Internet DRAFT - draft-mjsraman-panet-tcam-power-ratio
draft-mjsraman-panet-tcam-power-ratio
PANET Working Group Shankar Raman
INTERNET-DRAFT Balaji Venkat Venkataswami
Intended Status: Experimental RFC Prof.Kamakoti Veezhinathan
Expires: August 2013 IIT Madras
February 3, 2013
Computing Power Saving Paths using TCAM Power Ratio
draft-mjsraman-panet-tcam-power-ratio-02
Abstract
A power saving scheme for switching of TCAM banks of fine granularity
is discussed in [ID-TCAM-POWER-EFF]. This scheme switches of TCAM
banks of fine granularity and their corresponding SRAM banks
depending on the occupancy of routes and their rewrites within the
TCAM of a intelligent router line card (where one or more such TCAM
entities along with their SRAM banks may reside) by using an
algorithm specified in [ID-TCAM-POWER-EFF]. This takes care of
switching off TCAM and SRAM banks within a router's line card and
correspondingly saves power when the traffic matrix is not large with
respect to the routes the packets lookup where the occupancy of such
routes is low in the line card. This is with reference to both single
and multi-chassis devices. The algorithm specified therein tends to
switch off banks which are not in use. The aim of this draft is to
use the device level characteristic in the form of a TCAM Power Ratio
and disseminate it as a metric within an area or an Autonomous system
(where multiple such areas exist within an AS) to compute power
saving paths through the set of routers where the TCAM-POWER-RATIO is
low. The TCAM-POWER-RATIO is arrived at by dividing the number of
bits in the TCAM banks that are switched off by the Total Available
TCAM bank space in bits. This ratio is then subjected to the CSPF
algorithm as an additional constraint or the only constraint as the
case may be in a link state protocol like OSPF or IS-IS with Traffic
Engineering Extensions with available utilization on the links also
being a factor. This way those routers that have more TCAM banks
switched off are avoided and those with higher power consumption but
with available bandwidth are used hence not increasing the total
power consumed within the area and hence within the AS. This could be
achieved by using a PCE like entity that calculates the power
shortest paths using this TCAM-POWER-RATIO.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Methodology of the Proposal . . . . . . . . . . . . . . . . . 4
2.1 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 7
3 Security Considerations . . . . . . . . . . . . . . . . . . . . 8
4 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
5 References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1 Normative References . . . . . . . . . . . . . . . . . . . 8
5.2 Informative References . . . . . . . . . . . . . . . . . . 8
APPENDIX - A : References for power saving related material . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1 Introduction
A power saving scheme for switching of TCAM banks of fine granularity
is discussed in [ID-TCAM-POWER-EFF]. This scheme switches of TCAM
banks of fine granularity and their corresponding SRAM banks
depending on the occupancy of routes and their rewrites within the
TCAM of a intelligent router line card (where one or more such TCAM
entities along with their SRAM banks may reside) by using an
algorithm specified in [ID-TCAM-POWER-EFF]. This takes care of
switching of TCAM and SRAM banks within a router's line card and
correspondingly saves power when the traffic matrix is not large with
respect to the routes the packets lookup where the occupancy of such
routes is low in the line card. This is with reference to both single
and multi-chassis devices. The algorithm specified therein tends to
switch off banks which are not in use. The aim of this draft is to
use the device level characteristic in the form of a TCAM Power Ratio
and disseminate it as a metric within an area or an Autonomous system
(where multiple such areas exist within an AS) to compute power
saving paths through the set of routers where the TCAM-POWER-RATIO is
low. The TCAM-POWER-RATIO is arrived at by dividing the number of
bits in the TCAM banks that are switched off by the Total Available
TCAM bank space in bits. This ratio is then subjected to the CSPF
algorithm as an additional constraint or the only constraint as the
case may be in a link state protocol like OSPF or IS-IS with Traffic
Engineering Externsions with available utilization on the links also
being a factor. This way those routers that have more TCAM banks
switched off are avoided and those with higher power consumption but
with available bandwidth are used hence not increasing the total
power consumed within the area and hence within the AS. This could be
achieved by using a PCE like entity that calculates the power
shortest paths using this TCAM-POWER-RATIO.
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 of the Proposal
Consider a topology shown in Figure 1.0 that comprises several
chassis devices (in this case single chassis ones) that have multiple
line cards within each of them each of them having ports and
respective TCAM banks along with their corresponding SRAM banks that
contain the next-hop information and necessary re-write information.
The TCAM banks contain the routes where packets are subject to
longest prefix match lookup.
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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 | +---+---+
+---------------+ +------------------+
It is given that the power-saving scheme in [ID-TCAM-POWER-EFF] is in
vogue in each of these routers. It is possible that some of them are
not running the algorithm specified in the [ID-TCAM-POWER-EFF]. Each
of these routers consolidate the total number of bits in the TCAM
banks that have been switched off and the total number of bits
available in the TCAM banks.
The above 2 pieces of information or data are used to compute the
following TCAM-POWER-RATIO.
Here TCAM-POWER-RATIO = Bits in TCAM Banks switched off
---------------------------------
Total number of Bits in TCAM Banks.
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The said ratio is further fed into a computation which is as follows.
Link-Power-Metric = TCAM-POWER-RATIO
------------------
Available bandwidth of the said link on the line
card on which TCAM-POWER-RATIO is calculated.
