Network Working Group W. Cheng Internet-Draft L. Wang Intended status: Standards Track H. Li Expires: February 2, 2017 China Mobile K. Liu Huawei Technologies S. Davari Broadcom Corporation J. Dong Huawei Technologies A. D'Alessandro Telecom Italia August 1, 2016 Dual-Homing Coordination for MPLS Transport Profile (MPLS-TP) Pseudowires Protection draft-ietf-pals-mpls-tp-dual-homing-coordination-04 Abstract In some scenarios, the MPLS Transport Profile (MPLS-TP) Pseudowires (PWs) are provisioned through either static configuration or management plane, where a dynamic control plane is not available. A fast protection mechanism for MPLS-TP PWs is needed to protect against the failure of Attachment Circuit (AC), the failure of Provider Edge (PE) and also the failure in the Packet Switched Network (PSN). The framework and typical scenarios of dual-homing PW local protection are described in [draft-ietf-pals-mpls-tp-dual- homing-protection]. This document proposes a dual-homing coordination mechanism for MPLS-TP PWs, which is used for state exchange and switchover coordination between the dual-homing PEs for dual-homing PW local protection. Requirements Language 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 RFC 2119 [RFC2119]. 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 Cheng, et al. Expires February 2, 2017 [Page 1] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 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 February 2, 2017. 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 2. Overview of the Proposed Solution . . . . . . . . . . . . . . 3 3. Protocol Extensions for Dual-Homing MPLS-TP PW Protection . . 4 3.1. Information Exchange Between Dual-Homing PEs . . . . . . 4 3.2. Protection Procedures . . . . . . . . . . . . . . . . . . 8 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 6.1. Normative References . . . . . . . . . . . . . . . . . . 12 6.2. Informative References . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 1. Introduction [RFC6372], [RFC6378] and [RFC7771] describe the framework and mechanism of MPLS-TP Linear protection, which can provide protection for the MPLS LSP and PW between the edge nodes. These mechanisms cannot protect the failure of the Attachment Circuit (AC) or the edge nodes. [RFC6718] and [RFC6870] specifies the PW redundancy framework and mechanism for protecting the AC or edge node failure by adding one or more edge nodes, but it requires PW switchover in case of a AC Cheng, et al. Expires February 2, 2017 [Page 2] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 failure, also PW redundancy relies on PSN protection mechanisms to protect the failure of PW. In some scenarios such as mobile backhauling, the MPLS PWs are provisioned with dual-homing topology, in which at least the CE node on one side is dual-homed to two PEs. If a failure occurs in the primary AC, operators usually prefer to perform local switchover in the dual-homing PE side and keep the working pseudowire unchanged if possible. This is to avoid massive PW switchover in the mobile backhaul network due to the AC failure in the mobile core site, which may in turn lead to congestion due to the migration of traffic from the paths preferred by the network planners. Similarly, as muliple PWs share the physical AC in the mobile core site, it is preferable to keep using the working AC when one working PW fails in the PSN network, which could avoid unnecessary AC switchover for other PWs. A fast dual-homing PW protection mechanism is needed to protect the failure in AC, the PE node and the PSN network to meet the above requirements. [I-D.ietf-pals-mpls-tp-dual-homing-protection] describes a framework and several scenarios of dual-homing pseudowire (PW) local protection. This document proposes a dual-homing coordination mechanism for static MPLS-TP PWs, which is used for information exchange and switchover coordination between the dual-homing PEs for the dual-homing PW local protection. The proposed mechanism has been implemented and deployed in several mobile backhaul networks which use static MPLS-TP PWs for the backhauling of mobile traffic from the radio access sites to the core site. 2. Overview of the Proposed Solution Linear protection mechanisms for MPLS-TP network are defined in [RFC6378], [RFC7271] and [RFC7324]. When such mechanisms are applied to PW linear protection [RFC7771], both the working PW and the protection PW are terminated on the same PE node. In order to provide dual-homing protection for MPLS-TP PWs, some additional mechanisms are needed. In MPLS-TP PW dual-homing protection, the linear protection mechanism as defined in [RFC6378] [RFC7271] and [RFC7324] on the single-homing PE (e.g. PE3 in figure 1) is not changed, while on the dual-homing side, the working PW and protection PW are terminated on two dual- homing PEs (e.g. PE1 and PE2 in figure 1) respectively to protect the failure occurs in the dual-homing PEs and the connected ACs. As specified in [I-D.ietf-pals-mpls-tp-dual-homing-protection], a dedicated Dual-Node Interconnection (DNI) PW is provisioned between the two dual-homing PE nodes, which is used to bridge the traffic between the dual-homing PEs when a failure happens in the working PW Cheng, et al. Expires February 2, 2017 [Page 3] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 or the primary AC. In order to make the linear protection mechanism work in the dual-homing PEs scenario, coordination between the dual- homing PE nodes is needed, so that the dual-homing PEs can set the connection between the AC, the service PW and the DNI-PW properly in a coordinated fashion. +----------------+ / | +--------+ AC1 /| PE1 | Working PW | | / | X----------------X | / | | Service PW1 | | +---/+ +--------X-------+ | | +----+ | | | DNI PW | PE3 | | | | CE1| | | |---| CE2| +---\+ +--------X-------+ | | +----+ \ | | Protection PW | | \ | X----------------X | AC2 \| | Service PW2 | | \ PE2 | +--------+ +----------------+ Figure 1. Dual-homing Protection with DNI-PW 3. Protocol Extensions for Dual-Homing MPLS-TP PW Protection In dual-homing MPLS-TP PW local protection, the forwarding state of the dual-homing PEs are determined by the forwarding state machine as defined in [I-D.ietf-pals-mpls-tp-dual-homing-protection]. In order to achieve the dual-homing MPLS-TP PW protection, coordination between the dual-homing PE nodes is needed to exchange the PW status and protection coordination requests. 3.1. Information Exchange Between Dual-Homing PEs The coordination information will be sent on the DNI PW over the G-ACh as described in [RFC5586]. A new G-ACh channel type is defined for the dual-homing coordination between the dual-homing PEs of MPLS- TP PWs. This channel type can be used for the exchange of different kinds of information between the dual-homing PEs. This document uses this channel type for the exchange of PW status and switchover coordination between the dual-homing PEs. Other potential usages of this channel type are for further study and are out of the scope of this document. The MPLS-TP Dual-Homing Coordination (DHC) message is sent on the DNI PW between the dual-homing PEs. The format of MPLS-TP DHC message is shown below: Cheng, et al. Expires February 2, 2017 [Page 4] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 1|Version| Flags | DHC Code Point | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Dual-Homing PEs Group ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TLV Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ TLVs ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2. MPLS-TP Dual-Homing Coordination Message The Dual-Homing Group ID is a 4-octet unsigned integer to identify the dual-homing group which the dual-homing PEs belong to. It MUST be the same at both PEs in the same group. The TLV Length field specifies the total length in octets of the subsequent TLVs. In this document, two TLVs are defined in MPLS-TP Dual-Homing Coordination message for dual-homing MPLS-TP PW protection: Type Description Length 1 PW Status 20 Bytes 2 Dual-Node Switching 16 Bytes The PW Status TLV is used by a dual-homing PE to report its service PW status to the other dual-homing PE in the same dual-homing group. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type=1 (PW Status) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination Dual-homing PE Node_ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Dual-homing PE Node_ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DNI PW-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags |P| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Service PW Status |D|F| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3. PW Status TLV Cheng, et al. Expires February 2, 2017 [Page 5] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 - The Length field specifies the length in octets of the value field of the TLV. - The Destination Dual-homing PE Node_ID is the 32-bit identifier of the receiver PE. Usually it is the same as the LSR-ID of the receiver PE. - The Source Dual-homing PE Node_ID is the 32-bit identifier of the sending PE. Usually it is the same as the LSR-ID of the sending PE. - The DNI PW-ID field contains the 32-bit PW ID of the DNI PW. - The Flags field contains 32 bit flags, in which: o The P (Protection) bit indicates whether the Source Dual-homing PE is the working PE (P=0) or the protection PE (P=1). o Other bits are reserved for future use, which MUST be set to 0 on transmission and MUST be ignored upon receipt. - The Service PW Status field indicates the status of the Service PW between the sending PE and the remote PE. Currently two bits are defined in the Service PW Status field: o F bit: If set, it indicates Signal Fail (SF) [RFC6378] is generated on the service PW. It can be either a local request or a remote request received from the remote PE. o D bit: If set, it indicates Signal Degrade (SD) [RFC6378] generated on the service PW. It can be either a local request or a remote request received from the remote PE. o Other bits are reserved for future use, which MUST be set to 0 on transmission and MUST be ignored upon