wdiff rfc7882.original rfc7882.txt

Network Working Group
Internet Engineering Task Force (IETF) S. Aldrin
Internet-Draft
Request for Comments: 7882 Google, Inc
Intended status: Inc.
Category: Informational C. Pignataro
Expires: November 7, 2016
ISSN: 2070-1721 Cisco
G. Mirsky
Ericsson
N. Kumar
Cisco
May 6,
July 2016

Seamless Bidirectional Forwarding Detection (S-BFD) Use Cases
draft-ietf-bfd-seamless-use-case-08

Abstract

This document describes various use cases for a Seamless Bidirectional
Forwarding Detection (S-BFD), (S-BFD) and provides requirements such that
protocol mechanisms allow for a simplified detection of forwarding
failures.

These use cases support S-BFD, as which is a simplified mechanism to use
Bidirectional Forwarding Detection (BFD) for
using BFD with a large portions proportion of negotiation aspects eliminated,
accelerating the establishment of a BFD session. S-BFD The benefits of S-
BFD include quick provisioning provisioning, as well as improved control and
flexibility to for network nodes initiating the path monitoring.

Status of This Memo

This Internet-Draft document is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents not an Internet Standards Track specification; it is
published for informational purposes.

This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list It represents the consensus of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a maximum candidate for any level of Internet
Standard; see Section 2 of six months RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained 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 November 7, 2016.
http://www.rfc-editor.org/info/rfc7882.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 ....................................................3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 ................................................3
2. Introduction to Seamless BFD . . . . . . . . . . . . . . . . 4 ....................................4
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 5 .......................................................5
3.1. Unidirectional Forwarding Path Validation . . . . . . . . 5 ..................5
3.2. Validation of the Forwarding Path Prior prior to
Switching Traffic . . . . . . . . . . . . . . . . . . . . . . . . . 6 ..........................................6
3.3. Centralized Traffic Engineering . . . . . . . . . . . . . 7 ............................7
3.4. BFD in Centralized Segment Routing . . . . . . . . . . . 8 .........................8
3.5. Efficient BFD Operation under Resource Constraints . . . 8 .........8
3.6. BFD for Anycast Addresses . . . . . . . . . . . . . . . . 8 ..................................8
3.7. BFD Fault Isolation . . . . . . . . . . . . . . . . . . . 9 ........................................9
3.8. Multiple BFD Sessions to the Same Target Node . . . . . . 9 ..............9
3.9. An MPLS BFD Session Per per ECMP Path . . . . . . . . . . . . 10 .........................10
4. Detailed Requirements for a Seamless BFD . . . . . . . . . . 10 .........................11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 ........................................12
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 12
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
9.1. .....................................................12
6.1. Normative References . . . . . . . . . . . . . . . . . . 12
9.2. ......................................12
6.2. Informative References . . . . . . . . . . . . . . . . . 13 ....................................13
Acknowledgements ..................................................15
Contributors ......................................................15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 ................................................15

1. Introduction

Bidirectional Forwarding Detection (BFD) is a lightweight protocol, (BFD), as defined in [RFC5880], is
a lightweight protocol used to detect forwarding failures. Various
protocols
protocols, applications, and applications clients rely on BFD as its clients for failure
detection. Even though the protocol is lightweight and simple, there
are certain use cases where faster setting up setup of sessions and faster
continuity check checks of the data forwarding data-forwarding paths is are necessary. This
document identifies these use cases and consequent requirements, such
that enhancements and extensions result in a Seamless BFD (S-BFD)
protocol.

BFD is a simple and lightweight "Hello" protocol to detect data plane data-plane
failures. With dynamic provisioning of forwarding paths on a large
scale, establishing BFD sessions for each of those paths not only
creates operational complexity, complexity but also causes undesirable delay in
establishing or deleting sessions. The existing session
establishment mechanism of the BFD protocol has to be enhanced in
order to minimize the time for the session to come up to validate the
forwarding path.

This document specifically identifies various use cases and
corresponding requirements in order to enhance BFD and other
supporting protocols. Specifically, one key goal is removing the
time delay (i.e., the "seam") between when a network node wants to
perform a continuity test and when the node completes that continuity
test. Consequently, "Seamless BFD" (S-BFD) has been chosen as the
name for this mechanism.