The Link-Power-Metric is calculated for all the links on the line
cards within a router and advertised using a suitable TLV in the
opaque LSA or LSP packet in the IGP (Interior Gateway Protocol) such
as OSPF or IS-IS as a link metric.
The advertised Link-Power-Metric has 2 attached end-points for a link
in the above mentioned topology. The overall Link-Power-Metric for a
link is arrived at by assigning the Link-Power-Metric between the 2
attached end-points in the ingress direction towards the router which
is a candidate next-hop towards the prefix to be reached.
This is then used in the CSPF algorithm to choose the least cost
power path in the topology through which the packet can travel from
the head-end to tail-end within the area of the AS. This is primarily
an area specific calculation which ends up calculating the paths
through those routers in the area that are in lesser power saving
mode compared to other routers who are in more power saving mode and
have shut off more than their fair share of TCAM banks and their
corresponding SRAM banks.
Those routers that do not employ this scheme are given a TCAM-POWER-
RATIO of 1 since they are not employing the power saving scheme as
outlined in [ID-TCAM-POWER-EFF].
It is important to note that the TCAM banks switched off are not used
in the ratio as a discrete quantity but rather as in an interval of
thresholds. The Available bandwidth as well are calculated not in
discrete quantities but in intervals of thresholds. These intervals
are uniformly to be undertaken in all the routers where the scheme is
deployed.
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2.1 Discussion
Consider the following topology with the appropriate Link-Power-
Metric assigned to the links contained within it.
The shortest path is through A,B,D,X rather than through A,C,E,D and
X. This primarily owing to the reason that the Link-Power-Metric that
takes the TCAM-POWER-RATIO and the Available bandwidth on those links
is the least in the CSPF path.
0.2 0.1 0.2
(A).....>(B).....>(D).....>(X)
| ^
|0.2 0.02 | 0.2
+--->(C)-------->(E)
It is to be noted that if the prefix for the traffic whose Longest
prefix match entry is not loaded in the TCAM bank which is in ON
state in any of the chosen routers along the path, the usual scheme
in [ID-TCAM-POWER-EFF] kicks in and loads the prefix and its
associated re-write information on the traffic hitting the router in
the chosen power saving path. For more information read the reference
for scheme in [ID-TCAM-POWER-EFF].
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3 Security Considerations
There are no new security considerations within the scope of this
document.
4 IANA Considerations
A suitable TLV to carry the Link-Power-Metric is to be defined for
this purpose.
5 References
5.1 Normative References
5.2 Informative References
[ID-TCAM-POWER-EFF] Shankar Raman et.al, "TCAM power
reduction and optimization in Routers", draft-mjsraman-
panet-tcam-power-efficiency-00 (work in progress), 2012.
APPENDIX - A : References for power saving related material
S.Raman, B.V. Venkataswami, K. Veezhinathan, G. Raina,
"TCAM power reduction and optimization in Routers", draft-
mjsraman-panet-tcam-power-efficiency-00 (work in progress)
M. Zhang, J. Dong, B. Zhang, "Use Cases for Power-Aware
Networks", draft-zhang-panet-use-cases (work in progress)
B. Nordman, K. Christensen, "Nanogrids", draft-nordman-
nanogrids-00 (work in progress)
T. Suzuki, T. Tarui, "Requirements for an Energy-Efficient
Network System", draft-suzuki-eens-requirements (work in
progress)
Z. Cao, "Synchronization Layer: an Implementation Method
for Energy Efficient Sensor Stack", draft-cao-lwig-syn-
layer (work in progress)
A. Junior, R. Sofia, "Energy-awareness metrics global
applicability guideline", draft-ajunior-energy-awareness-
00 (work in progress)
B. Zhang, J. Shi, M. Zhang, J. Dong, "Power-aware Routing
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and Traffic Engineering: Requirements, Approaches, and
Issues", draft-zhang- greennet (work in progress)
T. Suganuma, N. Nakamura, S. Izumi, H. Tsunoda, M.
Matsuda, K. Ohta, "Green Usage Monitoring Information
Base", draft-suganuma-greenmib (work in progress)
S. Raman, B. V. Venkataswami, G. Raina, V. Srini, "Power
Based Topologies and TE-Shortest Power Paths in OSPF",
draft-mjsraman- rtgwg-ospf-power-topo-01 (work in
progress)
S. Raman, B. V. Venkataswami, G. Raina, V. Srini,
"Building power optimal Multicast Trees", draft-mjsraman-
rtgwg-pim-power-02 (work in progress)
S. Raman, B. V. Venkataswami, G. Raina, "Reducing Power
Consumption using BGP", draft-mjsraman-rtgwg-inter-as-psp-
03 (work in progress)
S. Raman, B. V. Venkataswami, G. Raina, "Building power
shortest inter-Area TE LSPs using pre-computed paths",
draft-mjsraman-rtgwg- intra-as-psp-te-leak-02 (work in
progress)
S. Raman, B. V. Venkataswami, G. Raina, V. Srini,
"Reducing Power Consumption using BGP path selection",
draft-mjsraman-rtgwg-bgp- power-path-02 (work in progress)
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
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EMail: balajivenkat299@gmail.com
Prof.Kamakoti Veezhinathan
Department of Computer Science and Engineering
IIT Madras
Chennai - 600036
TamilNadu
India
Email: kama@cse.iitm.ac.in
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