--- 1/draft-cui-mpls-tp-mfp-use-case-and-requirements-05.txt 2016-01-06 13:15:28.043661971 -0800 +++ 2/draft-cui-mpls-tp-mfp-use-case-and-requirements-06.txt 2016-01-06 13:15:28.067662560 -0800 @@ -1,24 +1,24 @@ Network Working Group Z. Cui Internet-Draft R. Winter Intended status: Informational NEC -Expires: January 7, 2016 H. Shah +Expires: July 9, 2016 H. Shah Ciena S. Aldrin Huawei Technologies M. Daikoku KDDI - July 6, 2015 + January 6, 2016 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 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. @@ -35,25 +35,25 @@ 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 January 7, 2016. + This Internet-Draft will expire on July 9, 2016. 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. 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 @@ -99,21 +99,21 @@ 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 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 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 @@ -171,21 +171,23 @@ 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. + 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| | |=============================| | | | .... | | | | working entity #n | | | |=============================| | | | | | | | | | | | protection entity #1 | | @@ -197,22 +199,23 @@ |--------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. During this time however, the - traffic is unprotected until the working entity is restored. + 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 @@ -226,21 +229,22 @@ as long as these entities do not carry protected traffic. 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. + 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 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 @@ -275,20 +279,24 @@ 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