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Versions: (draft-jiang-pwe3-mc-pon) 00 01 02 03 04 05 RFC 8024

Network Working Group                                  Y. Jiang, Ed.
Internet-Draft                                                Y. Luo
Intended status: Standards Track                              Huawei
                                                    E. Mallette, Ed.
                                              Charter Communications
                                                             Y. Shen
                                                    Juniper Networks
                                                            W. Cheng
                                                        China Mobile
Expires: March 2017                                September 28, 2016


       Multi-chassis Passive Optical Network (PON) Protection in MPLS
                         draft-ietf-pals-mc-pon-05


Abstract

   Multi-Protocol Label Switching (MPLS) is being extended to the edge
   of operator networks including the network access nodes. Separately
   network access nodes such as Passive Optical Network (PON) Optical
   Line Terminations (OLTs) have evolved to support first-mile access
   protection, where one or more physical OLTs provide first-mile
   diversity to the customer edge. Multi-homing support is needed on
   the MPLS-enabled PON OLT to provide resiliency for provided services.
   This document describes the multi-chassis PON protection
   architecture in MPLS and also specifies the Inter-Chassis
   Communication Protocol (ICCP) extension to support it.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with
   the provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on March 28, 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
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Table of Contents

   1.   Introduction .............................................. 3
      1.1. Conventions used in this document ...................... 5
      1.2. Terminology ............................................ 5
   2.   ICCP Protocol Extensions .................................. 6
      2.1. Multi-chassis PON Application TLVs ..................... 6
      2.1.1.  PON Connect TLV ..................................... 6
      2.1.2.  PON Disconnect TLV .................................. 7
      2.1.3.  PON System Configuration TLV ........................ 8
      2.1.4.  PON State TLV ....................................... 9
   3.   Considerations on PON ONU Database Synchronization ....... 10
   4.   Multi-chassis PON application procedures ................. 10
      4.1. Protection procedure upon PON link failures ........... 12
      4.2. Protection procedure upon PW failures ................. 12
      4.3. Protection procedure upon the working OLT failure ..... 13
   5.   Security Considerations .................................. 13
   6.   IANA Considerations ...................................... 14
   7.   References ............................................... 14
      7.1. Normative References .................................. 14
      7.2. Informative References ................................ 14
   8.   Acknowledgments .......................................... 15
   Contributors .................................................. 15
   Authors' Addresses ............................................ 16








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1. Introduction

   Multi-Protocol Label Switching (MPLS) is being extended to the edge
   of operator networks, as is described in the Multi-Segment
   Pseudowires with Passive Optical Network (PON) access use case
   [RFC6456]. Combining MPLS with Optical Line Termination (OLT) access
   further facilitates a low cost multi-service convergence.

   Tens of millions of Fiber-to-the-x (FTTx, x = H for home, P for
   premises, C for curb) lines have been deployed over the years, with
   many of those lines being some PON variant. PON provides operators a
   cost-effective solution for delivering high bandwidth (1Gbps or even
   10Gbps) to a dozen or more subscribers simultaneously.

   In the past, access technologies such as PON and Digital Subscriber
   Line (DSL) are usually used for subscribers, and no redundancy is
   provided in their deployment.

   But with the rapid growth of mobile data traffic, more and more Long
   Term Evolution (LTE) small cells and Wi-Fi hotspots are deployed.
   PON is considered a viable low cost backhaul solution for these
   mobile services. Besides its high bandwidth and scalability, PON
   further provides frequency and time synchronization features, e.g.,
   SyncE [G.8261] and IEEE 1588v2 [IEEE-1588] functionality, which can
   fulfill synchronization needs of mobile backhaul services.

   The Broadband Forum specifies reference architecture for mobile
   backhaul network using MPLS transport in [TR-221] where PON can be
   the access technology.

   Unlike typical residential service where a single or handful of end-
   users hangs off a single PON OLT port in a physical optical
   distribution network, a PON port that supports a dozen LTE small
   cells or Wi-Fi hotspots could be providing service to hundreds of
   simultaneous subscribers. Small cell backhaul often demands the
   economics of a PON first-mile and yet expects first-mile protection
   commonly available in a point-to-point access portfolio.

   Some optical layer protection mechanisms, such as Trunk and Tree
   protection, are specified in [IEEE-1904.1] to avoid single point of
   failure in the access. They are called Type B and Type C protection
   respectively in [G.983.1].







