draft-ietf-bess-evpn-virtual-eth-segment-03.txt   draft-ietf-bess-evpn-virtual-eth-segment-04.txt 
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Internet Working Group A. Sajassi Internet Working Group A. Sajassi
Internet Draft P. Brissette Internet Draft P. Brissette
Category: Standards Track Cisco Category: Standards Track Cisco
R. Schell R. Schell
Verizon Verizon
J. Drake J. Drake
Juniper Juniper
J. Rabadan J. Rabadan
Nokia Nokia
Expires: July 09, 2019 January 09, 2019 Expires: July 18, 2019 January 18, 2019
EVPN Virtual Ethernet Segment EVPN Virtual Ethernet Segment
draft-ietf-bess-evpn-virtual-eth-segment-03 draft-ietf-bess-evpn-virtual-eth-segment-04
Abstract Abstract
EVPN and PBB-EVPN introduce a family of solutions for multipoint EVPN and PBB-EVPN introduce a family of solutions for multipoint
Ethernet services over MPLS/IP network with many advanced features Ethernet services over MPLS/IP network with many advanced features
among which their multi-homing capabilities. These solutions define among which their multi-homing capabilities. These solutions define
two types of multi-homing for an Ethernet Segment (ES): 1) Single- two types of multi-homing for an Ethernet Segment (ES): 1) Single-
Active and 2) All-Active, where an Ethernet Segment is defined as a Active and 2) All-Active, where an Ethernet Segment is defined as a
set of links between the multi-homed device/network and the set of PE set of links between the multi-homed device/network and a set of PE
devices that they are connected to. devices that they are connected to.
Some Service Providers want to extend the concept of the physical Some Service Providers want to extend the concept of the physical
links in an ES to Ethernet Virtual Circuits (EVCs) where many of such links in an ES to Ethernet Virtual Circuits (EVCs) where many of such
EVCs can be aggregated on a single physical External Network-to- EVCs can be aggregated on a single physical External Network-to-
Network Interface (ENNI). An ES that consists of a set of EVCs Network Interface (ENNI). An ES that consists of a set of EVCs
instead of physical links is referred to as a virtual ES (vES). This instead of physical links is referred to as a virtual ES (vES). This
draft describes the requirements and the extensions needed to support draft describes the requirements and the extensions needed to support
vES in EVPN and PBB-EVPN. vES in EVPN and PBB-EVPN.
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12. Informative References . . . . . . . . . . . . . . . . . . . . 22 12. Informative References . . . . . . . . . . . . . . . . . . . . 22
13. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 22 13. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
[RFC7432] and [RFC7623] introduce a family of solutions for [RFC7432] and [RFC7623] introduce a family of solutions for
multipoint Ethernet services over MPLS/IP network with many advanced multipoint Ethernet services over MPLS/IP network with many advanced
features among which their multi-homing capabilities. These solutions features among which their multi-homing capabilities. These solutions
define two types of multi-homing for an Ethernet Segment (ES): 1) define two types of multi-homing for an Ethernet Segment (ES): 1)
Single-Active and 2) All-Active, where an Ethernet Segment is defined Single-Active and 2) All-Active, where an Ethernet Segment is defined
as a set of links between the multi-homed device/network and the set as a set of links between the multi-homed device/network and a set of
of PE devices that they are connected to. PE devices that they are connected to.
This document extends the Ethernet Segment concept so that an ES can This document extends the Ethernet Segment concept so that an ES can
be associated to a set of EVCs (e.g., VLANs) or other objects such as be associated to a set of EVCs (e.g., VLANs) or other objects such as
MPLS Label Switch Paths (LSPs) or Pseudowires (PWs). MPLS Label Switch Paths (LSPs) or Pseudowires (PWs).
1.1 Virtual Ethernet Segments in Access Ethernet Networks 1.1 Virtual Ethernet Segments in Access Ethernet Networks
Some Service Providers (SPs) want to extend the concept of the Some Service Providers (SPs) want to extend the concept of the
physical links in an ES to Ethernet Virtual Circuits (EVCs) where physical links in an ES to Ethernet Virtual Circuits (EVCs) where
many of such EVCs (e.g., VLANs) can be aggregated on a single many of such EVCs (e.g., VLANs) can be aggregated on a single
physical External Network-to-Network Interface (ENNI). An ES that physical External Network-to-Network Interface (ENNI). An ES that
consists of a set of EVCs instead of physical links is referred to as consists of a set of EVCs instead of physical links is referred to as
a virtual ES (vES). Figure below depicts two PE devices (PE1 and PE2) a virtual ES (vES). Figure 1 depicts two PE devices (PE1 and PE2)
each with an ENNI where a number of vES's are aggregated on - each of each with an ENNI where a number of vES's are aggregated on - each of
which through its associated EVC. which through its associated EVC.