While the identified requirements could meet various use cases, it is
outside the scope of this document to identify all of the possible
and necessary requirements. Solutions related to the identified uses use
cases and protocol specific protocol-specific enhancements or proposals are outside the
scope of this document as well. Protocol definitions to support
these use cases can be found at [I-D.ietf-bfd-seamless-base] in [RFC7880] and
[I-D.ietf-bfd-seamless-ip]. [RFC7881].

1.1. Terminology

The reader is expected to be familiar with the BFD [RFC5880], IP
[RFC0791]
[RFC791] [RFC2460], MPLS [RFC3031], and Segment Routing (SR)
[I-D.ietf-spring-segment-routing] terminologies [SR-ARCH]
terms and protocol constructs.

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
[RFC2119].

2. Introduction to Seamless BFD

BFD, as defined in [RFC5880], requires two network nodes to exchange
locally allocated discriminators. These discriminators enable the
identification of the sender and the receiver of BFD packets over the
particular session. Subsequently, BFD performs proactive continuity
monitoring of the forwarding path between the two. Several
specifications describe BFD's multiple deployment uses:

o [RFC5881] defines BFD over IPv4 and IPv6 for single IP hops hops.

o [RFC5883] defines BFD over multihop paths multi-hop paths.

o [RFC5884] defines BFD for MPLS Label Switched Paths (LSPs) (LSPs).

o [RFC5885] defines BFD for MPLS Pseudowires (PWs) (PWs).

Currently, BFD is best suited to verify for verifying that two endpoints are
mutually reachable or that an existing connection continues to be up
and alive. In order for BFD to be able to initially verify that a
connection is valid and that it connects the expected set of
endpoints, it is necessary to provide each endpoint with the
discriminators associated with the connection at each endpoint prior
to initiating BFD sessions. The discriminators are used to verify
that the connection is up and verifiable. valid. Currently, the exchange of
discriminators and the demultiplexing of the initial BFD packets is are
application dependent.

If this information is already known to the end-points endpoints of a potential
BFD session, the initial handshake including an exchange of
discriminators is unnecessary unnecessary, and it is possible for the endpoints
to begin BFD messaging seamlessly. A key objective of the S-BFD use
cases described in this document is to avoid needing to exchange the
initial packets before the BFD session can be established, with the
goal of getting to the established state more quickly; in other
words, the initial exchange of discriminator information is an
unnecessary extra step that may be avoided for these cases.

In a given scenario, an entity (such as an operator, operator or a centralized
controller) determines a set of network entities to which BFD
sessions might need to be established. In traditional BFD, each of
those network entities chooses a BFD discriminator Discriminator for each BFD
session that the entity will participate in (see Section 6.3 of
[RFC5880]). However, a key goal of a Seamless BFD S-BFD is to provide operational
simplification. In this context, for S-BFD, each of those network
entities is assigned one or more BFD discriminators, Discriminators, and allowing those
network entities are allowed to use one discriminator Discriminator value for
multiple sessions. Therefore, there may be only one or a few
discriminators assigned to a node. These network entities will
create an S-BFD listener session instance that listens for incoming
BFD control Control packets. When the mappings between specific network
entities and their corresponding BFD discriminators Discriminators are known to
other network nodes belonging to the same administrative domain,
then, without having received any BFD packet packets from a particular
target, a network entity in this network is able to send a BFD
control
Control packet to the target's assigned discriminator in the
Your Discriminator field. The target network node, upon reception of
such a BFD control Control packet, will transmit a response BFD control Control
packet back to the sender.

3. Use Cases

As per the BFD protocol [RFC5880], BFD sessions are established using
a handshake mechanism prior to validating the forwarding path. This
section outlines some use cases where the existing mechanism may not
be able to satisfy the requirements identified. In addition, some of
the use cases also stress the need for expedited BFD session
establishment while preserving the benefits of forwarding failure
detection using existing BFD mechanics. mechanisms. Both of these high-level
goals result in the S-BFD use cases. cases outlined in this document.