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   Trunk protection architecture is an economical PON resiliency
   mechanism, where the working OLT and the working link between the
   working splitter port and the working OLT (i.e., the working trunk
   fiber) is protected by a redundant protection OLT and a redundant
   trunk fiber between the protection splitter port and the protection
   OLT, however it only protects a portion of the optical path from OLT
   to Optical Network Units (ONUs). This is different from the more
   complex and costly Tree protection architecture where there is a
   working optical distribution network path from the working OLT and a
   complete protected optical distribution network path from the
   protection OLT to the ONUs. Figure 1 depicts a typical scenario of
   Trunk protection.

                        |                                 |
                        |<--Optical Distribution Network->|
                        |                                 |
                        |   branch               trunk    +-----+
                  +-----+   fibers               fibers   |     |
   Base     ------|     |     |                    |      . OLT |
   Stations ------| ONU |\    |                    |   ,'`|  A  |
            ------|     |  \  V                    V -`   +-----+
                  +-----+    \                    .'
                            .  \  +----------+ ,-`
                  +-----+   .    \|          -`   Working
   Base     ------|     |   .     | Optical  |
   Stations ------| ONU |---------| Splitter |
            ------|     |   .    /|          -,   Protection
                  +-----+   .  /  +----------+ `'.,
                             /                     `-,    +-----+
                  +-----+  /                          `'.,|     |
   Base     ------|     |/                                | OLT |
   Stations ------| ONU |                                 |  B  |
            ------|     |                                 +-----+
                  +-----+
               Figure 1 Trunk Protection Architecture in PON

   Besides small cell backhaul, this protection architecture can also
   be applicable to other services, for example, Digital Subscriber
   Line (DSL) and Multi-System Operator (MSO) services. In that case,
   an ONU in Figure 1 can play the similar role as a Digital Subscriber
   Line Access Multiplexer (DSLAM) or a DOCSIS Remote PHY device
   [remote-phy], and it may further be attached with dozens of Customer
   Premise devices.

   In some deployments, it is also possible that only some ONUs need to
   be protected.



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   The PON architecture as depicted in Figure 1 can provide redundancy
   in its physical topology, however, all traffic including link
   Operation Administration and Maintenance (OAM) are blocked on the
   protection link which frustrates end to end protection mechanisms
   such as those specified in ITU-T G.8031 [G.8031]. Therefore, some
   standard signaling mechanisms are needed between OLTs to exchange
   information, for example, PON link status, registered ONU
   information, and network status, so that protection and restoration
   can be done rapidly and reliably, especially when the OLTs also
   support MPLS.

   Inter-Chassis Communication Protocol (ICCP) [RFC7275] provides a
   framework for inter-chassis synchronization of state and
   configuration data between a set of two or more Provider Edges (PEs).
   Currently ICCP only defines application specific messages for
   Pseudowire (PW) redundancy and Multi-Chassis LACP (mLACP), but it
   can be easily extended to support PON as an Attachment Circuit (AC)
   redundancy.

   This document proposes the extension of ICCP to support Multi-
   chassis PON protection in MPLS.

1.1. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

1.2. Terminology

   DSL  Digital Subscriber Line

   FTTx  Fiber-to-the-x (FTTx, x = H for home, P for premises, C for
   curb)

   ICCP  Inter-Chassis Communication Protocol

   OLT  Optical Line Termination

   ONU  Optical Network Unit

   MPLS  Multi-Protocol Label Switching

   PON  Passive Optical Network

   RG   Redundancy Group



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2. ICCP Protocol Extensions

2.1. Multi-chassis PON Application TLVs

   A set of multi-chassis PON application Type-Length-Values (TLVs) are
   defined in the following sub-sections.

2.1.1.   PON Connect TLV

   This TLV is included in the Redundancy Group (RG) Connect message to
   signal the establishment of PON application connection.

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|   Type=0xTBD1             |    Length                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Protocol Version         |A|         Reserved            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Optional Sub-TLVs                          |
   ~                                                               ~
   |                                                               |
   +                                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             ...                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   - U and F Bits, both are set to 0.

   - Type, set to 0xTBD1 for "PON Connect TLV".

   - Length, Length of the TLV in octets excluding the U-bit, F-bit,
   Type, and Length fields.

   - Protocol Version, the version of this PON specific protocol for
   the purposes of inter-chassis communication. This is set to 0x0001.

   - A Bit, Acknowledgement Bit. It MUST be set to 1 if the sender has
   received a PON Connect TLV from the recipient. Otherwise, set to 0.

   - Reserved, Reserved for future use, and MUST be set to zero.

