Internet DRAFT - draft-malhotra-bess-evpn-unequal-lb
draft-malhotra-bess-evpn-unequal-lb
INTERNET-DRAFT N. Malhotra, Ed.
Arrcus
A. Sajassi
Intended Status: Proposed Standard Cisco
J. Rabadan
Nokia
J. Drake
Juniper
A. Lingala
AT&T
S. Thoria
Cisco
Expires: Jan 17, 2019 July 16, 2018
Weighted Multi-Path Procedures for EVPN All-Active Multi-Homing
draft-malhotra-bess-evpn-unequal-lb-04
Abstract
In an EVPN-IRB based network overlay, EVPN LAG enables all-active
multi-homing for a host or CE device connected to two or more PEs via
a LAG bundle, such that bridged and routed traffic from remote PEs
can be equally load balanced (ECMPed) across the multi-homing PEs.
This document defines extensions to EVPN procedures to optimally
handle unequal access bandwidth distribution across a set of multi-
homing PEs in order to:
o provide greater flexibility, with respect to adding or
removing individual PE-CE links within the access LAG
o handle PE-CE LAG member link failures that can result in unequal
PE-CE access bandwidth across a set of multi-homing PEs
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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other groups may also distribute working documents as
Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
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in progress."
The list of current Internet-Drafts can be accessed at
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Copyright and License Notice
Copyright (c) 2017 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
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without warranty as described in the Simplified BSD License.
Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 PE CE Link Provisioning . . . . . . . . . . . . . . . . . . 5
1.2 PE CE Link Failures . . . . . . . . . . . . . . . . . . . . 6
1.3 Design Requirement . . . . . . . . . . . . . . . . . . . . . 7
1.4 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 7
2. Solution Overview . . . . . . . . . . . . . . . . . . . . . . . 8
3. Weighted Unicast Traffic Load-balancing . . . . . . . . . . . 8
3.1 LOCAL PE Behavior . . . . . . . . . . . . . . . . . . . . . 8
3.1 Link Bandwidth Extended Community . . . . . . . . . . . . . 8
3.2 REMOTE PE Behavior . . . . . . . . . . . . . . . . . . . . . 9
4. Weighted BUM Traffic Load-Sharing . . . . . . . . . . . . . . 10
4.1 The BW Capability in the DF Election Extended Community . . 10
4.2 BW Capability and Default DF Election algorithm . . . . . . 11
4.3 BW Capability and HRW DF Election algorithm (Type 1 and
4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.3.1 BW Increment . . . . . . . . . . . . . . . . . . . . . . 11
4.3.2 HRW Hash Computations with BW Increment . . . . . . . . 12
4.3.3 Cost-Benefit Tradeoff on Link Failures . . . . . . . . . 13
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4.4 BW Capability and Preference DF Election algorithm . . . . 14
5. Real-time Available Bandwidth . . . . . . . . . . . . . . . . . 15
6. Routed EVPN Overlay . . . . . . . . . . . . . . . . . . . . . . 15
7. EVPN-IRB Multi-homing with non-EVPN routing . . . . . . . . . . 16
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.1 Normative References . . . . . . . . . . . . . . . . . . . 17
7.2 Informative References . . . . . . . . . . . . . . . . . . 17
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
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1 Introduction
In an EVPN-IRB based network overlay, with an access CE multi-homed
via a LAG interface, bridged and routed traffic from remote PEs can
be equally load balanced (ECMPed) across the multi-homing PEs:
o ECMP Load-balancing for bridged unicast traffic is enabled via
aliasing and mass-withdraw procedures detailed in RFC 7432.
o ECMP Load-balancing for routed unicast traffic is enabled via
existing L3 ECMP mechanisms.
o Load-sharing of bridged BUM traffic on local ports is enabled
via EVPN DF election procedure detailed in RFC 7432
All of the above load-balancing and DF election procedures implicitly
assume equal bandwidth distribution between the CE and the set of
multi-homing PEs. Essentially, with this assumption of equal "access"
bandwidth distribution across all PEs, ALL remote traffic is equally
load balanced across the multi-homing PEs. This assumption of equal
access bandwidth distribution can be restrictive with respect to
adding / removing links in a multi-homed LAG interface and may also
be easily broken on individual link failures. A solution to handle
unequal access bandwidth distribution across a set of multi-homing
EVPN PEs is proposed in this document. Primary motivation behind this
proposal is to enable greater flexibility with respect to adding /
removing member PE-CE links, as needed and to optimally handle PE-CE
link failures.
