RTGWG Working Group                                        Shankar Raman
Internet-Draft                                Balaji Venkat Venkataswami
Intended Status: Experimental RFC                           Gaurav Raina
                                                             Vasan Srini
Expires: February 2013                                      I.I.T Madras
                                                          August 5, 2012


          Reducing Power Consumption using BGP path selection
                 draft-mjsraman-rtgwg-bgp-power-path-02


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.



Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any



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   time.  It is inappropriate to use Internet-Drafts as reference
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Copyright and License Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors. All rights reserved.

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   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
         2.1.1.2 Earlier method of computing numerator of PWR
                 ratio. . . . . . . . . . . . . . . . . . . . . . . .  7
     2.2 LOW-POWER PATHS  . . . . . . . . . . . . . . . . . . . . . .  8
         2.2.0.1 Current BGP Best Path Selection Algorithm  . . . . .  9
         2.2.0.2 Algorithm 1 on ASBR  . . . . . . . . . . . . . . . . 11
         2.2.0.3 Modified Algorithm 0 on all BGP routers  . . . . . . 12
     2.3 Implementation notes and Discussion  . . . . . . . . . . . . 13
     2.4 Conclusion and Future Work . . . . . . . . . . . . . . . . . 15
     2.5 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
   3  Security Considerations . . . . . . . . . . . . . . . . . . . . 17
   4  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 17
   5  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 17



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     5.1  Normative References  . . . . . . . . . . . . . . . . . . . 17
     5.2  Informative References  . . . . . . . . . . . . . . . . . . 17
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
















































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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



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   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

   <Document text>

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



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   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.
















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                                 .__________________
                                (
                               (      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.

2.1.1.2 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



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   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
   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.


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.



























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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.




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   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



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   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































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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



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   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                             |
     +-------------------------------------------------------------+
     |          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.

   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



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   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
   the same AS, advertising PWR ratios that differ. This could lead to
   power values that belong to different classes of ratios with many



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   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 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.




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   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.






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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

   [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.



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              [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.

              [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.

   [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.



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   EMail: mjsraman@cse.iitm.ac.in



   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



   Vasan Srini,
   Department of Computer Science and Engineering,
   I.I.T Madras,
   Chennai - 600036,
   TamilNadu,
   India.

   Email: vasan.vs@gmail.com

















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