Carrier Carrier
Ethernet Ethernet
+-----+ Network +-----+ Network
| CE11|EVC1 +---------+ <---- EVPN Network -----> | CE11|EVC1 +---------+ <---- EVPN Network ----->
+-----+ \ | | +---+ +-----+ \ | | +---+
Cust. A \-0=========0--ENNI1| | Cust. A \-0=========0--ENNI1| |
+-----+ | | ENNI1| | +-------+ +---+ +-----+ | | ENNI1| | +-------+ +---+
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| |EVC5--0=========0--ENNI2| | +-------+ +---+ | |EVC5--0=========0--ENNI2| | +-------+ +---+
+-----+ | | +---+ +-----+ | | +---+
Cust. C +---------+ /\ Cust. C +---------+ /\
/\ || /\ ||
|| ENNI || ENNI
EVCs Interface EVCs Interface
<--------802.1Q----------> <-802.1Q-> <--------802.1Q----------> <-802.1Q->
Figure 1: DHD/DHN (both SA/AA) and SH on same ENNI Figure 1: DHD/DHN (both SA/AA) and SH on same ENNI
E-NNIs are commonly used to reach off-network / out-of-franchise ENNIs are commonly used to reach off-network / out-of-franchise
customer sites via independent Ethernet access networks or third- customer sites via independent Ethernet access networks or third-
party Ethernet Access Providers (EAP) (see Figure 1). E-NNIs can party Ethernet Access Providers (EAP) (see Figure 1). ENNIs can
aggregate traffic from hundreds to thousands of vES's; where, each aggregate traffic from hundreds to thousands of vES's; where, each
vES is represented by its associated EVC on that ENNI. As a result, vES is represented by its associated EVC on that ENNI. As a result,
ENNIs and their associated EVCs are a key element of SP off-networks ENNIs and their associated EVCs are a key element of SP off-networks
that are carefully designed and closely monitored. that are carefully designed and closely monitored.
In order to meet customer's Service Level Agreements (SLA), SPs build In order to meet customer's Service Level Agreements (SLA), SPs build
redundancy via multiple EVPN PEs and across multiple ENNIs (as shown redundancy via multiple EVPN PEs and across multiple ENNIs (as shown
in Figure 1) where a given vES can be multi-homed to two or more EVPN in Figure 1) where a given vES can be multi-homed to two or more EVPN
PE devices (on two or more ENNIs) via their associated EVCs. Just PE devices (on two or more ENNIs) via their associated EVCs. Just
like physical ES's in [RFC7432] and [RFC7623] solutions, these vES's like physical ES's in [RFC7432] and [RFC7623] solutions, these vES's
can be single-homed or multi-homed ES's and when multi-homed, then can be single-homed or multi-homed ES's and when multi-homed, then
can operate in either Single-Active or All-Active redundancy modes. can operate in either Single-Active or All-Active redundancy modes.
In a typical SP off-network scenario, an ENNI can be associated with In a typical SP off-network scenario, an ENNI can be associated with
several thousands of single-homed vES's, several hundreds of Single- several thousands of single-homed vES's, several hundreds of Single-
Active vES's and it may also be associated with tens or hundreds of Active vES's and it may also be associated with tens or hundreds of
All-Active vES's. All-Active vES's.
1.2 Virtual Ethernet Segments in Access MPLS Networks 1.2 Virtual Ethernet Segments in Access MPLS Networks
Other Service Providers (SPs) want to extend the concept of the Other Service Providers (SPs) want to extend the concept of the
physical links in an ES to individual Pseudowires (PWs) or to MPLS physical links in an ES to individual Pseudowires (PWs) or to MPLS
Label Switched Paths (LSPs) in Access MPLS networks. Figure 2 Label Switched Paths (LSPs) in Access MPLS networks - i.e., a vES
illustrates this concept. consisting of a set of PWs or a set of LSPs. Figure 2 illustrates
this concept.
MPLS Aggregation MPLS Aggregation
Network Network
+-----+ +----------------+ <---- EVPN Network -----> +-----+ +----------------+ <---- EVPN Network ----->
| CE11|EVC1 | | | CE11|EVC1 | |
+-----+ \+AG1--+ PW1 +-----+ +-----+ \+AG1--+ PW1 +-----+
Cust. A -0----|===========| | Cust. A -0----|===========| |
+-----+ | ---+===========| | +-------+ +---+ +-----+ | ---+===========| | +-------+ +---+
| CE12|EVC2-0/ | PW2 /\ | PE1 +---+ | | | | CE12|EVC2-0/ | PW2 /\ | PE1 +---+ | | |
+-----+ ++---+ ==||=| | | +---+PE3+- +-----+ ++---+ ==||=| | | +---+PE3+-
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virtual ES can be defined for LSP1 and LSP2. This vES will be shared virtual ES can be defined for LSP1 and LSP2. This vES will be shared
by two separate EVIs in the EVPN network. by two separate EVIs in the EVPN network.