3.1. Unidirectional Forwarding Path Validation

Even though bidirectional verification of forwarding path paths is useful,
there are scenarios where verification is only required in one
direction between a pair of nodes. One such case is, is when a static
route uses BFD to validate reachability to the next-hop IP router.
In this case, the static route is established from one network entity
to another. The requirement in this case is only to validate the
forwarding path for that statically established unidirectional path.
Validation of the forwarding path in the direction of the target
entity to the originating entity is not required, required in this scenario.
Many LSPs have the same unidirectional characteristics and
unidirectional validation requirements. Such LSPs are common in
Segment Routing and LDP based LDP-based MPLS networks. A final example is when
a unidirectional tunnel uses BFD to validate the reachability of an
egress node.

Additionally, there are operational implications to validation of the unidirectional path validation. has operational
implications. If the traditional BFD is to be used, the target network entity has to be provisioned
entity, as well as an initiator, has to be provisioned, even though the reverse path
reverse-path validation with the BFD session is not required.
However, in the case of unidirectional BFD, there is no need for
provisioning on the target network entity, entity -- only on the source one.
entity.

In this use case, a BFD session could be established in a single
direction. When the targeted target network entity receives the packet, it
identities
identifies the packet as BFD in an application-specific manner (for
example, a destination UDP port number). Subsequently, the BFD
module processes the packet, using the Your Discriminator value as
context. Then, the network entity sends a response to the
originator. This does not necessitate the requirement for
establishment of a bi-directional session, hence bidirectional session; hence, the two way two-way
handshake to exchange discriminators is not needed. The target node
does not need to know the My Discriminator value of the source node.

Thus, in this use case a requirement for BFD for this use case is to enable session
establishment from the source network entity to the target network
entity without the need to have a session (and state) for the reverse
direction. Further, another requirement is that the BFD response
from the target back to the sender can take any (in-band or
out-of-band) path. The BFD module in the target network entity (for
the BFD session), upon receipt of a BFD packet, starts processing the
BFD packet based on the discriminator received. The source network
entity can therefore establish a unidirectional BFD session without
the bidirectional handshake and exchange of discriminators for
session establishment.

3.2. Validation of the Forwarding Path Prior prior to Switching Traffic

This

In this use case is when case, BFD is used to verify reachability before sending
traffic via a path/LSP. This comes with at a cost, which is
that cost: traffic is prevented to use
from using the path/LSP until BFD is able to validate the reachability, which reachability;
this could take seconds due to BFD session bring-up sequences
[RFC5880], LSP ping Ping bootstrapping [RFC5884], etc. This use case
would be better supported by eliminating the need for the initial BFD
session negotiation.

All it takes to be able to send BFD packets to a target, target and for the
target to properly demultiplexing these, demultiplex these packets is for the source
network entities to know what the discriminator Discriminator values to will be used for
the session. The same This is also the case for S-BFD: the three-way
handshake mechanism is eliminated during the bootstrap bootstrapping of BFD
sessions. However, this information is required at each entity to
verify that BFD messages are being received from the expected end-points, hence
endpoints; hence, the handshake mechanism serves no purpose.
Elimination of the unnecessary handshake mechanism allows for faster
reachability validation of BFD provisioned paths/LSPs.

In addition, it is expected that some MPLS technologies will require
traffic engineered
traffic-engineered LSPs to be created dynamically, perhaps driven by
external applications, as e.g. as, for example, in Software Defined Networks Software-Defined
Networking (SDN). It will be desirable to perform BFD validation as
soon as the LSPs are created, so as to use them.

In order to support this use case, an S-BFD session is established
without the need for session negotiation and exchange of
discriminators.

3.3. Centralized Traffic Engineering

Various technologies in the SDN domain that involve controller-based
networks have evolved such that the intelligence, traditionally
placed in a distributed and dynamic control plane, is separated from
the networking entities themselves; instead, it resides in a
(logically) centralized place. There are various controllers that
perform the function in establishment of establishing forwarding paths for the data
flow. Traffic engineering (TE) is one important function, where the path
of the traffic flow is engineered, depending upon various attributes
and constraints of the traffic paths as well as the network state.