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1.1 PE CE Link Provisioning
+------------------------+
| Underlay Network Fabric|
+------------------------+
+-----+ +-----+
| PE1 | | PE2 |
+-----+ +-----+
\ /
\ ESI-1 /
\ /
+\---/+
| \ / |
+--+--+
|
CE1
Figure 1
Consider a CE1 that is dual-homed to PE1 and PE2 via EVPN-LAG with
single member links of equal bandwidth to each PE (aka, equal access
bandwidth distribution across PE1 and PE2). If the provider wants to
increase link bandwidth to CE1, it MUST add a link to both PE1 and
PE2 in order to maintain equal access bandwidth distribution and
inter-work with EVPN ECMP load-balancing. In other words, for a dual-
homed CE, total number of CE links must be provisioned in multiples
of 2 (2, 4, 6, and so on). For a triple-homed CE, number of CE links
must be provisioned in multiples of three (3, 6, 9, and so on). To
generalize, for a CE that is multi-homed to "n" PEs, number of PE-CE
physical links provisioned must be an integral multiple of "n". This
is restrictive in case of dual-homing and very quickly becomes
prohibitive in case of multi-homing.
Instead, a provider may wish to increase PE-CE bandwidth OR number of
links in ANY link increments. As an example, for CE1 dual-homed to
PE1 and PE2 in all-active mode, provider may wish to add a third link
to ONLY PE1 to increase total bandwidth for this CE by 50%, rather
than being required to increase access bandwidth by 100% by adding a
link to each of the two PEs. While existing EVPN based all-active
load-balancing procedures do not necessarily preclude such asymmetric
access bandwidth distribution among the PEs providing redundancy, it
may result in unexpected traffic loss due to congestion in the access
interface towards CE. This traffic loss is due to the fact that PE1
and PE2 will continue to attract equal amount of CE1 destined traffic
from remote PEs, even when PE2 only has half the bandwidth to CE1 as
PE1. This may lead to congestion and traffic loss on the PE2-CE1
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link. If bandwidth distribution to CE1 across PE1 and PE2 is 2:1,
traffic from remote hosts MUST also be load-balanced across PE1 and
PE2 in 2:1 manner.
1.2 PE CE Link Failures
More importantly, unequal PE-CE bandwidth distribution described
above may occur during regular operation following a link failure,
even when PE-CE links were provisioned to provide equal bandwidth
distribution across multi-homing PEs.
+------------------------+
| Underlay Network Fabric|
+------------------------+
+-----+ +-----+
| PE1 | | PE2 |
+-----+ +-----+
\\ //
\\ ESI-1 //
\\ /X
+\\---//+
| \\ // |
+---+---+
|
CE1
Consider a CE1 that is multi-homed to PE1 and PE2 via a link bundle
with two member links to each PE. On a PE2-CE1 physical link failure,
link bundle represented by ESI-1 on PE2 stays up, however, it's
bandwidth is cut in half. With the existing ECMP procedures, both PE1
and PE2 will continue to attract equal amount of traffic from remote
PEs, even when PE1 has double the bandwidth to CE1. If bandwidth
distribution to CE1 across PE1 and PE2 is 2:1, traffic from remote
hosts MUST also be load-balanced across PE1 and PE2 in 2:1 manner to
avoid unexpected congestion and traffic loss on PE2-CE1 links within
the LAG.
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1.3 Design Requirement
+-----------------------+
|Underlay Network Fabric|
+-----------------------+
+-----+ +-----+ +-----+ +-----+
| PE1 | | PE2 | ..... | PEx | | PEn |
+-----+ +-----+ +-----+ +-----+
\ \ // //
\ L1 \ L2 // Lx // Ln
\ \ // //
+-\-------\-----------//--------//-+
| \ \ ESI-1 // // |
+----------------------------------+
|
CE
To generalize, if total link bandwidth to a CE is distributed across
"n" multi-homing PEs, with Lx being the number of links / bandwidth
to PEx, traffic from remote PEs to this CE MUST be load-balanced
unequally across [PE1, PE2, ....., PEn] such that, fraction of total
unicast and BUM flows destined for CE that are serviced by PEx is:
Lx / [L1+L2+.....+Ln]
Solution proposed below includes extensions to EVPN procedures to
achieve the above.
1.4 Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
"LOCAL PE" in the context of an ESI refers to a provider edge switch
OR router that physically hosts the ESI.
