RTGWG Working Group Shankar Raman Internet-Draft Balaji Venkat Venkataswami Intended Status: Experimental RFC Gaurav Raina Expires: October 30, 2013 Vasan Srini IIT Madras April 28, 2013 Reducing Power Consumption using BGP path selection draft-mjsraman-rtgwg-bgp-power-path-04 Abstract In this paper, we propose a framework to reduce the aggregate power consumption of the Internet using a collaborative approach between Autonomous Systems (AS). We identify the low-power paths among the AS and then use suitable modifications to the BGP path selection algorithm to route the packets along the paths. Such low-power paths can be identified by using the consumed-power-to-available-bandwidth (PWR) ratio as an additional parameter in the BGP Path Selection Algorithm. For re-routing the data traffic through these low-power paths, the power based best path is selected and advertised as per the modified algorithm proposed in this document. Extensions to the Border Gateway Protocol (BGP) can be used to disseminate the PWR ratio metric among the AS thereby creating a collaborative approach to reduce the power consumption. The feasibility of our approaches is illustrated by applying our algorithm to a subset of the Internet. The techniques proposed in this paper for the Inter-AS power reduction require minimal modifications to the existing features of the Internet. The proposed techniques can be extended to other levels of Internet hierarchy, such as Intra-AS paths, through suitable modifications. A recent addition is the use of this method in AIGP domains and also the use of power source data in the calculation of low power paths using the BGP path selection algorithm. 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. Shankar Raman.et.al Expires October 30, 2013 [Page 1] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 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) 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 . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1 Low-power routers and switches . . . . . . . . . . . . . . . 4 1.2 Power reduction using routing and traffic engineering . . . 4 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Methodology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 Pre-requisites for the Proposed Method . . . . . . . . . . . 5 2.1.1 PWR ratio calculation . . . . . . . . . . . . . . . . . 5 2.1.1.1 Power Sources as additional factor . . . . . . . . . 7 2.1.1.2 Earlier method of computing numerator of PWR ratio. . . . . . . . . . . . . . . . . . . . . . . . 8 2.2 LOW-POWER PATHS . . . . . . . . . . . . . . . . . . . . . . 9 2.2.0.1 Current BGP Best Path Selection Algorithm . . . . . 10 2.2.0.2 Algorithm 1 on ASBR . . . . . . . . . . . . . . . . 12 2.2.0.3 Modified Algorithm 0 on all BGP routers . . . . . . 13 2.3 Implementation notes and Discussion . . . . . . . . . . . . 14 2.4 Applicability within ASes within a single Admin Domain . . . 16 2.4.1 PWR_SESSION . . . . . . . . . . . . . . . . . . . . . . 16 Shankar Raman.et.al Expires October 30, 2013 [Page 2] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 2.4.2 Power profiles of Routers and Switches . . . . . . . . . 17 2.4.2.1 Concave and Convex power curves . . . . . . . . . . 19 2.4.2.3 Need to advertise both available power and consumed power . . . . . . . . . . . . . . . . . . . 20 2.4.3 Conclusion and Future Work . . . . . . . . . . . . . . . 21 2.5 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22 3 Security Considerations . . . . . . . . . . . . . . . . . . . . 23 4 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 23 5 References . . . . . . . . . . . . . . . . . . . . . . . . . . 23 5.1 Normative References . . . . . . . . . . . . . . . . . . . 23 5.2 Informative References . . . . . . . . . . . . . . . . . . 23 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24 Shankar Raman.et.al Expires October 30, 2013 [Page 3] INTERNET DRAFT Reducing power using BGP path selection April 28, 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]. 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 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 Shankar Raman.et.al Expires October 30, 2013 [Page 4] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 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 not for Inter- AS cases. In our approach, we propose a collaborative approach by AS in power reduction. The core of the Internet at the Inter-AS level, uses the BGP best path selection algorithm. The AS use the Border Gateway Protocol (BGP) for exchanging routing related information. One of the attributes of BGP namely, AS-PATH-INFO is used to derive the topology of the Internet at the AS level. In this document we propose that the BGP best path selection algorithm is run in each AS at an appropriate BGP router with the consumed-power-to-available- bandwidth (PWR) ratio as a parameter, to determine the low-power paths from the head-end to the tail-end AS in order to reach a prefix or a set of prefixes. The PWR ratio can be exchanged among the collaborating AS using BGP attributes. 