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draft-ietf-mpls-tp-mfp-use-case-and-requirements
Network Working Group Z. Cui
Internet-Draft R. Winter
Intended status: Standards Track NEC
Expires: September 10, 2015 H. Shah
Ciena
S. Aldrin
Huawei Technologies
M. Daikoku
KDDI
March 9, 2015
Use Cases and Requirements for MPLS-TP multi-failure protection
draft-cui-mpls-tp-mfp-use-case-and-requirements-04
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]. That linear
protection mechanism has not been designed for handling multiple,
simultaneously occurring failures, e.g., 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 protection mechanism itself.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents 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 September 10, 2015.
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Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Document scope . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and References . . . . . . . . . . . . . . . . . 3
3. General m:n protection scenario . . . . . . . . . . . . . . . 4
4. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. m:1 (m > 1) protection . . . . . . . . . . . . . . . . . 5
4.1.1. Pre-configuration . . . . . . . . . . . . . . . . . . 5
4.1.2. On-demand configuration . . . . . . . . . . . . . . . 6
4.2. m:n (m, n > 1, n >= m > 1) protection . . . . . . . . . . 6
5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. 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 and even in off hours.
So, the network connectivity needs to keep all the time. This is
sometimes referred to five nines (99.999%) uptime in a time period.
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.
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There are various situations where above multiple failures to be
considered, e.g., 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 case above, when a working entity or
protection entity was closed for maintenance or construction work,
the network service becomes vulnerable to single failure since one
entity is already down. If a failure occurs during this time, an
operator might not be able 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 for recovers user
traffic after several failures occurred on both the working and
protection entity at the same time.
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
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].
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 are made in [RFC4427].
o 1+1 protection
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o 1:n (n >= 1) protection
o m:n (m, n > 1, n >= m > 1) protection
In this document, the following additional terminology is applied:
o "broadcast bridge", defined in [RFC4427].
o "selector bridge", defined in [RFC4427].
o "working entity", defined in [RFC4427].
o "protection entity", defined in [RFC4427].
This document defines a new protection type:
o m:1 (m > 1) protection: A set of m protection entities protects a
working entity.
3. 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, 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.
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+------+ +------+
|Node A| working entity #1 |Node Z|
| |=============================| |
| | .... | |
| | working entity #n | |
| |=============================| |
| | | |
| | | |
| | protection entity #1 | |
| |*****************************| |
| | .... | |
| | protection entity #m | |
| |*****************************| |
+------+ +------+
|--------Protection Domain--------|
Figure 1: m:n protection domain
4. Use cases
4.1. 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. 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.
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4.1.2. 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. 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.
5. 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 failures. This section extends
the list of requirements to support multiple failures scenarios.
R1. MPLS-TP MUST 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 and one or more
protection paths.
2 Pre-configuration of protection paths SHOULD be supported.
3 On-demand protection path configuration MAY be supported.
4 On-demand protection resource activation MAY be supported.
5 A priority scheme MUST be provided, since a protection path has to
chosen out of two or more protection paths.
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R2. MPLS-TP MUST 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 and
protection path or multiple working paths.
2 A priority scheme MUST be provided, since protection resources are
shared by multiple working paths dynamically.
6. 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.
7. 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.
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[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
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