Internet DRAFT - draft-lin-ccamp-gmpls-fgotn-applicability

draft-lin-ccamp-gmpls-fgotn-applicability



CCAMP Working Group                                              Y. Lin  
Internet Draft                                      Huawei Technologies 
                                                                 L. Han 
                                                                Y. Zhao 
                                                           China Mobile 
                                                               R. Munoz 
                                                                   CTTC 
                                                                       
Category: Informational                           
Expires: September 05, 2024                              March 04, 2024 
                                    
                                    
     Applicability of GMPLS for fine grain Optical Transport Network 
                                    
               draft-lin-ccamp-gmpls-fgotn-applicability-00 


Abstract 
 
ITU-T Recommendation G.709/Y.1331 Edition 6.5 [G709-E6.5] introduced 
new fine grain OTN (fgOTN) for the efficient transmission of sub-1G 
client signals. 

This document reviews the fgOTN control plane requirements, examines 
the applicability of using existing GMPLS control plane for fgOTN, and 
provides the standard gap analysis and considerations on GMPLS 
extensions. 

Status of this Memo 

   This Internet-Draft is submitted to IETF in full conformance with   
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   This Internet-Draft will expire on September 05, 2024. 

 
 
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Copyright Notice 

   Copyright (c) 2024 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 
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Table of Contents 

   1. Introduction .................................................. 3 
   2. G.709 Optical Transport Network Overview ...................... 3 
      2.1. fgOTN Mapping and Multiplexing Architecture .............. 4 
         2.1.1. fgODUflex(p) into ODUj(fgTS) or ODUflex(fgTS,n) 
         Multiplexing ............................................... 5 
         2.1.2. ODUj(fgTS) or ODUflex(fgTS,n) into ODUk Multiplexing  5 
      2.2. fgOTN Connection Model ................................... 5 
      2.3. fgOTN Use Cases .......................................... 7 
         2.3.1. Point-to-Point (P2P) Private Line Service............ 7 
         2.3.2. Multi-Point-to-Multi-Point (MP2MP) Cloud Access ..... 8 
   3. General fgOTN Control Consideration ........................... 8 
      3.1. Signal Type .............................................. 8 
      3.2. fgOTN Label .............................................. 9 
   4. fgOTN Connection Control Consideration ........................ 9 
      4.1. Connection Hierarchy ..................................... 9 
      4.2. Hitless Resizing ......................................... 9 
      4.3. Scalability Consideration ............................... 10 
   5. fgOTN Service Control Consideration .......................... 10 
   6. fgOTN Routing Consideration .................................. 12 
      6.1. fgOTN Resource Distribution ............................. 12 
      6.2. Scalability Consideration ............................... 12 
   7. fgOTN Link Management Consideration .......................... 12 
   8. Manageability Considerations ................................. 12 
   9. Security Considerations ...................................... 13 
   10. IANA Considerations.......................................... 13 
   11. References .................................................. 13 
      11.1. Normative References ................................... 13 
      11.2. Informative References ................................. 13 
   12. Authors' Addresses .......................................... 14 
 

 
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1. Introduction 

   Optical Transport Networks (OTN) is a mainstream layer 1 technology 
   for the transport network. Over the years, it has continued to 
   evolve, to improve its transport functions for the emerging 
   requirements. 

   OTN control plane capabilities are also introduced and improved 
   according to the evolution of OTN technologies. The OTN control 
   plane brings benefits to operators, including improving OTN network 
   resiliency and resource usage efficiency. Generalized Multi-Protocol 
   Label Switching (GMPLS) [RFC3945], as a control plane technology, 
   support different classes of interfaces and switching capabilities 
   including OTN.  

   In the latest version of OTN, ITU-T G.709/Y.1331 Edition 6.5 [G709-
   E6.5], the fine grain OTN (fgOTN) is introduced for the efficient 
   transmission of low rate signals (e.g., sub-1G). 

   This document reviews the latest OTN standard technologies 
   (especially the fgOTN) and their requirements to the OTN control 
   plane.  

   This document also examines the applicability of using existing 
   GMPLS control plane for fgOTN, and provides the standard gap 
   analysis and considerations on GMPLS extensions. 

    

2. G.709 Optical Transport Network Overview 

   Recommendation ITU-T G.709/Y.1331 [G709-E6.5] defines the 
   requirements for the optical transport network (OTN) interface 
   signals of the optical transport network. 

