Network Working Group. Intended status: Standards Track. J. Dong Huawei Technologies A. D Alessandro Telecom Italia April 26, 2017

Transcription

1 Network Working Group Internet-Draft Intended status: Standards Track Expires: October 28, 2017 W. Cheng L. Wang H. Li China Mobile J. Dong Huawei Technologies A. D Alessandro Telecom Italia April 26, 2017 Abstract Dual-Homing Coordination for MPLS Transport Profile (MPLS-TP) Pseudowires Protection draft-ietf-pals-mpls-tp-dual-homing-coordination-06 In some scenarios, MPLS Transport Profile (MPLS-TP) Pseudowires (PWs) (RFC 5921) may be statically configured, when a dynamic control plane is not available. A fast protection mechanism for MPLS-TP PWs is needed to protect against the failure of an Attachment Circuit (AC), the failure of a Provider Edge (PE), or a failure in the Packet Switched Network (PSN). The framework and typical scenarios of dualhoming PW local protection are described in [draft-ietf-pals-mpls-tpdual-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 working documents as Internet-Drafts. The list of current Internet- Drafts is at Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any Cheng, et al. Expires October 28, 2017 [Page 1]

2 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April 2017 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 October 28, Copyright Notice Copyright (c) 2017 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 ( 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 Overview of the Proposed Solution Protocol Extensions for Dual-Homing MPLS-TP PW Protection Information Exchange Between Dual-Homing PEs Protection Procedures IANA Considerations Security Considerations Contributors References Normative References Informative References Authors Addresses Introduction [RFC6372], [RFC6378] and [RFC7771] describe the framework and mechanism of MPLS Transport Profile (MPLS-TP) linear protection, which can provide protection for the MPLS Label Switched Path (LSP) and Pseudowires (PWs) 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 an AC failure, also PW redundancy relies on Packet Switched Network (PSN) protection mechanisms to protect the failure of PW. Cheng, et al. Expires October 28, 2017 [Page 2]

3 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April 2017 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 Provider Edge (PE) nodes. 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 multiple 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 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 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 dualhoming PEs (e.g. PE1 and PE2 in Figure 1) respectively to protect a failure occuring in a PE or a connected AC. As described in [I-D.ietf-pals-mpls-tp-dual-homing-protection], a dedicated Dual-Node Interconnection (DNI) PW is used between the two dual-homing PE nodes to forward the traffic. In order to utilize the linear protection mechanism [RFC7771] in the dual-homing PEs scenario, coordination between the dual-homing PE nodes is needed, so that the dual-homing PEs can switch the connection between the AC, the service PW and the DNI-PW properly in a coordinated fashion by the forwarder. Cheng, et al. Expires October 28, 2017 [Page 3]

4 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April PE Working X Forwarder + Service X X / PW Service PW1 AC1 / / DNI PW +---* X ^ CE1 DNI PW PE CE2 V +---* X \ DNI PW AC2 \ Protection \ Service X X X Forwarder + PW Service PW PE 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 in Table 1. Cheng, et al. Expires October 28, 2017 [Page 4]

5 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April Service PW AC DNI PW Forwarding Behavior Active Active Up Service PW <-> AC Active Standby Up Service PW <-> DNI PW Standby Active Up DNI PW <-> AC Standby Standby Up Drop all packets Active Active Down Service PW <-> AC Active Standby Down Drop all packets Standby Active Down Drop all packets Standby Standby Down Drop all packets Table 1. Dual-homing PE Forwarding State Machine 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 Information Exchange Between Dual-Homing PEs The coordination information will be sent on the DNI PW over the Generic Associated Channel (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 types of information between the dual-homing PEs. This document uses this channel type for the exchange of PW status and switchover coordination between the dualhoming 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 the MPLS-TP DHC message is shown below: Cheng, et al. Expires October 28, 2017 [Page 5]

6 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April Version Reserved DHC Channel Type Dual-Homing PEs Group ID TLV Length Reserved TLVs Figure 2. MPLS-TP Dual-Homing Coordination Message The first 4-octets is the common G-ACh header as specified in [RFC5586]. The DHC Channel Type is the G-ACh channel type code point to be assigned by IANA. 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. Cheng, et al. Expires October 28, 2017 [Page 6]

