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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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   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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