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]. 2. Methodology 2.1 Pre-requisites for the Proposed Method In this section we discuss the pre-requisites for the implementation of the proposed scheme. 2.1.1 PWR ratio calculation In this proposal each AS is expected to share its PWR ratio from as many ASBRs (Autonomous System Border Routers) that it has. Intuitively in order to calculate this ratio we need to calculate the consumed power representative of the AS and the maximum bandwidth available with an ASBR on its egress links into the AS. The entry point to the AS is through the ASBRs that advertise the prefixes reachable through the AS. Hence the numerator of the PWR ratio is Shankar Raman.et.al Expires October 30, 2013 [Page 5] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 calculated for the AS at each ingress ASBR. We first obtain the summation of power consumed at the Provider (P) and the Provider Edge (PE) routers within an AS. The numerator of the PWR ratio is calculated by summing up the consumed power of all the routers to be taken into account and then dividing this sum by the number of routers. A more intuitive approach would be to use a weighted average method by assigning routers to categories and having appropriate co- efficients for each of these categories, thus arriving at a weighted average which is more accurate. One of these alternatives can be used to arrive at the numerator of the PWR ratio. Yet another alternative would have been to sum up the total consumed power of all routers in the AS and represent that as the numerator of the PWR ratio. This average consumed power is divided by the maximum bandwidth available at each of the ASBR's egress link. This step is necessary as the requested bandwidth for any path from the head-end to the tail-end using the ASBR is limited by the bandwidth available in the ASBR's egress links. The highest available bandwidth amongst the egress links of the ASBR is used as the denominator in the PWR ratio computation. If the entry point to the AS is through a different ASBR then the PWR ratio assigned to the ingress link of the ASBR might vary. Hence, an head-end AS might see different PWR ratios for an intermediate AS, if the intermediate AS has different ASBRs as its entry point. We now illustrate the PWR ratio calculation. Consider an AS X which is one of the AS in the vicinity of another AS Y . Let this ASBR of X have 3 egress links into X denoted as E(1), E(2) and E(3), and 2 ingress links labeled I(1) and I(2). We now calculate the PWR ratio for I(1) and I(2). Assume that the routers in X have average consumed power of 200K Watts per hour. From figure 4 we can calculate the PWR ratio for I(1) and I(2) as 200K Watts / (60 * 60 * 1.5 Gigb = 3.7037 * (10 raised to -8) We could scale this to 0.37087 by multiplying with a base value of 10 raised to the 7th power. Shankar Raman.et.al Expires October 30, 2013 [Page 6] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 .__________________ ( ( E(1) \ ( +--------->(Core router) \ +-------+ / 1Gb +------>| |/ E(2) 200KW / (60*60*1.5Gb) | ASBR |------------>(Core router) +------>| of |\ 1Gb / | AS 100| \ / +-------+ \ E(3) ( +-------->(Core router) ( 1.5Gb .__________________ Figure 1:Calculation of PWR ratio by an ASBR associated with an AS. The I represents ingress links and E represents egress links. 200KW is the average consumed power in the AS. 1.5Gb is the maximum available bandwidth of the egress link in an ASBR. Note that this ratio is actually a mapping function that is defined for each of the ingress links of the ASBR associated with an AS. For the head-end which is the BGP Path selection running AS this mapping function does not exist as there is no ingress link. The PWR ratio can then be advertised to the other neighboring AS using the control plane through BGP extensions. BGP ensures that the information is percolated to other AS beyond the immediate neighbors. On receipt of these power metrics to the AS at the far-ends of the Internet, the overall AS level PWR ratio based Internet topology can be constructed. This view of the Internet is available with each of the routers without using any other complex discovery mechanism. Some sample link weights shown in Figure 1 is obtained by using such a mapping function on the ingress links. 