Power Based Topologies and Shortest Power Paths in OSPF
draft-mjsraman-rtgwg-ospf-power-topo-00
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| Authors | Shankar Raman , Balaji Venkat Venkataswami , Gaurav Raina , Vasan Srini | ||
| Last updated | 2012-03-25 | ||
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draft-mjsraman-rtgwg-ospf-power-topo-00
RTGWG Working Group Shankar Raman
INTERNET-DRAFT Balaji Venkat Venkataswami
Intended Status: Experimental RFC Gaurav Raina
Expires: September 2012 Vasan Srini
March 26, 2012
Power Based Topologies and Shortest Power Paths in OSPF
draft-mjsraman-rtgwg-ospf-power-topo-00
Abstract
In a Interior Gateway Protocol like OSPF (Open Shortest Path First)
the computation of the shortest path tree to all destinations is
computed for an area say a backbone or a non-backbone area. With
importance given to the reduction of power within a network it
becomes important to provide a solution that reduces the power
consumed amongst routers and links that make up the network (in this
case an area or a collection of areas including the backbone and non-
backbone areas). This proposal aims at providing such a solution by
producing a power topology of the area / areas. This power topology
is constructed by assigning metrics to links based on the power
consumed by the linecards (and hence their respective ports in an
indirect way) of adjacent routers that are interconnected by each
such link.
Status of this Memo
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Copyright and License Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Low-power routers and switches . . . . . . . . . . . . . . . 3
1.3 Power reduction using routing and traffic engineering . . . 3
2. Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Power Bias . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 ECMP links . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3 Dampening the side effects of constant change . . . . . . . 8
3. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3 Security Considerations . . . . . . . . . . . . . . . . . . . . 10
4 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 10
5 References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1 Normative References . . . . . . . . . . . . . . . . . . . 10
5.2 Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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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 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].
1.2 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].
1.3 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
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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. While
[6] handles optical networks and their corresponding power
consumption, it does not take into account other link layer
technologies. It is specialized for optical and not for heterogenous
links that will exist in common OSPF domains.
The proposal we make in this document indicates ways to solve the
power reduction problem, by calculating a POWER metric whose
importance is highlighted in the below mentioned sections. This POWER
metric is obtained by including the factors such as power consumed by
a linecard on a single chassis or multi-chassis router and
consequently a port on that linecard by proportionally calculating
power consumed for that port and hence for the link. The other factor
that is taken into account is the utilization on that port and hence
on that link.
2. Methodology
For each router / switch there exist linecards and each linecard has
a set of ports or sometimes just one port of high capacity. This
usually applies on routers and switches that are either single
chassis or multi-chassis in their characterisation. By single chassis
we mean that there exists a single chassis and slots for the Route
Processor Card (one or more of these) typically upto to two of them,
and one or more slots for linecards each having their respective
characteristics such as number of ports (port density), type of such
ports (SONET, ethernet, ATM etc..) usually depending on the link
layer technology they support. Links are connections between ports on
these linecards to other ports on linecards of other single chassis
or multi-chassis system. A multi-chassis system is one that has
multiple such chassis interconnceted amongst each other to form a
single logical view of the system. Both single and multi-chassis have
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linecards and respective ports on these linecards. Multi-chassis
typically have a switch fabric chassis which connects each of these
chassis to each other or to chassis of other multi-chassis or single
chassis systems.
Consider the following topology...
Router A Router B Router C
+---+---+ +---+---+ +-------+
| | | | | | | | |
|LC1|LC2| |LC1|LC2| |LC1|LC2|
| | | | | | L11 | | |
| P1| P1| | P1| P1|-------------- P1| P1|---+
| P2| P2|--+ | P2| P2| L12 | P2| P2| |
| P3| P3| | L4 | P3| P3|-------------- P3| P3| |
| P4| P4|--+----------- P4| P4| +---- P4| P4| |
| P5| P5| | +----P5| P5--+ L5 | | P5| P5| |
| | | | | | | | | | | | | | | | |
+-|-+-|-+ |L3 | +---+---+ | | +---+-|-+ | L13
| | | +------------+-------+ | |
| |L2 | L5 | | |
| +----+------------+ | | |
| | | | | |
|L1 | | |L6 | |
| | Router D | | Router E L12| | Router F
| | +---+---+ | | +---+---+ | |+-------+
| | | | | |L2 | | | | | || | |L
| | |LC1|LC2| | | |LC1|LC2| | ||LC1|LC2|1
| | | | | | | | | | | || | |4..