7 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April 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 - 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 [RFC6370] which supports both IPv4 and IPv6 environments. 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 [RFC6370] which supports both IPv4 and IPv6 environments. Usually it is the same as the LSR-ID of the sending PE. - The DNI PW-ID field contains the 32-bit PW ID [RFC4447] 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] on the service PW. It can be either a local request generated by the PE itself or a remote request received from the remote PE. Cheng, et al. Expires October 28, 2017 [Page 7]

8 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April 2017 o D bit: If set, it indicates Signal Degrade (SD) [RFC6378] 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 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 [RFC6370]. 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 [RFC6370]. Usually it is the same as the LSR-ID of the sending PE. - The DNI PW-ID field contains the 32-bit PW-ID [RFC4447] 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 Cheng, et al. Expires October 28, 2017 [Page 8]

9 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April 2017 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 as quickly as possible to allow for fast protection switching using 3 consecutive DHC messages. This set of three messages allows for fast protection switching even if one or two of these packets are lost or corrupted. After the transmission of the three rapid messages, the dual-homing PE MUST send the most recently transmitted service PW status periodically to the other dual-homing PE on a continual basis using the 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 as quickly as possible to allow for fast protection switching using 3 consecutive DHC messages. After the transmission of the three messages, the protection PW would become the active service PW, and the dual-homing PE MUST send the most recently transmitted Dual-Node Switching TLV periodically to the other dual-homing PE on a continual basis using the DHC message. It is RECOMMENDED that the default interval of the first three rapid DHC messages is 3.3 ms similar to [RFC6378], and the default interval of the subsequent messages is 1 second. Both the default interval of the three consecutive messages as well as the default interval of the periodical messages SHALL be configurable by the operator 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 if a failure occurs in the PSN network. This section uses the 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 the dual-homing PE side, the role of working and protection PE are set by the management system or local configuration. The service PW Cheng, et al. Expires October 28, 2017 [Page 9]

10 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April 2017 connecting to the working PE is the working PW, and the service PW connecting to the protection PE is called the protection PW. On the single-homing PE side, it 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 singlehoming PE. The forwarding behavior of the dual-homing PEs is determined by the components shown in the figure below: PE1 (Working PE) PW1 Working + Forwarder + Service X< >X / PW / AC1 / DNI PW / X / AC ^ DNI PW CE1 redundancy PE3 +-- CE mechanism DHC message \ V exchange AC2 \ X \ DNI PW \ PW2 \ Service Protection + Forwarder + PW X< >X PSC message PE2 (Protection PE) exchange Figure 5. Components of one-side dual-homing PW protection In Figure 5, for each dual-homing PE, the 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 Operation Administration and Maintanence (OAM) mechanisms between the dual-homing PEs and the remote PE. The DNI PW is provisioned between the two dual-homing PE nodes. It is used to bridge traffic when a failure occurs in the PSN network or in the ACs. The state of the DNI PW is determined by the OAM mechanism between the dual-homing PEs. Since the DNI PW is used to carry both the DHC 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 Cheng, et al. Expires October 28, 2017 [Page 10]

11 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April 2017 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. The AC is the link which connects a dual-homing PE to the dual-homed CE. The status of AC is determined by the existing AC redundancy mechanisms, this 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 in Section 3.1. 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 the 3 consecutive DHC messages. After the transmission of the three rapid messages, the dual-homing PE MUST send the most recently transmitted service PW status periodically to the other dual-homing PE on a continual basis using the DHC message. 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 the 3 consecutive 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 the DNI PW is determined by PW OAM mechanism as defined in [RFC5085], and the status of ACs are determined by existing AC redundancy mechanisms, both are 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. Using 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 Cheng, et al. Expires October 28, 2017 [Page 11]