2.1.1.1 Power Sources as additional factor It is envisaged that the power sources of the Autonomous system using which the routers in the AS are powered should be declared as a metric which is further incorporated in the PWR ratio. A suitable weight is provided to each type of source and the following table which is not claimed as totally exhaustive can be used to add this metric in the equation to compute the PWR ratio. A formal classification of power sources and their weights is a topic to be considered later. For now we will deal with 2 main categories. Renewable sources of energy and non-renewable sources. There would be multiple categories under each of these major categories. Each such power source is assigned a weight. Shankar Raman.et.al Expires October 30, 2013 [Page 7] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 Renewable Sources of Energy : Wind - HighWeightOne Solar - HighWeightTwo Hydro - HighWeightThree etc... Non-renewable Sources of Energy : Natural Gas - LowWeightOne Petroleum and Diesel - LowWeightTwo Nuclear - LowWeightThree etc... The PWR-SOURCE ratio is calculated in the proportion of how the above sources are combined to power the routers and its coolant systems and ancillary facilities in the AS. Thus PWR-RATIO = ( Consumed-Power / Available-Bandwidth) * (1 / Weighted Average of Power Sources) This compound metric could be used as the PWR metric in the calculations specified in this draft. 2.1.1.2 Earlier method of computing numerator of PWR ratio. Earlier in the previous versions of this document in order to calculate this PWR ratio we needed to calculate the available power and the maximum bandwidth available with an ASBR. The entry point to the AS is through ASBRs that advertise the prefixes reachable through the AS. Hence, the numerator of the PWR ratio is calculated for the AS at each ingress ASBR. We first obtained the summation of power consumed at the major Provider (P) and Provider Edge (PE) routers within an AS. The average available power is obtained by subtracting the consumed power from the maximum power rating and summing the values for all the routers and then dividing the result by the number of routers. As an alternative, one could use a weighted average for more accuracy depending on the category of the router advertising the consumed power. Yet another alternative is to take the average or sum of the maximum power rating of all the routers within an AS without taking into account the consumed power. One of these alternatives was chosen to calculate the numerator of the PWR ratio. Intuition however drives us towards consumed power as a better numerator since the lesser the power consumed the lesser the numerator and hence lesser the ratio if enough bandwidth is available at the ingress ASBR. The amount of consumed power per bit of information ought to be low for the shortest path to work out Shankar Raman.et.al Expires October 30, 2013 [Page 8] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 properly. One more aspect is that lesser the power consumed per available bit of bandwidth it could be a sign that routers are more optimal in their power consumption as they take on more traffic. This is a very crucial point to be considered. However additional research seems to indicate that both Available and Consumed Power for a router be advertised. The need that arises for such a proposition is that there exist power profiles of routers which is dealt in later sections (section 2.4.2). Please refer section 2.4.2.1 onwards for more analysis and research on this subject. 2.2 LOW-POWER PATHS In this section we present the low-power path BGP best path selection algorithm. The algorithm consists of two sub-algorithms: the first algorithm is executed by all the ASBRs in the network and the second by all the BGP routers in their respective AS. The algorithms for the ASBRs and BGP routers are given as Algorithm 1 and 2. The algorithm in 2.2.0.1 is the current BGP best path algorithm and is titled Algorithm 0. Shankar Raman.et.al Expires October 30, 2013 [Page 9] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 2.2.0.1 Current BGP Best Path Selection Algorithm As taken from [11] the following is the current BGP Best Path Selection Algorithm. Algorithm 0 : BEGIN BGP assigns the first valid path as the current best path. BGP then compares the best path with the next path in the list, until BGP reaches the end of the list of valid paths. This list provides the rules that are used to determine the best path: 1) Prefer the path with the highest WEIGHT. 2) Prefer the path with the highest LOCAL_PREF. 3) Prefer the path that was locally originated via a network or aggregate BGP subcommand or through redistribution from an IGP. Local paths that are sourced by the network or redistribute commands are preferred over local aggregates that are sourced by the aggregate-address command. 4) Prefer the path with the shortest AS_PATH. An AS_SET counts as 1, no matter how many ASs are in the set. The AS_CONFED_SEQUENCE and AS_CONFED_SET are not included in the AS_PATH length. 5) Prefer the path with the lowest origin type. Note: IGP is lower than Exterior Gateway Protocol (EGP), and EGP is lower than INCOMPLETE. 6) Prefer the path with the lowest multi-exit discriminator (MED). 