BESS WorkGroup Ali. Sajassi
Internet-Draft Mankamana. Mishra
Intended status: Standards Track Samir. Thoria
Expires: September 4, 2018 Cisco Systems
Jorge. Rabadan
Nokia
John. Drake
Juniper Networks
March 3, 2018
Per multicast flow Designated Forwarder Election for EVPN
draft-sajassi-bess-evpn-per-mcast-flow-df-election-00
Abstract
[RFC7432] describes mechanism to elect designated forwarder (DF) at
the granularity of (ESI, EVI) which is per VLAN (or per group of
VLANs in case of VLAN bundle or VLAN-aware bundle service). However,
the current level of granularity of per-VLAN is not adequate for some
of applications. [I-D.ietf-bess-evpn-ac-df] and
[I-D.ietf-bess-evpn-df-election] improves base line DF election.
This document is an extension to HRW base drafts
([I-D.ietf-bess-evpn-ac-df] and [I-D.ietf-bess-evpn-df-election]) and
further enhances HRW algorithm to do DF election at the granularity
of (ESI, VLAN, Mcast flow).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 4, 2018.
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Copyright Notice
Copyright (c) 2018 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
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. The DF Election Extended Community . . . . . . . . . . . . . 4
4. HRW base per multicast flow EVPN DF election . . . . . . . . 6
4.1. DF election for IGMP (S,G) membership request . . . . . . 6
4.2. DF election for IGMP (*,G) membership request . . . . . . 6
4.3. Default DF election procedure . . . . . . . . . . . . . . 7
5. Procedure to use per multicast flow DF election algorithm . . 7
6. Triggers for DF re-election . . . . . . . . . . . . . . . . . 9
7. Protocol Considerations . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 10
11. Normative References . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
EVPN based All-Active multi-homing is becoming the basic building
block for providing redundancy in next generation data center
deployments as well as service provider access/aggregation network.
[RFC7432] defines role of a designated forwarder as the node in the
redundancy group that is responsible to forward Broadcast, Unknown
unicast, Multicast (BUM) traffic on that Ethernet Segment (CE device
or network) in an All-Active multi-homing.
This DF election mechanism allows selecting a DF at the granularity
of (ES, VLAN) or (ES, VLAN bundle) for Broadcast, Unknown Unicast, or
Multicast (BUM) traffic. Though [I-D.ietf-bess-evpn-ac-df] and
[I-D.ietf-bess-evpn-df-election] improves the default DF election
procedure , still it does not fit well for some of service provider
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residential application, where whole multicast traffic is delivered
on single VLAN.
(Multicast sources)
|
|
+---+
|CE4|
+---+
|
|
+-----+-----+
+------------| PE-1 |------------+
| | | |
| +-----------+ |
| |
| EVPN |
| |
| |
| (DF) (NDF)|
+-----------+ +-----------+
| |EVI-1| | | |EVI-1| |
| PE-2 |------------------------| PE-3 |
+-----------+ +-----------+
AC1 \ / AC2
\ /
\ ESI-1 /
\ /
\ /
+---------------+
| CE2 |
+---------------+
|
|
(Multiple receivers)
Figure 1: Multi-homing Network of EVPN for IPTV deployments
Consider the above topology, which shows residential deployment
scenario, where multiple receivers are behind all active multihoming
segment. All of the multicast traffic is provisioned on EVI-1.
Assume PE-2 get elected as DF. According to [RFC7432] PE-2 will be
responsible for forwarding multicast traffic to that Ethernet
segment.
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o Forcing sole data plane forwarding responsibility on the PE-2
proves a limitation in the current DF election mechanism. In
topology at Figure 1 would always have only one of the PE to be
elected as DF irrespective of which current DF election mechanism
is in use (defined in [RFC7432] or [I-D.ietf-bess-evpn-ac-df] and
[I-D.ietf-bess-evpn-df-election]).
o In the above deployment we have to consider one more factor,
Network bandwidth is shared between multicast and unicast flow.
At any given point of time if AC1 already has unicast traffic flow
which is taking good amount of network bandwidth. we would have
very limited bandwidth available for multicast flows. Even though
PE-3 to CE2 (AC2) has not been used much, still we would end up
having limitation about how much multicast can flow though AC1.
In this document, we propose an extension to HRW base drafts to allow
DF election at the granularity of (ESI, VLAN, Mcast flow) which would
allow multicast flows to be distributed among redundancy group PE's
to share the load.
2. 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 [RFC2119] .
With respect to EVPN, this document follows the terminology that has
been defined in [RFC7432] and [RFC4601] for multicast terminology.
3. The DF Election Extended Community
[I-D.ietf-bess-evpn-ac-df] and [I-D.ietf-bess-evpn-df-election]
defines extended community, which would be used for PE's in
redundancy group to come to an agreement about which DF election
procedures is supported. A PE can notify other participating PE's in
redundancy group about its willingness to support Per multicast flow
base DF election capability by signaling a DF election extended
community along with Ethernet-Segment Route (Type-4). current
proposal extends the existing extended community defined in
[I-D.ietf-bess-evpn-ac-df] and [I-D.ietf-bess-evpn-df-election].