"REMOTE PE" in the context of an ESI refers to a provider edge switch
OR router in an EVPN overlay, who's overlay reachability to the ESI
is via the LOCAL PE.
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2. Solution Overview
In order to achieve weighted load balancing for overlay unicast
traffic, Ethernet A-D per-ES route (EVPN Route Type 1) is leveraged
to signal the ESI bandwidth to remote PEs. Using Ethernet A-D per-ES
route to signal the ESI bandwidth provides a mechanism to be able to
react to changes in access bandwidth in a service and host
independent manner. Remote PEs computing the MAC path-lists based on
global and aliasing Ethernet A-D routes now have the ability to setup
weighted load-balancing path-lists based on the ESI access bandwidth
received from each PE that the ESI is multi-homed to. If Ethernet A-D
per-ES route is also leveraged for IP path-list computation, as per
[EVPN-IP-ALIASING], it also provides a method to do weighted load-
balancing for IP routed traffic.
In order to achieve weighted load-balancing of overlay BUM traffic,
EVPN ES route (Route Type 4) is leveraged to signal the ESI bandwidth
to PEs within an ESI's redundancy group to influence per-service DF
election. PEs in an ESI redundancy group now have the ability to do
service carving in proportion to each PE's relative ESI bandwidth.
Procedures to accomplish this are described in greater detail next.
3. Weighted Unicast Traffic Load-balancing
3.1 LOCAL PE Behavior
A PE that is part of an ESI's redundancy group would advertise a
additional "link bandwidth" EXT-COMM attribute with Ethernet A-D per-
ES route (EVPN Route Type 1), that represents total bandwidth of PE's
physical links in an ESI. BGP link bandwidth EXT-COMM defined in
[BGP-LINK-BW] is re-used for this purpose.
3.1 Link Bandwidth Extended Community
Link bandwidth extended community described in [BGP-LINK-BW] for
layer 3 VPNs is re-used here to signal local ES link bandwidth to
remote PEs. link-bandwidth extended community is however defined in
[BGP-LINK-BW] as optional non-transitive. In inter-AS scenarios,
link-bandwidth may need to be signaled to an eBGP neighbor along with
next-hop unchanged. It is work in progress with authors of [BGP-LINK-
BW] to allow for this attribute to be used as transitive in inter-AS
scenarios.
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3.2 REMOTE PE Behavior
A receiving PE should use per-ES link bandwidth attribute received
from each PE to compute a relative weight for each remote PE, per-ES,
as shown below.
if,
L(x,y) : link bandwidth advertised by PE-x for ESI-y
W(x,y) : normalized weight assigned to PE-x for ESI-y
H(y) : Highest Common Factor (HCF) of [L(1,y), L(2,y), .....,
L(n,y)]
then, the normalized weight assigned to PE-x for ESI-y may be
computed as follows:
W(x,y) = L(x,y) / H(y)
For a MAC+IP route (EVPN Route Type 2) received with ESI-y, receiving
PE MUST compute MAC and IP forwarding path-list weighted by the above
normalized weights.
As an example, for a CE dual-homed to PE-1, PE-2, PE-3 via 2, 1, and
1 GE physical links respectively, as part of a link bundle
represented by ESI-10:
L(1, 10) = 2000 Mbps
L(2, 10) = 1000 Mbps
L(3, 10) = 1000 Mbps
H(10) = 1000
Normalized weights assigned to each PE for ESI-10 are as follows:
W(1, 10) = 2000 / 1000 = 2.
W(2, 10) = 1000 / 1000 = 1.
W(3, 10) = 1000 / 1000 = 1.
For a remote MAC+IP host route received with ESI-10, forwarding load-
balancing path-list must now be computed as: [PE-1, PE-1, PE-2, PE-3]
instead of [PE-1, PE-2, PE-3]. This now results in load-balancing of
all traffic destined for ESI-10 across the three multi-homing PEs in
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proportion to ESI-10 bandwidth at each PE.
Above weighted path-list computation MUST only be done for an ESI, IF
a link bandwidth attribute is received from ALL of the PE's
advertising reachability to that ESI via Ethernet A-D per-ES Route
Type 1. In the event that link bandwidth attribute is not received
from one or more PEs, forwarding path-list would be computed using
regular ECMP semantics.
4. Weighted BUM Traffic Load-Sharing
Optionally, load sharing of per-service DF role, weighted by
individual PE's link-bandwidth share within a multi-homed ES may also
be achieved.
