Internet Engineering Task Force V. Govindan
Internet-Draft M. Mudigonda
Intended status: Standards Track A. Sajassi
Expires: January 7, 2017 Cisco Systems
G. Mirsky
Ericsson
July 6, 2016
Fault Management for EVPN networks
draft-gmsm-bess-evpn-bfd-00
Abstract
This document proposes a proactive, in-band network OAM mechanism to
detect loss of continuity and miss-connection faults that affect
unicast and multi-destination paths, used by Broadcast, unknown
Unicast and Multicast traffic, in an EVPN network. The mechanisms
proposed in the draft use the principles of the widely adopted
Bidirectional Forwarding Detection protocol.
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
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Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on January 7, 2017.
Copyright Notice
Copyright (c) 2016 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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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Scope of the Document . . . . . . . . . . . . . . . . . . . . 3
3. Motivation for running BFD at the network layer of EVPN . . . 3
4. Fault Detection of unicast traffic . . . . . . . . . . . . . 4
5. Fault Detection of BUM traffic using ingress replication
(MP2P) . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Fault Detection of BUM traffic using P2MP tunnels (LSM) . . . 5
7. BFD packet encapsulation . . . . . . . . . . . . . . . . . . 5
7.1. Using GAL/G-ACh encapsulation without IP headers . . . . 5
7.1.1. Ingress replication . . . . . . . . . . . . . . . . . 5
7.1.1.1. Alternative encapsulation format . . . . . . . . 5
7.1.2. LSM . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1.3. Unicast . . . . . . . . . . . . . . . . . . . . . . . 6
7.1.3.1. Alternative encapsulation format . . . . . . . . 6
7.2. Using IP headers . . . . . . . . . . . . . . . . . . . . 7
8. Scalability Considerations . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
10. Security Considerations . . . . . . . . . . . . . . . . . . . 8
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
11.1. Normative References . . . . . . . . . . . . . . . . . . 8
11.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
[I-D.salam-l2vpn-evpn-oam-req-frmwk] and
[I-D.ooamdt-rtgwg-ooam-requirement] outlines the OAM requirements of
Ethernet VPN networks [RFC7432]. This document proposes mechanisms
for proactive fault detection at the network(overlay) OAM layer of
EVPN. EVPN fault detection mechanisms need to consider unicast and
Broadcast and unknown Unicast (BUM) traffic separately since they map
to different FECs in EVPN, hence this document proposes different
fault detection mechanisms to suit each type using the principles
of[RFC5880],[RFC5884] and Point-to-multipoint
BFD[I-D.ietf-bfd-multipoint] and
[I-D.ietf-bfd-multipoint-active-tail].
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1.1. Requirements Language
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 RFC 2119 [RFC2119].
2. Scope of the Document
This document proposes proactive fault detection for EVPN [RFC7432]
using BFD mechanisms for:
o Unicast traffic.
o BUM traffic using Multi-point-to-Point (MP2P) tunnels (ingress
replication).
o BUM traffic using Point-to-Multipoint (P2MP) tunnels (LSM).
This document does not discuss BFD mechanisms for:
o EVPN variants like PBB-EVPN [RFC7623]. This will be addressed in
future versions.
o IRB solution based on EVPN
[I-D.ietf-bess-evpn-inter-subnet-forwarding]. This will be
addressed in future versions.
o EVPN using other encapsulations like VxLAN, NVGRE and MPLS over
GRE [I-D.ietf-bess-evpn-overlay].
o BUM traffic using MP2MP tunnels will also be addressed in a future
version of this document.
This specification describes procedures only for BFD asynchronous
mode. BFD demand mode is outside the scope of this specification.
Further, the use of the Echo function is outside the scope of this
specification.
3. Motivation for running BFD at the network layer of EVPN
The choice of running BFD at the network layer of the OAM model for
EVPN [I-D.salam-l2vpn-evpn-oam-req-frmwk] and
[I-D.ooamdt-rtgwg-ooam-requirement] was made after considering the
following:
o In addition to detecting link failures in the EVPN network, BFD
sessions at the network layer can be used to monitor the
successful programming of labels used for setting up MP2P and P2MP
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EVPN tunnels transporting Unicast and BUM traffic. The scope of
reachability detection covers the ingress and the egress EVPN PE
nodes and the network connecting them.
o Monitoring a representative set of path(s) or a particular path
among the multiple paths available between two EVPN PE nodes could
be done by exercising the entropy labels when they are used.
However paths that cannot be realized by entropy variations cannot
be monitored. Fault monitoring requirements outlined by
[I-D.salam-l2vpn-evpn-oam-req-frmwk] are addressed by the
mechanisms proposed by this draft.
Successful establishment and maintenance of BFD sessions between EVPN
PE nodes does not fully guarantee that the EVPN service is
functioning. For example, an egress EVPN-PE can understand the EVPN
label but could switch data to incorrect interface. However, once
BFD sessions in the EVPN Network Layer reach UP state, it does
provide additional confidence that data transported using those
tunnels will reach the expected egress node. When the BFD session in
EVPN overlay goes down that can be used as indication of the Loss-of-
Connectivity defect in the EVPN underlay that would cause EVPN
service failure.