When the intelligence of the network resides in a centralized entity,
the ability to manage and maintain the dynamic network network, and its
multiple data paths and node reachability reachability, becomes a challenge. One
way to ensure that the forwarding paths are valid and working is done
by validation using BFD. When traffic engineered traffic-engineered tunnels are
created, it is operationally critical to ensure that the forwarding
paths are working, prior to switching the traffic onto the engineered
tunnels. In the absence of distributed control plane control-plane protocols, it
may be desirable to verify any arbitrary forwarding path in the
network. With tunnels being engineered by a centralized entity, when
the network state changes, traffic has to be switched with minimum
latency and without black-holing of the data.

It is highly desirable in this centralized traffic engineering traffic-engineering use
case that the traditional BFD session establishment and validation of
the forwarding path does do not become a bottleneck. If the controller or
other centralized entity is able to very rapidly verify the
forwarding path of a traffic engineered traffic-engineered tunnel, it could steer the
traffic onto the traffic engineered traffic-engineered tunnel very quickly quickly, thus
minimizing adverse effect effects on a service. This is even more useful
and necessary when the scale of the network and the number of traffic
engineered
traffic-engineered tunnels grows. grow.

The cost associated with the time required for BFD session
negotiation and establishment of BFD sessions to identify valid paths
is very high when providing network redundancy is a critical issue.

3.4. BFD in Centralized Segment Routing

A monitoring technique of for a Segment Routing network based on a
centralized controller is described in [I-D.ietf-spring-oam-usecase]. [SR-MPLS]. Specific OAM
Operations, Administration, and Maintenance (OAM) requirements for
Segment Routing are captured in
[I-D.ietf-spring-sr-oam-requirement]. [SR-OAM-REQS]. In validating this
use case, one of the requirements is to ensure that the BFD packet's
behavior is according to the monitoring specified for the segment, segment and
that the packet is U-turned at the expected node. This criteria criterion
ensures the continuity check to the adjacent segment-id. Segment Identifier.

To support this use case, the operational requirement is for BFD,
initiated from a centralized controller, to perform liveness
detection for any given segment under in its domain.

3.5. Efficient BFD Operation under Resource Constraints

When BFD sessions are being setup, set up, torn down down, or modified (i.e.,
when parameters such as interval intervals and multiplier multipliers are being
modified), BFD requires additional packets packets, other than scheduled
packet transmissions transmissions, to complete the negotiation procedures (i.e., P/F bits).
Poll (P) bits and Final (F) bits; see Section 4.1 of [RFC5880]).
There are scenarios where network resources are constrained: a node
may require BFD to monitor a very large number of paths, or BFD may
need to operate in low powered low-powered and traffic sensitive traffic-sensitive networks; these
include
microwave, low powered nano-cells, microwave systems, low-powered nanocells, and others. In
these scenarios, it is desirable for BFD to slow down, speed up,
stop, or resume at- at will and with a minimal number of additional BFD
packets exchanged to modify the session or establish a new one.

The established BFD session parameters parameters, and such attributes like as
transmission interval, interval and receiver interval, etc., need to be modifiable
without changing the state of the session.

3.6. BFD for Anycast Addresses

The BFD protocol requires two endpoints to host BFD sessions, both
sending packets to each other. This BFD model does not fit well with
anycast address monitoring, as BFD packets transmitted from a network
node to an anycast address will reach only one of potentially many
network nodes hosting the anycast address.

This use case verifies that a source node can send a packet to an
anycast address, address and that the target node to which the packet is
delivered can send a response packet to the source node. Traditional
BFD cannot fulfill this requirement, since it does not provide for a
set of BFD agents to collectively form one endpoint of a BFD session.
The concept of a Target Listener "target listener" in S-BFD solves fulfills this
requirement.

To support this use case, the BFD sender transmits BFD packets, which
are received by any of the nodes hosting the anycast address to which
the BFD packets are being sent. The anycast target that receives the
BFD
packet, packet responds. This use case does not imply the BFD session
establishment with every node hosting the anycast address.
Consequently, in this any cast anycast use case, target nodes that do not
happen to receive any of the BFD packets do not need to maintain any
state, and the source node does not need to maintain separate state
for each target node.