receipt. The Dual-Node Switching TLV is used by one dual-homing PE to send protection state coordination to the other PE in the same dual-homing group. Cheng, et al. Expires February 2, 2017 [Page 6] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type=2 (Dual-Node Switching) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination Dual-homing PE Node_ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Dual-homing PE Node_ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DNI PW-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags |S|P| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4. Dual-Node Switching TLV - The Length field specifies the length in octets of the value field of the TLV. - The Destination Dual-homing PE Node_ID is the 32-bit identifier of the receiver PE. Usually it is the same as the LSR-ID of the receiver PE. - The Source Dual-homing PE Node_ID is the 32-bit identifier of the sending PE. Usually it is the same as the LSR-ID of the sending PE. - The DNI PW-ID field contains the 32-bit PW-ID of the DNI PW. - The Flags field contains 32 bit flags, in which: o The P (Protection) bit indicates whether the Source Dual-homing PE is the working PE or the protection PE. It is set to 1 when the Source PE of the dual-node switching request is the protection PE. o The S (PW Switching) bit indicates which service PW is used for forwarding traffic. It is set to 0 when traffic will be transported on the working PW, and is set to 1 if traffic will be transported on the protection PW. The value of the S bit is determined by the protection coordination mechanism between the dual-homing PEs and the remote PE. o Other bits are reserved for future use, which MUST be set to 0 on transmission and MUST be ignored upon receipt. When a change of the service PW status is detected by one of the dual-homing PEs, it MUST be reflected in the PW Status TLV and sent to the other dual-homing PE immediately using 3 consecutive rapid DHC messages. After the transmission of the three rapid messages, the dual-homing PE MUST send the most recently transmitted service PW Cheng, et al. Expires February 2, 2017 [Page 7] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 status periodically to the other dual-homing PE using the continual DHC message. When one dual-homing PE determines that the active service PW needs to be switched from the working PW to the protection PW, It MUST send the Dual-Node Switching TLV to the other dual-homing PE immediately using 3 consecutive rapid DHC messages. After the transmission of the three rapid messages, the dual-homing PE MUST send the most recently transmitted Dual-Node Switching TLV periodically to the other dual-homing PE using the continual DHC messages. It is RECOMMENDED that the default interval of the first three rapid DHC messages is 3.3 ms, and the default interval of the subsequent messages is 1 second. Both the default frequency of the three rapid messages as well as the default frequency of the continual message transmission SHALL be configurable by the operator. 3.2. Protection Procedures The dual-homing MPLS-TP PW protection mechanism can be deployed with the existing AC redundancy mechanisms. On the PSN network side, PSN tunnel protection mechanism is not required, as the dual-homing PW protection can also protect the failure occurred in the PSN network. This section takes one-side dual-homing scenario as an example to describe the dual-homing PW protection procedures, the procedures for two-side dual-homing scenario would be similar. On dual-homing PE side, the role of working and protection PE are set by NMS or local configuration. The service PW connecting to the working PE is the working PW, and the service PW connecting to the protection PE is called the protection PW. On single-homing PE side, it just treats the working PW and protection PW as if they terminate on the same remote PE node, thus normal MPLS-TP protection coordination procedures still apply on the single-homing PE. The forwarding behavior of the dual-homing PEs is determined by the components shown in the figure below: Cheng, et al. Expires February 2, 2017 [Page 8] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 +---------------------------------+ +-----+ | PE1 (Working PE) | | | +---------------------------------+ | | | | | PW1 | | + Forwarder + Service X<-------->X | /| | PW | Working | | / +--------+--------+ | PW | | AC1 / | DNI PW | | | | / +--------X--------+---------------+ | | +-----+/ ^ | | | CE1 | | DNI PW | PE3 | +---+ +-----+ | | ---|CE3| \ V | | +---+ AC2 \ +--------X--------+---------------+ | | \ | DNI PW | | | | \ +--------+--------+ | | | \| | Service | PW2 | | + Forwarder + PW X<-------->X | | | |Protection| | +---------------------------------+ PW | | | PE2 (Protection PE) | | | +---------------------------------+ +-----+ Figure 5. Components of one-side dual-homing PW protection In figure 5, for each dual-homing PE, service PW is the PW used to carry service between the dual-homing PE and the remote PE. The state of the service PW is determined