In order to do that, a new DF Election Capability [EVPN-DF-ELECT-
FRAMEWORK] called "BW" (Bandwidth Weighted DF Election) is defined.
BW may be used along with some DF Election Types, as described in the
following sections.
4.1 The BW Capability in the DF Election Extended Community
[EVPN-DF-ELECT-FRAMEWORK] defines a new extended community for PEs
within a redundancy group to signal and agree on uniform DF Election
Type and Capabilities for each ES. This document requests a bit in
the DF Election extended community Bitmap:
Bit 28: BW (Bandwidth Weighted DF Election)
ES routes advertised with the BW bit set will indicate the desire of
the advertising PE to consider the link-bandwidth in the DF Election
algorithm defined by the value in the "DF Type".
As per [EVPN-DF-ELECT-FRAMEWORK], all the PEs in the ES MUST
advertise the same Capabilities and DF Type, otherwise the PEs will
fall back to Default [RFC7432] DF Election procedure.
The BW Capability MAY be advertised with the following DF Types:
o Type 0: Default DF Election algorithm, as in [RFC7432]
o Type 1: HRW algorithm, as in [EVPN-DF-ELECT-FRAMEWORK]
o Type 2: Preference algorithm, as in [EVPN-DF-PREF]
o Type 4: HRW per-multicast flow DF Election, as in [XXX]
The following sections describe how the DF Election procedures are
modified for the above DF Types when the BW Capability is used.
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4.2 BW Capability and Default DF Election algorithm
When all the PEs in the ES agree to use the BW Capability with DF
Type 0, the Default DF Election procedure is modified as follows:
o Each PE advertises a "Link Bandwidth" EXT-COMM attribute along
with the ES route to signal the PE-CE link bandwidth (LBW) for
the ES.
o A receiving PE MUST use the ES link bandwidth attribute
received from each PE to compute a relative weight for each
remote PE.
o The DF Election procedure MUST now use this weighted list of PEs
to compute the per-VLAN Designated Forwarder, such that the DF
role is distributed in proportion to this normalized weight.
Considering the same example as in Section 3, the candidate PE list
for DF election is:
[PE-1, PE-1, PE-2, PE-3].
The DF for a given VLAN-a on ES-10 is now computed as (VLAN-a % 4).
This would result in the DF role being distributed across PE1, PE2,
and PE3 in portion to each PE's normalized weight for ES-10.
4.3 BW Capability and HRW DF Election algorithm (Type 1 and 4)
[EVPN-DF-ELECT-FRAMEWORK] introduces Highest Random Weight (HRW)
algorithm (DF Type 1) for DF election in order to solve potential DF
election skew depending on Ethernet tag space distribution. [EVPN-
PER-MCAST-FLOW-DF] further extends HRW algorithm for per-multicast
flow based hash computations (DF Type 4). This section describes
extensions to HRW Algorithm for EVPN DF Election specified in [EVPN-
DF-ELECT-FRAMEWORK] and in [EVPN-PER-MCAST-FLOW-DF] in order to
achieve DF election distribution that is weighted by link bandwidth.
4.3.1 BW Increment
A new variable called "bandwidth increment" is computed for each [PE,
ES] advertising the ES link bandwidth attribute as follows:
In the context of an ES,
L(i) = Link bandwidth advertised by PE(i) for this ES
L(min) = lowest link bandwidth advertised across all PEs for this ES
Bandwidth increment, "b(i)" for a given PE(i) advertising a link
bandwidth of L(i) is defined as an integer value computed as:
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b(i) = L(i) / L(min)
As an example,
with PE(1) = 10, PE(2) = 10, PE(3) = 20
bandwidth increment for each PE would be computed as:
b(1) = 1, b(2) = 1, b(3) = 2
with PE(1) = 10, PE(2) = 10, PE(3) = 10
bandwidth increment for each PE would be computed as:
b(1) = 1, b(2) = 1, b(3) = 1
Note that the bandwidth increment must always be an integer,
including, in an unlikely scenario of a PE's link bandwidth not being
an exact multiple of L(min). If it computes to a non-integer value
(including as a result of link failure), it MUST be rounded down to
an integer.
4.3.2 HRW Hash Computations with BW Increment
HRW algorithm as described in [EVPN-DF-ELECT-FRAMEWORK] and in [EVPN-
PER-MCAST-FLOW-DF] compute a random hash value (referred to as
affinity here) for each PE(i), where, (0 < i <= N), PE(i) is the PE
at ordinal i, and Address(i) is the IP address of PE at ordinal i.