In some cases, this aggregation of PWs into common LSPs may not be In some cases, this aggregation of PWs into common LSPs may not be
possible. For instance, if PW3 were terminated into a third PE, e.g. possible. For instance, if PW3 were terminated into a third PE, e.g.
PE3, instead of PE1, the vES would need to be defined on a per PE3, instead of PE1, the vES would need to be defined on a per
individual PW on each PE, i.e. PW3 and PW5 would belong to ES-1, individual PW on each PE, i.e. PW3 and PW5 would belong to ES-1,
whereas PW4 and PW6 would be associated to ES-2. whereas PW4 and PW6 would be associated to ES-2.
For MPLS/IP access networks where a vES represents a set of PWs or For MPLS/IP access networks where a vES represents a set of PWs or
LSPs, this document extended Single-Active multi-homing procedures of LSPs, this document extends Single-Active multi-homing procedures of
[RFC7432] and [7623] to vES. The vES extension to All-Active multi- [RFC7432] and [7623] to vES. The vES extension to All-Active multi-
homing is outside of the scope of this document for MPLS/IP access homing is outside of the scope of this document for MPLS/IP access
networks. networks.
This draft describes requirements and the extensions needed to This draft describes requirements and the extensions needed to
support vES in [RFC7432] and [RFC7623]. Section 3 lists the set of support vES in [RFC7432] and [RFC7623]. Section 3 lists the set of
requirements for virtual ES's. Section 4 describes the solution for requirements for vES's. Section 4 describes extensions for vES that
[RFC7432], [RFC7623], and [RFC8214] to meet these requirements. are applicable to EVPN solutions including [RFC7432], [RFC7623], and
Section 5 describes the failure handling and recovery for Virtual [RFC8214]. Furthermore, these extensions meet the requirements
ES's in [RFC7432] and [RFC7623]. Section 6 covers scalability and described in section 3. Section 5 describes the failure handling and
fast convergence required for Virtual ES's in [RFC7432] and recovery for vES's in [RFC7432] and [RFC7623]. Section 6 covers
scalability and fast convergence required for vES's in [RFC7432] and
[RFC7623]. [RFC7623].
2. Terminology 2. Terminology
AC: Attachment Circuit AC: Attachment Circuit
BEB: Backbone Edge Bridge BEB: Backbone Edge Bridge
B-MAC: Backbone MAC Address B-MAC: Backbone MAC Address
CE: Customer Edge CE: Customer Edge
CFM: Connectivity Fault Management CFM: Connectivity Fault Management
C-MAC: Customer/Client MAC Address C-MAC: Customer/Client MAC Address
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3.4. EVC Service Types 3.4. EVC Service Types
A physical port (e.g., ENNI) of a PE can aggregate many EVCs each of A physical port (e.g., ENNI) of a PE can aggregate many EVCs each of
which is associated with a vES. Furthermore, an EVC may carry one or which is associated with a vES. Furthermore, an EVC may carry one or
more VLANs. Typically, an EVC carries a single VLAN and thus it is more VLANs. Typically, an EVC carries a single VLAN and thus it is
associated with a single broadcast domain. However, there is no associated with a single broadcast domain. However, there is no
restriction on an EVC to carry more than one VLAN. restriction on an EVC to carry more than one VLAN.
(R4a) An EVC can be associated with a single broadcast domain - e.g., (R4a) An EVC can be associated with a single broadcast domain - e.g.,
VLAN-based service or VLAN bundle service VLAN-based service or VLAN bundle service
(R4b) An EVC MAY be associated with several broadcast domains - e.g., (R4b) An EVC MAY be associated with several broadcast domains - e.g.,
VLAN-aware bundle service VLAN-aware bundle service
In the same way, a PE can aggregate many LSPs and PWs. In the case of In the same way, a PE can aggregate many LSPs and PWs. In the case of
individual PWs per vES, typically a PW is associated with a single individual PWs per vES, typically a PW is associated with a single
broadcast domain, but there is no restriction on the PW to carry more broadcast domain, but there is no restriction on the PW to carry more
than one VLAN if the PW is defined as vc-type VLAN. than one VLAN if the PW is of type Raw mode.