7) Prefer eBGP over iBGP paths. If bestpath is selected, go to Step 9 (multipath). Note: Paths that contain AS_CONFED_SEQUENCE and AS_CONFED_SET are local to the confederation. Therefore, these paths are treated as internal paths. There is no distinction between Confederation External and Confederation Internal. 8) Prefer the path with the lowest IGP metric to the BGP next hop. Shankar Raman.et.al Expires October 30, 2013 [Page 10] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 Continue, even if bestpath is already selected. 9) Determine if multiple paths require installation in the routing table for BGP Multipath. Continue, if bestpath is not yet selected. 10) When both paths are external, prefer the path that was received first (the oldest one). This step minimizes route-flap because a newer path does not displace an older one, even if the newer path would be the preferred route based on the next decision criteria (Steps 11, 12, and 13). Skip this step if any of these items is true: You have enabled the bgp best path compare-routerid command. The router ID is the same for multiple paths because the routes were received from the same router. There is no current best path. The current best path can be lost when, for example, the neighbor that offers the path goes down. 11) Prefer the route that comes from the BGP router with the lowest router ID. The router ID is the highest IP address on the router, with preference given to loopback addresses. Also, you can use the bgp router-id command to manually set the router ID. Note: If a path contains route reflector (RR) attributes, the originator ID is substituted for the router ID in the path selection process. 12) If the originator or router ID is the same for multiple paths, prefer the path with the minimum cluster list length. This is only present in BGP RR environments. It allows clients to peer with RRs or clients in other clusters. In this scenario, the client must be aware of the RR-specific BGP attribute. 13) Prefer the path that comes from the lowest neighbor address. This address is the IP address that is used in the BGP neighbor configuration. The address corresponds to the remote peer that is Shankar Raman.et.al Expires October 30, 2013 [Page 11] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 used in the TCP connection with the local router. Algorithm 0: END 2.2.0.2 Algorithm 1 on ASBR 1: Begin 2: if ROUTER == ASBR then 3: /* As part of IGP-TE */ 4: Trigger exchange of available bandwidth on bandwidth change, to the AS internal neighbors; 5: BEGIN PROCESS 1 6: while PWR ratio changes do 7: Assign the PWR ratio to the Ingress links; 8: Exchange the PWR ratio with its external neighbors; 9: Exchange the PWR ratio with AS's (internal) ASBRs; 10: end while 11: END PROCESS 1 12: End Shankar Raman.et.al Expires October 30, 2013 [Page 12] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 2.2.0.3 Modified Algorithm 0 on all BGP routers 1: Begin 2: If ROUTER is Configured with BGP then 3: Run all steps from 1 to 3 in BGP regular path selection algorithm; /* when comparing AS_PATHS (MODIFICATION HERE) */ 4: Check if there are no multiple AS_PATHS then goto regular step (4); 5: if PWR metric based path selection is configured then 6: For each AS_PATH(1..n) in this set in step (4) 7: if there exists a PWR metric for all elements in AS_PATH then 8: PWR_SUM[i] = sum the PWR metrices for that AS_PATH; 9: else 10: ignore the AS_PATH; 11: endif 12: endFor 13: If there exists multiple PWR_SUM[i] then 14: Choose the AS_PATH / AS_PATHS with least PWR_SUM; 15: if multiple least PWR_SUMs (equal valued) exist then 16: Take up the set of such AS_PATHS and goto step 5; 17: endif 18: else 19: if there exist no PWR_SUM because of exclusion then 20: do regular step(4) to select best paths; 21: endif 22: endif 23: else 24: Do regular step(4); 25: endif 26: Run all steps from 5 to 13 in BGP regular path selection algorithm; 27: endif 28: End Shankar Raman.et.al Expires October 30, 2013 [Page 13] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 It is to be noted that the PWR metric based path selection will ensue only if the modified steps are activated as a result of specific user configuration. 2.3 Implementation notes and Discussion We propose addition of some BGP attributes with no change to the protocol implementation. There may be a time lag when the far ends of the Internet receive the attribute and the time it originated. This however cannot be avoided as with other attributes and metrics. 