For 'N' PEs sharing an Ethernet segment, this results in 'N'
candidate hash computations. PE that has the highest hash value is
selected as the DF.
Affinity computation for each PE(i) is extended to be computed one
per-bandwidth increment associated with PE(i) instead of a single
affinity computation per PE(i).
PE(i) with b(i) = j, results in j affinity computations:
affinity(i, x), where 1 < x <= j
This essentially results in number of candidate HRW hash computations
for each PE that is directly proportional to that PE's relative
bandwidth within an ES and hence gives PE(i) a probability of being
DF in proportion to it's relative bandwidth within an ES.
As an example, consider an ES that is multi-homed to two PEs, PE1 and
PE2, with equal bandwidth distribution across PE1 and PE2. This would
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result in a total of two candidate hash computations:
affinity(PE1, 1)
affinity(PE2, 1)
Now, consider a scenario with PE1's link bandwidth as 2x that of PE2.
This would result in a total of three candidate hash computations to
be used for DF election:
affinity(PE1, 1)
affinity(PE1, 2)
affinity(PE2, 1)
which would give PE1 2/3 probability of getting elected as a DF, in
proportion to its relative bandwidth in the ES.
Depending on the chosen HRW hash function, affinity function MUST be
extended to include bandwidth increment in the computation.
For e.g.,
affinity function specified in [EVPN-PER-MCAST-FLOW-DF] MAY be
extended as follows to incorporate bandwidth increment j:
affinity(S,G,V, ESI, Address(i,j)) =
(1103515245.((1103515245.Address(i).j + 12345) XOR
D(S,G,V,ESI))+12345) (mod 2^31)
affinity or random function specified in [EVPN-DF-ELECT-FRAMEWORK]
MAY be extended as follows to incorporate bandwidth increment j:
affinity(v, Es, Address(i,j)) = (1103515245((1103515245.Address(i).j
+ 12345) XOR D(v,Es))+12345)(mod 2^31)
4.3.3 Cost-Benefit Tradeoff on Link Failures
While incorporating link bandwidth into the DF election process
provides optimal BUM traffic distribution across the ES links, it
also implies that affinity values for a given PE are re-computed, and
DF elections are re-adjusted on changes to that PE's bandwidth
increment that might result from link failures or link additions. If
the operator does not wish to have this level of churn in their DF
election, then they should not advertise the BW capability. Not
advertising BW capability may result in less than optimal BUM traffic
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distribution while still retaining the ability to allow a remote
ingress PE to do weighted ECMP for its unicast traffic to a set of
multi-homed PEs, as described in section 3.2.
Same also applies to use of BW capability with service carving (DF
Type 0), as specified in section 4.2.
4.4 BW Capability and Preference DF Election algorithm
This section applies to ES'es where all the PEs in the ES agree use
the BW Capability with DF Type 2. The BW Capability modifies the
Preference DF Election procedure [EVPN-DF-PREF], by adding the LBW
value as a tie-breaker as follows:
o Section 4.1, bullet (f) in [EVPN-DF-PREF] now considers the LBW
value:
f) In case of equal Preference in two or more PEs in the ES, the
tie-breakers will be the DP bit, the LBW value and the lowest
IP PE in that order. For instance:
o If vES1 parameters were [Pref=500,DP=0,LBW=1000] in PE1 and
[Pref=500,DP=1, LBW=2000] in PE2, PE2 would be elected due
to the DP bit.
o If vES1 parameters were [Pref=500,DP=0,LBW=1000] in PE1 and
[Pref=500,DP=0, LBW=2000] in PE2, PE2 would be elected due
to a higher LBW, even if PE1's IP address is lower.
o The LBW exchanged value has no impact on the Non-Revertive
option described in [EVPN-DF-PREF].
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5. Real-time Available Bandwidth
PE-CE link bandwidth availability may sometimes vary in real-time
disproportionately across PE_CE links within a multi-homed ESI due to
various factors such as flow based hashing combined with fat flows
and unbalanced hashing. Reacting to real-time available bandwidth is
at this time outside the scope of this document. Procedures described
in this document are strictly based on static link bandwidth
parameter.
