< draft-ietf-mpls-bfd-directed-01.txt   draft-ietf-mpls-bfd-directed-02.txt >
MPLS Working Group G. Mirsky MPLS Working Group G. Mirsky
Internet-Draft J. Tantsura Internet-Draft J. Tantsura
Intended status: Standards Track Ericsson Intended status: Standards Track Ericsson
Expires: March 11, 2016 I. Varlashkin Expires: September 3, 2016 I. Varlashkin
Google Google
M. Chen M. Chen
Huawei Huawei
September 8, 2015 March 2, 2016
Bidirectional Forwarding Detection (BFD) Directed Return Path Bidirectional Forwarding Detection (BFD) Directed Return Path
draft-ietf-mpls-bfd-directed-01 draft-ietf-mpls-bfd-directed-02
Abstract Abstract
Bidirectional Forwarding Detection (BFD) is expected to monitor bi- Bidirectional Forwarding Detection (BFD) is expected to monitor bi-
directional paths. When a BFD session monitors in its forward directional paths. When a BFD session monitors an explicit routed
direction an explicitly routed path there is a need to be able to path there is a need to be able to direct egress BFD peer to use
direct egress BFD peer to use specific path as reverse direction of specific path for the reverse direction of the BFD session.
the BFD session.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 11, 2016. This Internet-Draft will expire on September 3, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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skipping to change at page 2, line 20 skipping to change at page 2, line 19
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3 1.1. Conventions used in this document . . . . . . . . . . . . 3
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
3. Direct Reverse BFD Path . . . . . . . . . . . . . . . . . . . 4 3. Direct Reverse BFD Path . . . . . . . . . . . . . . . . . . . 4
3.1. Case of MPLS Data Plane . . . . . . . . . . . . . . . . . 4 3.1. Case of MPLS Data Plane . . . . . . . . . . . . . . . . . 4
3.1.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . 4 3.1.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . 4
3.1.2. Static and RSVP-TE sub-TLVs . . . . . . . . . . . . . 5 3.1.2. Static and RSVP-TE sub-TLVs . . . . . . . . . . . . . 5
3.1.3. Segment Routing Tunnel sub-TLV . . . . . . . . . . . 5 3.1.3. Segment Routing: MPLS Data Plane Case . . . . . . . . 5
3.2. Case of IPv6 Data Plane . . . . . . . . . . . . . . . . . 6 3.2. Segment Routing: IPv6 Data Plane Case . . . . . . . . . . 6
3.3. Bootstrapping BFD session with BFD Reverse Path over 3.3. Bootstrapping BFD session with BFD Reverse Path over
Segment Routed tunnel . . . . . . . . . . . . . . . . . . 6 Segment Routed tunnel . . . . . . . . . . . . . . . . . . 6
3.4. Return Codes . . . . . . . . . . . . . . . . . . . . . . 7 3.4. Return Codes . . . . . . . . . . . . . . . . . . . . . . 7
4. Use Case Scenario . . . . . . . . . . . . . . . . . . . . . . 7 4. Use Case Scenario . . . . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
5.1. TLV . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.1. TLV . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.2. Sub-TLV . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.2. Sub-TLV . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.3. Return Codes . . . . . . . . . . . . . . . . . . . . . . 8 5.3. Return Codes . . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
8. Normative References . . . . . . . . . . . . . . . . . . . . 9 8. Normative References . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
RFC 5880 [RFC5880], RFC 5881 [RFC5881], and RFC 5883 [RFC5883] RFC 5880 [RFC5880], RFC 5881 [RFC5881], and RFC 5883 [RFC5883]
established the BFD protocol for IP networks and RFC 5884 [RFC5884] established the BFD protocol for IP networks and RFC 5884 [RFC5884]
set rules of using BFD asynchronous mode over IP/MPLS LSPs. All set rules of using BFD asynchronous mode over IP/MPLS LSPs. These
standards implicitly assume that the egress BFD peer will use the four standards implicitly assume that the egress BFD peer will use
shortest path route regardless of route being used to send BFD the shortest path route regardless of route being used to send BFD
control packets towards it. As result, if the ingress BFD peer sends control packets towards it.
its BFD control packets over explicit path that is diverging from the
best route, then reverse direction of the BFD session is likely not
to be on co-routed bi-directional path with the forward direction of
the BFD session. And because BFD control packets are not guaranteed
to cross the same links and nodes in both directions detection of
Loss of Continuity (LoC) defect in forward direction may demonstrate
positive negatives.