| +-| P1| P1---+ | | P1| P1|------+ || P1| P1|->
| | P2| P2| L7 +--- P2| P2| +--P2| P2|->
| | P3| P3|-------------- P3| P3| L10 | P3| P3|->
+----------| P4| P4| +---- P4| P4|-------------- P4| P4|
| P5| P5| | +-- P5| P5| +----- P5| P5|
| | | | | | | | | | | | |
+-|-+---+ L8 | | +---+---+ L9 | +---+---+
+---------------+ +------------------+
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The table of links between the various routers (which are assumed to
be single chassis systems) is as follows...
+--------+----------+-----------+-----------+-----------+----------+
| Links | Routers | LC <> LC | Port Conn.| Capacity |Utiln. |
| | | | | |betw. 0..1|
+--------+----------+-----------+-----------+-----------+----------+
| L1 | A <> D | LC1<>LC1 | P5<>P4 | 10G | .75 |
| L2 | A <> D | LC2<>LC2 | P5<>P1 | 10G | .60 |
| L3 | A <> D | LC2<>LC1 | P2<>P1 | 10G | .60 |
| L4 | A <> B | LC2<>LC1 | P4<>P4 | 10G | .20 |
| L5 | B <> C | LC1<>LC1 | P5<>P4 | 10G | .35 |
| L6 | B <> E | LC1<>LC1 | P6<>P2 | 10G | .10 |
| L7 | D <> E | LC2<>LC1 | P3<>P3 | 10G | .60 |
| L8 | D <> E | LC1<>LC1 | P5<>P4 | 10G | .15 |
| L9 | E <> F | LC1<>LC2 | P5<>P5 | 100G | .20 |
| L10 | E <> F | LC2<>LC1 | P4<>P4 | 10G | .15 |
| L11 | B <> C | LC2<>LC1 | P1<>P1 | 10G | .30 |
| L12 | E <> C | LC2<>LC2 | P1<>P5 | 10G | .20 |
| L13 | C <> F | LC2<>LC1 | P1<>P2 | 10G | .10 |
| L14 | F <> OA | LC2<> | P1<> | | .20 |
| | | | | | |
+--------+----------+-----------+-----------+------------+---------+
In the above topology assume all point-to-point links between the
routers. For now we will deal with P2P links alone and not venture
into Broadcast Multi-access links or Non-Broadcast Multi-access links
etc.. It is suffice to show how the scheme works for P2P links and
then move more specifically to other types of networks to demonstrate
this method of calculating the power topology of the network in the
figure.
Each linecard consumes a certain amount of power and it is vendor
dependent as to how the power consumed relates to the utilization on
any of the links to which the linecard connects to. It is possible
that the said topology of routers come from one vendor or from
multiple vendors. It is assumed that the algorithm proposed will have
the power consumed by a linecard available as a readable value in
terms of W or kW or whichever measurable metric that is provided by
the vendor.
It is possible that some of the Linecards are more capable than the
others. Consider that Router A is a more capable router with more
powerful linecard with higher port density. This is not shown in the
figure, but assume so. LC1, LC2 on Router A could be consuming more
power than the other Linecards on other routers. The main reason
could be that LC1 and LC2 may have higher port density or higher
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speed ports than the other routers. In order to calculate the power
consumed on a link by a linecard it is important that we normalize
the power as power consumed per port. Here the ports are normalized
to lowest common denominator. If all links in the topology have 10G
port capacity then the power calculated should be in terms power
consumed per 10G port.
Assuming we have done this normalization we go on to calculate the
POWER metric for each of the ports involved in a link which is
derived as follows...
POWER metric = Power consumed per XG (normalized bandwidth) port
for a given -------------------------------------------------
Port on a LC Available Utilization on that port
Assume link L1. The ports concerned are both 10G and the ports are P5
on Router A and P4 on Router D. For calculating the POWER metric for
a link which we will call PWRLINK we calculate the POWER metric for
each side of the link and average the two to get PWRLINK.
