PBB-EVPN ISID-based CMAC-Flush
draft-ietf-bess-pbb-evpn-isid-cmacflush-02
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9541.
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|
|---|---|---|---|
| Authors | Jorge Rabadan , Senthil Sathappan , Kiran Nagaraj , Masahiro Miyake , Taku Matsuda | ||
| Last updated | 2021-11-08 (Latest revision 2021-04-26) | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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draft-ietf-bess-pbb-evpn-isid-cmacflush-02
BESS Workgroup J. Rabadan, Ed.
Internet-Draft S. Sathappan
Intended status: Standards Track K. Nagaraj
Expires: October 28, 2021 Nokia
M. Miyake
T. Matsuda
Softbank
April 26, 2021
PBB-EVPN ISID-based CMAC-Flush
draft-ietf-bess-pbb-evpn-isid-cmacflush-02
Abstract
Provider Backbone Bridging (PBB) can be combined with Ethernet VPN
(EVPN) to deploy Ethernet Local Area Network (ELAN) services in large
Multi-Protocol Label Switching (MPLS) networks (PBB-EVPN). Single-
Active Multi-homing and per-ISID Load-Balancing can be provided to
access devices and aggregation networks. In order to speed up the
network convergence in case of failures on Single-Active Multi-Homed
Ethernet Segments, PBB-EVPN defines a flush mechanism for Customer
MACs (CMAC-flush) that works for different Ethernet Segment Backbone
MAC (BMAC) address allocation models. This document complements
those CMAC-flush procedures for cases in which no PBB-EVPN Ethernet
Segments are defined (the attachment circuit is associated to a zero
Ethernet Segment Identifier) and a Service Instance Identifier based
(ISID-based) CMAC-flush granularity is required.
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 October 28, 2021.
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Copyright Notice
Copyright (c) 2021 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology and Conventions . . . . . . . . . . . . . . . 4
2. Solution requirements . . . . . . . . . . . . . . . . . . . . 5
3. EVPN BGP Encoding for ISID-based CMAC-flush . . . . . . . . . 6
4. Solution description . . . . . . . . . . . . . . . . . . . . 7
4.1. ISID-based CMAC-Flush activation procedures . . . . . . . 8
4.2. CMAC-Flush generation . . . . . . . . . . . . . . . . . . 8
4.3. CMAC-flush process upon receiving a CMAC-flush
notification . . . . . . . . . . . . . . . . . . . . . . 9
5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
[RFC7623] defines how Provider Backbone Bridging (PBB) can be
combined with Ethernet VPN (EVPN) to deploy ELAN services in very
large MPLS networks. [RFC7623] also describes how Single-Active
Multi-homing and per-ISID Load-Balancing can be provided to access
devices and aggregation networks. When Access Ethernet/MPLS Networks
exists, [I-D.ietf-bess-evpn-virtual-eth-segment] describes how
virtual Ethernet Segments can be associated to a group of Ethernet
Virtual Circuits (EVCs) or even Pseudowires (PWs). In order to speed
up the network convergence in case of failures on Single-Active
Multi-Homed Ethernet Segments, [RFC7623] defines a CMAC-flush
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mechanism that works for different Ethernet Segment BMAC address
allocation models.
In some cases, the administrative entities that manage the access
devices or aggregation networks don't demand Multi-Homing Ethernet
Segments (ES) from the PBB-EVPN provider, but simply multiple single-
homed ES. If that is the case, the PBB-EVPN network is no longer
aware of the redundancy offered by the access administrative entity.
Figure 1 shows an example where the PBB-EVPN network provides four
different Attachment Circuits (ACs) for ISID1, with those ACs not
being part of any ES or vES (therefore they are referred to as null
vES).
<--PBB-EVPN Network--->
ISID1 vES +-----+ +-----+
+----+ null| PE1 +---------+ PE3 |vES null
|CE1 +--------+ BM1 | | BM3 | +---------+
+-+--+ act| | | |===== |
| G.8032 +-+---+ +---+-+ | \act | ISID1
| Access | | | \ +-+--+
| Ring | IP/MPLS | | ==|CE3 |
| | | | / +-+--+
|stb vES +-+---+ +---+-+ | /stb |
+-+--+ null| PE2 | | PE4 +----- |
|CE2 +--------+ BM2 | | BM4 | +---------+
+----+ act| +---------+ |vES null
ISID1 +-----+ +-----+ <-MPLS Ag->
Network
Figure 1: PBB-EVPN and non-ES based redundancy
In the example in Figure 1, CE1 and CE2 provide redundant
connectivity for ISID1 through the use of G.8032 Ethernet Ring
Protection Switching. CE3 provides redundant active-standby PW
connectivity for ISID1. In the two cases the ACs are connected to
null ES, hence the PEs will keep their ACs active and the CEs will be
responsible for the per-ISID load balancing while avoiding loops.