This draft defines new a DF type.
o DF type (1 octet) - Encodes the DF Election algorithm values
(between 0 and 255) that the advertising PE desires to use for the
ES.
* Type 0: Default DF Election algorithm, or modulus-based
algorithms in [RFC7432].
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* Type 1: HRW algorithm defined in [I-D.ietf-bess-evpn-ac-df] and
[I-D.ietf-bess-evpn-df-election]
* Type 4: HRW base per multicast flow DF election (explained in
this document)
* Type 5 - 254: Unassigned
* Type 255: Reserved for Experimental Use.
o The [I-D.ietf-bess-evpn-ac-df] and
[I-D.ietf-bess-evpn-df-election] describes encoding of
capabilities associated to the DF election algorithm using Bitmap
field. When these capabilities bits are set along with the DF
type-4, then these capabilities need to be interpreted in context
of this new DF type-4. For example consider a scenario where all
PEs in the same redundancy group (same ES) can support both AC-DF
and DF type-4 and thus they receive such indications from the
other PEs in the ES. In this scenario, if a VLAN is not active in
a PE, then the DF election procedure on all PEs in the ES should
factor that in and exclude that PE in the DF election per
multicast flow.
o A PE SHOULD attach the DF election Extended Community to ES route
and Extended Community MUST be sent if the ES is locally
configured for DF type Per Multicast flow DF election. Only one
DF Election Extended community can be sent along with an ES route.
o When a PE receives the ES Routes from all the other PE's for the
ES, it check if all of other PE's have advertised their capability
about Per multicast flow DF election procedure. If all of them
have advertised capability, it performs DF election based on Per
multicast flow procedure. But if
* There is at least one PE which advertised route-4 ( AD per ES
Route) which does not indicates its capability to perform Per
multicast flow DF election. OR
* There is at least one PE signals single active in the AD per ES
route
It MUST be considered as an indication to support of only Default
DF election [RFC7432] and DF election procedure in [RFC7432] MUST
be used.
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4. HRW base per multicast flow EVPN DF election
This document is an extension of [I-D.ietf-bess-evpn-ac-df] and
[I-D.ietf-bess-evpn-df-election], so this draft does not repeat
description of HRW algorithm itself.
EVPN PE does the discovery of redundancy group based on [RFC7432].
If redundancy group consists of N EVPN PE nodes. Then after the
discovery all PEs build an unordered list of IP address of all the
nodes in redundancy group. Procedure defined in this draft does not
require PE's to be ordered list.Address [i] denotes the IP address of
i'th EVPN PE in redundancy group where (0 < i <= N ).
4.1. DF election for IGMP (S,G) membership request
The DF is the PE who has maximum affinity for (S, G, V, ESI) where
o S - Multicast Source
o G - Multicast Group
o V - Vlan ID for Ethernet Tag V.
o ESI - Ethernet Segment Identifier
In case of tie choose the PE whose IP address is numerically least.
The affinity of PE(i) to (S,G,VLAN ID, ESI) is calculated by
function, affinity (S,G,V, ESI, Address(i)), where (0 < i <= N),
PE(i) is the PE at ordinal i, address(i) is the IP address of PE at
ordinal i
o affinity (S,G,V, ESI, Address(i)) = (1103515245.
((1103515245.Address(i) + 12345) XOR D(S,G,V,ESI))+12345) (mod
2^31)
o D(S,G,V, ESI) = CRC_32(S,G,V, ESI).
Here D(S,G,V,ESI) is the 32-bit digest (CRC_32) of the Source IP,
Group IP, Vlan ID for Ethernet Tag V. Source and Group IP address
length does not matter as only the lower order 31 bits are modulo
significant.
4.2. DF election for IGMP (*,G) membership request
In case of IGMP membership request where source is not known. The DF
is the PE which has maximum affinity for (G,V, ESI) where
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o G - Multicast Group
o V - Vlan ID for Ethernet Tag V.
o ESI - Ethernet Segment Identifier
In case of tie choose the PE whose IP address is numerically least.
The affinity of PE(i) to (G,V, ESI) is calculated by function,
affinity (G,V, ESI, Address(i)), where (0 < i <= N), PE(i) is the PE
at ordinal i, address(i) is the IP address of PE at ordinal i
o affinity (G, V, ESI, Address(i)) = (1103515245.
((1103515245.Address(i) + 12345) XOR D(G,V,ESI))+12345) (mod 2^31)
o D(G,V, ESI) = CRC_32(G,V, ESI).
Here D(G,V,ESI) is the 32-bit digest (CRC_32) of the Group IP, Vlan
ID for Ethernet Tag V. Source and Group IP address length does not
matter as only the lower order 31 bits are modulo significant.
4.3. Default DF election procedure
Even if all of the PE's indicate their availability to participate in
per multicast flow DF election procedure, there is need to have
default DF election algorithm. Since Per multicast flow DF election
is applicable for only those multicast flows for which PE has
received membership request. For other BUM traffic, forwarding plane
need default DF election procedure. And we use HRW based DF election
procedure as default one in these cases which is defined in
[I-D.ietf-bess-evpn-ac-df] and [I-D.ietf-bess-evpn-df-election].