(R4c) A PW can be associated with a single broadcast domain - e.g., (R4c) A PW can be associated with a single broadcast domain - e.g.,
VLAN-based service or VLAN bundle service. VLAN-based service or VLAN bundle service.
(R4d) An PW MAY be associated with several broadcast domains - e.g., (R4d) An PW MAY be associated with several broadcast domains - e.g.,
VLAN-aware bundle service." VLAN-aware bundle service."
3.5. Designated Forwarder (DF) Election 3.5. Designated Forwarder (DF) Election
Section 8.5 of [RFC7432] describes the default procedure for DF Section 8.5 of [RFC7432] describes the default procedure for DF
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(R8a) There SHOULD be a mechanism equivalent to EVPN mass-withdraw (R8a) There SHOULD be a mechanism equivalent to EVPN mass-withdraw
such that upon an ENNI failure, only a single BGP message is needed such that upon an ENNI failure, only a single BGP message is needed
to indicate to the remote PEs to trigger DF election for all impacted to indicate to the remote PEs to trigger DF election for all impacted
vES associated with that ENNI. vES associated with that ENNI.
4. Solution Overview 4. Solution Overview
The solutions described in [RFC7432] and [RFC7623] are leveraged as The solutions described in [RFC7432] and [RFC7623] are leveraged as
is with one simple modification and that is the ESI assignment is is with one simple modification and that is the ESI assignment is
performed for a group of EVCs or LSPs/PWs instead of a group of performed for a group of EVCs or LSPs/PWs instead of a group of
links. In other words, the ESI is associated with a virtual ES (vES) physical links. In other words, the ESI is associated with a virtual
and that's why it will be referred to as vESI. ES (vES) and that's why it will be referred to as vESI.
For the EVPN solution, everything basically remains the same except For the EVPN solution, everything basically remains the same except
for the handling of physical port failure where many vES's can be for the handling of physical port failure where many vES's can be
impacted. Section 5.1 and 5.3 below describe the handling of physical impacted. Section 5.1 and 5.3 below describe the handling of physical
port/link failure for EVPN. In a typical multi-homed operation, MAC port/link failure for EVPN. In a typical multi-homed operation, MAC
addresses are learned behind a vES are advertised with the ESI addresses are learned behind a vES are advertised with the ESI
corresponding to the vES (i.e., vESI). EVPN aliasing and mass- corresponding to the vES (i.e., vESI). EVPN aliasing and mass-
withdraw operations are performed with respect to vES. In other withdraw operations are performed with respect to vES. In other
words, the Ethernet A-D routes for these operations are advertised words, the Ethernet A-D routes for these operations are advertised
with vESI instead of ESI. with vESI instead of ESI.
For PBB-EVPN solution, the main change is with respect to the BMAC For PBB-EVPN solution, the main change is with respect to the BMAC
address assignment which is performed similar to what is described in address assignment which is performed similar to what is described in
section 7.2.1.1 of [RFC7623] with the following refinements: section 7.2.1.1 of [RFC7623] with the following refinements:
- One shared BMAC address is used per PE for the single-homed vES's. - One shared BMAC address SHOULD used per PE for the single-homed
In other words, a single BMAC is shared for all single-homed vES's on vES's. In other words, a single BMAC is shared for all single-homed
that PE. vES's on that PE.
- One shared BMAC address should be used per PE per physical port - One shared BMAC address SHOULD be used per PE per physical port
(e.g., ENNI) for the Single-Active vES's. In other words, a single (e.g., ENNI) for the Single-Active vES's. In other words, a single
BMAC is shared for all Single-Active vES's that shared the same ENNI. BMAC is shared for all Single-Active vES's that share the same ENNI.
- One shared BMAC address can be used for all Single-Active vES's on - One shared BMAC address MAY be used for all Single-Active vES's on
that PE. that PE.
- One BMAC address is used per EVC per physical port per PE for each - One BMAC address SHOULD be used per set of EVCs representing an
All-Active multi-homed vES. In other words, a single BMAC address is All-Active multi-homed vES. In other words, a single BMAC address is
used per vES for All-Active multi-homing scenarios. used per vES for All-Active multi-homing scenarios.
- A single BMAC address may also be used per vES per PE for Single- - A single BMAC address MAY also be used per vES per PE for Single-
Active multi-homing scenarios. Active multi-homing scenarios.