   - Optional Sub-TLVs, there are no optional Sub-TLVs defined for this
   version of the protocol. The structure of Optional Sub-TLVs is
   defined as follows:




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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Sub-TLV Type  |    Length     |    Variable Length Value      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Variable Length Value                 |
      |                             "                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   - The Optional Sub-TLV Type values will be allocated by IANA in a
   registry of name "TLV Type Name Space" for Label Distribution
   Protocol (LDP) Parameters. Processing of the Sub-TLV Types should
   continue when unknown Sub-TLV Type parameters are encountered, and
   they MUST be silently ignored.

   - The Length field is defined as the length of the Sub-TLV Type
   including the Sub-TLV Type field and Length field itself.

2.1.2.   PON Disconnect TLV

   This TLV is included in the RG Disconnect message to indicate that
   the connection for the PON application is to be terminated.

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|   Type=0xTBD2             |    Length                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Optional Sub-TLVs                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   - U and F Bits, both are set to 0.

   - Type, set to 0xTBD2 for "PON Disconnect TLV".

   - Length, Length of the TLV in octets excluding the U-bit, F-bit,
   Type, and Length fields.

   - Optional Sub-TLVs, there are no optional Sub-TLVs defined for this
   version of the protocol.







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2.1.3.   PON System Configuration TLV

   The "PON System Configuration TLV" is included in the "RG
   Application Data" message, and announces an OLT's system parameters
   to other members in the same RG.
   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|   Type=0xTBD3             |    Length                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         System ID                             |
   |                                                              |
   |                                                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     System Priority           |             Port ID           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   - U and F Bits, both are set to 0.

   - Type, set to 0xTBD3 for "PON System Configuration TLV".

   - Length, Length of the TLV in octets excluding the U-bit, F-bit,
   Type, and Length fields.

   - System ID, 8 octets encoding the System ID used by the OLT, which
   is the Chassis MAC address. If a 6 octet System ID is used, the
   least significant 2 octets of the 8-octet field will be encoded as
   0000.

   - System Priority, a 2-octet value assigned by management or
   administration policy, the OLT with the numerically lower value of
   System Priority has the higher priority.

   - Port ID, 2 octets PON Port ID.













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2.1.4.  PON State TLV

   The "PON State TLV" is included in the "RG Application Data" message,
   and used by an OLT to report its PON states to other members in the
   same RG.

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|   Type=0xTBD4             |    Length                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ROID                             |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Local PON Port state                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Remote PON Port state                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   - U and F Bits, both are set to 0.

   - Type, set to 0xTBD4 for "PON State TLV"

   - Length, Length of the TLV in octets excluding the U-bit, F-bit,
   Type, and Length fields.

   - ROID, Redundant Object ID (ROID) as defined in Section 4.3 of
   [RFC7275].

   - Local PON Port State, the status of the local PON port as
   determined by the sending OLT (PE). The last bit is defined as Fault
   indication of the PON Port associated with this PW (1 - in fault; 0
   - in normal).

   - Remote PON Port State, the status of the remote PON port as
   determined by the remote peer of the sending OLT (i.e., the sending
   PE). The last bit is defined as Fault indication of the PON Port
   associated with this PW (1 - in fault; 0 - in normal).








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3. Considerations on PON ONU Database Synchronization

   Without an effective mechanism to communicate the registered ONUs
   between the working and protection OLT, all registered ONUs would be
   de-registered and go through re-registration during a switchover,
   which would significantly increase protection time. To enable faster
   switchover capability, the working and protection OLTs need to know
   about the protected ONUs. To enable service continuity a mechanism
   needs to be employed such that the operational state and significant
   configuration data of both the protected ONU and the services
   provisioned to it can be distributed to the working and protection
   OLT.

   The specific ONUs configuration and operational data can be
   synchronized by some policy mechanism or provisioned in the
   management plane. Alternatively said synchronization could occur by
   some other signaling options. Describing how to synchronize the
   configuration objects associated with both protected ONU as well as
   the services constructed to the ONU (e.g. ONU MAC address, IPv4
   addresses, IPv6 addresses, VLAN identifiers, etc.) is outside of the
   scope of this document.


4. Multi-chassis PON application procedures

   Two typical MPLS protection network architectures for PON access are
   depicted in Fig.2 and Fig.3 (their PON access segments are the same
   as in Fig.1 and thus omitted for simplification). OLTs with MPLS
   functionality are connected to a single PE (Fig.2) or dual home PEs
   (Fig.3) respectively, i.e., the working OLT to PE1 by a working PW
   and the protection OLT to PE1 or PE2 by a protection PW, thus these
   devices constitute an MPLS network which provides PW transport
   services between ONUs and a Customer Edge (CE), and the PWs can
   provide protection for each other.