12 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April 2017 to the AC redundancy mechanism. According to the forwarding state machine in Table 1, 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, 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. If a failure in the PSN network brings PW1 down, the failure can be detected by PE1 or PE3 using existing OAM mechanisms. 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, 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 [RFC6378] over the protection PW (PW2) to PE3 for the remote side to 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. 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 is useful for a unidirectional failure which cannot be detected by PE1. If a failure brings the working PE (PE1) down, the failure can be detected by both PE2 and PE3 using existing OAM mechanisms. Both PE2 and PE3 SHOULD change the forwarding status of PW2 to active, and send a protection coordination message [RFC6378] on the protection PW (PW2) to inform the remote side to switchover. According to the existing AC redundancy mechanisms, the status of AC1 changes to standby, and the state of AC2 changes to active. According to the forwarding state machine in Table 1, PE2 starts to forward traffic between the PW2 and AC2. Cheng, et al. Expires October 28, 2017 [Page 12]

13 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April IANA Considerations This document 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 document 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: 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 as specified in [RFC5226]. 5. Security Considerations MPLS-TP is a subset of MPLS and so builds upon many of the aspects of the security model of MPLS. Please refer to [RFC5920] for generic MPLS security issues and methods for securing traffic privacy and integrity. The DHC message defined in this document contains control information, if it is injected or modified by an attacker, the dualhoming PEs might not agree on which PE should be used to deliver the CE traffic, and this could be used as a denial of service attack against the CE. It is important that the DHC message is used within a trusted MPLS-TP network domain as described in [RFC6941]. The DHC message is carried in the G-ACh [RFC5586], so it is dependent on the security of the G-ACh itself. The G-ACh is a generalization of the Associated Channel defined in [RFC4385]. Thus, this document relies on the security mechanisms provided for the Associated Channel as described in those two documents. As described in the security considerations of [RFC6378], the G-ACh is essentially connection oriented so injection or modification of control messages requires the subversion of a transit node. Such subversion is generally considered hard in connection oriented MPLS networks and impossible to protect against at the protocol level. Cheng, et al. Expires October 28, 2017 [Page 13]

14 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April 2017 Management level techniques are more appropriate. The procedures and protocol extensions defined in this document do not affect the security model of MPLS-TP linear protection as defined in [RFC6378]. Uniqueness of the identifiers defined in this document is guaranteed by the assigner (e.g. the operator). Failure by an assigner to use unique values within the specified scoping for any of the identifiers defined herein could result in operational problems. Please refer to [RFC6370] for more details about the uniqueness of the identifiers. 6. Contributors The following individuals substantially contributed to the content of this document: Kai Liu Huawei Technologies Shahram Davari Broadcom Corporation 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI /RFC2119, March 1997, < [RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, DOI /RFC4447, April 2006, < [RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires", RFC 5085, DOI /RFC5085, December 2007, < [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., "MPLS Generic Associated Channel", RFC 5586, DOI /RFC5586, June 2009, < Cheng, et al. Expires October 28, 2017 [Page 14]

15 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April 2017 [RFC6370] Bocci, M., Swallow, G., and E. Gray, "MPLS Transport Profile (MPLS-TP) Identifiers", RFC 6370, DOI /RFC6370, September 2011, < [RFC6378] Weingarten, Y., Ed., Bryant, S., Osborne, E., Sprecher, N., and A. Fulignoli, Ed., "MPLS Transport Profile (MPLS- TP) Linear Protection", RFC 6378, DOI /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 /RFC7271, June 2014, < [RFC7324] Osborne, E., "Updates to MPLS Transport Profile Linear Protection", RFC 7324, DOI /RFC7324, July 2014, < Informative References [I-D.ietf-pals-mpls-tp-dual-homing-protection] Cheng, W., Wang, L., Li, H., Davari, S., and J. Dong, "Dual-Homing Protection for MPLS and MPLS-TP Pseudowires", draft-ietf-pals-mpls-tp-dual-homing-protection-05 (work in progress), January [RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, DOI /RFC4385, February 2006, < [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, DOI /RFC5226, May 2008, < [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS Networks", RFC 5920, DOI /RFC5920, July 2010, < [RFC6372] Sprecher, N., Ed. and A. Farrel, Ed., "MPLS Transport Profile (MPLS-TP) Survivability Framework", RFC 6372, DOI /RFC6372, September 2011, < Cheng, et al. Expires October 28, 2017 [Page 15]

