Internet DRAFT - draft-mjsraman-panet-ecmp-redirect-power-repl-cap
draft-mjsraman-panet-ecmp-redirect-power-repl-cap
PANET Working Group Shankar Raman
Internet-draft Balaji Venkat Venkataswami
Intended Status: Standards Track Gaurav Raina
Expires: May 9, 2013 I.I.T Madras.
November 5, 2012
PIM ECMP Redirect based on Linecard Replication Capacity and Power
draft-mjsraman-panet-ecmp-redirect-power-repl-cap-00
Abstract
This work derives itself from [1] which proposes a ECMP redirect from
a PIM upstream neighbor that instructs or advices the PIM downstream
neighbor to choose another of its own ECMP links between the former
and the latter. What we propose in this document is a criterion based
on power consumed in the linecards that comprise the ECMP links
between the former and the latter. Also the multicast replication
capacity available within the said linecards which form the ECMP
links between the two is taken into consideration while making a ECMP
redirect.
A PIM router uses RPF procedure to select an upstream interface and
router to build forwarding state. When there are equal cost multiple
paths (ECMP), existing implementations often use hash algorithms to
select a path. Such algorithms do not allow the spread of traffic
among the ECMPs according to administrative metrics. This usually
leads to inefficient or ineffective use of network resources. This
document introduces the ECMP Redirect, a mechanism to improve the RPF
procedure over ECMPs. It allows ECMP path selection to be based on
administratively selected metrics, such as data transmission delays,
path preferences and routing metrics.
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
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other groups may also distribute working documents as
Internet-Drafts.
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conditions where this mechanism applies. . . . . . . . . . . . 3
3 Security Considerations . . . . . . . . . . . . . . . . . . . . 6
4 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
5 References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1 Normative References . . . . . . . . . . . . . . . . . . . 6
5.2 Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1 Introduction
This work derives itself from [1] which proposes a ECMP redirect from
a PIM upstream neighbor that instructs or advices the PIM downstream
neighbor to choose another of its own ECMP links between the former
and the latter. What we propose in this document is a criterion based
on power consumed in the linecards that comprise the ECMP links
between the former and the latter. Also the multicast replication
capacity available within the said linecards which form the ECMP
links between the two is taken into consideration while making a ECMP
redirect.
A PIM router uses RPF procedure to select an upstream interface and
router to build forwarding state. When there are equal cost multiple
paths (ECMP), existing implementations often use hash algorithms to
select a path. Such algorithms do not allow the spread of traffic
among the ECMPs according to administrative metrics. This usually
leads to inefficient or ineffective use of network resources. This
document introduces the ECMP Redirect, a mechanism to improve the RPF
procedure over ECMPs. It allows ECMP path selection to be based on
administratively selected metrics, such as data transmission delays,
path preferences and routing metrics.
As mentioned earlier this document also proposes the use of the power
being consumed by the linecards (if the ECMP links fall on multiple
linecards with respect to their ECMP link ports) and the available
replication capacity of the linecard within its ASICs as a measure of
which ECMP link to which the PIM-Join is to be redirected to. If for
example there exist multiple replication engines within different
linecards then the lightly loaded replication engine and its
corresponding ECMP link on that linecard can be recommended to the
PIM downstream neighbor which sends the upstream neighbor a PIM join
for a specific (S,G) or (*,G) group.
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. Conditions where this mechanism applies.
Assume there are multiple ECMP links between a PIM upstream and
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downstream router. Lets assume they fall on different linecards on
the upstream neighbor with respect to the port placement of these
ECMP links. Assume one linecard A, which is already carrying multiple
data streams in either the incoming direction on its ports and
replicating it to multiple other outgoing linecards through the
switch fabric. Assume another linecard B that is lightly loaded with
respect to multicast traffic and heavily loaded with respect to the
unicast traffic. Assume another linecard C which is lightly loaded
with respect to both. Now also assume that these linecards A,B and C
are all members of the group of linecards whose ports place
themselves within the ECMP links between the upstream and downstream
neighbor.
It is possible to decipher from this is that linecard C would be a
better point of placement of the replication for the group for which
the PIM-Join comes from the downstream neighbor. Assume now that the
downstream neighbor selects the linecard A. It is now possible as a
result of using the mechanism dictated to in [1], to send a redirect
to the downstream neighbor that it would be a better choice to choose
linecard C. This it does by recommending the neighbor address field
as the port IP address which falls on linecard C. The PDU format for
the ECMP redirect specified in [1] and the procedures that go along
with it follow.
It is also possible to make this decision in combination with the
above or solely on a metric which we will call PWR-REPLIC-CAP. This
metric is derived as follows...
PWR-REPLIC-CAP = Power Consumed on that linecard
-------------------------------
Available replication capacity on the linecard.
In the metric case the lowest PWR-REPLIC-CAP metric is chosen. This
optimizes on the power being spent on replication to the extent
possible.
It is important to note that a linecard may have multiple replication
engines and ports assigned to each replication engine or to all of
them. It is possible that the ECMP links and their ports fall on the
same linecard and in that case it would be possible to choose a
specific replication engine from among the multiple replication
engines available. that has better available replication capacity by
choosing a neighbor address belonging to the port that falls in a set
that belongs to the superior replication engine (with respect to the
available replication capacity at that point in time). If there is no
distinction amongst ports with respect to the multiple replication
then it actually makes no difference since it would be an internal
decision as to where the replication for that port actually happens.
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It is also important to note here that the linecards that are
multicast capable have well advertised replication capacities which
the vendors advice in the linecard data sheets. This could be placed
in a variable that can be monitored for shifts within intervals of
threshold values. The same goes for the power consumed by the
linecards as well.
Pseudo code for the steps to be followed to implement this scheme is
as follows...
if (multiple ECMP links exist to the PIM neighbor
from which PIM-Join was received) then
Get the list of ECMP ports which are members of the ECMP links;
Get the list of linecards on which these ECMP ports are placed;
LCA = Consider the least used linecard with respect
to the replication capacity;
if (port on LCA is the same on which PIM-Join was received)
do nothing; return;
else if (choice is to be made on replication capacity)
LCA = Consider the least used linecard with respect
to replication capacity;
else if (choice is to be made on PWR-REPLIC-CAP)
LCA = Consider the linecard with the best
PWR-REPLIC-CAP metric;
end if
Send PIM redirect to PIM downstream neighbor
recommending LCA ECMP link;
end if
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3 Security Considerations
<Security considerations text>
4 IANA Considerations
<IANA considerations text>
5 References
5.1 Normative References
5.2 Informative References
[1] Yiqun, Cai et.al, Protocol Independent Multicast ECMP
Redirect, "draft-ietf-pim-ecmp-02.txt", Work in Progress,
October 2011.
[2] Shankar Raman, et.al, Building power optimal Multicast
Trees, "draft-mjsraman-rtgwg-pim-power-01.txt", Work in
Progress, February 2011.
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,
Chennai - 600036,
TamilNadu,
India.
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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
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