This document defines the extension to LSP Ping [RFC4379], BFD For the case where an LSP is explicitly routed, if it is desired that
Reverse Path TLV, and proposes that it to be used to instruct the BFD control packets follow the same path in the reverse direction
egress BFD peer to use explicit path for its BFD control packets (for support of common fault detection for explicitly routed
associated with the particular BFD session. The TLV will be bidirectional co-routed LSPs, for example), it is likely that the
allocated from the TLV and sub-TLV registry defined by RFC 4379 shortest return path to the ingress BFD peer may not follow the same
[RFC4379]. As a special case, forward and reverse directions of the path as the LSP in the forward direction. The fact that BFD control
BFD session can form bi-directional co-routed associated channel. packets are not guaranteed to cross the same links and nodes in both
forward and reverse directions is a significant factor in producing
false positive defect notifications, i.e. false alarms, if used by
the ingress BFD peer to deduce the state of the forward direction.
This document defines the BFD Reverse Path TLV as an extension to LSP
Ping [RFC4379] and proposes that it to be used to instruct the egress
BFD peer to use explicit path for its BFD control packets associated
with the particular BFD session. The TLV will be allocated from the
TLV and sub-TLV registry defined by RFC 4379 [RFC4379]. As a special
case, forward and reverse directions of the BFD session can form a
bi-directional co-routed associated channel.
1.1. Conventions used in this document 1.1. Conventions used in this document
1.1.1. Terminology 1.1.1. Terminology
BFD: Bidirectional Forwarding Detection BFD: Bidirectional Forwarding Detection
MPLS: Multiprotocol Label Switching MPLS: Multiprotocol Label Switching
LSP: Label Switching Path LSP: Label Switching Path
skipping to change at page 3, line 36 skipping to change at page 3, line 38
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. [RFC2119].
2. Problem Statement 2. Problem Statement
BFD is best suited to monitor bi-directional co-routed paths. In BFD is best suited to monitor bi-directional co-routed paths. In
most cases, given stable environments, the forward and reverse most cases, given stable environments, the forward and reverse
direction between two nodes is likely to be co-routed, this directions between two nodes are likely to be co-routed, thus
fulfilling the implicit BFD requirements. If BFD is used to monitor fulfilling the implicit BFD requirement. If BFD is used to monitor
unidirectional explicitly routed paths, e.g. MPLS-TE LSPs, its unidirectional explicitly routed path, e.g. MPLS-TE LSP, BFD control
control packets in forward direction would be in-band using the packets in forward direction would be in-band using the mechanism
mechanism defined in [RFC5884] and [RFC5586]. But the reverse defined in [RFC5884] and [RFC5586]. But the reverse direction of the
direction of the BFD session would still follow the shortest path BFD session would still follow the shortest path route and that might
route and that might lead to the following problem in detecting lead to the following problem in detecting failures on a
failures on the unidirectional explicit path: unidirectional explicit path:
o a failure detection by ingress node on the reverse path cannot be o a failure detection by ingress node on the reverse path cannot be
interpreted as bi-directional failure with all the certainty and interpreted as bi-directional failure with all the certainty and
thus trigger, for example, protection switchover of the forward thus trigger, for example, protection switchover of the forward
direction without possibility of being false positive or false direction without possibility of being a false positive defect
negative. notification.
To address these challenges the egress BFD peer should be instructed To address this scenario the egress BFD peer should be instructed to
to use specific path for its control packets. use a specific path for BFD control packets.
3. Direct Reverse BFD Path 3. Direct Reverse BFD Path
3.1. Case of MPLS Data Plane 3.1. Case of MPLS Data Plane
LSP ping, defined in [RFC4379], uses BFD Discriminator TLV [RFC5884] LSP ping, defined in [RFC4379], uses BFD Discriminator TLV [RFC5884]
to bootstrap a BFD session over an MPLS LSP. This document defines a to bootstrap a BFD session over an MPLS LSP. This document defines a
new TLV, BFD Reverse Path TLV, that MUST contain a single sub-TLV new TLV, BFD Reverse Path TLV, that MUST contain a single sub-TLV
that can be used to carry information about reverse path for the that can be used to carry information about the reverse path for the
specified in BFD Discriminator TLV session. BFD session that is specified by value in BFD Discriminator TLV.