16 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April 2017 [RFC6718] Muley, P., Aissaoui, M., and M. Bocci, "Pseudowire Redundancy", RFC 6718, DOI /RFC6718, August 2012, < [RFC6870] Muley, P., Ed. and M. Aissaoui, Ed., "Pseudowire Preferential Forwarding Status Bit", RFC 6870, DOI /RFC6870, February 2013, < [RFC6941] Fang, L., Ed., Niven-Jenkins, B., Ed., Mansfield, S., Ed., and R. Graveman, Ed., "MPLS Transport Profile (MPLS-TP) Security Framework", RFC 6941, DOI /RFC6941, April 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 /RFC7771, January 2016, < Authors Addresses Weiqiang Cheng China Mobile No.32 Xuanwumen West Street Beijing China chengweiqiang@chinamobile.com Lei Wang China Mobile No.32 Xuanwumen West Street Beijing China Wangleiyj@chinamobile.com Han Li China Mobile No.32 Xuanwumen West Street Beijing China Lihan@chinamobile.com Cheng, et al. Expires October 28, 2017 [Page 16]

17 Internet-Draft Dual-Homing Coordination for MPLS-TP PWs April 2017 Jie Dong Huawei Technologies Huawei Campus, No. 156 Beiqing Rd. Beijing China Alessandro D Alessandro Telecom Italia via Reiss Romoli, 274 Torino Italy alessandro.dalessandro@telecomitalia.it Cheng, et al. Expires October 28, 2017 [Page 17]

18 INTERNET-DRAFT Intended Status: Standard Track Updates: RFC7385 Sami Boutros(Ed.) VMware Siva Sivabalan(Ed.) Cisco Systems Expires: May 16, 2018 November 12, 2017 Signaling Root-Initiated Point-to-Multipoint Pseudowire using LDP draft-ietf-pals-p2mp-pw-04.txt Abstract This document specifies a mechanism to signal Point-to-Multipoint (P2MP) Pseudowires (PW) tree using LDP. Such a mechanism is suitable for any Layer 2 VPN service requiring P2MP connectivity over an IP or MPLS enabled PSN. A P2MP PW established via the proposed mechanism is root initiated. This document updates RFC7385 by re-assigning reserved value 0xFF to be the wildcard transport tunnel type. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at The list of Internet-Draft Shadow Directories can be accessed at Copyright and License Notice Copyright (c) 2017 IETF Trust and the persons identified as the Sivabalan & Boutros Expires May 16, 2018 [Page 1]

19 INTERNET DRAFT P2MP PW November 12, 2017 document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust s Legal Provisions Relating to IETF Documents ( 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 Terminology Signaling P2MP PW PW ingress to egress incompatibility issues P2MP PW FEC P2MP PW Upstream FEC Element P2P PW Downstream FEC Element Typed Wildcard FEC Format for new FEC Group ID usage Generic Label TLV LDP Capability Negotiation P2MP PW Status Security Considerations Acknowledgment IANA Considerations FEC Type Name Space LDP TLV Type mldp Opaque Value Element TLV Type Selective Tree Interface Parameter sub-tlv Type WildCard PMSI tunnel type References Normative References Informative References Contributors Authors Addresses Sivabalan & Boutros Expires May 16, 2018 [Page 2]