BEB +--------------+ BEB BEB +--------------+ BEB
|| | | || || | | ||
\/ | | \/ \/ | | \/
+----+ EVC1 +----+ | | +----+ +----+ +----+ EVC1 +----+ | | +----+ +----+
| CE1|------| | | | | |---| CE2| | CE1|------| | | | | |---| CE2|
+----+\ | PE1| | IP/MPLS | | PE3| +----+ +----+\ | PE1| | IP/MPLS | | PE3| +----+
\ +----+ | Network | +----+ \ +----+ | Network | +----+
\ | | \ | |
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unblock traffic for that EVPN instance. Note that the DF PE unblocks unblock traffic for that EVPN instance. Note that the DF PE unblocks
all traffic in both ingress and egress directions for Single-Active all traffic in both ingress and egress directions for Single-Active
vES and unblocks multi-destination in egress direction for All-Active vES and unblocks multi-destination in egress direction for All-Active
Multi-homed vES. All non-DF PEs block all traffic in both ingress and Multi-homed vES. All non-DF PEs block all traffic in both ingress and
egress directions for Single-Active vES and block multi-destination egress directions for Single-Active vES and block multi-destination
traffic in the egress direction for All-Active multi-homed vES. traffic in the egress direction for All-Active multi-homed vES.
In the case of an EVC failure, the affected PE withdraws its Ethernet In the case of an EVC failure, the affected PE withdraws its Ethernet
Segment route if there are no more EVCs associated to the vES in the Segment route if there are no more EVCs associated to the vES in the
PE. This will re-trigger the DF Election procedure on all the PEs in PE. This will re-trigger the DF Election procedure on all the PEs in
the RG. For PE node failure, or upon PE commissioning or the Redundancy Group. For PE node failure, or upon PE commissioning
decommissioning, the PEs re-trigger the DF Election Procedure across or decommissioning, the PEs re-trigger the DF Election Procedure
all affected vES's. In case of a Single-Active multi-homing, when a across all affected vES's. In case of a Single-Active multi-homing,
service moves from one PE in the Redundancy Group to another PE as a when a service moves from one PE in the Redundancy Group to another
result of DF re-election, the PE, which ends up being the elected DF PE as a result of DF re-election, the PE, which ends up being the
for the service, SHOULD trigger a MAC address flush notification elected DF for the service, SHOULD trigger a MAC address flush
towards the associated vES. This can be done, for e.g. using IEEE notification towards the associated vES. This can be done, for e.g.
802.1ak MVRP 'new' declaration. using IEEE 802.1ak MVRP 'new' declaration.
For LSP and PW based vES, the non-DF PE SHOULD signal PW-status For LSP and PW based vES, the non-DF PE SHOULD signal PW-status
'standby' signaling to the AG PE, and the new DF MAY send an LDP MAC 'standby' signaling to the Aggregation PE (e.g., AG PE in Figure 2),
withdraw message as a MAC address flush notification. It should be and the new DF PE MAY send an LDP MAC withdraw message as a MAC
noted that the PW-status is signaled for the scenarios where there is address flush notification. It should be noted that the PW-status is
a one-to-one mapping between EVI/BD and the PW. signaled for the scenarios where there is a one-to-one mapping
between EVI/BD and the PW.
5. Failure Handling & Recovery 5. Failure Handling & Recovery
There are a number of failure scenarios to consider such as: There are a number of failure scenarios to consider such as:
A: CE Uplink Port Failure A: CE Uplink Port Failure
B: Ethernet Access Network Failure B: Ethernet Access Network Failure
C: PE Access-facing Port or link Failure C: PE Access-facing Port or link Failure
D: PE Node Failure D: PE Node Failure
E: PE isolation from IP/MPLS network E: PE isolation from IP/MPLS network
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+-----+ | | | | +-------+ +-----+ | | | | +-------+
+-----+ +---+ +-----+ +---+
/\ /\ /\ /\ /\ /\
|| || || || || ||
A C E A C E
Figure 4: Failure Scenarios A,B,C,D and E Figure 4: Failure Scenarios A,B,C,D and E
5.1. Failure Handling for Single-Active vES in EVPN 5.1. Failure Handling for Single-Active vES in EVPN
When a PE connected to a Single-Active multi-homed Ethernet Segment When a DF PE connected to a Single-Active multi-homed Ethernet
loses connectivity to the segment, due to link or port failure, it Segment loses connectivity to the segment, due to link or port
signals the remote PE to flush all CMAC addresses associated with failure, it signals to the remote PEs to withdraw all MAC addresses
that Ethernet Segment. This is done by advertising a mass-withdraw associated with that Ethernet Segment. This is done by advertising a
message using Ethernet A-D per-ES route. To be precise, there is no mass-withdraw message using Ethernet A-D per-ES route. It should be
MAC flush per-se if there is only one backup PE for a given ES - noted that for dual-homing use cases where there is only a single
i.e., only an update of the forwarding entries per backup-path backup path, MAC withdraw can be avoided by the remote PEs as they
procedure in [RFC 7432]. can simply update their nexthop associated with the affected MAC
entries to the backup path per procedure described in section 8.2 of
[RFC7432].
