SPRING Working Group G. Mirsky
Internet-Draft ZTE Corp.
Intended status: Standards Track J. Tantsura
Expires: April 27, 2018 Individual
I. Varlashkin
Google
M. Chen
Huawei
October 24, 2017
Bidirectional Forwarding Detection (BFD) in Segment Routing Networks
Using MPLS Dataplane
draft-mirsky-spring-bfd-02
Abstract
Segment Routing architecture leverages the paradigm of source
routing. It can be realized in the Multiprotocol Label Switching
(MPLS) network without any change to the data plane. A segment is
encoded as an MPLS label and an ordered list of segments is encoded
as a stack of labels. Bidirectional Forwarding Detection (BFD) is
expected to monitor any kind of paths between systems. This document
defines how to use Label Switched Path Ping to bootstrap and control
path in reverse direction of a BFD session on the Segment Routing
static MPLS tunnel.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 27, 2018.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3
2. Bootstrapping BFD session over Segment Routed tunnel . . . . 3
3. Use BFD Reverse Path TLV over SDN-provisioned Segment Routed
MPLS Tunnel . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. BFD Reverse Path TLV over Segment Routed MPLS Tunnel with
Dynamic Control Plane . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5.1. Segment Routing Static MPLS Tunnel sub-TLV . . . . . . . 6
5.2. Return Code . . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
[RFC5880], [RFC5881], and [RFC5883] established the Bidirectional
Forwarding Detection (BFD) protocol for IP networks. [RFC5884] and
[RFC7726] set rules of using BFD Asynchronous mode over Multiprotocol
Label Switching (MPLS) Label Switched Path (LSP). These latter
standards implicitly assume that the egress BFD peer, which is the
egress Label Edge Router (LER), will use the shortest path route
regardless of the path the ingress LER uses to send BFD control
packets towards it.
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This document defines use of LSP Ping for Segment Routing networks
over MPLS dataplane [I-D.ietf-mpls-spring-lsp-ping] to bootstrap and
control path of a BFD session from the egress to ingress LER using
static MPLS tunnel.
1.1. Conventions used in this document
1.1.1. Terminology
BFD: Bidirectional Forwarding Detection
FEC: Forwarding Equivalence Class
MPLS: Multiprotocol Label Switching
LSP: Label Switching Path
LER: Label Edge Router
1.1.2. Requirements Language
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.
2. Bootstrapping BFD session over Segment Routed tunnel
As demonstrated in [I-D.ietf-mpls-spring-lsp-ping] introduction of
Segment Routing network domains with an MPLS data plane requires
three new sub-TLVs that MAY be used with Target Forwarding
Equivalence Class (FEC) TLV. Section 6.1 addresses use of the new
sub-TLVs in Target FEC TLV in LSP ping and LSP traceroute. For the
case of LSP ping the [I-D.ietf-mpls-spring-lsp-ping] states that:
Initiator MUST include FEC(s) corresponding to the destination
segment.
Initiator, i.e. ingress LSR, MAY include FECs corresponding to
some or all of segments imposed in the label stack by the ingress
LSR to communicate the segments traversed.
It has been noted in [RFC5884] that a BFD session monitors for
defects particular <MPLS LSP, FEC> tuple. [RFC7726] clarified how to
establish and operate multiple BFD sessions for the same <MPLS LSP,
FEC> tuple. Because only ingress edge router is aware of the SR-
based explicit route the egress edge router can associate the LSP
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ping with BFD Discriminator TLV with only one of the FECs it
advertised for the particular segment. Thus this document clarifies
that:
When LSP Ping is used to bootstrap a BFD session the FEC
corresponding to the destination segment to be associated with the
BFD session MUST be as the very last sub-TLV in the Target FEC
TLV.
Encapsulation of a BFD Control packet in Segment Routing network with
MPLS dataplane MUST follow Section 7 [RFC5884] when IP/UDP header
used and MUST follow Section 3.4 [RFC6428] without IP/UDP header
being used.
3. Use BFD Reverse Path TLV over SDN-provisioned Segment Routed MPLS
Tunnel
For BFD over MPLS LSP case, per [RFC5884], egress LER MAY send BFD
control packet to the ingress LER either over IP network or an MPLS
LSP. Similarly, for the case of BFD over p2p segment tunnel with
MPLS data plane, the ingress LER MAY route BFD control packet over IP
network, as described in [RFC5883], or transmit over a segment
tunnel, as described in Section 7 [RFC5884]. In some cases there may
be a need to direct egress BFD peer to use specific path for the
reverse direction of the BFD session by using the BFD Reverse Path
TLV [I-D.ietf-mpls-bfd-directed]. For the case of MPLS dataplane,
Segment Routing Architecture [I-D.ietf-spring-segment-routing]
explains that "a segment is encoded as an MPLS label. An ordered
list of segments is encoded as a stack of labels." YANG Data Model
for MPLS Static LSPs [I-D.ietf-mpls-static-yang] models outgoing MPLS
labels to be imposed as leaf-list [RFC6020], i.e., as array of rt-
types:mpls-label [I-D.ietf-rtgwg-routing-types] Following on that,
this document defines Segment Routing Static MPLS Tunnel sub-TLV that
MAY be used with the BFD Reverse Path TLV
[I-D.ietf-mpls-bfd-directed]. The format of the sub-TLV is presented
in Figure 1. BFD Reverse TLV MAY include zero or one SR Static MPLS
Tunnel sub-TLV.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SegRouting MPLS sub-TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Entry 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Entry 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Entry N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Segment Routing Static MPLS Tunnel sub-TLV
The Segment Routing Tunnel sub-TLV Type is two octets in length, and
has a value of TBD (to be assigned by IANA as requested in
Section 5).