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 +-------------------------------------------------------------+ | Owning 32 bit Autonomous System Number | +-------------------------------------------------------------+ | Other 32 bit Autonomous System Number | +-------------------------------------------------------------+ | PWR Ratio for the AS (Consumed PWR) | +-------------------------------------------------------------+ | PWR Ratio for the AS (Available PWR) | +-------------------------------------------------------------+ | Advertising ASBR's IP router ID | +-------------------------------------------------------------+ | Peer ASBR's IP router ID | +-------------------------------------------------------------+ | 64 bit sequence number for restarts, aging | | and comparison of current PWR Ratio. | +-------------------------------------------------------------+ Figure 2: Proposed PDU format with an added attribute for AS-PATH- POWER-METRIC The additions to the above Attribute have been added to optimize and correctly correlate the connecting ASes and the inter-AS links among them. For the traffic direction into the Advertising AS the above information will be easier to correlate than the previous version which did not advertise the peer AS which had the ingress links into the advertising Router. In MPLS-TE for example, when the TE metrics are modified, there is a reliable flooding process within an Interior Gateway Protocol (IGP). Such triggered updates apply to the PWR ratio in BGP as well. The proposed PWR ratio is advertised to the neighboring AS and the information percolated to all the AS, in a AS-PATH-POWER-METRIC attribute. This attribute can be implemented as shown in Figure 2. The frequency of the updates for this attribute should be fixed to avoid network flooding. Shankar Raman.et.al Expires October 30, 2013 [Page 14] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 The AS-PATH-POWER-METRIC for each ASBR is calculated, and advertised as the PWR ratio for the AS. This AS-PATH-POWER-METRIC is filled into the appropriate transitive non-discretionary attribute and inserted into a unique vector for a set of prefixes advertised from the AS. Such advertised prefixes may have originated from the AS or be the transit prefixes. The filled vector is sent to the ASBR of the neighboring AS and the information propagates to all the ASBRs. If the elements denoting AS in a vector of AS-PATH-INFO is not the same as the ones that need to be advertised in a AS-PATH-POWER-METRIC, then a suitable subset of AS-PATH-POWER-METRIC is identified and sent in the BGP updates. A vector of size 1 also can be employed if the AS in question is the only one for which PWR ratio has changed in the originating AS. The collation can be done depending on availability of such metrics and their mapping to a valid AS-PATH-INFO metric. 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. 0.1 0.2 0.1 (A) ---> (B) ---> (D) 0.1 0.2 0.02 0.2 (A) ---> (C) ---> (E) ---> (D) 0.1 0.2 (D) ---> (X) Figure 4: Example of strands where more than one PWR ratio is advertised by "D" 0.2 0.1 0.2 (A).....>(B).....>(D).....>(X) | ^ |0.2 0.02 | 0.2 +--->(C)-------->(E) Figure 5:Choice of low-power path derived using the algorithm which uses lower value of the ingress link but through the same AS A use case of multiple ASBRs advertising differing PWR ratio shows that an AS may be seen as green through one ingress link and not through the other. Consider the case of multiple ASBRs that belong to Shankar Raman.et.al Expires October 30, 2013 [Page 15] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 the same AS, advertising PWR ratios that differ. This could lead to power values that belong to different classes of ratios with many intervening classes in between. These advertised PWR ratios could lead to one ASBR being preferred over the other thus taking a different path from head-end to tail-end. This also entails that there may be multiple paths to the AS through these different ASBRs. Consider Figure 4 which shows a set of strands that derive a topology as in Figure 5. Here D is reachable via two paths but the PWR ratios differ. This illustrates the case where the better metric wins out. The average power consumed would not have an effect but the bandwidth available on these ASBR egress links would definitely influence the path. 2.4 Applicability within ASes within a single Admin Domain As per [draft-ietf-idr-aigp] there are deployments in which a single administration runs a network which has been sub-divided into multiple, contiguous ASes, each running BGP. There are several reasons why a single administrative domain may be broken into several ASes (which, in this case, are not really "autonomous".) It may be that the existing IGPs do not scale well in the particular environment; it may be that a more generalized topology is desired than could be obtained by use of a single IGP domain; it may be that a more finely grained routing policy is desired than can be supported by an IGP. In such deployments, it can be useful to allow BGP to make its routing decisions based on the IGP metric, so that BGP chooses the "shortest" path between two nodes, even if the nodes are in two different ASes within that same administrative domain. The authors refer to the