   The most important new feature introduced by G.709/Y.1331 [G709-
   E6.5], compared with the previous editions of G.709 series 
   standards, is the introduction of fine grain OTN (fgOTN) for the 
   efficient transmission of low rate signals (e.g., sub-1G). This can 
   be an alternative to the existing SDH networks, which phases out in 
   operators' networks. 

   Recommendation ITU-T G.709.20 [G709.20] provides an overview of 
   functions provided by the fgOTN layer network. 

   The main functional requirements of fgOTN, described in G.709.20 
   [G709.20], include: 

   -  Support TDM hard isolation with deterministic latency to 
      guaranteed performance of OTN networks. 
 
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   -  Support mapping packet services and Constant Bit Rate (CBR) 
      services into fgODUflex path layer.  

   -  Support multiplexing multiple fgODUflex signals into 
      ODU0/1/2/flex(fgTS,n) (where n = 3 to 7). 

   -  Support fgODUflex SNCP 1+1 protection. 

   -  Support timing transparent transport for CBR services. 

   -  Support fgODUflex hitless bandwidth adjustment function for packet 
      services. 

   The detail definition of fgOTN, including frame format, mapping of 
   client signals into fgOTN and mapping of fgOTN into ODUk, is 
   described in G.709 [G709-E6.5]. 

2.1. fgOTN Mapping and Multiplexing Architecture  

   fgOTN layer network is a service layer network of the OTN ODU layer 
   network. Figure 1 shows the overview of fgOTN mapping and 
   multiplexing architecture.  

                       p=1~119 
        +------+   +------------+   +---------------+   +------+ 
        |Client|-->|fgODUflex(p)|-->|               |   |      | 
        +------+   +------------+   |ODUflex(fgTS,n)|-->|      | 
           ...  -->    ......    -->|     n=3~7     |   |      | 
                                    +---------------+   |      | 
        +------+   +------------+   +---------------+   |      | 
        |Client|-->|fgODUflex(p)|-->|               |   |      | 
        +------+   +------------+   |   ODU0(fgTS)  |-->|      | 
           ...  -->    ......    -->|               |   |      | 
                                    +---------------+   |      | 
        +------+   +------------+   +---------------+   |      | 
        |Client|-->|fgODUflex(p)|-->|               |   |      | 
        +------+   +------------+   |   ODU1(fgTS)  |-->| ODUk | 
           ...  -->    ......    -->|               |   |      | 
                                    +---------------+   |      | 
        +------+   +------------+   +---------------+   |      | 
        |Client|-->|fgODUflex(p)|-->|               |   |      | 
        +------+   +------------+   |   ODU2(fgTS)  |-->|      | 
           ...  -->    ......    -->|               |   |      | 
                                    +---------------+   |      | 
                                                        |      | 
                                    +---------------+   |      | 
        +------+                    |               |   |      | 
        |Client|------------------->|     ODUj      |-->|      | 
        +------+                    |               |   |      | 
                                    +---------------+   +------+ 
 
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           Figure 1: fgOTN mapping and multiplexing architecture 

   Note that, similar to ODUj into OTUj mapping, the ODUj(fgTS) 
   (j=0,1,2) may also be mapped into OTUj directly, which is not shown 
   in Figure 1 for simplicity. 

    

2.1.1. fgODUflex(p) into ODUj(fgTS) or ODUflex(fgTS,n) Multiplexing 

   The ODUj(fgTS) (j=0,1,2) and the ODUflex(fgTS,n) are the new 
   containers used for fgODUflex(p), which contain multiple fine grain 
   Tributary Slots (fgTSs) with an approximate bit rate of 10 Mbit/s. 
   More specifically: 

   -  The ODU0(fgTS) contains 119 fine grain Tributary Slots (fgTSs), 
      and the bit rate of each fgTS is approximately 10411 kbit/s. 

   -  The ODU1(fgTS) contains 238 fgTSs, and the bit rate of each fgTS 
      is approximately 10455 kbit/s. 

   -  The ODU2(fgTS) contains 952 fgTSs, and the bit rate of each fgTS 
      is approximately 10499 kbit/s. 

   -  The ODUflex(fgTS,n) (3<=n<=7) contains n*119 fgTSs, and the bit 
      rate of each fgTS is approximately 10411 kbit/s. 

   When multiplexing an fgODUflex(p) into an ODUj(fgTS) (j=0,1,2) or an 
   ODUflex(fgTS,n), the fgODUflex(p) occupies p fgTSs of the ODUj(fgTS) 
   or ODUflex(fgTS,n), where p is an integer that less than or equal to 
   119. 