by the OAM mechanisms between the dual-homing PEs and the remote PE. DNI PW is provisioned between the two dual-homing PE nodes. It is used to bridge traffic when failure occurs in the PSN network or in the ACs. The state of DNI PW is determined by the OAM mechanism between the dual-homing PEs. Since DNI PW is used to carry both the coordination messages and the service traffic during protection switching, it is important to ensure the robustness of the DNI PW. In order to avoid the DNI PW failure due to the failure of a particular link, it is RECOMMENDED that multiple diverse links be deployed between the dual-homing PEs and the underlay LSP protection mechanism SHOULD be enabled. AC is the link which connects a dual-homing PE to the dual-homed CE. The status of AC is determined by some existing AC redundancy mechanisms, which is out of the scope of this document. In order to perform dual-homing PW local protection, the service PW status and Dual-node switching coordination requests are exchanged between the dual-homing PEs using the DHC message defined above. Cheng, et al. Expires February 2, 2017 [Page 9] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 Whenever a change of service PW status is detected by a dual-homing PE, it MUST be reflected in the PW Status TLV and sent to the other dual-homing PE immediately using using 3 consecutive rapid DHC messages. This way, both dual-homing PEs have the status of the working and protection PW consistently. When there is a switchover request either generated locally or received on the protection PW from the remote PE, based on the status of the working and protection service PW, along with the local and remote request of the protection coordination between the dual-homing PEs and the remote PE, the active/standby state of the service PW can be determined by the dual-homing PEs. As the remote protection coordination request is transmitted over the protection path, in this case the active/standby status of the service PW is determined by the protection PE in the dual-homing group. If it is determined on one dual-homing PE that switchover of service PW is needed, this dual-homing PE MUST set the S bit in the Dual-Node Switching TLV and send it to the other dual-homing PE immediately using 3 consecutive rapid DHC messages. With the exchange of service PW status and the switching request, both dual-homing PEs are consistent on the Active/Standby forwarding status of the working and protection service PWs. The status of DNI PW is determined by OAM mechanism, and the status of ACs are determined by existing AC redundancy mechanism, which is out of the scope of this document. The forwarding behavior on the dual-homing PE nodes is determined by the forwarding state machine as shown in table 1 of [I-D.ietf-pals-mpls-tp-dual-homing-protection]. Take the topology in figure 5 as an example, in normal state, the working PW (PW1) is in active state, the protection PW (PW2) is in standby state, the DNI PW is up, and AC1 is in active state according to the AC redundancy mechanism. According to the forwarding state machine in table 1 of [I-D.ietf-pals-mpls-tp-dual-homing-protection], traffic will be forwarded through the working PW (PW1) and the primary AC (AC1). No traffic will go through the protection PE (PE2) or the DNI PW, as both the protection PW (PW2) and the AC connecting to PE2 are in standby state. If a failure occurs in AC1, the state of AC2 changes to active according to the AC redundancy mechanism, while there is no change in the state of the working and protection PWs. According to the forwarding state machine in table 1 of [I-D.ietf-pals-mpls-tp-dual-homing-protection], PE1 starts to forward traffic between the working PW and the DNI PW, and PE2 starts to forward traffic between AC2 and the DNI PW. It should be noted that in this case only AC switchover takes place, in the PSN network traffic is still forwarded using the working PW. Cheng, et al. Expires February 2, 2017 [Page 10] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 If a failure in the PSN network brings PW1 to down, the failure can be detected by PE1 or PE3 using some OAM mechanism. If PE1 detects the failure of PW1, it MUST inform PE2 the state of working PW using the PW Status TLV in the DHC messages and change the forwarding status of PW1 to standby. On receipt of the DHC message, PE2 SHOULD change the forwarding status of PW2 to active. Then according to the forwarding state machine in table 1 of [I-D.ietf-pals-mpls-tp-dual-homing-protection], PE1 SHOULD set up the connection between the DNI PW and AC1, and PE2 SHOULD set up the connection between PW2 and the DNI PW. According to the linear protection mechanism [RFC6378], PE2 also sends an appropriate protection coordination message over the protection PW (PW2) to PE3, so that PE3 changes the forwarding status of PW2 to active, thus switchover from PW1 to PW2. If PE3 detects the failure of PW1, according to linear protection mechanism [RFC6378], it sends a protection coordination message on the protection PW (PW2) to