set of ASes in a common administrative domain as an "AIGP Administrative Domain". A combination of the AIGP administrative metric and the Path selection algorithm could be combined to arrive at a set of a suitable number of equal k power-shortest paths and then use a tie- break amongst such k power-shortest-paths with the least AIGP metric. This is provided the set of ASes where the decision is being made all fall under a AIGP Administrative domain. This provides a trade-off of power shortest paths and least number of hops (link wise) to get from source to destination across these ASes. 2.4.1 PWR_SESSION An implementation that supports the PWR attribute CAN support a per- session configuration item, PWR_SESSION, that indicates whether the PWR attribute is enabled or disabled for use on that session. - The default value of PWR_SESSION, for EBGP sessions, between Shankar Raman.et.al Expires October 30, 2013 [Page 16] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 providers (distinct operators) CAN be "disabled". - The default value of PWR_SESSION, for IBGP and confederation- EBGP sessions, MUST be "enabled." The PWR attribute MUST NOT be sent on any BGP session for which PWR_SESSION is disabled. If an PWR attribute is received on a BGP session for which PWR_SESSION is disabled, the attribute MUST be treated exactly as if it were an unrecognized transitive attribute. That is, " The handling of an unrecognized optional attribute is determined by the setting of the Transitive bit in the attribute flags octet. Paths with unrecognized transitive optional attributes SHOULD be accepted. If a path with an unrecognized transitive optional attribute is accepted and passed to other BGP peers, then the unrecognized transitive optional attribute of that path MUST be passed, along with the path, to other BGP peers with the Partial bit in the Attribute Flags octet set to 1. If a path with a recognized, transitive optional attribute is accepted and passed along to other BGP peers and the Partial bit in the Attribute Flags octet is set to 1 by some previous AS, it MUST NOT be set back to 0 by the current AS". This helps in confining the distribution of the attribute and use in calculation of the power shortest paths only amongst ASes that have trust relationships with other ASes. Of course, this includes and promotes the use of PWR attribute within a AIGP administrative domain. 2.4.2 Power profiles of Routers and Switches 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 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 October 30, 2013 [Page 17] INTERNET DRAFT Reducing power using BGP path selection April 28, 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 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. Shankar Raman.et.al Expires October 30, 2013 [Page 18] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 ^ | P | . o | . w | . e | . r | . | . c | . o | . n | . s | . u.| . ------------------------------------> | Available Bandwidth exhausted 2.4.2.1 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 (b) If the confrontation is between 2 second profile routers the upper curve offers more power savings per GB of bandwidth. Shankar Raman.et.al Expires October 30, 2013 [Page 19] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 ^ | 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. ^ . | . P | . . o | (*) w | . . e | . . r | . . | . . c | . . o | . . n | . . s | . . u.| .. ------------------------------------> | Available Bandwidth exhausted (*) Metric switchover point from Consumed Power to Available Power. 2.4.2.3 Need to advertise both available power and consumed power Shankar Raman.et.al Expires October 30, 2013 [Page 20] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 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]. 2.4.3 Conclusion and Future Work In this paper, we proposed a scheme for reducing the power consumption of the Internet using collaborative effort between AS. The BGP best path algorithm is run with suitable modifications in step (4) as described by using the PWR ratio as a parameter. The PWR ratio is advertised through the ingress links of the ASBRs associated with AS using BGP updates. The Modified BGP Best Path Selection Algorithm finds out the low-power consuming AS that can route data packets for a set of prefixes. This entails adopting routes by choosing entry points to an AS that give energy saving paths. Our work complements the current schemes for reducing power consumption within a router such as switching off or bringing to power-idle-state certain select components within the forwarding and lookup mechanisms. Normally the ASes have SLA agreements between each other to carry X amount of traffic from say a provider A. If the AS representing the ISP then advertises fake figures to carry more traffic than is mandated by the SLA agreement with other providers, then it is to