In case of an EVC failure that impacts a single vES, the exact same In case of an EVC failure which impacts a single vES, the exact same
EVPN procedure is used. In this case, the message using Ethernet A-D EVPN procedure is used. In this case, the message using Ethernet A-D
per ES route carries the vESI representing the vES which is in turn per ES route carries the vESI representing the vES which in turn is
associated with the failed EVC. The remote PEs upon receiving this associated with the failed EVC. The remote PEs upon receiving this
message perform the same procedures outlined in section 8.2 of message perform the same procedures outlined in section 8.2 of
[RFC7432]. [RFC7432].
5.2. EVC Failure Handling for Single-Active vES in PBB-EVPN 5.2. EVC Failure Handling for Single-Active vES in PBB-EVPN
When a PE connected to a Single-Active multi-homed Ethernet Segment When a PE connected to a Single-Active multi-homed Ethernet Segment
loses connectivity to the segment, due to link or port failure, it loses connectivity to the segment, due to link or port failure, it
signals the remote PE to flush all CMAC addresses associated with signals the remote PE to flush all CMAC addresses associated with
that Ethernet Segment. This is done by advertising a BMAC route along that Ethernet Segment. This is done by advertising a BMAC route along
with MAC Mobility Extended community. with MAC Mobility Extended community.
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CMACs corresponding to the advertised BMAC only across the advertised CMACs corresponding to the advertised BMAC only across the advertised
list of I-ISIDs. list of I-ISIDs.
The new I-SID Extended Community provides a way to encode upto 24 I- The new I-SID Extended Community provides a way to encode upto 24 I-
SIDs in each Extended Community if the impacted I-SIDs are sequential SIDs in each Extended Community if the impacted I-SIDs are sequential
(the base I-SID value plus the next 23 I-SID values). If the number (the base I-SID value plus the next 23 I-SID values). If the number
of I-SIDs associated with a failed EVC is large or if the affected I- of I-SIDs associated with a failed EVC is large or if the affected I-
SIDs are not sequential, then multiple I-SID Extended Communities can SIDs are not sequential, then multiple I-SID Extended Communities can
be sent along with the flush message. However, if the number of be sent along with the flush message. However, if the number of
affected I-SIDs is very large such that the corresponding I-SID affected I-SIDs is very large such that the corresponding I-SID
Extended Communities don't fit in a single BGP attribute, then the Extended Communities cannot be fitted in a single BGP attribute, then
EVC failure can be treated as a port failure and the procedures of the EVC failure can be treated as a port failure and the procedures
section 5.4 can be exercised (i.e., a single BGP flush message of section 5.4 can be exercised (i.e., a single BGP flush message
without the I-SID list can be transmitted). When the BGP flush without the I-SID list can be transmitted). When the BGP flush
message is transmitted without the I-SID list, then it instructs the message is transmitted without the I-SID list, then it instructs the
receiving PEs to flush CMACs associated with that BMAC across all I- receiving PEs to flush CMACs associated with that BMAC across all I-
SIDs. SIDs.
There can be scenarios (although unlikely) where multiple EVCs within There can be scenarios (although unlikely) where multiple EVCs within
the same physical port can fail within a short time resulting in the the same physical port can fail within a short time resulting in the
PE advertising multiple BGP flush messages each with their own list PE advertising multiple BGP flush messages each with their own list
of I-SIDs; however, the route reflector receiving these messages will of I-SIDs; however, the route reflector receiving these messages will
only send the last flush message. This results in PEs receiving such only send the last flush message. This results in PEs receiving such
flush messages not to properly flush all the affected I-SIDs. In flush messages not to properly flush all the affected I-SIDs. In
order to address such scenarios, a timer T1 is started upon an EVC1 order to address such scenarios, a timer T1 is started upon an EVC1
failure on the advertising PE. If there is another EVC2 failure failure on the advertising PE. If there is another EVC2 failure
within T1, affected I-SIDs are aggregated for both EVC1 and EVC2 to within T1, affected I-SIDs are aggregated for both EVC1 and EVC2 to
be sent along the new flush message. Furthermore when EVC2 failure be sent along the new flush message. Furthermore when EVC2 failure
occurs, another timer T2 (with the same value as T1) is started to occurs, another timer T2 (with the same value as T1) is started to
keep track of the affected I-SIDs for EVC2. Such I-SID aggregation keep track of the affected I-SIDs for EVC2. Such I-SID aggregation
may result in multiple flushing for the same I-SID(s) on the may result in multiple flushing for the same I-SID(s) on the
receiving PEs. The default value for this timer T is 30 seconds. receiving PEs. The default value for this timer T is 10 seconds.
