Internet DRAFT - draft-cui-mpls-tp-mfp-use-case-and-requirements
draft-cui-mpls-tp-mfp-use-case-and-requirements
Network Working Group Z. Cui
Internet-Draft R. Winter
Intended status: Informational NEC
Expires: July 15, 2016 H. Shah
Ciena
S. Aldrin
Huawei Technologies
M. Daikoku
KDDI
January 12, 2016
Use Cases and Requirements for MPLS-TP multi-failure protection
draft-cui-mpls-tp-mfp-use-case-and-requirements-08
Abstract
For the Multiprotocol Label Switching Transport Profile (MPLS-TP)
linear protection capable of 1+1 and 1:1 protection has already been
defined. That linear protection mechanism has not been designed for
handling multiple, simultaneously occuring failures, 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
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 July 15, 2016.
Cui, et al. Expires July 15, 2016 [Page 1]
Internet-Draft Multi-failure protection requirements January 2016
Copyright Notice
Copyright (c) 2016 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
carefully, as they describe your rights and restrictions with respect
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
1.2. Requirements notation . . . . . . . . . . . . . . . . . . 3
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. General m:n protection scenario . . . . . . . . . . . . . . . 4
3. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. m:1 (m > 1) protection . . . . . . . . . . . . . . . . . 5
3.1.1. Pre-configuration . . . . . . . . . . . . . . . . . . 5
3.1.2. On-demand configuration . . . . . . . . . . . . . . . 6
3.2. m:n (m, n > 1, n >= m > 1) protection . . . . . . . . . . 6
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Today's packet optical transport networks concentrate large volumes
of traffic onto a relatively small number of nodes and links. As a
result, the failure of a single network element can potentially
interrupt a 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 end-to-end linear protection
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.
Cui, et al. Expires July 15, 2016 [Page 2]
Internet-Draft Multi-failure protection requirements January 2016
There are various scenarios where 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. During this time, the
network service becomes vulnerable to single failures 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).
Thus, a technical means for multi-failure protection 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. 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 schemes are defined in
[RFC4427] and used as terms in this document:
Cui, et al. Expires July 15, 2016 [Page 3]
Internet-Draft Multi-failure protection requirements January 2016
o 1+1 protection
o 1:n (n >= 1) protection
o m:n (m, n > 1, n >= m > 1) protection
o Further, the following additional terminology is from [RFC4427] is
used:
o "broadcast bridge"
o "selector bridge"
o "working entity"
o "protection entity"
This document defines a new protection type:
o m:1 (m > 1) protection: A set of m protection entities protecting
a single working 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 Node 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 Node Z, the
traffic is selected from either its working entity or one of the
protection entities. Note that any of the n working entities and m
protection entities should follow a disjoint path through the network
from Node A to Node Z.
Cui, et al. Expires July 15, 2016 [Page 4]
Internet-Draft Multi-failure protection requirements January 2016
+------+ +------+
|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
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. However, during the time the
protection is active 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.
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.
Cui, et al. Expires July 15, 2016 [Page 5]
Internet-Draft Multi-failure protection requirements January 2016
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 entities. In case a management
system is used, there is no need for a standardized solution.
3.2. m:n (m, n > 1, n >= m > 1) protection
Because m:1 protecion introduces additional protection entities
compared to 1:1 protection, an additional cost has to be paid. In
order to reduce the cost of these additional 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
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 occuring failures. This section extends the
list of requirements to support multiple failures scenarios.
R1. MPLS-TP 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 entity and one or
more protection entities.
2. Pre-configuration of protection entities SHOULD be supported.
3. On-demand protection entity configuration MAY be supported.
4. On-demand protection resource activation MAY be supported.
Cui, et al. Expires July 15, 2016 [Page 6]
Internet-Draft Multi-failure protection requirements January 2016
5. A priority scheme MUST be provided, since a protection entity has
to be chosen out of two or more protection entities.
R2. MPLS-TP 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
entity and a protection entity or multiple working entities.
2. A priority scheme MUST be provided, since protection resources
are shared by multiple working entities dynamically.
If a solution is designed based on an existing mechanism such as PSC,
then this solution MUST be backward compatible and not break such
mechanisms.
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.
Cui, et al. Expires July 15, 2016 [Page 7]
Internet-Draft Multi-failure protection requirements January 2016
[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
Cui, et al. Expires July 15, 2016 [Page 8]