3.1.1. BFD Reverse Path TLV 3.1.1. BFD Reverse Path TLV
The BFD Reverse Path TLV is an optional TLV within the LSP ping The BFD Reverse Path TLV is an optional TLV within the LSP ping
protocol. However, if used, the BFD Discriminator TLV MUST be protocol. However, if used, the BFD Discriminator TLV MUST be
included in an Echo Request message as well. If the BFD included in an Echo Request message as well. If the BFD
Discriminator TLV is not present when the BFD Reverse Path TLV is Discriminator TLV is not present when the BFD Reverse Path TLV is
included, then it MUST be treated as malformed Echo Request, as included, then it MUST be treated as malformed Echo Request, as
described in [RFC4379]. described in [RFC4379].
The BFD Reverse Path TLV carries the specified path that BFD control The BFD Reverse Path TLV carries information about the path onto
packets of the BFD session referenced in the BFD Discriminator TLV which the egress BFD peer of the BFD session referenced by the BFD
are required to follow. The format of the BFD Reverse Path TLV is as Discriminator TLV MUST transmit BFD control packets. The format of
presented in Figure 1. the BFD Reverse Path TLV is as presented in Figure 1.
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BFD Reverse Path TLV Type | Length | | BFD Reverse Path TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reverse Path | | Reverse Path |
~ ~ ~ ~
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: BFD Reverse Path TLV Figure 1: BFD Reverse Path TLV
BFD Reverse Path TLV Type is 2 octets in length and value to be BFD Reverse Path TLV Type is 2 octets in length and has a value of
assigned by IANA. TB1 (to be assigned by IANA as requested in Section 5).
Length is 2 octets in length and defines the length in octets of the Length field is 2 octets long and defines the length in octets of the
Reverse Path field. Reverse Path field.
Reverse Path field contains a sub-TLV. Any Target FEC sub-TLV, Reverse Path field contains a sub-TLV. Any Target FEC sub-TLV
already or in the future defined, from IANA sub-registry Sub-TLVs for (already defined, or to be defined in the future) for TLV Types 1,
TLV Types 1, 16, and 21 of MPLS LSP Ping Parameters registry MAY be 16, and 21 of MPLS LSP Ping Parameters registry MAY be used in this
used in this field. Only one sub-TLV MUST be included in the Reverse field. Exactly one sub-TLV MUST be included in the Reverse Path TLV.
Path TLV. If more than one sub-TLVs are present in the Reverse Path If more than one sub-TLV is present in the Reverse Path TLV, then, in
TLV, then only the first sub-TLV MUST be used and the rest MUST be order to avoid ambiguity of which of TLVs to use, the egress BFD peer
silently discarded. MUST send Echo Reply with the received Reverse Path TLVs and set the
Return Code to "Too Many TLVs Detected" Section 3.4.
If the egress LSR cannot find path specified in the Reverse Path TLV If the egress LSR cannot find the path specified in the Reverse Path
it MUST send Echo Reply with the received Reverse Path TLV and set TLV it MUST send Echo Reply with the received Reverse Path TLV and
the return code to "Failed to establish the BFD session. The set the Return Code to "Failed to establish the BFD session. The
specified reverse path was not found" Section 3.4. The egress LSR specified reverse path was not found" Section 3.4. The egress BFD
MAY establish the BFD session over IP network according to [RFC5884]. peer MAY establish the BFD session over IP network as defined in
[RFC5884].
3.1.2. Static and RSVP-TE sub-TLVs 3.1.2. Static and RSVP-TE sub-TLVs
When explicit path on MPLS data plane set either as Static or RSVP-TE When an explicit path on an MPLS data plane is set either as Static
LSP respective sub-TLVs defined in [RFC7110] identify explicit return or RSVP-TE LSP respective sub-TLVs defined in [RFC7110] MAY be used
path. to identify the explicit reverse path for the BFD session.
3.1.3. Segment Routing Tunnel sub-TLV 3.1.3. Segment Routing: MPLS Data Plane Case
In addition to Static and RSVP-TE, Segment Routing with MPLS data In addition to Static and RSVP-TE, Segment Routing with MPLS data
plane can be used to set explicit path. In this case a new sub-TLV plane can be used to set an explicit path. In this case a new sub-
is defined in this document as presented in Figure 2. TLV is defined in this document as presented in Figure 2.
