned to the links that are ingress links in the path leading towards the TE endpoint. Potentially for all TE endpoints west of the non-backbone area core router the PWR metric is usually the same. For TE endpoints east of the router the reverse directional traffic TE-LSP computation would take into account the PWR metric to be taken into consideration. For a Area Border Router having part of its links in Area 1 and the rest in Area 0 (backbone area) the PWR metric would be assigned to the incoming links I(1) and I(2) of the ABR router as follows. .__________________ ( Area 1 ....> ( E(1) \ I(1) ( +--------->(Area 1 router) \ +-------+ / 1Gb +------>| |/ E(2) 200KW / (60*60*1.5Gb) | ABR |------------>(Area 1 router) +------>| of |\ 1Gb / I(2) | Area 1| \ / +-------+ \ E(3) ( +-------->(Area 1 router) ( 1.5Gb .__________________ Shankar Raman et.al Expires February 2013 [Page 7] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 For a Area 1 core router the following would be the PWR metric assigned to the incoming links I(1) and I(2) respectively of the said Core Area 1 router as follows. In an Area core router the maximum condition is modified. The "X" most highest bandwidths of all the egress links towards the TE endpoint are taken where "X" is <= "k" and the appropriate calculations done for PWR derivation. PWR = (Power Consumed by the router) DIVIDED BY ("X" highest bandwidth of all links that are potentially leading to a TE endpoint). Here "X" is decremented step by step to derive at least "k" shortest paths from the calculating router. In other words PWR = POWER-CONSUMED / MAX BANDWIDTH OF EGRESS LINKS is calculated at each step after excluding the link whose bandwidth was included in the previous step till "X" becomes 0. If there exist no such link after excluding one link after another then the algorithm stops. The intention is to calculate as many disjoint paths as possible initially. It is possible to compute partially disjoint paths as well with suitable modifications to the above steps. Area 1 ....> E(1) \ I(1) +--------->(Area 1 router) \ +-------+ / 1Gb PWR metric +------>| |/ E(2) 300KW / (60*60*1.5Gb) | Core |------------>(Area 1 router) +------>| Router|\ 1Gb / I(2) | Area 1| \ / +-------+ \ E(3) +-------->(Area 1 router) 1.5Gb After computing the ingress link PWR metrices in a given step there is a flooding done within the area of the assigned metrices of given Ingress links of a router with a new TLV that we will call "PWR metric TLV". This TLV contains details of the calculating router and the link metric for the assigned Ingress links of the said router. This TLV is taken into account to produce various PWR metric assigned topologies such as the one seen in the next page. Dampening is done to avoid frequent flooding based on the bandwidth and PWR fluctuations (which are produced as intervals of power rather than a discrete quantity). This is implementation dependent and its study is Shankar Raman et.al Expires February 2013 [Page 8] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 out of scope of this document. Assume the following topology in a non-backbone area after calculating the PWR ratio in a given stage of the algorithm. 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 Here (B) is a Area Border Router and has to ingress links into it from (C) and (A) which are in the backbone area. Connectivity within the backbone area are not shown here. Assume (C) and (A) are connected in some way with other routers in the backbone area. Routers (D), (G), (E), (H), (X) are routers in the non-backbone area. Routers (H), (E) and (X) are potential TE endpoints. The PWR metrics shown here on the edges within the area represent metrics for a specific TE endpoint. The metrics on edges (C)->(B) and (A)->(B) are for any traffic ingressing through (B) into the non-backbone area heading towards any TE endpoint (H), (E) or (X). The number of constraints is likely to be few and the most widely used constraints are TE metric, link groups and bandwidth. But no restriction is assumed on use of other constraints. Thus here we add the PWR metric of a link as an additional constraint. Once the ABR computes k-power-shortest-paths to every {Ai, Nj} it has topology information about, it advertises the k-power-shortest-paths as a reachability vector in a newly defined "TE Reachability Vector TLV". Consider an example network show below. TEh is head-end and TEt is tail-end of a TE path, ABR1 and ABR2 are area border routers. TEh2---R2 R4-----TEt2 \ / \ / TEh1---R1----ABR1-----Rb1-----Rb2-----ABR2----R3----TEt1 Area 1 Backbone Area2 In this example, ABR1's TE Reachability vector TLV for area 1 and area 0 are given below. Shankar Raman et.al Expires February 2013 [Page 9] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 { ABR1, [>, >]} { ABR1, ABR2, [>, >]} Here the vector TLVs are arranged as per increasing PWR metric associated with each path. That is the summation of all PWR metrics of the links in the path is done and the vector TLVs are ordered in increasing order of PWR metric sums. So the lowest-cost-power path is listed first and so on. If the least cost power path is to be chosen then the path in the first TLV is chosen. Similarly ABR2's TE Reachability vector TLV for area 2 and area 0 are given below. { ABR2, [>, >]} { ABR2, ABR1, [>, >]} The first thing to be noted is that head-ends are also considered as TE-endpoints. Essentially this means any head-end or tail-end of a inter-area TE-LSP can be considered as tail-end or head-end respectively. Note that the reachability vector advertised by ABR1 also contains the reachability vector of ABR2. For example, if ABR2 is brought up first, then it is likely that ABR1 would only have the following as TE Reachability vector TLV for area 0 before ABR2 computes path to the TE endpoints in area 2. { ABR1, ABR2 } Note that TLV would only contain the aggregate of link attributes namely cost, bandwidth etc and most importantly the PWR metric as well but not the complete path of intermediate nodes. For example, may be a set of <2, admin-group-1|admin-group- 2, 1Gbps> (where the 1Gbps could be the minimum bw available along the path). The above example topology has only one path from ABRs to TE endpoints. The number of path info "k" may have a default value or can be configured by the operator on all nodes. 