For instance, CE2 will block its link to CE1 and CE3 will block its
forwarding path to PE4. In this situation, a failure in one of the
redundant ACs will make the CEs to start using their redundant paths,
however those failures will not trigger any CMAC-flush procedures in
the PEs that implement [RFC7623]. For example, if the active PW from
CE3 fails, PE3 will not issue any CMAC-flush message and therefore
the remote PEs will continue pointing at PE3's BMAC to reach CE3's
CMACs, until the CMACs age out in the ISID1 forwarding tables.
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[RFC7623] provides a CMAC-flush solution based on a shared BMAC
update along with the MAC Mobility extended community where the
sequence number is incremented. However, the procedure is only used
along with Ethernet Segments. Even if that procedure could be used
for null Ethernet Segments, as in the example of Figure 1, the
[RFC7623] CMAC-flush procedure would result in unnecessary flushing
of unaffected ISIDs on the remote PEs, and subsequent flooding of
unknown unicast traffic in the network.
This document describes an extension of the [RFC7623] CMAC-flush
procedures, so that in the above failure example, PE3 can trigger a
CMAC-flush notification that makes PE1, PE2 and PE4 flush all the
CMACs associated to PE3's BMAC and (only) ISID1. This new CMAC-flush
procedure explained in this document will be referred to as "PBB-EVPN
ISID-based CMAC-flush" and can be used in PBB-EVPN networks with null
or non-null (virtual) Ethernet Segments.
1.1. Terminology and Conventions
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 BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
EVPN: Ethernet Virtual Private Networks, as in [RFC7432].
EVI: EVPN Instance.
MAC-VRF: A Virtual Routing and Forwarding table for MAC addresses.
PBB-EVPN: Provider-Backbone-Bridging and EVPN, as in [RFC7623].
PE: Provider Edge router.
CE: Customer Edge router.
CMAC: Customer MAC address.
BMAC or BM: Backbone MAC address.
ISID: Service Instance Identifier.
B-Component: Backbone Component, as in [RFC7623].
I-Component: Service Instance Component, as in [RFC7623].
PW: Pseudowire.
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AC: Attachment Circuit.
ES and ESI: Ethernet Segment and Ethernet Segment Identifier.
Act: Active state, used with ACs or PWs that are operationally
active.
Stb: Standby state, used with ACs or PWs that are in a state where
they cannot transmit traffic.
G.8032: Ethernet Ring Protection.
RD: Route Distinguisher.
RT: Route Target.
BMAC/ISID route: an EVPN MAC/IP Advertisement route that uses a BMAC
in the MAC address field and an ISID in the Ethernet Tag field, and
it is used to notify remote PEs about the required CMAC-flush
procedure for the CMACs associated with the advertised BMAC and ISID.
BMAC/0 route: an EVPN MAC/IP Advertisement route that uses a BMAC in
the MAC address field and a zero Ethernet Tag ID.
Familiarity with the terminology in [RFC7623] is expected.
2. Solution requirements
The following requirements are followed by the CMAC-flush solution
described in this document:
a. The solution solves black-hole scenarios in case of failures on
null ES ACs (Attachment Circuits not associated to ES, that is,
ESI=0) when the access device/network is responsible for the
redundancy.
b. This extension works with Single-Active non-null ES and virtual
ES, irrespective of the PE BMAC address assignment (dedicated
per-ES BMAC or shared BMAC, as in [RFC7623]).
c. In case of failure on the egress PE, the solution provides a
CMAC-flush notification at BMAC and ISID granularity level.
d. The solution provides a reliable CMAC-flush notification in PBB-
EVPN networks that use Route-Reflectors (RRs), without causing
"double flushing" or no flushing for certain ISIDs due to the
notification messages being aggregated at the RR.
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e. The solution coexists in [RFC7623] networks where there are PEs
that do not support this specification.
f. The solution SHOULD be enabled/disabled by an administrative
option on a per-PE and per-ISID basis.
3. EVPN BGP Encoding for ISID-based CMAC-flush
The solution does not use any new BGP attributes but reuses the MAC
Mobility extended community as an indication of CMAC-flush (as in
[RFC7623]) and encodes the ISID in the Ethernet Tag field of the EVPN
MAC/IP advertisement route. As a reference, Figure 2 shows the MAC
Mobility extended community and the EVPN MAC/IP advertisement route
that are used specified in [RFC7432] and used in this document as a
CMAC-flush notification message.