6. Routed EVPN Overlay
An additional use case is possible, such that traffic to an end host
in the overlay is always IP routed. In a purely routed overlay such
as this:
o A host MAC is never advertised in EVPN overlay control plane o
Host /32 or /128 IP reachability is distributed across the
overlay via EVPN route type 5 (RT-5) along with a zero or non-
zero ESI
o An overlay IP subnet may still be stretched across the underlay
fabric, however, intra-subnet traffic across the stretched
overlay is never bridged
o Both inter-subnet and intra-subnet traffic, in the overlay is
IP routed at the EVPN GW.
Please refer to [RFC 7814] for more details.
Weighted multi-path procedure described in this document may be used
together with procedures described in [EVPN-IP-ALIASING] for this use
case. Ethernet A-D per-ES route advertised with Layer 3 VRF RTs would
be used to signal ES link bandwidth attribute instead of the Ethernet
A-D per-ES route with Layer 2 VRF RTs. All other procedures described
earlier in this document would apply as is.
If [EVPN-IP-ALIASING] is not used for routed fast convergence, link
bandwidth attribute may still be advertised with IP routes (RT-5) to
achieve PE-CE link bandwidth based load-balancing as described in
this document. In the absence of [EVPN-IP-ALIASING], re-balancing of
traffic following changes in PE-CE link bandwidth will require all IP
routes from that CE to be re-advertised in a prefix dependent manner.
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7. EVPN-IRB Multi-homing with non-EVPN routing
EVPN-LAG based multi-homing on an IRB gateway may also be deployed
together with non-EVPN routing, such as global routing or an L3VPN
routing control plane. Key property that differentiates this set of
use cases from EVPN IRB use cases discussed earlier is that EVPN
control plane is used only to enable LAG interface based multi-homing
and NOT as an overlay VPN control plane. EVPN control plane in this
case enables:
o DF election via EVPN RT-4 based procedures described in [RFC7432]
o LOCAL MAC sync across multi-homing PEs via EVPN RT-2
o LOCAL ARP and ND sync across multi-homing PEs via EVPN RT-2
Applicability of weighted ECMP procedures proposed in this document
to these set of use cases will be addressed in subsequent revisions.
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7. References
7.1 Normative References
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
2015, <http://www.rfc-editor.org/info/rfc7432>.
[BGP-LINK-BW] Mohapatra, P., Fernando, R., "BGP Link Bandwidth
Extended Community", January 2013,
<https://tools.ietf.org/html/draft-ietf-idr-link-
bandwidth-06>.
[EVPN-IP-ALIASING] Sajassi, A., Badoni, G., "L3 Aliasing and Mass
Withdrawal Support for EVPN", July 2017,
<https://tools.ietf.org/html/draft-sajassi-bess-evpn-ip-
aliasing-00>.
[EVPN-DF-PREF] Rabadan, J., Sathappan, S., Przygienda, T., Lin, W.,
Drake, J., Sajassi, A., and S. Mohanty, "Preference-based
EVPN DF Election", internet-draft ietf-bess-evpn-pref-df-
01.txt, April 2018.
[EVPN-PER-MCAST-FLOW-DF] Sajassi, et al., "Per multicast flow
Designated Forwarder Election for EVPN", March 2018,
<https://tools.ietf.org/html/draft-sajassi-bess-evpn-per-
mcast-flow-df-election-00>.
[EVPN-DF-ELECT-FRAMEWORK] Rabadan, Mohanty, et al., "Framework for
EVPN Designated Forwarder Election Extensibility", March
2018, <https://tools.ietf.org/html/draft-ietf-bess-evpn-
df-election-framework-03>.
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", March 1997,
<https://tools.ietf.org/html/rfc2119>.
[RFC8174] B. Leiba, "Ambiguity of Uppercase vs Lowercase in RFC 2119
Key Words", May 2017,
<https://tools.ietf.org/html/rfc8174>.
7.2 Informative References
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8. Acknowledgements
Authors would like to thank Satya Mohanty for valuable review and
inputs with respect to HRW algorithm refinements proposed in this
document.
Authors' Addresses
Neeraj Malhotra, Ed.
Arrcus
Email: neeraj.ietf@gmail.com
Ali Sajassi
Cisco
Email: sajassi@cisco.com
Jorge Rabadan
Nokia
Email: jorge.rabadan@nokia.com
John Drake
Juniper
EMail: jdrake@juniper.net
Avinash Lingala
AT&T
Email: ar977m@att.com
Samir Thoria
Cisco
Email: sthoria@cisco.com
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