The I-SID dependent flushing mechanism described in this section is The I-SID dependent flushing mechanism described in this section is
backward compatible for the PEs only supporting [RFC7623] such that also backward compatible for the PEs supporting [RFC7623] such that
the PEs that don't understand the I-SID list (i.e., the new I-SID the PEs that don't understand the I-SID list (i.e., the new I-SID
Extended Community) simply ignore it and default to flushing all the Extended Community) simply ignore it and default to flushing all the
I-SIDs for the B-MAC - i.e., the PEs default to per-port flushing I-SIDs for the B-MAC - i.e., the PEs default to per-port flushing
described in section 5.4. described in section 5.4.
The above BMAC route that is advertised with the MAC Mobility The above BMAC route that is advertised with the MAC Mobility
Extended Community, can either represent the MAC address of the Extended Community, can either represent the MAC address of the
physical port that the failed EVC is associated with, or it can physical port that the failed EVC is associated with, or it can
represent the MAC address of the PE. In the latter case, this is the represent the MAC address of the PE. In the latter case, this is the
dedicated per-PE MAC address used for all Single-Active vES's on that dedicated per-PE MAC address used for all Single-Active vES's on that
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address of the port and the 3-octet local discriminator field set to address of the port and the 3-octet local discriminator field set to
0xFFFFFF. This mass-withdraw route is advertised with a list of Route 0xFFFFFF. This mass-withdraw route is advertised with a list of Route
Targets corresponding to the impacted service instances. If the Targets corresponding to the impacted service instances. If the
number of Route Targets is more than they can fit into a single number of Route Targets is more than they can fit into a single
attribute, then a set of Ethernet A-D per ES routes are advertised. attribute, then a set of Ethernet A-D per ES routes are advertised.
The remote PEs upon receiving this message, realize that this is a The remote PEs upon receiving this message, realize that this is a
special mass-withdraw message and they access the list of the vES's special mass-withdraw message and they access the list of the vES's
for the specified color. Next, they initiate mass-withdraw procedure for the specified color. Next, they initiate mass-withdraw procedure
for each of the vES's in the list. for each of the vES's in the list.
In scenarios where a logical ENNI is used the above procedure equally
applies. The logical ENNI is represented by type 3 ESI and the MAC
address used in the ENNI's ESI is used as a color for vES's as
described above.
5.4. Port Failure Handling for Single-Active vES's in PBB-EVPN 5.4. Port Failure Handling for Single-Active vES's in PBB-EVPN
When a large number of EVCs are aggregated via a single physical port When a large number of EVCs are aggregated via a single physical port
on a PE; where each EVC corresponds to a vES, then the port failure on a PE; where each EVC corresponds to a vES, then the port failure
impacts all the associated EVCs and their corresponding vES's. If the impacts all the associated EVCs and their corresponding vES's. If the
number of EVCs corresponding to the Single-Active vES's for that number of EVCs corresponding to the Single-Active vES's for that
physical port is in thousands, then thousands of service instances physical port is in thousands, then thousands of service instances
(I-SIDs) are impacted. In such failure scenarios, the following two (I-SIDs) are impacted. In such failure scenarios, the following two
MAC flushing mechanisms per [RFC7623] can be performed. MAC flushing mechanisms per [RFC7623] can be performed.
1) If the MAC address of the physical port is used for PBB 1) If the MAC address of the physical port is used for PBB
encapsulation as BMAC SA, then upon the port failure, the PE MUST use encapsulation as BMAC SA, then upon the port failure, the PE MUST use
the EVPN MAC route withdrawal message to signal the flush the EVPN MAC route withdrawal message to signal the flush.
2) If the PE shared MAC address is used for PBB encapsulation as BMAC 2) If the PE shared MAC address is used for PBB encapsulation as BMAC
SA, then upon the port failure, the PE MUST re-advertise this MAC SA, then upon the port failure, the PE MUST re-advertise this MAC
route with the MAC Mobility Extended Community to signal the flush route with the MAC Mobility Extended Community to signal the flush.
The first method is recommended because it reduces the scope of The first method is recommended because it reduces the scope of
flushing the most. flushing the most.