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=0x06 | Sub-Type=0x03 | Flags | Reserved=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+---------------------------------------+
| RD |
+---------------------------------------+
| ESI = 0 |
+---------------------------------------+
| Ethernet Tag ID = ISID |
+---------------------------------------+
| MAC Address Length = 48 |
+---------------------------------------+
| BMAC Address |
+---------------------------------------+
| IP Address Length = 0 |
+---------------------------------------+
| MPLS Label1 |
+---------------------------------------+
Figure 2: CMAC-Flush notification encoding: BMAC/ISID route
Where:
o The route's RD and RT are the ones corresponding to its EVI.
Alternatively to the EVI's RT, the route MAY be tagged with an RT
auto-derived from the Ethernet Tag (ISID) instead. [RFC7623]
describes how the EVPN MAC/IP Advertisement routes can be
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advertised along with the EVI RT or an RT that is derived from the
ISID.
o The Ethernet Tag encodes the ISID for which the PE that receives
the route must flush the CMACs upon reception of the route.
o The MAC address field encodes the BMAC Address for which the PE
that receives the route must flush the CMACs upon reception of the
route.
o The MAC Mobility extended community is used as in [RFC7623], where
a delta in the sequence number between two updates for the same
BMAC/ISID will be interpreted as a CMAC-flush notification for the
corresponding BMAC and ISID.
All the other fields are set and used as defined in [RFC7623]. This
document will refer to this route as the BMAC/ISID route, as opposed
to the [RFC7623] BMAC/0 route (BMAC route sent with Ethernet Tag ID =
0).
Note that this BMAC/ISID route will be accepted and reflected by any
[RFC7432] RR, since no new attributes or values are used. A PE
receiving the route will process the received BMAC/ISID update only
in case of supporting the procedures described in this document.
4. Solution description
Figure 1 will be used in the description of the solution. CE1, CE2
and CE3 are connected to ACs associated to ISID1, where no (Multi-
Homed) Ethernet Segments have been enabled, and the ACs and PWs are
in active or standby state as per Figure 1.
Enabling or disabling ISID-based CMAC-flush SHOULD be an
administrative choice on the system that MAY be configured per ISID
(I-Component). When enabled on a PE:
a. The PE will be able to generate BMAC/ISID routes as CMAC-Flush
notifications for the remote PEs.
b. he PE will be able to process BMAC/ISID routes received from
remote PEs.
When ISID-based CMAC-flush is disabled, the PE will follow the
[RFC7623] procedures for CMAC-flush.
This CMAC-flush specification is described in three sets of
procedures:
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o ISID-based CMAC-flush activation
o CMAC-flush notification generation upon AC failures
o CMAC-flush process upon receiving a CMAC-flush notification
4.1. ISID-based CMAC-Flush activation procedures
The following behavior MUST be followed by the PBB-EVPN PEs following
this specification. Figure 1 is used as a reference.
o As in [RFC7623], each PE advertises a shared BMAC in a BMAC/0
route (with BM1, BM2, BM3 and BM4 in the MAC address field,
respectively). This is the BMAC that each PE will use as BMAC SA
(Source Address) when encapsulating the frames received on any
local single-homed AC. Each PE will import the received BMAC/0
routes from the remote PEs and will install the BMACs in its
B-component MAC-VRF. For instance, PE1 will advertise BM1/0 and
will install BM2, BM3 and BM4 in its MAC-VRF.
o Assuming ISID-based CMAC-flush is activated for ISID 1, the PEs
will advertise the shared BMAC with ISID 1 encoded in the Ethernet
Tag. That is, PE1 will advertise BM1/1 and will receive BM2/1,
BM3/1 and BM4/1. The receiving PEs MUST use these BMAC/ISID
routes only for CMAC-flush procedures and they MUST NOT be used
them to add/withdraw any BMAC entry in the MAC-VRFs. As per
[RFC7623], only BMAC/0 routes can be used to add/withdraw BMACs in
the MAC-VRFs.
o The above procedure MAY also be used for dedicated BMACs (BMACs
allocated per Ethernet Segment).