4. Fault Detection of unicast traffic
The mechanisms specified in BFD for MPLS LSPs [RFC5884] [RFC7726] can
be applied to bootstrap and maintain BFD sessions for unicast EVPN
traffic. The discriminators required for de-multiplexing the BFD
sessions MUST be exchanged using EVPN LSP ping specifying the Unicast
EVPN FEC [I-D.jain-bess-evpn-lsp-ping] before establishing the BFD
session. This is needed since the MPLS label stack does not contain
enough information to disambiguate the sender of the packet. The
usage of MPLS entropy labels take care of addressing the requirement
of monitoring various paths of the multi-path server layer network
[RFC6790]. Each unique realizable path between the participating PE
routers MAY be monitored separately when entropy labels are used.
The multi-path connectivity between two PE routers MUST be tracked by
at least one representative BFD session, in which case the
granularity of fault-detection would be coarser. The PE node
receiving the EVPN LSP ping MUST allocate BFD discriminators using
the procedures defined in [RFC7726]. Note that once the BFD session
for the EVPN label is UP, either end of the BFD session MUST NOT
change the local discriminator values of the BFD Control packets it
generates, unless it first brings down the session as specified in
[RFC5884].
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5. Fault Detection of BUM traffic using ingress replication (MP2P)
Ingress replication uses separate MP2P tunnels for transporting BUM
traffic from the ingress PE (head) to a set of one or more egress PEs
(tails). The fault detection mechanism proposed by this document
takes advantage of the fact that a unique copy is made by the head
for each tail. Another key aspect to be considered in EVPN is the
advertisement of the inclusive multicast route. The BUM traffic
flows from a head node to a particular tail only after the head
receives the inclusive multicast route containing the BUM EVPN label
(downstream allocated) corresponding to the MP2P tunnel. The head-
end PE performing ingress replication MUST initiate an EVPN LSP ping
using the inclusive multicast FEC [I-D.jain-bess-evpn-lsp-ping] upon
receiving an inclusive multicast route from a tail to bootstrap the
BFD session. There MAY exist multiple BFD sessions between a head PE
an individual tail due to the usage of entropy labels [RFC6790] for
an inclusive multicast FEC. The PE node receiving the EVPN LSP ping
MUST allocate BFD discriminators using the procedures defined in
[RFC7726]. Note that once the BFD session for the EVPN label is UP,
either end of the BFD session MUST NOT change the local discriminator
values of the BFD Control packets it generates, unless it first
brings down the session as specified in [RFC5884].
6. Fault Detection of BUM traffic using P2MP tunnels (LSM)
TBD.
7. BFD packet encapsulation
7.1. Using GAL/G-ACh encapsulation without IP headers
7.1.1. Ingress replication
The packet contains the following labels: LSP label (transport) when
not using PHP, the optional entropy label, the BUM label and the SH
label[RFC7432] (where applicable). The G-ACh type is set to TBD.
The G-Ach payload of the packet MUST contain the L2 header (in
overlay space) followed by the IP header encapsulating the BFD
packet. The MAC address of the inner packet is used to validate the
<EVI, MAC> in the receiving node. The discriminator values of BFD
are obtained through negotiation through the out-of-band EVPN LSP
ping.
7.1.1.1. Alternative encapsulation format
A new TLV can be defined as proposed in Sec 3 of [RFC6428] to include
the EVPN FEC information as a TLV following the BFD Control packet.
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The format of the TLV can be reused from the EVPN Inclusive Multicast
sub-TLV proposed by Fig 2 of [I-D.jain-bess-evpn-lsp-ping].
A new type (TBD3) to indicate the EVPN Inclusive Multicast SubTLV is
requested from the "CC/ CV MEP-ID TLV" registry [RFC6428].
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Flags | BFD CV Code Point TBD2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ BFD Control Packet ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ EVPN Inclusive Multicast TLV ~
| (Type = TBD3) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: BFD-EVPN CV Message for EVPN Multicast
(Ingress Replication)
7.1.2. LSM
TBD.
7.1.3. Unicast
The packet contains the following labels: LSP label (transport) when
not using PHP, the optional entropy label and the EVPN Unicast label.
The G-ACh type is set to TBD. The G-Ach payload of the packet MUST
contain the L2 header (in overlay space) followed by the IP header
encapsulating the BFD packet. The MAC address of the inner packet is
used to validate the <EVI, MAC> in the receiving node. The
discriminator values of BFD are obtained through negotiation through
the out-of-band EVPN ping.
7.1.3.1. Alternative encapsulation format
A new TLV can be defined as proposed in Sec 3 of [RFC6428] to include
the EVPN FEC information as a TLV following the BFD Control packet.
The format of the TLV can be reused from the EVPN MAC sub-TLV
proposed by Fig 1 of [I-D.jain-bess-evpn-lsp-ping]. A new type
(TBD4) to indicate the EVPN MAC SubTLV is requested from the "CC/ CV
MEP-ID TLV" registry [RFC6428].