0 1 2 3 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 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 | | SegRouting MPLS sub-TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Entry 1 | | Label Entry 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Entry 2 | | Label Entry 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~ ~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Entry N | | Label Entry N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Segment Routing MPLS Tunnel sub-TLV Figure 2: Segment Routing MPLS Tunnel sub-TLV
The Segment Routing Tunnel sub-TLV Type is two octets in length, and The Segment Routing Tunnel sub-TLV Type is two octets in length, and
will be allocated by IANA. has a value of TB2 (to be assigned by IANA as requested in
Section 5).
The egress LSR MUST use the Value field as label stack for BFD The egress LSR MUST use the Value field as label stack for BFD
control packets for the BFD session identified by source IP address control packets for the BFD session identified by the source IP
and value in BFD Discriminator TLV. address of the MPLS LSP Ping packet and the value in the BFD
Discriminator TLV. Label Entries MUST be in network order.
The Segment Routing Tunnel sub-TLV MAY be used in Reply Path TLV The Segment Routing Tunnel sub-TLV MAY be used in Reply Path TLV
defined in [RFC7110] defined in [RFC7110]
3.2. Case of IPv6 Data Plane 3.2. Segment Routing: IPv6 Data Plane Case
IPv6 can be data plane of choice for Segment Routed tunnels IPv6 can be used as the data plane of choice for Segment Routed
[I-D.previdi-6man-segment-routing-header]. In such networks the BFD tunnels [I-D.previdi-6man-segment-routing-header]. In this case the
Reverse Path TLV described in Section 3.1.1 can be used as well. To BFD Reverse Path TLV described in Section 3.1.1 can be used as well.
specify reverse path of a BFD session in IPv6 environment the BFD To specify the reverse path of a BFD session for an IPv6 explicitly
Discriminator TLV MUST be used along with the BFD Reverse Path TLV. routed path the BFD Discriminator TLV MUST be used along with the BFD
The BFD Reverse Path TLV in IPv6 network MUST include sub-TLV. Reverse Path TLV. The BFD Reverse Path TLV in IPv6 network MUST
include the Segment Routing IPv6 Tunnel sub-TLV.
0 1 2 3 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 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 IPv6 sub-TLV Type | Length | | SegRouting IPv6 sub-TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
| IPv6 Prefix | | IPv6 Prefix |
| | | |
| | | |
skipping to change at page 6, line 34 skipping to change at page 6, line 40
| | | |
| IPv6 Prefix | | IPv6 Prefix |
| | | |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~ ~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Segment Routing IPv6 Tunnel sub-TLV Figure 3: Segment Routing IPv6 Tunnel sub-TLV
The Segment Routing IPv6 Tunnel sub-TLV Type is two octets in length,
and has a value of TB3 (to be assigned by IANA as requested in
Section 5).
3.3. Bootstrapping BFD session with BFD Reverse Path over Segment 3.3. Bootstrapping BFD session with BFD Reverse Path over Segment
Routed tunnel Routed tunnel
As discussed in [I-D.kumarkini-mpls-spring-lsp-ping] introduction of As discussed in [I-D.kumarkini-mpls-spring-lsp-ping] introduction of
Segment Routing network domains with MPLS data plane adds three new Segment Routing network domains with an MPLS data plane adds three
sub-TLVs that may be used with Target FEC TLV. Section 6.1 addresses new sub-TLVs that MAY be used with Target FEC TLV. Section 6.1
use of new sub-TLVs in Target FEC TLV in LSP ping and LSP traceroute. addresses use of the new sub-TLVs in Target FEC TLV in LSP ping and
For the case of LSP ping the [I-D.kumarkini-mpls-spring-lsp-ping] LSP traceroute. For the case of LSP ping the
states that: [I-D.kumarkini-mpls-spring-lsp-ping] states that:
"Initiator MUST include FEC(s) corresponding to the destination "Initiator MUST include FEC(s) corresponding to the destination
segment. segment. "
Initiator, i.e. ingress LSR, MAY include FECs corresponding to some "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 or all of segments imposed in the label stack by the ingress LSR to
communicate the segments traversed. " communicate the segments traversed. "
When LSP ping is used to bootstrap BFD session this document updates When LSP ping is used to bootstrap BFD session this document updates
this and defines that LSP Ping MUST include the FEC corresponding to the statement and defines that LSP Ping MUST include the FEC
the destination segment and SHOULD NOT include FECs corresponding to corresponding to the destination segment and SHOULD NOT include FECs
some or all of segment imposed by the ingress LSR. Operationally corresponding to some or all of other segments imposed by the ingress
such restriction would not cause any problem or uncertainty as LSP LSR. Operationally such restriction would not cause any problem or
ping with FECs corresponding to some or all segments or traceroute uncertainty as LSP ping with FECs corresponding to some or all
MAY precede the LSP ping that bootstraps the BFD session. segments or traceroute that validate the segment route MAY precede
the LSP ping that bootstraps the BFD session.