5.5. Fast Convergence in PBB-EVPN 5.5. Fast Convergence in PBB-EVPN
As described above, when a large number of EVCs are aggregated via a As described above, when a large number of EVCs are aggregated via a
physical port on a PE; where each EVC corresponds to a vES, then the physical port on a PE; where each EVC corresponds to a vES, then the
port failure impacts all the associated EVCs and their corresponding port failure impacts all the associated EVCs and their corresponding
vES's. Two actions must be taken as the result of such port failure: vES's. Two actions must be taken as the result of such port failure:
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In order to devise such fast convergence mechanism that can be In order to devise such fast convergence mechanism that can be
triggered via a single BGP message, all vES's associated with a given triggered via a single BGP message, all vES's associated with a given
physical port (e.g., ENNI) are colored with the same color physical port (e.g., ENNI) are colored with the same color
representing that physical port. The MAC address of the physical port representing that physical port. The MAC address of the physical port
is used for this coloring purposes and when the PE advertises an ES is used for this coloring purposes and when the PE advertises an ES
route for a vES associated with that physical port, it advertises it route for a vES associated with that physical port, it advertises it
with an EVPN Router's MAC Extended Community indicating the color of with an EVPN Router's MAC Extended Community indicating the color of
that port. that port.
The receiving PEs take note of this color and for each such color, The receiving PEs take note of this color and for each such color,
they create a list of vES's associated with this color (with this MAC they create a list of vES's associated with this color (i.e.,
address). Now, when a port failure occurs, the impacted PE needs to associated with this MAC address). Now, when a port failure occurs,
notify the other PEs of this color so that these PEs can identify all the impacted PE needs to notify the other PEs of this color so that
the impacted vES's associated with that color (from the above list) these PEs can identify all the impacted vES's associated with this
and re-execute DF election procedures for all the impacted vES's. color (from the above list) and re-execute DF election procedures for
all the impacted vES's. This is done by withdrawing the BMAC address
In PBB-EVPN, there are two ways to convey this color to other PEs associated with the failed port.
upon a port failure - one corresponding to each method for signaling
flush message as described in section 5.4. If for PBB encapsulation,
the MAC address of the physical port is used as BMAC SA, then upon
the port failure, the PE sends MAC withdrawal message with the MAC
address of the failed port as the color. However, if for PBB
encapsulation, the shared MAC address of the PE (dedicated for all
Single-Active vES's) is used as BMAC SA, then upon the port failure,
the PE re-advertises the MAC route (that carries the shared BMAC)
along with this new EVPN Router's MAC Extended Community to indicate
the color along with MAC Mobility Extended Community.
+-----+ +-----+
+----+ | | +---+ +----+ | | +---+
| CE1|AC1--0=====0--ENNI1| | +-------+ | CE1|AC1--0=====0--ENNI1| | +-------+
| |AC2--0 | |PE1|--| | | |AC2--0 | |PE1|--| |
+----+ |\ ==0--ENNI2| | | | +----+ |\ ==0--ENNI2| | | |
| \/ | +---+ | | | \/ | +---+ | |
| /\ | |IP/MPLS| | /\ | |IP/MPLS|
+----+ |/ \ | +---+ |Network| +---+ +---+ +----+ |/ \ | +---+ |Network| +---+ +---+
| CE2|AC4--0 =0--ENNI3| | | |---|PE4|--|CE4| | CE2|AC4--0 =0--ENNI3| | | |---|PE4|--|CE4|
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convergence using this color in more details: convergence using this color in more details:
1- When a vES is configured, the PE colors the vES with the MAC 1- When a vES is configured, the PE colors the vES with the MAC
address of the corresponding physical port and advertises the address of the corresponding physical port and advertises the
Ethernet Segment route for this vES with this color. Ethernet Segment route for this vES with this color.
2- All other PEs (in the redundancy group) take note of this color 2- All other PEs (in the redundancy group) take note of this color
and add the vES to the list for this color. and add the vES to the list for this color.
3- Upon the occurrence of a port failure (e.g., an ENNI failure), the 3- Upon the occurrence of a port failure (e.g., an ENNI failure), the
PE sends the flush message in one of the two ways described above PE sends the flush message by withdrawing the BMAC address associated
indicating this color. The PE should prioritize sending this flush with the failed port. The PE should prioritize sending this flush
message over ES route withdrawal messages of impacted vES's. message over ES route withdrawal messages of impacted vES's.
4- On reception of the flush message, other PEs use this info to 4- On reception of the flush message, other PEs use this info to
flush their impacted CMACs and to initiate DF election procedures flush their impacted CMACs and to initiate DF election procedures
across all their affected vES's. across all their affected vES's.
5- The PE with the physical port failure (ENNI failure), also sends 5- The PE with the physical port failure (ENNI failure), also sends
ES route withdrawal for every impacted vES's. The other PEs upon ES route withdrawal for every impacted vES's. The other PEs upon
receiving these messages, clear up their BGP tables. It should be receiving these messages, clear up their BGP tables. It should be
noted the ES route withdrawal messages are not used for executing DF noted the ES route withdrawal messages are not used for executing DF
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