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                  +-----+
                  |     |
                  |OLT  -,
                  | A   | `.,
                  +-----+    ', PW1
                               `',
                                  `.,   +-----+          +-----+
                                     ', |     |          |     |
                                       `. PE1 ------------  CE |
                                     .'`|     |          |     |
                                  ,-`   +-----+          +-----+
                                .`
                  +-----+    .'` PW2
                  |     | ,-`
                  |OLT  -`
                  | B   |
                  +-----+
                 Figure 2 An MPLS Network with a Single PE


                  +-----+               +-----+
                  |     |     PW1       |     |
                  |OLT  ----------------- PE1 -,
                  | A   |               |     | ',
                  +-----+               +--/--+   ',
                                           |        `.
                                           |          `. +-----+
                                           |            `'     |
                                           |             |  CE |
                                           |             .     |
                                           |           ,'+-----+
                                           |        ,-`
                  +-----+               +--\--+   ,'
                  |     |     PW2       |     | .`
                  |OLT  ----------------- PE2 -`
                  | B   |               |     |
                  +-----+               +-----+
               Figure 3 An MPLS Network with Dual-homing PEs


   Faults may be encountered in PON access links, or in the MPLS
   network (including the working OLT). Procedures for these cases are
   described in this section (it is assumed that both OLTs and PEs are
   working in the independent mode of PW redundancy [RFC6870]).





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4.1. Protection procedure upon PON link failures

   When a fault is detected on a working PON link, a working OLT
   switches to the corresponding protection PON link attached with its
   protection OLT, i.e., the working OLT turns off its faulty PON
   interface so that the protection trunk link to its protection OLT
   can be activated. The working OLT then MUST send an LDP fault
   notification message (i.e., with the status bit "Local AC (ingress)
   Receive Fault" being set) to its peer PE on the remote end of the PW.
   At the same time, the working OLT MUST send an ICCP message with PON
   State TLV with local PON Port State being set to notify the
   protection OLT of the PON fault.

   Upon receiving a PON state TLV where Local PON Port state is set, a
   protection OLT MUST activate the protection PON link in the
   protection group, and advertise a notification message for the
   protection PW with the Preferential Forwarding status bit of active
   to the remote PE.

   According to [RFC6870], the remote PE(s) can match the local and
   remote Preferential Forwarding status and select PW2 as the new
   active PW over which data traffic is sent.



4.2. Protection procedure upon PW failures

   Usually MPLS networks have its own protection mechanism such as LSP
   protection or Fast Reroute (FRR). But in a link sparse access or
   aggregation network where protection for a PW is impossible in its
   LSP layer, the following PW layer protection procedures can be
   enabled.

   When a fault is detected on its working PW (e.g., by VCCV BFD), a
   working OLT SHOULD turn off its associated PON interface and then
   send an ICCP message with PON State TLV with local PON Port State
   being set to notify the protection OLT of the PON fault.

   Upon receiving a PON state TLV where Local PON Port state is set,
   the protection OLT MUST activate its PON interface to the protection
   trunk fiber. At the same time, the protection OLT MUST send a
   notification message for the protection PW with the Preferential
   Forwarding status bit of active to the remote PE, so that traffic
   can be switched to the protection PW.





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4.3. Protection procedure upon the working OLT failure

   As depicted in Fig. 2, a service is provisioned with a working PW
   and a protection PW, both PW terminated on PE1. If PE1 lost its
   connection to the working OLT, it SHOULD send an LDP notification
   message on the protection PW with the Request Switchover bit set.

   Upon receiving an LDP notification message from its remote PE with
   the Request Switchover bit set, a protection OLT MUST activate its
   optical interface to the protection trunk fiber and activate the
   associated protection PW, so that traffic can be reliably switched
   to the protection trunk PON link and the protection PW.

   In the case of Fig.3, PW-RED State TLV as described in Section 7.1
   of [RFC7275] can be used by PE1 to notify PE2 the faults in all the
   scenarios, and PE2 operates the same as described in Section 5.1 to
   5.3.



5. Security Considerations

   Similar to ICCP itself, this ICCP application SHOULD only be used in
   well-managed and highly monitored service provider PON access
   networks in a single administrative domain, including the
   implementation of rogue ONU attachment detection and mitigation via
   device authentication. Thus many of the security considerations as
   described in [RFC7275] apply here as well.