The egress LSR MUST use the Value field as label stack for BFD
control packets for the BFD session identified by the source IP
address of the MPLS LSP Ping packet and the value in the BFD
Discriminator TLV. Label Entries MUST be in network order.
As in [I-D.ietf-mpls-bfd-directed], empty BFD Reverse TLV requires
the egress BFD peer switch the reverse path of the BFD session,
specified by BFD Discriminator TLV, to the path selected based on
locally defined policy. If more than one SR Static MPLS Tunnel sub-
TLV is present, then the egress BFD peer MUST send Echo Reply with
Return Code field set to "Too Many TLVs Detected" Table 2.
The Segment Routing Tunnel sub-TLV MAY be used in Reply Path TLV
defined in [RFC7110]
4. BFD Reverse Path TLV over Segment Routed MPLS Tunnel with Dynamic
Control Plane
When Segment Routed domain with MPLS data plane uses distributed
tunnel computation BFD Reverse Path TLV MAY use Target FEC sub-TLVs
defined in [I-D.ietf-mpls-spring-lsp-ping].
5. IANA Considerations
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5.1. Segment Routing Static MPLS Tunnel sub-TLV
The IANA is requested to assign new sub-TLV type from "Multiprotocol
Label Switching Architecture (MPLS) Label Switched Paths (LSPs) Ping
Parameters - TLVs" registry, "Sub-TLVs for TLV Types 1, 16, and 21"
sub-registry.
+----------+----------------------------------------+---------------+
| Value | Description | Reference |
+----------+----------------------------------------+---------------+
| X (TBD1) | Segment Routing Static MPLS Tunnel | This document |
| | sub-TLV | |
+----------+----------------------------------------+---------------+
Table 1: New Segment Routing Tunnel sub-TLV
5.2. Return Code
The IANA is requested to assign a new Return Code value from the
"Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs)
Ping Parameters" registry, "Return Codes" sub-registry, as follows
using a Standards Action value.
+----------+-------------------------+---------------+
| Value | Description | Reference |
+----------+-------------------------+---------------+
| X (TBD2) | Too Many TLVs Detected. | This document |
+----------+-------------------------+---------------+
Table 2: New Return Code
6. Security Considerations
Security considerations discussed in [RFC5880], [RFC5884], [RFC7726],
and [RFC8029] apply to this document.
7. Acknowledgements
TBD
8. References
8.1. Normative References
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[I-D.ietf-mpls-bfd-directed]
Mirsky, G., Tantsura, J., Varlashkin, I., and M. Chen,
"Bidirectional Forwarding Detection (BFD) Directed Return
Path", draft-ietf-mpls-bfd-directed-07 (work in progress),
June 2017.
[I-D.ietf-mpls-spring-lsp-ping]
Kumar, N., Pignataro, C., Swallow, G., Akiya, N., Kini,
S., and M. Chen, "Label Switched Path (LSP) Ping/
Traceroute for Segment Routing IGP Prefix and Adjacency
SIDs with MPLS Data-plane", draft-ietf-mpls-spring-lsp-
ping-13 (work in progress), October 2017.
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and R. Shakir, "Segment Routing Architecture", draft-ietf-
spring-segment-routing-12 (work in progress), June 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
DOI 10.17487/RFC5881, June 2010,
<https://www.rfc-editor.org/info/rfc5881>.
[RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,
June 2010, <https://www.rfc-editor.org/info/rfc5883>.
[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, <https://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,
<https://www.rfc-editor.org/info/rfc6428>.
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[RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord,
"Return Path Specified Label Switched Path (LSP) Ping",
RFC 7110, DOI 10.17487/RFC7110, January 2014,
<https://www.rfc-editor.org/info/rfc7110>.
[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,
<https://www.rfc-editor.org/info/rfc7726>.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017,
<https://www.rfc-editor.org/info/rfc8029>.
[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>.
8.2. Informative References
[I-D.ietf-mpls-static-yang]
Saad, T., Raza, K., Gandhi, R., Liu, X., Beeram, V., Shah,
H., Bryskin, I., Chen, X., Jones, R., and B. Wen, "A YANG
Data Model for MPLS Static LSPs", draft-ietf-mpls-static-
yang-04 (work in progress), July 2017.
[I-D.ietf-rtgwg-routing-types]
Liu, X., Qu, Y., Lindem, A., Hopps, C., and L. Berger,
"Routing Area Common YANG Data Types", draft-ietf-rtgwg-
routing-types-17 (work in progress), October 2017.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
Authors' Addresses
Greg Mirsky
ZTE Corp.
Email: gregimirsky@gmail.com
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Jeff Tantsura
Individual
Email: jefftant.ietf@gmail.com
Ilya Varlashkin
Google
Email: Ilya@nobulus.com
Mach(Guoyi) Chen
Huawei
Email: mach.chen@huawei.com
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