3.4. Return Codes 3.4. Return Codes
This document defines the following Return Codes: This document defines the following Return Codes for MPLS LSP Echo
Reply:
o "Too Many TLVs Detected", (TBD4). When more than one Reverse Path
TLV found in the recieved Echo Request by the egress BFD peer, an
Echo Reply with the return code set to "Too Many TLVs Detected"
MUST be sent to the ingress BFD peer Section 3.1.1.
o "Failed to establish the BFD session. The specified reverse path o "Failed to establish the BFD session. The specified reverse path
was not found", (TBD4). When a specified reverse path is not was not found", (TBD5). When a specified reverse path is not
available at the egress LSR, an Echo Reply with the return code available at the egress BFD peer, an Echo Reply with the return
set to "Failed to establish the BFD session. The specified code set to "Failed to establish the BFD session. The specified
reverse path was not found" MUST be sent back to the ingress LSR . reverse path was not found" MUST be sent back to the ingress BFD
(Section 3.1.1) peer Section 3.1.1.
4. Use Case Scenario 4. Use Case Scenario
In network presented in Figure 4 node A monitors two tunnels to node In the network presented in Figure 4 node A monitors two tunnels to
H: A-B-C-D-G-H and A-B-E-F-G-H. To bootstrap BFD session to monitor node H: A-B-C-D-G-H and A-B-E-F-G-H. To bootstrap a BFD session to
the first tunnel, node A MUST include BFD Discriminator TLV with monitor the first tunnel, node A MUST include a BFD Discriminator TLV
Discriminator value foobar-1 and MAY include BFD Reverse Path TLV with Discriminator value (e.g. foobar-1) and MAY include a BFD
that references H-G-D-C-B-A tunnel. To bootstrap BFD session to Reverse Path TLV that references H-G-D-C-B-A tunnel. To bootstrap a
monitor the second tunnel, node A MUST include BFD Discriminator TLV BFD session to monitor the second tunnel, node A MUST include a BFD
with Discriminator value foobar-2 Discriminator TLV with a different Discriminator value (e.g. foobar-
[I-D.ietf-bfd-rfc5884-clarifications] and MAY include BFD Reverse 2) [RFC7726] and MAY include a BFD Reverse Path TLV that references
Path TLV that references H-G-F-E-B-A tunnel. H-G-F-E-B-A tunnel.
C---------D C---------D
| | | |
A-------B G-----H A-------B G-----H
| | | |
E---------F E---------F
Figure 4: Use Case for BFD Reverse Path TLV Figure 4: Use Case for BFD Reverse Path TLV
If an operator needs node H to monitor path to node A, e.g. If an operator needs node H to monitor a path to node A, e.g.
H-G-D-C-B-A tunnel, then by looking up list of known Reverse Paths it H-G-D-C-B-A tunnel, then by looking up list of known Reverse Paths it
MAY find and use existing BFD sessions. MAY find and use the existing BFD session.
5. IANA Considerations 5. IANA Considerations
5.1. TLV 5.1. TLV
The IANA is requested to assign a new value for BFD Reverse Path TLV The IANA is requested to assign a new value for BFD Reverse Path TLV
from the "Multiprotocol Label Switching Architecture (MPLS) Label from the "Multiprotocol Label Switching Architecture (MPLS) Label
Switched Paths (LSPs) Ping Parameters - TLVs" registry, "TLVs and Switched Paths (LSPs) Ping Parameters - TLVs" registry, "TLVs and
sub-TLVs" sub-registry. sub-TLVs" sub-registry.
skipping to change at page 8, line 41 skipping to change at page 9, line 15
5.3. Return Codes 5.3. Return Codes
The IANA is requested to assign a new Return Code value from the The IANA is requested to assign a new Return Code value from the
"Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs) "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs)
Ping Parameters" registry, "Return Codes" sub-registry, as follows Ping Parameters" registry, "Return Codes" sub-registry, as follows
using a Standards Action value. using a Standards Action value.