3.7. BFD Fault Isolation

BFD for multihop multi-hop paths [RFC5883] and BFD for MPLS LSPs [RFC5884]
perform end-to-end validation, traversing multiple network nodes.
BFD has been designed to declare a failure upon lack to receive some number of
consecutive
packet reception, which packets. This failure can be caused by a fault anywhere
along these
path. paths. Fast failure detection allows for rapid fault
detection and consequent rapid path recovery procedures. However,
operators often have to follow up, manually or automatically, to
attempt to identify and localize the fault that caused BFD sessions
to fail (i.e., fault isolation). The If Equal-Cost Multipath (ECMP) is
used, the usage of other tools to isolate the fault (e.g.,
traceroute) may cause the packets to traverse a different path
through the network, if Equal-Cost Multipath (ECMP) is used. network. In addition, the longer it takes from the time
of BFD session failure to starting the time that fault isolation, isolation begins, the
more likely that the fault will not be able to
be isolated (e.g., a fault can get may be
corrected via rerouting or routed around). some other means during that time). If
BFD had built-in fault isolation fault-isolation capability, fault isolation can get would be
triggered at when the earliest sign of fault detection. was first detected. This embedded fault
isolation will would be more effective when (i.e., faults would be detected
sooner) if those BFD fault isolation fault-isolation packets are load balanced were load-balanced in
the same way as the BFD packets that were dropped, detecting the fault. dropped.

This use case describes S-BFD fault isolation fault-isolation capabilities, utilizing
a TTL field (e.g., as described in Section 5.1.1 of [I-D.ietf-bfd-seamless-ip]) [RFC7881]) or
using status indicating fields. fields that indicate status.

3.8. Multiple BFD Sessions to the Same Target Node

BFD is capable of providing very fast failure detection, as relevant
network nodes continuously transmit BFD packets at the negotiated
rate. If BFD packet transmission is interrupted, even for a very
short period of time, BFD can declare a failure irrespective of path
liveliness. It is possible, on
liveness. On a system where BFD is running, it is possible for
certain events to (intentionally or unintentionally) to cause a short brief
interruption of BFD packet transmissions. With distributed
architectures of BFD implementations, this case can be protected. In
this case, the prevented.
This use case of is for an S-BFD node running multiple BFD sessions to a targets,
the same target node, with those sessions hosted on different system
modules (e.g., in different CPU instances). This can reduce BFD false
failures, resulting in a more stable network.

To support this use case, a mapping between the multiple
discriminators on a single system, system and the specific entity within the that
system is required.

3.9. An MPLS BFD Session Per per ECMP Path

BFD for MPLS LSPs, defined in [RFC5884], describes procedures to run for
running BFD as an LSP in-band continuity check mechanism, through usage of mechanism by using
MPLS
echo request Echo Request messages [RFC4379] to bootstrap the BFD session on
the target (i.e., egress) node. Section 4 of [RFC5884] also
describes a the possibility of running multiple BFD sessions per
alternative paths of
LSP. LSPs. [RFC7726] further clarified clarifies the procedures, both for
both ingress and egress nodes, of regarding how to bootstrap, maintain,
and remove multiple BFD sessions for the same <MPLS LSP, FEC> tuple. tuple
("FEC" means Forwarding Equivalence Class). However, this mechanism
still requires the use of MPLS LSP Ping for bootstrapping,
round-trips
round trips for initialization, and keeping state at the receiver.

In the presence of ECMP within an MPLS LSP, it may be desirable to
run in-band monitoring that exercises every path of this ECMP.
Otherwise
Otherwise, there will be scenarios where an in-band BFD session
remains up through one path but traffic is black-holing over another
path. A BFD session per ECMP path of an LSP requires the definition
of procedures that update [RFC5884] in terms of how to bootstrap and
maintain the correct set of BFD sessions on the egress node.
However, for traditional BFD, that requires the constant use of MPLS
Echo Request messages to create and delete BFD sessions on the egress
node,
node when ECMP paths and/or corresponding load balance load-balance hash keys
change. If a BFD session over any paths of the LSP can be
instantiated, stopped stopped, and resumed without requiring additional
procedures of for bootstrapping via an MPLS echo request Echo Request message, it
would greatly simplify both implementations and operations, operations and
benefits
would benefit network devices devices, as less processing are would be required
by them.