that ISPs detriment since by advertising a better PWR ratio it invites more traffic through it thus getting paid less and carrying more traffic. This is not in the best interest of the ISP. This is so because in the final analysis the Power Shortest Path computed would include it regardless of the amount of traffic to be carried thus causing it to invite more traffic through it than it has accepted, even much more than its capacity. Hence it would be advisable for that ISP to advertise proper PWR ratios and NOT on the lower side of the spectrum. If it advertises HIGHER PWR ratios it would not be chosen, and hence that could be a policy measure NOT to accept any traffic at all since its capacity may be filled up with existing traffic. So advertising on the LOWER side would lead to lesser amount of benefit with respect to dollar per bit transported, and on the HIGHER side would be to exclude it from carrying any traffic that wanted to use the Power Shortest Path. Shankar Raman.et.al Expires October 30, 2013 [Page 21] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 We also propose that there be a governing body in the IETF or outside it or sponsored by the IETF to verify the power ratios advertised are indeed valid or approximately closer to the actual consumption. A link up for each ISP with a power application level gateway to ensure proper ratios are advertised could be mandated amongst at least the co-operating ISPs (ASes). The aspect of innovation in this proposal is to use BGP as the piggyback protocol upon which this scheme stands. When links and switches are gated or put into low-power state within an AS, the power-consumption automatically drops at the aggregate level, as a result of which the PWR ratio would be a lower figure advertised through BGP and thus this AS would attract more Power Shortest Path traffic through it. Thus the links within the AS and the switches within it would function more optimally if it had more traffic that went along paths that were originally put in low-power state thus utilizing the paths more effectively, when attracting traffic. There exist MIBs today that have object identifier for power consumed in a router. Maybe all the related components within it may NOT be listed with regards to power consumed. But the overall power consumed by the Router / Switch is gettable. Once it is advertised in a opaque Link-State-Advertisement say in the form of a TLV (Type Length Value) and the LSAs (Link State Advertisements) are flooded through the network in an AS, all routers get a uniform picture of which router consumes what power. This method already exists for Traffic engineering Database LSAs that are advertised as LSAs for the purpose of traffic engineering within an AS. We are merely piggybacking on this capability to calculate the PWR ratio at the ASBR which amongst others is yet another Router / Switch of the AS. Our future work includes looking into computing low-power paths within AS as well. 2.5 Acknowledgements Shankar Raman would like to acknowledge the support by BT Public Limited (UK) under the BT IITM PhD Fellowship award. Balaji Venkat and Gaurav Raina would like to acknowledge the UK EPSRC Digital Economy Programme and the Government of India Department of Science and Technology (DST) for funding given to the IU-ATC. Vasan Srini would like to thank Dr.(Prof).Kamakoti of the Computer Science and Engineering department for his support. Shankar Raman.et.al Expires October 30, 2013 [Page 22] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 3 Security Considerations No specific security considerations apart from the usual considerations with respect to authenticating BGP messages / updates from BGP neighbors is necessary for this scheme. 4 IANA Considerations A new optional transitive non-discretionary attribute needs to be provided by IANA for carrying the PWR ratio across the Internet in the specified format in BGP. 5 References 5.1 Normative References TBD 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 Systems, 2010. [6] M. Xia et. al., Greening the optical backbone network: A traffic engineering approach, IEEE ICC Proceedings, May 2010, pp. 1-5. Shankar Raman.et.al Expires October 30, 2013 [Page 23] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 [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] http://www.cisco.com/en/US/tech/tk365/ technologies_tech_note09186a0080094431.shtml, BGP best path selection algorithm. [draft-ietf-idr-aigp] P. Mohapatra et.al, The Accumulated IGP metric attribute for BGP, https://datatracker.ietf.org/doc/draft-ietf-idr-aigp/, November 2012. 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. Shankar Raman.et.al Expires October 30, 2013 [Page 24] INTERNET DRAFT Reducing power using BGP path selection April 28, 2013 EMail: balajivenkat299@gmail.com 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 October 30, 2013 [Page 25]