   Packet or CBR client signals which are less than 1 Gbit/s can be 
   carried by an fgODUflex(p) to improve the efficiency of OTN 
   bandwidth utilization. 

    

2.1.2. ODUj(fgTS) or ODUflex(fgTS,n) into ODUk Multiplexing 

   The ODUj(fgTS) or ODUflex(fgTS,n) into ODUk multiplexing is similar 
   to the ODUj (including ODUflex) into ODUk multiplexing. Traditional 
   ODUj and ODUj(fgTS) / ODUflex(fgTS,n) can be multiplexed into the 
   same ODUk.  

    

2.2. fgOTN Connection Model 

   Figure 2 shows a simple example about the fgOTN connection model. 
 
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         +-----+ ODUk +-----+ ODUk +-----+ ODUk +-----+ ODUk +-----+ 
         |     | Link |     | Link |     | Link |     | Link |     | 
         |  A  |======|  B  |======|  C  |======|  D  |======|  E  | 
         |     |      |     |      |     |      |     |      |     | 
         +-----+      +-----+      +-----+      +-----+      +-----+ 
    
                    Conn#1                         Conn#2 
         ****************************   **************************** 
        ODUj(fgTS) or ODUflex(fgTS,n)   ODUj(fgTS) or ODUflex(fgTS,n) 
    
         ------------------------------------------------------------ 
                            Conn#3: fgODUflex(p) 
    
                Figure 2: example of fgOTN connection model 

   In this example, there are five OTN nodes which are interconnected 
   by ODUk links. Two ODUj(fgTS) or ODUflex(fgTS,n) connections are 
   created: 

   -  Conn#1: ODUj(fgTS) or ODUflex(fgTS,n), A-B-C 

   -  Conn#2: ODUj(fgTS) or ODUflex(fgTS,n), C-D-E 

   These two connections form two virtual links, which are used for the 
   fgODUflex(p) connection. 

   -  Conn#3: fgODUflex(p), A-C-E 

   From the OTN node point of view (only describe one connection 
   direction for simplicity. The other connection direction is exactly 
   the same): 

   -  Node A multiplexes the fgODUflex(p) into an ODUj(fgTS) or 
      ODUflex(fgTS,n), which are further multiplexed into ODUk. 

   -  Node B and D perform the cross-connect for the ODUj(fgTS) or 
      ODUflex(fgTS,n), without being awareness of the fgODUflex(p) 
      inside. 

   -  Node C demultiplexes the Conn#1 signal from the ODUk, 
      demultiplexes the fgODUflex(p) from the Conn#1, perform 
      fgODUflex(p) cross-connect, and multiplexes the fgODUflex(p) into 
      Conn#2 and then into ODUk. 

   -  Node E demultiplexes the Conn#2 signal from the ODUk, and further 
      demultiplexes the fgODUflex(p) from the Conn#2. 

    

 
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2.3. fgOTN Use Cases 

2.3.1. Point-to-Point (P2P) Private Line Service 

   One of the motivations of fgOTN is to provide an alternative to 
   carry sub-1G private line services. Figure 3 below shows an example 
   of reference network model for multi-domain fgOTN private line 
   service (also see Annex A of G.709.20 [G709.20]).  

   In this example, there are one backbone OTN domain, two Metro OTN 
   domains and two fgOTN CPEs in the network. The Metro OTN networks 
   support both fgODUflex and ODUk switching. At the boundary nodes 
   (e.g., metro core nodes) of the metro OTN domains, the fgODUflexes 
   to other metro OTN networks are multiplexed into ODUk of backbone 
   networks. Therefore, the backbone OTN nodes could only support ODUk 
   switching. 

