wdiff draft-cui-mpls-tp-mfp-use-case-and-requirements-04.txt draft-cui-mpls-tp-mfp-use-case-and-requirements-05.txt

Network Working Group Z. Cui
Internet-Draft R. Winter
Intended status: Standards Track Informational NEC
Expires: September 10, 2015 January 7, 2016 H. Shah
Ciena
S. Aldrin
Huawei Technologies
M. Daikoku
KDDI
March 9,
July 6, 2015

Use Cases and Requirements for MPLS-TP multi-failure protection
draft-cui-mpls-tp-mfp-use-case-and-requirements-04
draft-cui-mpls-tp-mfp-use-case-and-requirements-05

Abstract

For the Multiprotocol Label Switching Transport Profile (MPLS-TP)
linear protection capable of 1+1 and 1:1 protection has already been
defined in [RFC6378], [RFC7271] and [RFC7324].
defined. That linear protection mechanism has not been designed for
handling multiple, simultaneously occurring occuring failures, e.g., i.e. multiple
failures that affect the working and the protection entity during the
same time period. In these situations currently defined protection
mechanisms would fail.

This document introduces use cases and requirements for mechanisms
that are capable of protecting against such failures. It does not
specify a multi-failure protection mechanism itself.

Status of This Memo

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Document scope . . . . . . . . . . . . . . . . . . . . . 3
2.
1.2. Requirements notation . . . . . . . . . . . . . . . . . . 3
1.3. Terminology and References . . . . . . . . . . . . . . . . . . . . . . . 3
3.
2. General m:n protection scenario . . . . . . . . . . . . . . . 4
4.
3. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1.
3.1. m:1 (m > 1) protection . . . . . . . . . . . . . . . . . 5
4.1.1.
3.1.1. Pre-configuration . . . . . . . . . . . . . . . . . . 5
4.1.2.
3.1.2. On-demand configuration . . . . . . . . . . . . . . . 6
4.2.
3.2. m:n (m, n > 1, n >= m > 1) protection . . . . . . . . . . 6
5.
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 6
6.
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7.
6. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8

1. Introduction

Today's businesses require reliable network connectivity and access
to corporate resources. Connections to and from business units,
vendors and SOHOs are all equally important to keep the continuity
when needed. Business runs all day, every day packet optical transport networks concentrate large volumes
of traffic onto a relatively small number of nodes and even in off hours.
So, links. As a
result, the failure of a single network connectivity needs to keep all the time. This is
sometimes referred to five nines (99.999%) uptime in element can potentially
interrupt a time period. large amount of traffic. For this reason, ensuring
survivability through careful network design and appropriate
technical means is important.

In MPLS-TP networks, a basic survivability technique is available as
specified in [RFC6378], [RFC7271] and [RFC7324]. That protocol
however is limited to 1+1 and 1:1 protection and not designed to
handle multiple failures that affect both the working and protection
entity at the same time.

There are various situations scenarios where above multiple failures to be
considered, e.g., multi-failure protection is an
important requirement for network survivability. E.g for disaster
recovery, after catastrophic events such as earthquakes or tsunamis.
During the period after such events, network availability is crucial,
in particular for high-priority services such as emergency telephone
calls. Existing 1+1 or 1:n protection however is limited to cover
single failures which has proven as not sufficient during past
events.

Beyond the natural disaster use case above, multi-failure protection
is also beneficial in situations where the network is particularly
vulnerable, e.g., when a working entity or protection entity was
closed for maintenance or construction work, work. During this time, the
network service becomes vulnerable to single failure failures since one
entity is already down. If a failure occurs during this time, an
operator might not be able ablt to meet service level agreements (SLA).

[RFC5654] establishes that MPLS-TP SHOULD MUST support 1+1 protection
and 1:n protection (including 1:1 protection). This document
provides an expansion of the basic requirements of MPLS-TP presented
in [RFC5654] for supports m:1 and m:n protection
Thus, a technical means for recovers user
traffic after several failures occurred on both the working and multi-failure protection entity at the same time. could take
pressure off network operations.

1.1. Document scope

This document describes use cases and requirements for m:1 and m:n
protection in MPLS-TP networks without the use of control plane
protocols. Existing solutions based on a control plane such as GMPLS
may be able to restore user traffic when multiple failures occur.
Some networks however do not use full control plane operation for
reasons such as service provider preferences, certain limitations or
the requirement for fast service restoration (faster than achievable
with control plane mechanisms). These networks are the focus of this
document which defines a set of requirements for m:1 and m:n
protection not based on control plane support.

2. Terminology and References This document imposes
no formal time constraints on detection times.

1.2. Requirements notation

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 [RFC2119].

1.3. Terminology

The terminology used in this document is based on the terminology
defined in the MPLS-TP Survivability Framework document [RFC6372],
which in turn is based on [RFC4427].

In particular, the following protection types schemes are made defined in [RFC4427].
[RFC4427] and used as terms in this document:

o 1+1 protection

o 1:n (n >= 1) protection

o m:n (m, n > 1, n >= m > 1) protection

In this document,

o Further, the following additional terminology is applied: from [RFC4427] is
used:

o "broadcast bridge", defined in [RFC4427]. bridge"

o "selector bridge", defined in [RFC4427]. bridge"

o "working entity", defined in [RFC4427]. entity"

o "protection entity", defined in [RFC4427]. entity"

This document defines a new protection type:

o m:1 (m > 1) protection: A set of m protection entities protects protecting
a single working entity.

3. entity

2. General m:n protection scenario

The general underlying assumption of this work is that an m:n
relationship between protection entity and working entity exists,
i.e. there is no artificial limitation on the ratio between
protection and working entities.