inform PE2 of the failure on the working PW. Upon receipt of the message, PE2 SHOULD change the forwarding status of PW2 to active and set up the connection according to the forwarding state machine in table 1 of [I-D.ietf-pals-mpls-tp-dual-homing-protection]. PE2 SHOULD send a DHC message to PE1 with the S bit set in the Dual-Node Switching TLV to coordinate the switchover on PE1 and PE2. This could be useful for a unidirectional failure which cannot be detected by PE1. If a failure brings the working PE (PE1) to down, the failure can be detected by both PE2 and PE3 using some OAM mechanisms. Both PE2 and PE3 SHOULD change the forwarding status of PW2 to active, and send a protection coordination message on the protection PW (PW2) to inform the remote side to switchover. According to AC redundancy mechanism, the status of AC1 changes to standby, and the state of AC2 changes to active. According to the forwarding state machine in table 1 of [I-D.ietf-pals-mpls-tp-dual-homing-protection], PE2 starts to forward traffic between the PW2 and AC2. 4. IANA Considerations This documnet requests that IANA assigns one new channel type for "MPLS-TP Dual-Homing Coordination message" from the "MPLS Generalized Associated Channel (G-ACh) Types (including Pseudowire Associated Channel Types)" registry of the "Generic Associated Channel (G-ACh) Parameters" registry. Value Description Reference TBD MPLS-TP Dual-Homing Coordination message [This document] This documnet requests that IANA creates a new sub-registry called "MPLS-TP DHC TLVs" in the "Generic Associated Channel (G-ACh) Parameters" registry, with fields and initial allocations as follows: Cheng, et al. Expires February 2, 2017 [Page 11] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 Type Description Length Reference 0x00 Reserved 0x01 PW Status 20 Bytes [this document] 0x02 Dual-Node Switching 16 Bytes [this document] The allocation policy for this registry is IETF Review or IESG Approval. 5. Security Considerations Procedures and protocol extensions defined in this document do not affect the security model of MPLS-TP linear protection as defined in [RFC6378]. Please refer to [RFC5920] for MPLS security issues and generic methods for securing traffic privacy and integrity. 6. References 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., "MPLS Generic Associated Channel", RFC 5586, DOI 10.17487/RFC5586, June 2009, . [RFC6378] Weingarten, Y., Ed., Bryant, S., Osborne, E., Sprecher, N., and A. Fulignoli, Ed., "MPLS Transport Profile (MPLS- TP) Linear Protection", RFC 6378, DOI 10.17487/RFC6378, October 2011, . [RFC7271] Ryoo, J., Ed., Gray, E., Ed., 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, DOI 10.17487/RFC7271, June 2014, . [RFC7324] Osborne, E., "Updates to MPLS Transport Profile Linear Protection", RFC 7324, DOI 10.17487/RFC7324, July 2014, . Cheng, et al. Expires February 2, 2017 [Page 12] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 6.2. Informative References [I-D.ietf-pals-mpls-tp-dual-homing-protection] Cheng, W., Wang, L., Li, H., Liu, K., Davari, S., Dong, J., and A. D'Alessandro, "Dual-Homing Protection for MPLS and MPLS-TP Pseudowires", draft-ietf-pals-mpls-tp-dual- homing-protection-03 (work in progress), June 2016. [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010, . [RFC6372] Sprecher, N., Ed. and A. Farrel, Ed., "MPLS Transport Profile (MPLS-TP) Survivability Framework", RFC 6372, DOI 10.17487/RFC6372, September 2011, . [RFC6718] Muley, P., Aissaoui, M., and M. Bocci, "Pseudowire Redundancy", RFC 6718, DOI 10.17487/RFC6718, August 2012, . [RFC6870] Muley, P., Ed. and M. Aissaoui, Ed., "Pseudowire Preferential Forwarding Status Bit", RFC 6870, DOI 10.17487/RFC6870, February 2013, . [RFC7771] Malis, A., Ed., Andersson, L., van Helvoort, H., Shin, J., Wang, L., and A. D'Alessandro, "Switching Provider Edge (S-PE) Protection for MPLS and MPLS Transport Profile (MPLS-TP) Static Multi-Segment Pseudowires", RFC 7771, DOI 10.17487/RFC7771, January 2016, . Authors' Addresses Weiqiang Cheng China Mobile No.32 Xuanwumen West Street Beijing 100053 China Email: chengweiqiang@chinamobile.com Cheng, et al. Expires February 2, 2017 [Page 13] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 Lei Wang China Mobile No.32 Xuanwumen West Street Beijing 100053 China Email: Wangleiyj@chinamobile.com Han Li China Mobile No.32 Xuanwumen West Street Beijing 100053 China Email: Lihan@chinamobile.com Kai Liu Huawei Technologies Huawei Base, Bantian, Longgang District Shenzhen 518129 China Email: alex.liukai@huawei.com Shahram Davari Broadcom Corporation 3151 Zanker Road San Jose 95134-1933 United States Email: davari@broadcom.com Jie Dong Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing 100095 China Email: jie.dong@huawei.com Cheng, et al. Expires February 2, 2017 [Page 14] Internet-Draft Dual-Homing Coordination for MPLS-TP PWs August 2016 Alessandro D'Alessandro Telecom Italia via Reiss Romoli, 274 Torino 10148 Italy Email: alessandro.dalessandro@telecomitalia.it Cheng, et al. Expires February 2, 2017 [Page 15]