To support this requirement, multiple S-BFD sessions need to be
established over different ECMP paths from between the same pair of source to
and target
node. nodes.

4. Detailed Requirements for a Seamless BFD

REQ#1: A

REQ 1: Upon receipt of an S-BFD packet, a target network entity
(for the S-BFD session), upon
receipt of the S-BFD packet, session) MUST process the packet based on the
discriminator received in the BFD packet. If the S-BFD
context is found, the target network entity MUST be able to
send a response.

REQ#2:

REQ 2: The source network entity MUST be able to establish a
unidirectional S-BFD session without the bidirectional
handshake of discriminators for session establishment.

REQ#3:

REQ 3: The S-BFD session MUST be able to be established without the
need for the exchange of discriminators in during session
negotiation.

REQ#4:

REQ 4: In a Segment Routed network, S-BFD MUST be able to perform
liveness detection initiated from a centralized controller
for any given segment under in its domain.

REQ#5:

REQ 5: The established S-BFD session parameters and attributes,
such as transmission interval, interval and reception interval, etc., MUST
be modifiable without changing the state of the session.

REQ#6:

REQ 6: An S-BFD source network entity MUST be able to send S-BFD
control Control
packets to an anycast address which address. These packets are received
and processed by any node hosting that address, and must the anycast address. The
S-BFD entity MUST be able to receive responses to S-BFD
Control packets from any of these anycast nodes, without
establishing a separate BFD S-BFD session with every node hosing
hosting the anycast address.

REQ#7:

REQ 7: S-BFD SHOULD support fault isolation fault-isolation capability, which MAY
be triggered when a fault is encountered.

REQ#8:

REQ 8: S-BFD SHOULD be able to establish multiple sessions between
the same pair of source and target nodes. This requirement
enables but does not guarantee the ability to monitor
diverge
divergent paths in ECMP environments. It also provides
resiliency in distributed router architectures. The mapping
between BFD discriminators Discriminators and particular entities (e.g.,
ECMP paths, or Line Cards) line cards) is out the scope of scope for the S-BFD
specification.

REQ#9:
protocol.

REQ 9: The S-BFD protocol MUST provide mechanisms for loop
detection and prevention, protecting against malicious
attacks attempting to create packet loops.

REQ#10:

REQ 10: S-BFD MUST incorporate robust security protections against
impersonators, malicions malicious actors, and various active and
passive attacks. The simple and accelerated establishment
of an S-BFD session should not negatively affect security.

5. Security Considerations

This document details the use cases for S-BFD and identifies various
associated requirements. Some of these requirements are security
related. The use cases herein described herein do not expose a system to
abuse or to additional security risks. Since some negotiation aspects
are eliminated, a misconfiguration can result in S-BFD packets being
sent to an incorrect node. If this receiving node runs S-BFD, the
packet will be discarted because of the discarded due to discriminator mismatch. If the node
does not run S-BFD, the packet will be naturally discarded.

The proposed new protocols, extensions, and enhancements for a
Seamless BFD S-BFD
supporting these use cases and realizing these requirements will
address the associated security considerations. A
Seamless BFD S-BFD should not have
reduced security capabilities as compared to traditional BFD.

6. IANA Considerations

There are no IANA considerations introduced by this document.

7. Acknowledgements

The authors would like to thank Tobias Gondrom and Eric Gray, for
their insightful and useful comments. The authors appreciate the
thorough review and comments provided by Dale R. Worley.

8. Contributors

The following are key contributors to this document:

Manav Bhatia, Ionos Networks
Satoru Matsushima, Softbank
Glenn Hayden, ATT
Santosh P K
Mach Chen, Huawei
Nobo Akiya, Big Switch Networks

9. References

9.1.

6.1. Normative References

[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>.

[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>.