This general scenario is illustrated in Figure 1 which shows a
protection domain with n working entities and m protection entities
between Node A and Node Z.

At the Node A and in the absence of faults, A, traffic is transported over its respective working entity
and may be simultaneously transported over one of its protection
entities (in case of a broadcast bridge), or it is transported over
its working entity and only in case of failure over one of the
protection entities (in case of a selector bridge). At the Node Z, the
traffic is selected from either its working entity or one of the
protection entities.

+------+ +------+
|Node A| working entity #1 |Node Z|
| |=============================| |
| | .... | |
| | working entity #n | |
| |=============================| |
| | | |
| | | |
| | protection entity #1 | |
| |*****************************| |
| | .... | |
| | protection entity #m | |
| |*****************************| |
+------+ +------+
|--------Protection Domain--------|

Figure 1: m:n protection domain

3. Use cases

4.1.

3.1. m:1 (m > 1) protection

With MPLS-TP linear protection such as 1+1/1:1 protection, when a
single failure is detected on the working entity, the service can be
restored using the protection entity. During this time however, the
traffic is unprotected until the working entity is restored.

m:1 protection can increase service availability and reduce
operational pressure since multiple protection entities are
available. For any m > 1, m - 1 protection entities may fail and the
service still would have a protection entity available.

There are different ways to provision these alternative protection
entities which are outlined in the following sub-sections.

4.1.1.

3.1.1. Pre-configuration

The relationship between the working entity and the protection
entities is part of the system configuration and needs to be
configured before the working entity is being used. The same applies
to additional protection entities.

Unprotected traffic can be transported over the m protection entities
as long as these entities do not carry protected traffic.

4.1.2.

3.1.2. On-demand configuration

The protection relationship between a working entity and a protection
entity is configured while the system is in operation.

Additional protection entities are configured by either a control
plane protocol or static configuration using a management system
directly after failure detection and/or notification of either the
working entity or the protection entity.

4.2. entities.

3.2. m:n (m, n > 1, n >= m > 1) protection

In order to reduce the cost of protection entities, in the m:n
scenario, m dedicated protection transport entities are sharing
protection resources for n working transport entities.

The bandwidth of each protection entity should be allocated in such a
way that it may be possible to protect any of the n working entities
in case at least one of the m protection entities is available. When
a working entity is determined to be impaired, its traffic first must
be assigned to an available protection transport entity followed by a
transition from the working to the assigned protection entity at both
the
Node A and Node Z of the protected domain. It is noted that when
more than m working entities are impaired, only m working entities
can be protected.

4. Requirements

A number of recovery requirements are defined in [RFC5654]. These
requirements however are limited to cover single failure case and not
multiple, simultaneously occurring occuring failures. This section extends the
list of requirements to support multiple failures scenarios.

R1. MPLS-TP MUST SHOULD support m:1 (m > 1) protection.

1. An m:1 protection mechanism MUST protect against multiple
failures that are detected on both the working path entity and one or
more protection paths.

2 entities.

2. Pre-configuration of protection paths entities SHOULD be supported.

3. On-demand protection path entity configuration MAY be supported.

4. On-demand protection resource activation MAY be supported.

5. A priority scheme MUST be provided, since a protection path entity has
to be chosen out of two or more protection paths. entities.

R2. MPLS-TP MUST SHOULD support m:n (m, n > 1, n >= m > 1) protection.

1. An m:n protection mechanism MUST protect against multiple
failures that are simultaneously detected on both a working path
entity and a protection path entity or multiple working paths.

2 entities.

2. A priority scheme MUST be provided, since protection resources
are shared by multiple working paths entities dynamically.

5. Security Considerations

General security considerations for MPLS-TP are covered in [RFC5921].
The security considerations for the generic associated control
channel are described in [RFC5586]. The requirements described in
this document are extensions to the requirements presented in
[RFC5654] and does not introduce any new security risks.

6. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC4427] Mannie, E. and D. Papadimitriou, "Recovery (Protection and
Restoration) Terminology for Generalized Multi-Protocol
Label Switching (GMPLS)", RFC 4427, March 2006.

[RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic
Associated Channel", RFC 5586, June 2009.

[RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,
and S. Ueno, "Requirements of an MPLS Transport Profile",
RFC 5654, September 2009.

[RFC5921] Bocci, M., Bryant, S., Frost, D., Levrau, L., and L.
Berger, "A Framework for MPLS in Transport Networks", RFC
5921, July 2010.

[RFC6372] Sprecher, N. and A. Farrel, "MPLS Transport Profile (MPLS-
TP) Survivability Framework", RFC 6372, September 2011.

[RFC6378] Weingarten, Y., Bryant, S., Osborne, E., Sprecher, N., and
A. Fulignoli, "MPLS Transport Profile (MPLS-TP) Linear
Protection", RFC 6378, October 2011.

[RFC7271] Ryoo, J., Gray, E., van Helvoort, H., D'Alessandro, A.,
Cheung, T., and E. Osborne, "MPLS Transport Profile (MPLS-
TP) Linear Protection to Match the Operational
Expectations of Synchronous Digital Hierarchy, Optical
Transport Network, and Ethernet Transport Network
Operators", RFC 7271, June 2014.

[RFC7324] Osborne, E., "Updates to MPLS Transport Profile Linear
Protection", RFC 7324, July 2014.

Authors' Addresses

Zhenlong Cui
NEC

Email: c-sai@bx.jp.nec.com

Rolf Winter
NEC

Email: Rolf.Winter@neclab.eu

Himanshu Shah
Ciena

Email: hshah@ciena.com

Sam Aldrin
Huawei Technologies

Email: aldrin.ietf@gmail.com

Masahiro Daikoku
KDDI

Email: ms-daikoku@kddi.com