4.2. CMAC-Flush generation
If, for instance, there is a failure on PE1's AC, PE1 will generate
an update including BM1/1 along with the MAC Mobility extended
community where the Sequence Number has been incremented. The
reception of the BM1/1 with a delta in the sequence number will
trigger the CMAC-flush procedures on the receiving PEs.
o An AC going operationally down MUST generate a BMAC/ISID with a
higher Sequence Number. If the AC going down makes the entire
local ISID go operationally down, the PE will withdraw the BMAC/
ISID route for the ISID.
o An AC going operationally up SHOULD NOT generate any BMAC/ISID
update, unless it activates its corresponding ISID, in which case
the PE will advertise the BMAC/ISID route.
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o An AC receiving a G.8032 flush notification or a flush message in
any other protocol from the access network MAY propagate it to the
remote PEs by generating a BMAC/ISID route update with higher
Sequence Number.
4.3. CMAC-flush process upon receiving a CMAC-flush notification
A PE receiving a CMAC-flush notification will follow these
procedures:
o A received BMAC/ISID route (with non-zero ISID) MUST NOT add/
remove any BMAC to/from the MAC-VRF.
o An update of a previously received BMAC/ISID route with a delta
Sequence Number, MUST flush all the CMACs associated to that ISID
and BMAC. CMACs associated to the same ISID but different BMAC
MUST NOT be flushed.
o A received BMAC/ISID withdraw (with non-zero ISID) MUST flush all
the CMACs associated to that BMAC and ISID.
Note that the CMAC-flush procedures described in [RFC7623] for BMAC/0
routes are still valid and a PE receiving [RFC7623] CMAC-flush
notification messages MUST observe the behavior specified in
[RFC7623].
5. Conclusions
The ISID-based CMAC-flush solution described in this document has the
following benefits:
a. The solution solves black-hole scenarios in case of failures on
null ES ACs, since the CMAC-flush procedures are independent of
the Ethernet Segment definition.
b. This extension can also be used with Single-Active non-null ES
and virtual ES, irrespective of the PE BMAC address assignment
(dedicated per-ES BMAC or shared BMAC).
c. It provides a CMAC-flush notification at BMAC and ISID
granularity level, therefore flushing a minimum number of CMACs
and reducing the amount of unknown unicast flooding in the
network.
d. It provides a reliable CMAC-flush notification in PBB-EVPN
networks that use RRs. RRs will propagate the CMAC-flush
notifications for all the affected ISIDs and irrespective of the
order in which the notifications make it to the RR.
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e. The solution can coexist in a network with systems supporting or
not supporting this specification.
6. Security Considerations
Security considerations described in [RFC7623] apply to this
document.
In addition, this document suggests additional procedures, that can
be activated on a per ISID basis, and generate additional EVPN MAC/IP
Advertisement routes in the network. The format of these additional
EVPN MAC/IP Advertisement routes is backwards compatible with
[RFC7623] procedures and should not create any issues on receiving
PEs not following this specification, however, the additional routes
may consume extra memory and processing resources on the receiving
PEs. Because of that, it is RECOMMENDED to activate this feature
only when necessary (when multi-homed networks or devices are
attached to the PBB-EVPN PEs), and not by default in any PBB-EVPN PE.
7. IANA Considerations
8. Acknowledgments
The authors want to thank Vinod Prabhu, Sriram Venkateswaran, Laxmi
Padakanti, Ranganathan Boovaraghavan for their review and
contributions.
9. Contributors
10. References
10.1. Normative References
[RFC7623] Sajassi, A., Ed., Salam, S., Bitar, N., Isaac, A., and W.
Henderickx, "Provider Backbone Bridging Combined with
Ethernet VPN (PBB-EVPN)", RFC 7623, DOI 10.17487/RFC7623,
September 2015, <https://www.rfc-editor.org/info/rfc7623>.
[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>.
[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>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
10.2. Informative References
[I-D.ietf-bess-evpn-virtual-eth-segment]
Sajassi, A., Brissette, P., Schell, R., Drake, J., and J.
Rabadan, "EVPN Virtual Ethernet Segment", draft-ietf-bess-
evpn-virtual-eth-segment-06 (work in progress), March
2020.
Authors' Addresses
Jorge Rabadan (editor)
Nokia
777 Middlefield Road
Mountain View, CA 94043
USA
Email: jorge.rabadan@nokia.com
Senthil Sathappan
Nokia
701 E. Middlefield Road
Mountain View, CA 94043 USA
Email: senthil.sathappan@nokia.com
Kiran Nagaraj
Nokia
701 E. Middlefield Road
Mountain View, CA 94043 USA
Email: kiran.nagaraj@nokia.com
M. Miyake
Softbank
Email: masahiro.miyake@g.softbank.co.jp
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T. Matsuda
Softbank
Email: taku.matsuda@g.softbank.co.jp
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