BESS Workgroup J. Rabadan, Ed.
Internet Draft S. Sathappan
Intended status: Standards Track K. Nagaraj
Nokia
M. Miyake
T. Matsuda
Softbank
Expires: January 27, 2020 July 26, 2019
PBB-EVPN ISID-based CMAC-Flush
draft-snr-bess-pbb-evpn-isid-cmacflush-06
Abstract
Provider Backbone Bridging (PBB) can be combined with Ethernet VPN
(EVPN) to deploy ELAN services in very large 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 CMAC-Flush
mechanism that works for different Ethernet Segment BMAC address
allocation models. This document complements those CMAC-Flush
procedures for cases in which no PBB-EVPN Ethernet Segments are
defined (ESI 0) and an ISID-based CMAC-Flush granularity is desired.
Status of this Memo
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Table of Contents
1. Problem Statement . . . . . . . . . . . . . . . . . . . . . . . 2
2. Solution requirements . . . . . . . . . . . . . . . . . . . . . 4
3. EVPN BGP Encoding for ISID-based CMAC-flush . . . . . . . . . . 5
4. Solution description . . . . . . . . . . . . . . . . . . . . . 6
4.1 ISID-based CMAC-Flush activation procedures . . . . . . . . 7
4.2 CMAC-Flush generation . . . . . . . . . . . . . . . . . . . 7
4.3 CMAC-Flush process upon receiving a CMAC-Flush
notification . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Conventions used in this document . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1 Normative References . . . . . . . . . . . . . . . . . . . . 9
9.2 Informative References . . . . . . . . . . . . . . . . . . . 10
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 10
17. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 10
1. Problem Statement
[RFC7623] defines how Provider Backbone Bridging (PBB) can be
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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, [vES] describes how virtual ES 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 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
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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. 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 FDBs.
[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, while that procedure could
be used in the example of Figure 1, it would result in unnecessary
flushing of unaffected ISIDs on the remote PEs, and subsequent
flooding.
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.
2. Solution requirements
The following requirements must be met by the CMAC-Flush solution
described in this document:
a) The solution MUST solve 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 SHOULD work with Single-Active non-null ES and
virtual ES, irrespective of the PE BMAC address assignment
(dedicated per-ES BMAC or shared BMAC).
c) In case of failure on the egress PE, the solution MUST provide a
CMAC-Flush notification at BMAC AND ISID granularity level.
d) The solution MUST provide a reliable CMAC-Flush notification in
PBB-EVPN networks that use Route-Reflectors (RRs).
e) The solution MUST coexist in [RFC7623]-compliant networks where
there are systems not supporting this extension.
f) The solution SHOULD be enabled/disabled by an administrative
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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
MAC/IP route. As a reference, Figure 2 shows the MAC Mobility
extended community and the MAC/IP route that are used in this
document as a CMAC-Flush notification.
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 RT can be derived from the ISID.
o The Ethernet Tag encodes the ISID for which the PE that receives
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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 =
0).
Note that this BMAC/ISID route will be accepted and reflected by any
RFC7432-compliant 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. All the ACs are
operationally active and ready to forward frames.
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) The 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.
These new CMAC-flush procedures are described in sections 4.1, 4.2
and 4.3 respectively:
o ISID-based CMAC-flush activation
o CMAC-flush notification generation upon AC failures
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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 (see
Figure 1):
o As in [RFC7623], each PE has previously advertised a shared BMAC in
a BMAC/0 route (BM1, BM2, BM3 and BM4 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 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.
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.
o An AC receiving a CMAC-Flush notification from the access network,
e.g. by G.8032, MAY propagate it to the remote PEs by generating a
BMAC/ISID update with higher Sequence Number.
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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 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.
e) The solution can coexist in a network with systems supporting or
not supporting the CMAC-flush extensions.
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6. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
7. 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
BGP EVPN MAC/IP advertisements in the network. The format of these
additional MAC/IP 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 resources on the receiving systems. Because of
that, this feature should be activated only when necessary, and not
by default in any PBB-EVPN PE.
8. IANA Considerations
9. References
9.1 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>.
[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>.
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9.2 Informative References
[vES] Sajassi et al. "EVPN Virtual Ethernet Segment", draft-ietf-
bess-evpn-virtual-eth-segment-04, work-in-progress, January, 2019.
10. Acknowledgments
The authors want to thank Vinod Prabhu, Sriram Venkateswaran, Laxmi
Padakanti, Ranganathan Boovaraghavan for their review and
contributions.
11. Contributors
17. Authors' Addresses
Jorge Rabadan
Nokia
777 E. 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
Masahiro Miyake
Softbank
Email: masahiro.miyake@g.softbank.co.jp
Taku Matsuda
Softbank
Email: taku.matsuda@g.softbank.co.jp
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