+----------+----------------------------------------+---------------+ +----------+----------------------------------------+---------------+
| Value | Description | Reference | | Value | Description | Reference |
+----------+----------------------------------------+---------------+ +----------+----------------------------------------+---------------+
| X (TBD4) | Failed to establish the BFD session. | This document | | X (TBD4) | Too Many TLVs Detected. | This document |
| X (TBD5) | Failed to establish the BFD session. | This document |
| | The specified reverse path was not | | | | The specified reverse path was not | |
| | found. | | | | found. | |
+----------+----------------------------------------+---------------+ +----------+----------------------------------------+---------------+
Table 3: New Return Code Table 3: New Return Code
6. Security Considerations 6. Security Considerations
Security considerations discussed in [RFC5880], [RFC5884], and Security considerations discussed in [RFC5880], [RFC5884], and
[RFC4379], apply to this document. [RFC4379], apply to this document.
7. Acknowledgements 7. Acknowledgements
8. Normative References Authors greatly appreciate thorough review and the most helpful
comments from Eric Gray.
[I-D.ietf-bfd-rfc5884-clarifications] 8. Normative References
Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S.
Aldrin, "Clarifications to RFC 5884", draft-ietf-bfd-
rfc5884-clarifications-02 (work in progress), June 2015.
[I-D.kumarkini-mpls-spring-lsp-ping] [I-D.kumarkini-mpls-spring-lsp-ping]
Kumar, N., Swallow, G., Pignataro, C., Akiya, N., Kini, Kumar, N., Swallow, G., Pignataro, C., Akiya, N., Kini,
S., Gredler, H., and M. Chen, "Label Switched Path (LSP) S., Gredler, H., and M. Chen, "Label Switched Path (LSP)
Ping/Trace for Segment Routing Networks Using MPLS Ping/Trace for Segment Routing Networks Using MPLS
Dataplane", draft-kumarkini-mpls-spring-lsp-ping-04 (work Dataplane", draft-kumarkini-mpls-spring-lsp-ping-05 (work
in progress), July 2015. in progress), January 2016.
[I-D.previdi-6man-segment-routing-header] [I-D.previdi-6man-segment-routing-header]
Previdi, S., Filsfils, C., Field, B., Leung, I., Vyncke, Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova,
E., and D. Lebrun, "IPv6 Segment Routing Header (SRH)", J., Kosugi, T., Vyncke, E., and D. Lebrun, "IPv6 Segment
draft-previdi-6man-segment-routing-header-07 (work in Routing Header (SRH)", draft-previdi-6man-segment-routing-
progress), July 2015. header-08 (work in progress), October 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol [RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379, Label Switched (MPLS) Data Plane Failures", RFC 4379,
DOI 10.17487/RFC4379, February 2006, DOI 10.17487/RFC4379, February 2006,
<http://www.rfc-editor.org/info/rfc4379>. <http://www.rfc-editor.org/info/rfc4379>.
skipping to change at page 10, line 24 skipping to change at page 10, line 38
[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
"Bidirectional Forwarding Detection (BFD) for MPLS Label "Bidirectional Forwarding Detection (BFD) for MPLS Label
Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884, Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
June 2010, <http://www.rfc-editor.org/info/rfc5884>. June 2010, <http://www.rfc-editor.org/info/rfc5884>.
[RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord, [RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord,
"Return Path Specified Label Switched Path (LSP) Ping", "Return Path Specified Label Switched Path (LSP) Ping",
RFC 7110, DOI 10.17487/RFC7110, January 2014, RFC 7110, DOI 10.17487/RFC7110, January 2014,
<http://www.rfc-editor.org/info/rfc7110>. <http://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,
<http://www.rfc-editor.org/info/rfc7726>.
Authors' Addresses Authors' Addresses
Greg Mirsky Greg Mirsky
Ericsson Ericsson
Email: gregory.mirsky@ericsson.com Email: gregory.mirsky@ericsson.com
Jeff Tantsura Jeff Tantsura
Ericsson Ericsson
Email: jeff.tantsura@ericsson.com Email: jeff.tantsura@ericsson.com
Ilya Varlashkin Ilya Varlashkin
Google Google
Email: Ilya@nobulus.com Email: Ilya@nobulus.com
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