Network Working Group Z. Cui
Internet-Draft R. Winter
Intended status: Standards Track NEC
Expires: January 5, 2015 H. Shah
Ciena
S. Aldrin
Huawei Technologies
M. Daikoku
KDDI
July 4, 2014
Use Cases and Requirements for MPLS-TP multi-failure protection
draft-cui-mpls-tp-mfp-use-case-and-requirements-02
Abstract
The basic survivability technique has been defined in Multiprotocol
Label Switching Transport Profile (MPLS-TP) network [RFC6378]. That
protocol however is limited to 1+1 and 1:1 protection, not designed
to handle multi-failure protection.
This document introduces some use cases and requirements for multi-
failure protection functionality.
Status of This Memo
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Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Document scope . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements notation . . . . . . . . . . . . . . . . . . 3
2. m:n protection architecture . . . . . . . . . . . . . . . . . 3
3. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Increase service availability . . . . . . . . . . . . . . 4
3.2. Reduce the backup costs . . . . . . . . . . . . . . . . . 5
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Today's packet optical transport networks are able to 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 fault-tolerant network design is an
important network design objective.
The basic survivability technique has been defined in MPLS-TP network
[RFC6378]. That protocol however is limited to 1+1 and 1:1
protection, not designed to handle multi-failure protection.
The case of multi-failure condition is very rare, but not unheard of.
For example, when a working path was closed by network operator for
construction work, the network service will become a hazardous
condition. During this time, if another failure (e.g. a human-error
or network entities failure) is occurred on the protection path, than
the operator can't meet service level agreements (SLA).
A network must be able to handle multiple failures even that are a
rare case, because especially some high-priority services such as
emergency telephone calls request to network service provider
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guarantee their service connections in a timely manner in any
situation.
On the other hand, many network operators have a very limited budget
for improving network survivability. This requires a design
approach, which takes budget limitations into consideration.
To increase the service availability and to reduce the backup network
costs, we propose extend the 1+1 and 1:1 protection protocol to
support the m:n architecture type.
1.1. Document scope
This document describes the use cases and requirements for multi-
failure protection in MPLS-TP networks without the use of control
plane protocols. Existing solutions based on 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 multi-
failure protection not based on control plane support.
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].
2. m:n protection architecture
The following Figure 1 shows a protection domain with n working paths
and m protection paths. when a working path is determined to
impaired, its normal traffic must be assigned to a protection path if
a protection path is available. To reduce the backup network costs,
m protection paths are sharing backup resource for n working paths,
where m <= n typically. The bandwidth of each protection paths
should be allocated enough to protect any of the n working paths.
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+-----+ +-----+
| |=============================| |
|LER-A| Working Path #1 |LER-Z|
| | | |
| |=============================| |
| | .... | |
| | | |
| |=============================| |
| | Working Path #n | |
| | | |
| | | |
| | | |
| |*****************************| |
| | Protection Path #1 | |
| | | |
| |*****************************| |
| | .... | |
| | | |
| |*****************************| |
| | Protection Path #m | |
| | | |
+-----+ +-----+
|--------Protection Domain--------|
Figure 1: m:n ptorection domain
3. Use cases
3.1. Increase service availability
With technological advancement of mobile services or data center
services, dependencies and business impact of network services have
been increased phenomenally. End-users expectations of service
availability also are increasing, which is driving service providers
enhance their network's availability.
Network availability must be maintained especially for high-priority
services such as emergency telephone calls, even during natural
disasters and other catastrophic events such as earthquake or
tsunami. Existing 1+1 or 1:n protection however is limited to cover
single failure and no sufficient to maintain disaster recovery.
The m:n protection can increase service availability because it take
multiple protection paths to ensuring high-priority services continue
to operate on the 2nd, 3rd or Nth alternate backup, at least one of m
protection paths is a available.
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3.2. Reduce the backup costs
Network costs driven by high traffic growth rates are rising
steadily, but revenues are no increased in direct proportion to
traffic growth rates. This requires a design approach, which takes
budget limitations into consideration.
Existing protection schemes such as 1+1 protection meet the sub 50 ms
performance requirement but only protect against a single failure and
are too costly.
The m:n protection is a useful solution, that can reduce the backup
costs because m dedicated protection paths are sharing backup paths
for n working paths, where m =< n typically.
The shared Mesh Protection (SMP) also can reduce the backup costs as
described in [I-D.ietf-mpls-smp-requirements]. SMP however is based
the 1:1 protection and does not able to care that the multiple
failures are occurred on both working and protection paths. However,
combine use of SMP and a set of m:1 protections to make a m:n
protection likely, may be better able to recovers the multiple
failures.
4. Requirements
Some recovery requirements are defined [RFC5654]. That however is
limited to cover single failure and is not able to care that the
multiple failures. This Section 4 extends the requirements to
support the multiple failures scenarios.
MPLS-TP MUST support m:n protection with the following requirements:
R1 The m:n protection MUST protects against multiple failures that
are simultaneously-detected on both of working path and
protection path or more than one multiple working paths.
R2 Some priority schemes MUST be provided, because the backup
resources are shared by multiple working paths dynamically.
R3 TBD
5. Security Considerations
TBD
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6. IANA Considerations
TBD
7. Normative References
[I-D.ietf-mpls-smp-requirements]
Weingarten, Y., Aldrin, S., Pan, P., Ryoo, J., and G.
Mirsky, "Requirements for MPLS-TP Shared Mesh Protection",
draft-ietf-mpls-smp-requirements-06 (work in progress),
June 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching
(GMPLS) Architecture", RFC 3945, October 2004.
[RFC4427] Mannie, E. and D. Papadimitriou, "Recovery (Protection and
Restoration) Terminology for Generalized Multi-Protocol
Label Switching (GMPLS)", RFC 4427, March 2006.
[RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N.,
and S. Ueno, "Requirements of an MPLS Transport Profile",
RFC 5654, September 2009.
[RFC6378] Weingarten, Y., Bryant, S., Osborne, E., Sprecher, N., and
A. Fulignoli, "MPLS Transport Profile (MPLS-TP) Linear
Protection", RFC 6378, October 2011.
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
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Sam Aldrin
Huawei Technologies
Email: aldrin.ietf@gmail.com
Masahiro Daikoku
KDDI
Email: ms-daikoku@kddi.com
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