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0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Flags | BFD CV Code Point TBD2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ BFD Control Packet ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ EVPN MAC Sub TLV ~
| (Type = TBD4) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: BFD-EVPN CV Message for EVPN Unicast
7.2. Using IP headers
The encapsulation option using IP headers will not be suited for
EVPN, as using different values in the destination IP address for
data and OAM (BFD) packets could cause the BFD packets to follow a
different path than that of data packets. Hence this option MUST NOT
be used for EVPN.
8. Scalability Considerations
The mechanisms proposed by this draft could affect the packet load on
the network and its elements especially when supporting
configurations involving a large number of EVIs. The option of
slowing down or speeding up BFD timer values can be used by an
administrator or a network management entity to maintain the overhead
incurred due to fault monitoring at an acceptable level.
9. IANA Considerations
IANA is requested for two channel types from the "Pseudowire
Associated Channel Types" registry in [RFC4385].
TBD1 BFD-EVPN CC message
TBD2 BFD-EVPN CV message
Ed Note: Do we need a CC code point? TBD
IANA is requested to allocate the following code-points from the "CC/
CV MEP-ID TLV" registry [RFC6428]. The parent registry is the
"Pseudowire Associated Channel Types" registry of [RFC4385] . All
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code points within this registry shall be allocated according to the
"Standards Action" procedures as specified in [RFC5226]. The items
tracked in the registry will be the type, associated name, and
reference. The requested values are:
TBD3 - CV code-point for BFD EVPN Inclusive multicast.
TBD4 - CV code-point for BFD EVPN Unicast.
10. Security Considerations
TBD.
11. References
11.1. Normative References
[I-D.ietf-bess-evpn-inter-subnet-forwarding]
Sajassi, A., Salam, S., Thoria, S., Rekhter, Y., Drake,
J., Yong, L., and L. Dunbar, "Integrated Routing and
Bridging in EVPN", draft-ietf-bess-evpn-inter-subnet-
forwarding-01 (work in progress), October 2015.
[I-D.ietf-bess-evpn-overlay]
Sajassi, A., Drake, J., Bitar, N., Shekhar, R., Uttaro,
J., and W. Henderickx, "A Network Virtualization Overlay
Solution using EVPN", draft-ietf-bess-evpn-overlay-04
(work in progress), June 2016.
[I-D.ietf-bfd-multipoint]
Katz, D., Ward, D., and J. Networks, "BFD for Multipoint
Networks", draft-ietf-bfd-multipoint-08 (work in
progress), April 2016.
[I-D.ietf-bfd-multipoint-active-tail]
Katz, D., Ward, D., and J. Networks, "BFD Multipoint
Active Tails.", draft-ietf-bfd-multipoint-active-tail-02
(work in progress), May 2016.
[I-D.jain-bess-evpn-lsp-ping]
Jain, P., Boutros, S., and S. Salam, "LSP-Ping Mechanisms
for EVPN and PBB-EVPN", draft-jain-bess-evpn-lsp-ping-03
(work in progress), May 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
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[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
February 2006, <http://www.rfc-editor.org/info/rfc4385>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<http://www.rfc-editor.org/info/rfc5880>.
[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
"Bidirectional Forwarding Detection (BFD) for MPLS Label
Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
June 2010, <http://www.rfc-editor.org/info/rfc5884>.
[RFC6428] Allan, D., Ed., Swallow, G., Ed., and J. Drake, Ed.,
"Proactive Connectivity Verification, Continuity Check,
and Remote Defect Indication for the MPLS Transport
Profile", RFC 6428, DOI 10.17487/RFC6428, November 2011,
<http://www.rfc-editor.org/info/rfc6428>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012,
<http://www.rfc-editor.org/info/rfc6790>.
[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, <http://www.rfc-editor.org/info/rfc7432>.
[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, <http://www.rfc-editor.org/info/rfc7623>.
[RFC7726] Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S.
Aldrin, "Clarifying Procedures for Establishing BFD
Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726,
DOI 10.17487/RFC7726, January 2016,
<http://www.rfc-editor.org/info/rfc7726>.
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11.2. Informative References
[I-D.ooamdt-rtgwg-ooam-requirement]
Kumar, N., Pignataro, C., Kumar, D., Mirsky, G., Chen, M.,
Nordmark, E., Networks, J., and D. Mozes, "Overlay OAM
Requirements", draft-ooamdt-rtgwg-ooam-requirement-00
(work in progress), March 2016.
[I-D.salam-l2vpn-evpn-oam-req-frmwk]
Salam, S., Sajassi, A., Aldrin, S., and J. Drake, "E-VPN
Operations, Administration and Maintenance Requirements
and Framework", draft-salam-l2vpn-evpn-oam-req-frmwk-02
(work in progress), January 2014.
Authors' Addresses
Vengada Prasad Govindan
Cisco Systems
Email: venggovi@cisco.com
Mudigonda Mallik
Cisco Systems
Email: mmudigon@cisco.com
Ali Sajassi
Cisco Systems
Email: sajassi@cisco.com
Gregory Mirsky
Ericsson
Email: gregory.mirsky@ericsson.com
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