20 INTERNET DRAFT P2MP PW November 12, Introduction A Point-to-Multipoint (P2MP) Pseudowire (PW) emulates the essential attributes of a unidirectional P2MP Telecommunications service such as P2MP ATM over PSN. A major difference between a Point-to-Point (P2P) PW outlined in [RFC3985] and a P2MP PW is that the former is intended for bidirectional service whereas the latter is intended for both unidirectional, and optionally bidirectional service. Requirements for P2MP PW are described in [RFC7338]. P2MP PW can be constructed as either Single Segment (P2MP SS-PW) or Multi Segment (P2MP MS-PW) Pseudowires as mentioned in [RFC7338]. P2MP MS-PW is outside the scope of this document. A reference model or a P2MP PW is depicted in Figure 1 below. A transport LSP associated with a P2MP SS-PW SHOULD be a P2MP MPLS LSP (i.e., P2MP TE tunnel established via RSVP-TE [RFC4875] or P2MP LSP established via mldp [RFC6388]) spanning from the Root-PE to the Leaf-PE(s) of the P2MP SS-PW tree. For example, in Figure 1, PW1 can be associated with a P2MP TE tunnel or P2MP LSP setup using mldp originating from PE1 and terminating at PE2, PE3 and PE4. < P2MP PW > Native Native Service <--PSN1-> <--PSN2-> Service (AC) V V V V V V (AC) P1 ========= T-PE2 AC PW1...> > CE3 T-PE1 =========. ========= PW ========= ========= T-PE3 AC AC1....PW1...> > CE4 CE >... ========= ========= P2 ========= T-PE4 AC PW1...PW1...> > CE5 ========= ========= Figure 1: P2MP PW Mechanisms for establishing P2P SS-PW using LDP are described in [RFC4447bis]. This document specify a method of signaling P2MP PW using LDP. In particular, this document defines new FEC, TLVs, parameters, and status codes to facilitate LDP to signal and maintain P2MP PWs. Sivabalan & Boutros Expires May 16, 2018 [Page 3]

21 INTERNET DRAFT P2MP PW November 12, 2017 As outlined in [RFC7338], even though the traffic flow from a Root-PE (R-PE) to Leaf-PE(s) (L-PEs) is P2MP in nature, it may be desirable for any L-PE to send unidirectional P2P traffic destined only to the R-PE. The proposed mechanism takes such option into consideration. The P2MP PW requires an MPLS LSP to carry the PW traffic, and the MPLS packets carrying the PW upstream label will be encapsulated according to the methods described in [RFC5332]. 1.1 Terminology 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]. FEC: Forwarding Equivalence Class LDP: Label Distribution Protocol mldp: Label Distribution Protocol for P2MP/MP2MP LSP LSP: Label Switching Path MS-PW: Multi-Segment Pseudowire P2P: Point to Point P2MP: Point to Multipoint PE: Provider Edge PSN: Packet Switched Network PW: Pseudowire SS-PW: Single-Segment Pseudowire S-PE: Switching Provider Edge of MS-PW TE: Traffic Engineering R-PE: Root-PE - ingress PE, PE initiating P2MP PW setup. L-PE: Leaf-PE - egress PE. 2. Signaling P2MP PW Sivabalan & Boutros Expires May 16, 2018 [Page 4]

22 INTERNET DRAFT P2MP PW November 12, 2017 In order to advertise labels as well as exchange PW related LDP messages, PEs must establish LDP sessions among themselves. A PE discovers other PEs that are to be connected via P2MP PWs either via manual configuration or autodiscovery [RFC6074]. R-PE and each L-PE MUST be configured with the same FEC as defined in the following section. P2MP PW requires that there is an active P2MP PSN LSP set up between R-PE and L-PE(s). Note that the procedure to set up the P2MP PSN LSP is different depending on the signaling protocol used (RSVP-TE or mldp). In case of mldp, a Leaf-PE can decide to join the P2MP LSP at any time. In the case of RSVP-TE, the P2MP LSP is set up by the R-PE, generally at the initial service provisioning time. It should be noted that local policy can override any decision to join, add or prune existing or new L-PE(s) from the tree. In any case, the PW setup can ignore these differences, and simply assume that the P2MP PSN LSP is available when needed. P2MP PW signaling is initiated by the R-PE which sends a separate P2MP-PW LDP label mapping message to each of the the L-PE(s) belonging to that P2MP PW. This label mapping message will contain the following: 1. A FEC TLV containing P2MP PW Upstream FEC element that includes Transport LSP sub TLV. 2. An Interface Parameters TLV, as described in [RFC4447bis]. 3. A PW Grouping TLV, as described in [RFC4447bis]. 4. A label TLV for the upstream-assigned label used by R-PE for the traffic going from R-PE to L-PE(s). The R-PE imposes the upstream-assigned PW label on the outbound packets sent over the P2MP-PW, and using this label an L-PE identifies the inbound packets arriving over the P2MP PW. Additionally, the R-PE MAY send label mapping message(s) to one or more L-PE(s) to signal unidirectional P2P PW(s). The L-PE(s) can use such PW(s) to send traffic to the R-PE. This optional label mapping message will contain the following: 1. P2P PW Downstream FEC element. 2. A label TLV for the down-stream assigned label used by the corresponding L-PE to send traffic to the R-PE. The LDP liberal label retention mode MUST be used, and per requirements specified in [RFC5036], the Label Request message MUST also be supported. Sivabalan & Boutros Expires May 16, 2018 [Page 5]