2.2 TE Path Head-end Operation When any TE application requests TE path to be setup to an endpoint that is not present in the same area, the head-end scans the TE Reachability vector TLVs advertised by ABRs and selects the path using the contained in the vector TLVs. Here is an example with multiple paths in area 1, backbone and area 2 called Figure 2.0 Shankar Raman et.al Expires February 2013 [Page 10] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 TEh3----R5---ABR3----Rb3-----Rb4------ABR4----R6--TEt4 \ / ___/ \ ___/ \ / / \/ TEh2---R2---ABR5------Rb5--------ABR6---R4-----TEt2 / \ \____ /\___ / \ \ / \ TEh1---R1----ABR1-----Rb1-----Rb2-----ABR2----R3----TEt1 Area 1 Backbone Area2 In this topology in figure 2.0 taking the tail-ends represented in the diagram, it is noted that TEt4 is reachable via ABR4, ABR6 and ABR2 as well. The TE reachability TLVs advertised by ABR6 for area 2 would be multiple to each tail-end since there exist multiple paths to reach at least most of them in area 2 once a packet reaches any of the ABRs in area 2. Here again the least cost power shortest path is listed first and so on. { ABR6, [>, >, >, etc.. } For area 0 the TE reachability TLV would be { ABR6, ABR1, [>, >...]} { ABR6, ABR5, [>, >...]} { ABR6, ABR3, [>, >...]} For the sake of brevity we do not enumerate all path information possible as it would be quite extensive. It is possible that there may be already setup LSPs which are being used for transit traffic on the backbone or in other non-backbone areas. It is also feasible to advertize already set up LSPs in the path info; no additional TLV is required for that purpose. The case where this may be useful would be if such transport LSPs exist in the backbone area and there is a willingness to provide higher preference to these LSPs to carry transit LSPs over backbone. There can be selective suppression of advertisements to other areas (backbone or non-backbone) of LSPs if these are existing LSPs setup along a path which are utilized to a greater degree. If underutilized with respect to the PWR metric a more favourable metric could be advertized to other areas. For example, backbone area transport LSPs will be advertized as transit LSPs which would provide connectivity to LSP sections lying Shankar Raman et.al Expires February 2013 [Page 11] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 in non-backbone areas and would be updated more frequently since they facilitate inter-Area TE. Once a path in the TLV has been used for reserving bandwidth for traffic over that path, then it is withdrawn from the advertisements so that it becomes unusable. Another path may be computed over the same path but with possibly a different PWR metric sum since it is possible that the traffic over that path could have changed the PWR metrices in the edges along that path. 2.3 Suppression of Frequent updates owing to fluctuation in power and bandwidth Using the power consumed and the bandwidth available as discrete quantities will result in frequent oscillations. Such a step would result will result in frequent re-computations of the shortest power paths. For the sake of suppression of such frequent updates, it is possible to handle the PWR metric as falling within reasonable intervals of thresholds. If the interval in which PWR metric lies is moved out of and another interval is reached then the update is sent out in the IGP-TE mechanism. Otherwise if the interval in which the PWR metric lies is not moved out of then the updates are not sent. Suitable thresholds can be arrived at after suitable calibration through tests. 2.4 Advantages 1) The TE Reachability vector TLV contains the aggregate of all link attributes along with TE constraints and so the head-end of the TE path can explicitly select the ABR that connects the destination area even though it does not know the complete topology of the backbone area. 2) As the TE reachability vector contains only the aggregate attributes of k-power-shortest-paths, the flooding overhead to suppose the mechanism is limited. 3) Centralized path computation element is not required for supporting inter-area power-shortest-path TE. The additional overhead of computing k-power-shortest-paths on ABR can be solved by offloading the computation overhead to additional processor in multi- core platforms. Shankar Raman et.al Expires February 2013 [Page 12] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 Shankar Raman et.al Expires February 2013 [Page 13] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 3 Security Considerations None. 4 IANA Considerations New TLV types for OSPF and IS-IS for the new TLVs that have been introduced need to be assigned. Their format needs to be arrived at in future versions of the document. 5 References 5.1 Normative References [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC1776] Crocker, S., "The Address is the Message", RFC 1776, April 1 1995. [TRUTHS] Callon, R., "The Twelve Networking Truths", RFC 1925, April 1 1996. 5.2 Informative References REFERENCES [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 Shankar Raman et.al Expires February 2013 [Page 14] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 Systems, 2010. [6] M. Xia et. al., Greening the optical backbone network: A traffic engineering approach, IEEE ICC Proceedings, May 2010, pp. 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 [11] Shankar Raman et al., draft-mjsraman-rtgwg-inter-as- psp-01.txt, Work in Progress, February 2012. [EVILBIT] Bellovin, S., "The Security Flag in the IPv4 Header", RFC 3514, April 1 2003. [RFC5513] Farrel, A., "IANA Considerations for Three Letter Acronyms", RFC 5513, April 1 2009. [RFC5514] Vyncke, E., "IPv6 over Social Networks", RFC 5514, April 1 2009. Authors' Addresses Shankar Raman Department of Computer Science and Engineering I.I.T Madras, Chennai - 600036 TamilNadu, India. EMail: mjsraman@cse.iitm.ac.in Shankar Raman et.al Expires February 2013 [Page 15] INTERNET DRAFT Building power shortest inter-Area TE-LSPs August 2012 Balaji Venkat Venkataswami Department of Electrical Engineering, I.I.T Madras, Chennai - 600036, TamilNadu, India. EMail: balajivenkat299@gmail.com Prof.Gaurav Raina Department of Electrical Engineering, I.I.T Madras, Chennai - 600036, TamilNadu, India. EMail: gaurav@ee.iitm.ac.in Shankar Raman et.al Expires February 2013 [Page 16]