                       *********************** 
                       *                     * 
                +------* Backbone OTN (ODUk) * -----+ 
                |      *                     *      | 
                |      ***********************      | 
        Metro A |                                   | Metro B 
        *****************                   ***************** 
        * +-----+-----+ *                   * +-----+-----+ * 
        * |   fgOTN   | *                   * |   fgOTN   | * 
        * |   core    | *                   * |   core    | * 
        * +-----+-----+ *                   * +-----+-----+ * 
        *       |       *                   *       |       * 
        * +-----+-----+ *                   * +-----+-----+ * 
        * |   fgOTN   | *     Metro OTN     * |   fgOTN   | * 
        * |aggregation| *   (fgOTN & ODUk)  * |aggregation| * 
        * +-----+-----+ *                   * +-----+-----+ * 
        *       |       *                   *       |       * 
        * +-----+-----+ *                   * +-----+-----+ * 
        * |   fgOTN   | *                   * |   fgOTN   | * 
        * |   access  | *                   * |   access  | * 
        * +-----+-----+ *                   * +-----+-----+ * 
        *****************                   ***************** 
                |                                   | 
          +-----+-----+                       +-----+-----+ 
          |   fgOTN   |                       |   fgOTN   | 
          |    CPE    |    Customer network   |    CPE    | 
          +-----------+                       +-----------+ 

       Figure 3: Example of fgOTN-based private line (from [G709.20]) 

    


 
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2.3.2. Multi-Point-to-Multi-Point (MP2MP) Cloud Access 

   Cloud applications are becoming widely deployed in enterprises and 
   vertical industries. Organizations with multiple campuses are 
   interconnected together with the remote cloud Data Centers (DCs) for 
   storage and computing. Such cloud services demand that the 
   underlying network provides Multi-Point-to-Multi-Point connectivity 
   with high quality of experience, such as high availability, low 
   latency, and on-demand bandwidth adjustments. fgOTN, as a TDM-based 
   technology, can be used to meet such requirements. This could be 
   seen as an MP2MP private network service. 

   [F5G-UC] provides several use cases on how OTN is used for multi 
   cloud access, including enterprise private line connectivity to 
   multiple clouds and premium home broadband connectivity to multiple 
   clouds. 

   [opt2cloud] also provides similar multi cloud access use cases, and 
   further provides the problem statement and control plane technical 
   gap analysis on using fgOTN for multi cloud access. See Figure 4 
   below and see more detail description in [opt2cloud]. 

      __________                                             ________ 
     /          \                                           /        \ 
    | Enterprise |          ___________                    | Vertical | 
    |    CPE     |\        /           \          +-----+ /|  Cloud   | 
     \__________/  \ +---+/             \+---+    |Cloud|/  \________/ 
                    \|O-A*               *O-E|----+ GW  | 
                     +---+               +---+    +-----+ 
       ________          |       OTN     |                    _______ 
      /        \     +---+               +---+    +-----+    /       \ 
     | Vertical |----+O-A*               *O-E|----+Cloud|---| Private | 
     |   CPE    |    +---+\             /+---+    | GW  |   | Cloud   | 
      \________/           \___________/          +-----+    \_______/ 

       Figure 4: Multi-cloud access through an OTN (from [opt2cloud]) 

    

3. General fgOTN Control Consideration 

3.1. Signal Type 

   [G709-E6.5] introduces new signal types including fgODUflex, 
   ODUj(fgTS) (j=0,1,2) and ODUflex(fgTS,n). 

   The fgOTN control plane needs to support these fgOTN related signal 
   types.   
 
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3.2. fgOTN Label 

   In a control plane for a TDM network, labels are used to indicate 
   the tributary slots in a link which are used by a connection. 

   In [FRC7139], the ODU label for ODUj into ODUk multiplexing is 
   defined. There are at most 80 tributary slots in an ODUk (i.e., ODU4 
   link). 

   In [G709-E6.5], the bit rate of the tributary slot (10 Mbit/s) is 
   much smaller than before (1.25 Gbit/s), therefore the total number 
   of fgOTN tributary slots will be much larger. There are 119*n 
   (1<=n<=8) tributary slots in an ODUj(fgTS) or ODUflex(fgTS,n) (952 
   tributary slots in maximum).  

   An fgODUflex(p) occupies p (1<=p<=119) tributary slots of the 
   ODUj(fgTS) or ODUflex(fgTS,n).  

   New fgOTN label needs to be designed to support the maximum number 
   of tributary slots. 

    

4. fgOTN Connection Control Consideration 

4.1. Connection Hierarchy 

   As described in Section 2 of this document, two-stage multiplexing 
   may happen when creating an fgODUflex connections (e.g., fgODUflex 
   into ODUflex(fgTS,n) and then into ODUk multiplexing). The fgOTN 
   control plane needs to support the control of the multi-stage 
   multiplexing. 

    

4.2. Hitless Resizing 

   [RFC7139] supports the control of hitless resizing of ODUflex. 

   [G709-E6.5] defines the data plane procedure to support fgODUflex 
   hitless resizing. The support of control of hitless resizing of 
   fgODUflex needs to be further considered. 