23 INTERNET DRAFT P2MP PW November 12, 2017 The upstream-assigned label is allocated according to the rules in [RFC5331]. When an L-PE receives a PW Label Mapping Message, it MUST verify the associated P2MP PSN LSP is in place. If the associated P2MP PSN LSP is not in place, and its type is LDP P2MP LSP, the L-PE MUST attempt to join the P2MP LSP associated with the P2MP PW. If the associated P2MP PSN LSP is not in place, and its type is RSVP-TE P2MP LSP, the L-PE SHOULD wait till the P2MP transport LSP is signaled. If an L-PE fails to join the P2MP PSN LSP, that L-PE MUST not enable the PW, and MUST notify the user. In this case, a PW status message with status code of 0x (Local PSN-facing PW (ingress) Receive Fault) MUST also be sent to the R-PE. 2.1 PW ingress to egress incompatibility issues If an R-PE signals a PW with a pw type, CW mode, or interface parameters that a particular L-PE cannot accept, then the L-PE MUST not enable the PW, and notify the user. In this case, a PW status message with status code of 0x (Pseudowire Not Forwarding) MUST also be sent to the R-PE. Note that this procedure does not apply if the L-PE had not been provisioned with this particular P2MP PW. In this case according to the LDP liberal label retention rules, no action is taken. 2.2 P2MP PW FEC [RFC4447bis] specifies two types of LDP FEC elements called "PWid FEC Element" and "Generalized PWid FEC Element" used to signal P2P PWs. This document defines two new types of FEC elements called "P2MP PW Upstream FEC Element" and "P2P PW Downstream FEC Element". These FEC elements are associated with a mandatory upstream assigned label and an optional downstream assigned label respectively P2MP PW Upstream FEC Element A new FEC type for the P2MP PW Upstream FEC Element is encoded as follows: Sivabalan & Boutros Expires May 16, 2018 [Page 6]

24 INTERNET DRAFT P2MP PW November 12, P2MP PW Up=0x82 C PW Type PW Info Length AGI Type Length AGI Value AGI Value (contd.) AII Type Length SAII Value SAII Value (contd.) PMSI Tunnel typ Length Transport LSP ID Optional Parameters * P2MP PW Up: Figure 2: P2MP PW Upstream FEC Element 8 bits representation for the P2MP PW Upstream FEC type. * PW Type: 15 bits representation of PW type as specified in [RFC4447bis]. * C bit: A value of 1 or 0 indicates whether control word is present or absent for the P2MP PW. * PW Info Length: Sum of the lengths of AGI, SAII, PMSI Tunnel info, and Optional Parameters field in octets. If this value is 0, then it references all PWs using the specified grouping ID. In this case, there are neither other FEC element fields (AGI, SAII, etc.) present, nor any Sivabalan & Boutros Expires May 16, 2018 [Page 7]

25 INTERNET DRAFT P2MP PW November 12, 2017 interface parameters TLVs. Alternatively, typed wildcard FEC described in section 3.3, can be used to achieve the same or to have better filtering. * AGI: Attachment Group Identifier can be used to uniquely identify VPN or VPLS instance associated with the P2MP PW. This has the same format as the Generalized PWid FEC element [RFC4447bis]. * SAII: Source Attachment Individual Identifier is used to identify the root of the P2MP PW. The root is represented using AII type 2 format specified in [RFC5003]. Note that the SAII can be omitted by simply setting the length and type to zero. P2MP PW is identified by the Source Attachment Identifier (SAI). If the AGI is non-null, the SAI is the combination of the SAII and the AGI, if the AGI is null, the SAI is the SAII. * PMSI Tunnel info PMSI Tunnel info is the combination of PMSI Tunnel Type, Length and Transport LSP ID. A P2MP PW MUST be associated with a transport LSP which can be established using RSVP-TE or mldp. * PMSI Tunnel Type: The PMSI tunnel type is defined in [RFC6514]. When the type is set to mldp P2MP LSP, the Tunnel Identifier is a P2MP FEC Element as defined in [RFC6388]. A new mldp Opaque Value Element type for L2VPN-MCAST application as specified in the IANA considerations MUST be used. * Transport LSP ID: This is the Tunnel Identifier which is defined in [RFC6514]. An R-PE sends Label Mapping Message as soon as the transport LSP ID associated with the P2MP PW is known (e.g., via configuration) regardless of the operational state of that transport LSP. Similarly, an R-PE does not withdraw the labels when the corresponding transport LSP goes down. Furthermore, an L-PE retains the P2MP PW labels regardless of the operational status of the transport LSP. Sivabalan & Boutros Expires May 16, 2018 [Page 8]

