draft-cui-mpls-tp-mfp-use-case-and-requirements-05.txt   draft-cui-mpls-tp-mfp-use-case-and-requirements-06.txt 
Network Working Group Z. Cui Network Working Group Z. Cui
Internet-Draft R. Winter Internet-Draft R. Winter
Intended status: Informational NEC Intended status: Informational NEC
Expires: January 7, 2016 H. Shah Expires: July 9, 2016 H. Shah
Ciena Ciena
S. Aldrin S. Aldrin
Huawei Technologies Huawei Technologies
M. Daikoku M. Daikoku
KDDI KDDI
July 6, 2015 January 6, 2016
Use Cases and Requirements for MPLS-TP multi-failure protection Use Cases and Requirements for MPLS-TP multi-failure protection
draft-cui-mpls-tp-mfp-use-case-and-requirements-05 draft-cui-mpls-tp-mfp-use-case-and-requirements-06
Abstract Abstract
For the Multiprotocol Label Switching Transport Profile (MPLS-TP) For the Multiprotocol Label Switching Transport Profile (MPLS-TP)
linear protection capable of 1+1 and 1:1 protection has already been linear protection capable of 1+1 and 1:1 protection has already been
defined. That linear protection mechanism has not been designed for defined. That linear protection mechanism has not been designed for
handling multiple, simultaneously occuring failures, i.e. multiple handling multiple, simultaneously occuring failures, i.e. multiple
failures that affect the working and the protection entity during the failures that affect the working and the protection entity during the
same time period. In these situations currently defined protection same time period. In these situations currently defined protection
mechanisms would fail. mechanisms would fail.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 7, 2016. This Internet-Draft will expire on July 9, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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calls. Existing 1+1 or 1:n protection however is limited to cover calls. Existing 1+1 or 1:n protection however is limited to cover
single failures which has proven as not sufficient during past single failures which has proven as not sufficient during past
events. events.
Beyond the natural disaster use case above, multi-failure protection Beyond the natural disaster use case above, multi-failure protection
is also beneficial in situations where the network is particularly is also beneficial in situations where the network is particularly
vulnerable, e.g., when a working entity or protection entity was vulnerable, e.g., when a working entity or protection entity was
closed for maintenance or construction work. During this time, the closed for maintenance or construction work. During this time, the
network service becomes vulnerable to single failures since one network service becomes vulnerable to single failures since one
entity is already down. If a failure occurs during this time, an entity is already down. If a failure occurs during this time, an
operator might not be ablt to meet service level agreements (SLA). operator might not be able to meet service level agreements (SLA).
Thus, a technical means for multi-failure protection could take Thus, a technical means for multi-failure protection could take
pressure off network operations. pressure off network operations.
1.1. Document scope 1.1. Document scope
This document describes use cases and requirements for m:1 and m:n This document describes use cases and requirements for m:1 and m:n
protection in MPLS-TP networks without the use of control plane protection in MPLS-TP networks without the use of control plane
protocols. Existing solutions based on a control plane such as GMPLS protocols. Existing solutions based on a control plane such as GMPLS
may be able to restore user traffic when multiple failures occur. may be able to restore user traffic when multiple failures occur.
Some networks however do not use full control plane operation for Some networks however do not use full control plane operation for
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This general scenario is illustrated in Figure 1 which shows a This general scenario is illustrated in Figure 1 which shows a
protection domain with n working entities and m protection entities protection domain with n working entities and m protection entities
between Node A and Node Z. between Node A and Node Z.
At Node A, traffic is transported over its respective working entity At Node A, traffic is transported over its respective working entity
and may be simultaneously transported over one of its protection and may be simultaneously transported over one of its protection
entities (in case of a broadcast bridge), or it is transported over 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 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 protection entities (in case of a selector bridge). At Node Z, the
traffic is selected from either its working entity or one of the traffic is selected from either its working entity or one of the
protection entities. 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.
+------+ +------+ +------+ +------+
|Node A| working entity #1 |Node Z| |Node A| working entity #1 |Node Z|
| |=============================| | | |=============================| |
| | .... | | | | .... | |
| | working entity #n | | | | working entity #n | |
| |=============================| | | |=============================| |
| | | | | | | |
| | | | | | | |
| | protection entity #1 | | | | protection entity #1 | |
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|--------Protection Domain--------| |--------Protection Domain--------|
Figure 1: m:n protection domain Figure 1: m:n protection domain
3. Use cases 3. Use cases
3.1. m:1 (m > 1) protection 3.1. m:1 (m > 1) protection
With MPLS-TP linear protection such as 1+1/1:1 protection, when a 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 single failure is detected on the working entity, the service can be
restored using the protection entity. During this time however, the restored using the protection entity. However, during the time the
traffic is unprotected until the working entity is restored. protection is active the traffic is unprotected until the working
entity is restored.
m:1 protection can increase service availability and reduce m:1 protection can increase service availability and reduce
operational pressure since multiple protection entities are operational pressure since multiple protection entities are
available. For any m > 1, m - 1 protection entities may fail and the available. For any m > 1, m - 1 protection entities may fail and the
service still would have a protection entity available. service still would have a protection entity available.
There are different ways to provision these alternative protection There are different ways to provision these alternative protection
entities which are outlined in the following sub-sections. entities which are outlined in the following sub-sections.
3.1.1. Pre-configuration 3.1.1. Pre-configuration
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as long as these entities do not carry protected traffic. as long as these entities do not carry protected traffic.
3.1.2. On-demand configuration 3.1.2. On-demand configuration
The protection relationship between a working entity and a protection The protection relationship between a working entity and a protection
entity is configured while the system is in operation. entity is configured while the system is in operation.
Additional protection entities are configured by either a control Additional protection entities are configured by either a control
plane protocol or static configuration using a management system plane protocol or static configuration using a management system
directly after failure detection and/or notification of either the directly after failure detection and/or notification of either the
working entity or the protection entities. 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 3.2. m:n (m, n > 1, n >= m > 1) protection
In order to reduce the cost of protection entities, in the m:n In order to reduce the cost of protection entities, in the m:n
scenario, m dedicated protection transport entities are sharing scenario, m dedicated protection transport entities are sharing
protection resources for n working transport entities. protection resources for n working transport entities.
The bandwidth of each protection entity should be allocated in such a 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 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 in case at least one of the m protection entities is available. When
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R2. MPLS-TP SHOULD support m:n (m, n > 1, n >= m > 1) protection. R2. MPLS-TP SHOULD support m:n (m, n > 1, n >= m > 1) protection.
1. An m:n protection mechanism MUST protect against multiple 1. An m:n protection mechanism MUST protect against multiple
failures that are simultaneously detected on both a working failures that are simultaneously detected on both a working
entity and a protection entity or multiple working entities. entity and a protection entity or multiple working entities.
2. A priority scheme MUST be provided, since protection resources 2. A priority scheme MUST be provided, since protection resources
are shared by multiple working entities dynamically. 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 5. Security Considerations
General security considerations for MPLS-TP are covered in [RFC5921]. General security considerations for MPLS-TP are covered in [RFC5921].
The security considerations for the generic associated control The security considerations for the generic associated control
channel are described in [RFC5586]. The requirements described in channel are described in [RFC5586]. The requirements described in
this document are extensions to the requirements presented in this document are extensions to the requirements presented in
[RFC5654] and does not introduce any new security risks. [RFC5654] and does not introduce any new security risks.
6. Normative References 6. Normative References
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