5. Procedure to use per multicast flow DF election algorithm
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Multicast Source
|
|
|
|
+---------+
+--------------+ PE-4 +--------------+
| | | |
| +---------+ |
| |
| EVPN CORE |
| |
| |
| |
+---------+ +---------+ +---------+
| PE-1 +--------+ PE-2 +---------+ PE-3 |
| EVI-1 | | EVI-1 | | EVI-1 |
+---------+ +---------+ +---------+
|__________________|___________________|
AC-1 ESI-1 | AC-2 AC-3
+---------+
| CE-1 |
| |
+---------+
|
|
|
|
Multicast Receivers
Figure-2 : Multihomed network
Figure-2 shows multihomed network. Where EVPN PE-1, PE-2, PE-3 are
multihomed to CE-1. Multiple multicast receivers are behind all
active multihoming segment.
1. PE's connected to the same Ethernet segment can automatically
discover each other through exchange of the Ethernet Segment
Route. This draft does not change any of this procedure, it
still uses procedure defined in [RFC7432].
2. Each of the PE's in redundancy group advertise Ethernet segment
route with extended community indicating their ability to
participate in per multicast flow DF election procedure. Since
Per multicast flow would not be applicable unless PE learns about
membership request from receiver, there is need to have default
DF election among PE's in redundancy group for BUM traffic. In
initial phase we use Section 4.3 DF election procedure.
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3. When receiver starts sending membership request for (s1,g1) where
s1 is multicast source address and g1 is multicast group address,
CE-1 could hash membership request (IGMP join) to any of the PE's
in redundancy group. Lets consider it is hashed to PE-2.
[I-D.ietf-bess-evpn-igmp-mld-proxy] defines procedure to sync
IGMP join state among redundancy group of PE's. Now each of the
PE would have information about membership request (s1,g1) and
each of them run DF election procedure Section 4.1 to elect DF
among participating PE's in redundancy group. Consider PE-2 gets
elected as DF for multicast flow (s1,g1).
1. PE-1 forwarding state would be nDF for flow (s1,g1) and DF
for rest other BUM traffic.
2. PE-2 forwarding state would be DF for flow (s1,g1) and nDF
for rest other BUM traffic.
3. PE-3 forwarding state would be nDF for flow (s1,g1) and rest
other BUM traffic.
4. As and when new multicast membership request comes, same
procedure as above would continue.
6. Triggers for DF re-election
There are multiple triggers which can cause DF re-election. Some of
the triggers could be
1. Local ES going down due to physical failure or configuration
change
2. Detection of new PE through ES route.
3. AC going up / down
This document does not provide any new mechanism to handle DF re-
election procedure. it does uses existing mechanism defined in
[RFC7432]. When ever either of trigger occur, DF re-election would
be done. and all of the flows would be redistributed among existing
PE's in redundancy group for ES.
7. Protocol Considerations
More details to be added in next version.
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8. Security Considerations
The same Security Considerations described in [RFC7432] are valid for
this document.
9. IANA Considerations
There are no new IANA considerations in this document.
10. Acknowledgement
11. Normative References
[HRW1999] IEEE, "Using name-based mappings to increase hit rates",
IEEE HRW, February 1998.
[I-D.ietf-bess-evpn-ac-df]
Rabadan, J., Nagaraj, K., Sathappan, S., Prabhu, V., Liu,
A., and W. Lin, "AC-Influenced Designated Forwarder
Election for EVPN", draft-ietf-bess-evpn-ac-df-03 (work in
progress), January 2018.
[I-D.ietf-bess-evpn-df-election]
satyamoh@cisco.com, s., Patel, K., Sajassi, A., Drake, J.,
and T. Przygienda, "A new Designated Forwarder Election
for the EVPN", draft-ietf-bess-evpn-df-election-03 (work
in progress), October 2017.
[I-D.ietf-bess-evpn-igmp-mld-proxy]
Sajassi, A., Thoria, S., Patel, K., Yeung, D., Drake, J.,
and W. Lin, "IGMP and MLD Proxy for EVPN", draft-ietf-
bess-evpn-igmp-mld-proxy-00 (work in progress), March
2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601,
DOI 10.17487/RFC4601, August 2006,
<https://www.rfc-editor.org/info/rfc4601>.
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[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, <https://www.rfc-editor.org/info/rfc7432>.
Authors' Addresses
Ali Sajassi
Cisco Systems
821 Alder Drive,
MILPITAS, CALIFORNIA 95035
UNITED STATES
Email: sajassi@cisco.com
Mankamana Mishra
Cisco Systems
821 Alder Drive,
MILPITAS, CALIFORNIA 95035
UNITED STATES
Email: mankamis@cisco.com
Samir Thoria
Cisco Systems
821 Alder Drive,
MILPITAS, CALIFORNIA 95035
UNITED STATES
Email: sthoria@cisco.com
Jorge Rabadan
Nokia
777 E. Middlefield Road
Mountain View, CA 94043
UNITED STATES
Email: jorge.rabadan@nokia.com
John Drake
Juniper Networks
Email: jdrake@juniper.net
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