26 INTERNET DRAFT P2MP PW November 12, 2017 Note that a given transport LSP can be associated with more than one P2MP PWs in which case P2MP PWs will be sharing the same R-PE and L- PE(s). An R-PE may also have many P2MP PWs with disjoint L-PE sets. In the case of LDP P2MP LSP, when an L-PE receives the Label Mapping Message, it can initiate the process of joining the P2MP LSP tree associated with the P2MP PW. In the case of RSVP-TE P2MP LSP, only the R-PE initiates the signaling of P2MP LSP. * Optional Parameters: The Optional Parameter field can contain some TLVs that are not part of the FEC, but are necessary for the operation of the PW. This proposed mechanism uses two such TLVs: Interface Parameters TLV, and Group ID TLV. The Interface Parameters TLV and Group ID TLV specified in [RFC4447bis] can also be used in conjunction with P2MP PW FEC in a label message. For Group ID TLV, the sender and receiver of these TLVs should follow the same rules and procedures specified in [RFC4447bis]. For Interface Parameters TLV, the procedure differs from the one specified in [RFC4447bis] due to specifics of P2MP connectivity. When the interface parameters are signaled by a R-PE, each L-PE must check if its configured value(s) is less than or equal to the threshold value provided by the R-PE (e.g. MTU size (Ethernet), max number of concatenated ATM cells, etc)). For other interface parameters like CEP/TDM Payload bytes (TDM), the value MUST exactly match the values signaled by the R-PE. Multicast traffic stream associated with a P2MP PW can be selective or inclusive. To support the former, this document defines a new optional Selective Tree Interface Parameter sub-tlv, as described in the IANA considerations and according to the format described in [RFC4447bis]. The value of the sub-tlv contains the source and the group for a given multicast tree as shown in Figure 3. Also, if a P2MP PW is associated with multiple selective trees, the corresponding label mapping message will carry more than one instance of this Sub-TLV. Furthermore, in the absence of this sub-tlv, the P2MP PW is associated with all multicast traffic stream originating from the root Sub-TLV Type (1 Octet) Length (1 Octet) Sivabalan & Boutros Expires May 16, 2018 [Page 9]

27 INTERNET DRAFT P2MP PW November 12, 2017 Multicast Source Length (1 Octet) Multicast Source (variable length) Multicast Group Length (1 Octet) Multicast Group (variable length) Figure 3: Selective Tree Interface Parameter Sub-TLV Value Note that since the LDP label mapping message is only sent by the R- PE to all the L-PEs, it is not possible to negotiate any interface parameters P2P PW Downstream FEC Element The optional P2P PW Downstream FEC Element is encoded as follows: P2P PWDown=0x83 C PW Type PW Info Length AGI Type Length AGI Value AGI Value (contd.) AII Type Length SAII Value SAII Value (contd.) Figure 4: P2P PW Downstream FEC Element The definition of the fields in the P2P PW Downstream FEC Element is the same as those of P2MP PW Upstream FEC Element shown in Figure Typed Wildcard FEC Format for new FEC [RFC5918] defines the general notion of a "Typed Wildcard" FEC Element, and requires FEC designer to specify a typed wildcard FEC element for newly defined FEC element types. This document defines two new FEC elements, "P2MP PW Upstream" and "P2P PW Downstream" FEC Sivabalan & Boutros Expires May 16, 2018 [Page 10]