So PWRLINK for L1 = POWER for P5 on LC1 + Power for P4 on LC1
on Router A on Router D
============================================
2
The above can also be weighted if there is a multi-capacity port on
one side of the link and not on the other. A multi-capacity link is
one which provides multiple bandwidth capabilities such (1G/10G/100G)
for example but auto-negotiates with other end to provide a lesser
than highest capacity service.
The PWRLINK metrices once calculated are flooded in already defined
OSPF-TE-LSA as an adapted TE-metric and is typically flooded as a
link characteristic.
It is important to note that the denominator for POWER metric is
Available Utilization on that port. The Available Utilization is
measured in terms of intervals and not as discrete quantities. This
is in order not to flood PWRLINK metrics into the OSPF area in LSAs
very frequently as utilization may constantly change. The same
applies to POWER metric as well.
Once the LSAs have been flooded the Routers run SPF on the tree with
PWRLINKs assigned to the topology and calculate the PWRLINK based
topology. This Power based topology can be used for forwarding high
bandwidth streams and to optimally use power within the area.
The Utilization column shows the utilization of the link
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corresponding to the row and column intersection a figure between 0
and 1. If utilized 100% then the figure shown will be 1 and if none
then 0 and for the rest somewhere in the middle. This figure is used
as the numerator in the POWER metric computation for that port.
2.1 Power Bias
Assume in the figure that there exist Routers A and D and that there
is a bias on the link L1 in such a way that Router D computes a POWER
metric of 10 and the Router D computes a POWER metric of 2 on the
ports P5 and P4 respectively. Now the PWRLINK would be 6 for that
link L1. Thus even if one side is excessively power guzzling then the
PWRLINK moves up and thus is less preferred in the SPF tree and next
hop computation for the Power topology.
If there is no bias and both the sides of the link are optimal in
their power usage then the metric stays low even if more streams are
sent on it. This is the main objective that is set out for router and
switch manufacturers in the single chassis and multi-chassis world,
in that they are incentivized to manufacture linecards that are not
power hungry even if the number of packets flowing through them is
high and thus the utilization is also high.
For those manufacturers who set a high power value for even minimal
traffic, the vendors that dont would win out in the end.
2.2 ECMP links
It is possible that multiple links would have the same PWRLINK metric
after a computation cycle. In such a case load-balancing techniques
can be used to keep the ECMP links in a steady state with respect to
each other. Depending on the utilization thereafter it is possible
that the ECMP links may no longer be Equal cost but UCMP or Unequal
Cost Paths.
2.3 Dampening the side effects of constant change
It is recommended in this draft that the implementation of the
proposal be adaptive, infrequent in computation to the extent
possible without sacrificing adapting to the dynamism and also reduce
any frequent oscillations. The actual methods to adopt for this
computation are outside the scope of this document.
3. Conclusion
Routers may have step levels in which they increase power consumption
when they additively are loaded with more large bandwidth consuming
multicast or unicast streams. Calibrating these levels may be useful
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for implementing this scheme. It is possible that such calibrated
thresholds can be used for advertising the PWRLINK ratios in the OSPF
LSA advertisements. This would be useful for bringing down the
frequency of updates or advertisements from a line-card about its
PWRLINK ratio. When power consumption meanders within a certain given
interval these ratios need not be re-advertised even if further
unicast and/or multicast streams are added to it. The incentive is to
recognize a linecard that does not drastically change power
consumption even if large bandwidth streams are added onto it for
forwarding and thus give it credit for its power optimal functioning.
If a router tends to consume the highest level of power even when
carrying low amounts of unicast and multicast streams on its line
card, it would automatically have a poor ratio when compared to a
router that efficiently uses power when considering the utilization
being observed. The best case would be a low power consuming line-
card or a router filled with such line cards that does not leave its
power interval no matter how much ever capacity is sought to be used
on it. But that would be an ideal condition but it is definitely an
idealistic scenario towards which the router manufacturers should
look at.
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3 Security Considerations
<Security considerations text>
4 IANA Considerations
No new requirements are required from IANA for any new TLV as the TE-
metric is adaptively changed to reflect the PWRLINK metric as well.
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
[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.
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INTERNET DRAFT Power based Topologies and SPF in OSPF March 26, 2012
[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
[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
Balaji Venkat Venkataswami,
Department of Electrical Engineering,
I.I.T Madras,
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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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