   Again, similar to ICCP, activity on the attachment circuits may
   cause security threats or be exploited to create denial-of-service
   attacks. In many passive optical networks, the optical paths between
   OLT and ONUs traverse publicly accessible facilities including
   public attachments (e.g. telephone poles), which opens up the risk
   of excessive link bouncing by optical layer impairment. While ICCP
   for MC-PON interconnects in the MPLS domain and does not traverse
   the PON network, risks do include introduction of a malicious ONU
   which could cause, for example, excessive link bouncing. This link
   bouncing could result in increased ICCP exchanges similar to the
   malicious CE case described in [RFC7275]. Operators of such networks
   should take additional care to restrict unauthorized ONUs and to
   limit the impact of link bouncing at the OLT, as these could result
   in service impairment.






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6. IANA Considerations

   The IANA maintains a top-level registry called "Pseudowire Name
   Spaces (PWE3)".  It has a subregistry called "ICC RG Parameter
   Types". The following values are requested from this subregistry:
   0xTBD1         PON Connect TLV
   0xTBD2         PON Disconnect TLV
   0xTBD3         PON Configuration TLV
   0xTBD4         PON State TLV

   [Note to IANA, to be removed by the RFC Editor: consecutive values
   in the IETF Review range are requested.]

7. References

7.1.  Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997

   [RFC6870] Muley, P., Aissaoui, M., "Pseudowire Preferential
             Forwarding Status Bit", RFC 6870, February 2013

   [RFC7275] Martini, L. et al, "Inter-Chassis Communication Protocol
             for L2VPN PE Redundancy", RFC 7275, June 2014

7.2. Informative References

   [RFC6456] Li, H., Zheng, R., and Farrel, A., "Multi-Segment
             Pseudowires in Passive Optical Networks", RFC 6456,
             November 2011

   [G.983.1] ITU-T, "Broadband optical access systems based on Passive
             Optical Networks (PON)", ITU-T G.983.1, January, 2005

   [G.8031] ITU-T, "Ethernet Linear Protection Switching", ITU-T G.8031,
             January, 2015

   [G.8261] ITU-T, "Timing and synchronization aspects in packet
             networks", ITU-T G.8261, August, 2013

   [IEEE-1588] IEEE Std. 1588, "IEEE Standard for a Precision Clock
             Synchronization Protocol for Networked Measurement and
             Control Systems", IEEE Instrumentation and Measurement
             Society, July, 2008




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   [IEEE-1904.1] IEEE Std. 1904.1, "Standard for Service
             Interoperability in Ethernet Passive Optical Networks
             (SIEPON)", IEEE Computer Society, June, 2013

   [TR-221] BBF TR-221, "Technical Specifications for MPLS in Mobile
             Backhaul Networks", https://www.broadband-
             forum.org/technical/download/TR-221.pdf, the Broadband
             Forum, October, 2011

   [remote-phy] CableLabs, "Remote PHY Specification",
             http://www.cablelabs.com/wp-content/uploads/specdocs/CM-
             SP-R-PHY-I01_150615.pdf, June, 2015



8. Acknowledgments

   The authors would like to thank Min Ye, Hongyu Li, Wei Lin, Xifeng
   Wan, Yannick Legoff, Shrinivas Joshi, Alexey Melnikov and Stephen
   Farrell for their valuable discussions and comments.


Contributors

   The following people made significant contributions to this document:

   Chengbin Shen
   China Telecom
   1835 South Pudong Road
   Shanghai 200122, China
   Email: shencb@sttri.com.cn

   Guangtao Zhou
   China Unicom
   No.9 Shouti South Road
   Beijing 100048, China
   Email: zhouguangtao@chinaunicom.cn










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Authors' Addresses

   Yuanlong Jiang (Editor)
   Huawei Technologies Co., Ltd.
   Bantian, Longgang district
   Shenzhen 518129, China
   Email: jiangyuanlong@huawei.com

   Yong Luo
   Huawei Technologies Co., Ltd.
   Bantian, Longgang district
   Shenzhen 518129, China
   Email: dennis.luoyong@huawei.com

   Edwin Mallette (Editor)
   Charter Communications
   4145 S. Falkenburg Road
   Tampa, FL 33578 USA
   Email: edwin.mallette@gmail.com


   Yimin Shen
   Juniper Networks
   10 Technology Park Drive
   Westford, MA 01886, USA
   Email: yshen@juniper.net

   Weiqiang Cheng
   China Mobile
   No.32 Xuanwumen West Street
   Beijing 100053, China
   Email: chengweiqiang@chinamobile.com
















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