[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
DOI 10.17487/RFC5881, June 2010,
<http://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, <http://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, <http://www.rfc-editor.org/info/rfc5884>.

[RFC5885] Nadeau, T., Ed. Ed., and C. Pignataro, Ed., "Bidirectional
Forwarding Detection (BFD) for the Pseudowire Virtual
Circuit Connectivity Verification (VCCV)", RFC 5885,
DOI 10.17487/RFC5885, June 2010,
<http://www.rfc-editor.org/info/rfc5885>.

9.2.

6.2. Informative References

[I-D.ietf-bfd-seamless-base]
Akiya, N., Pignataro, C., Ward, D., Bhatia, M., and J.
Networks, "Seamless Bidirectional Forwarding Detection
(S-BFD)", draft-ietf-bfd-seamless-base-09 (work in
progress), April 2016.

[I-D.ietf-bfd-seamless-ip]
Akiya, N., Pignataro, C., and D. Ward, "Seamless
Bidirectional Forwarding Detection (S-BFD) for IPv4, IPv6
and MPLS", draft-ietf-bfd-seamless-ip-04 (work in
progress), April 2016.

[I-D.ietf-spring-oam-usecase]
Geib, R., Filsfils, C., Pignataro, C., and N. Kumar, "A
Scalable and Topology-Aware MPLS Dataplane Monitoring
System", draft-ietf-spring-oam-usecase-03 (work in
progress), April 2016.

[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-07 (work in progress), December
2015.

[I-D.ietf-spring-sr-oam-requirement]
Kumar, N., Pignataro, C., Akiya, N., Geib, R., Mirsky, G.,
and S. Litkowski, "OAM Requirements for Segment Routing
Network", draft-ietf-spring-sr-oam-requirement-01 (work in
progress), December 2015.

[RFC0791]

[RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, 10.17487/RFC791, September 1981,
<http://www.rfc-editor.org/info/rfc791>.

[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.

[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<http://www.rfc-editor.org/info/rfc3031>.

[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
DOI 10.17487/RFC4379, February 2006,
<http://www.rfc-editor.org/info/rfc4379>.

[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>.

[RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.
Pallagatti, "Seamless Bidirectional Forwarding Detection
(S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016,
<http://www.rfc-editor.org/info/rfc7880>.

[RFC7881] Pignataro, C., Ward, D., and N. Akiya, "Seamless
Bidirectional Forwarding Detection (S-BFD) for IPv4, IPv6,
and MPLS", RFC 7881, DOI 10.17487/RFC7881, July 2016,
<http://www.rfc-editor.org/info/rfc7881>.

[SR-ARCH] Filsfils, C., Ed., Previdi, S., Ed., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing
Architecture", Work in Progress,
draft-ietf-spring-segment-routing-09, July 2016.

[SR-MPLS] Geib, R., Ed., Filsfils, C., Pignataro, C., Ed., and N.
Kumar, "A Scalable and Topology-Aware MPLS Dataplane
Monitoring System", Work in Progress,
draft-ietf-spring-oam-usecase-03, April 2016.

[SR-OAM-REQS]
Kumar, N., Pignataro, C., Akiya, N., Geib, R., Mirsky, G.,
and S. Litkowski, "OAM Requirements for Segment Routing
Network", Work in Progress,
draft-ietf-spring-sr-oam-requirement-02, July 2016.

Acknowledgements

The authors would like to thank Tobias Gondrom and Eric Gray for
their insightful and useful comments. The authors appreciate the
thorough review and comments provided by Dale R. Worley.

Contributors

The following are key contributors to this document:

Manav Bhatia, Ionos Networks
Satoru Matsushima, Softbank
Glenn Hayden, ATT
Santosh P K
Mach Chen, Huawei
Nobo Akiya, Big Switch Networks

Authors' Addresses

Sam Aldrin
Google, Inc Inc.

Email: aldrin.ietf@gmail.com

Carlos Pignataro
Cisco Systems, Inc.

Email: cpignata@cisco.com

Greg Mirsky
Ericsson

Email: gregory.mirsky@ericsson.com

Nagendra Kumar
Cisco Systems, Inc.

Email: naikumar@cisco.com