    




 
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4.3. Scalability Consideration 

   fgOTN support much finer granularity of ODU connections. Therefore, 
   the number of ODU connections will be significantly increased. 

   For example, there could be up to 952 (119*8) fgOTN connections 
   within a single ODU2 link. As a comparison, there are at most 8 ODU0 
   connections within an ODU2 link and 80 ODU0 connections within an 
   ODU4 link in a traditional OTN network. 

   Therefore, the scalability and the performance of fgOTN connection 
   control need to be considered. Specifically, when an ODU link fails, 
   there may be thousands of fgOTN connections which are affected by 
   the failure and need to be rerouted at the same time. Even in such 
   case, the performance of fgOTN connection restoration still needs to 
   be guaranteed. 

   If the General Communication Channel (GCC) overhead bytes are used 
   as the Data Communication Network (DCN) of the OTN, the DCN 
   bandwidth may become the bottleneck when transmitting thousands of 
   rerouting signaling messages at the same time. 

   Further analysis on the scalability of using RSVP-TE for fgOTN 
   connection control is needed. 

    

5. fgOTN Service Control Consideration  

   Section 2.3.2 of this document describes the scenarios where fgOTN 
   is used for multi-cloud access services. In such scenarios, multiple 
   fgODUflex connections will be created for a customer, to form an 
   MP2MP private network interconnecting multiple customer's branches 
   and multiple cloud DCs. 

   Since an OTN edge node may have multiple fgOTN connections connected 
   to different destinations for a customer, the OTN edge node needs to 
   support identification of customer's service flows, and support 
   mapping different service flows (with different destination 
   addresses) into corresponding fgOTN connections. This requires the 
   OTN edge nodes to be able to: 

   -  Collect the client side (including the customer side and the cloud 
      side) service address information; 

   -  Generate the service mapping rules; 

   -  Identify the service identification information (e.g., source and 
      destination IP or MAC addresses) from the packet headers of the 
      received service flow; 
 
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   -  Mapping the received service flow into corresponding fgOTN 
      connections, according to the generated service mapping rules. 

         Service packets 
           +-----+---+ 
           |Ser-A|   | 
           +-----+---+ 
           +-----+---+      fgOTN domain       +-----+---+ 
           |Ser-B|   |     ***************     |Ser-A|   | 
   +-----+ +-----+---+ +---*+  Conn-1   +*---+ +-----+---+ +---------+ 
   | C-1 |-------------|OE1*|===========|*OE3|-------------| Cloud-A | 
   +-----+   ------>   +---*+=====      +*---+   ------>   +---------+ 
                           *     =       * 
                           *     =       * 
   +-----+             +---*+    =      +*---+   ------>   +---------+ 
   | C-2 |-------------|OE2*|    =======|*OE4|-------------| Cloud-B | 
   +-----+             +---*+  Conn-2   +*---+ +-----+---+ +---------+ 
                           ***************     |Ser-B|   | 
                                               +-----+---+ 

              Figure 5: Example of multi-cloud access service 

   Figure 5 shows an example on multi-cloud access service. In this 
   example, an fgOTN-based private network service is provisioned, with 
   multiple fgOTN connections interconnecting customer's branches (C-1 
   and C-2) and two cloud DCs (Cloud-A and Cloud-B). When the OTN Edge 
   node OE1 receives the service flow packets with service 
   identifications (e.g., the destination addresses) Ser-A and Ser-B, 
   OE1 needs to map the service packets identified as "Ser-A" into 
   fgOTN connection #1, and map the service packets identified as "Ser-
   B" into fgOTN connection #2. In this way, the service flow can be 
   transmitted to the correct destination cloud DCs. 

   New protocol in the control plane is needed for the OTN edge nodes, 
   so that they can know which fgOTN connections can be selected to 
   transmit a certain service flow. 

   Note that traditional OTN with 1.25 Gbit/s or 2.5 Gbit/s tributary 
   slots can also be used in this scenario. 

   [opt2cloud] provides more detail description on how the service 
   address information is learned, and how the service flows are mapped 
   to the fgOTN connections. 

   [PCE-fg] further provides the extension to the PCEP to support the 
   service address learning and service flow mapping. 

    


 
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6. fgOTN Routing Consideration 

6.1. fgOTN Resource Distribution 

   [RFC7138] defines the routing protocol for the traditional OTN with 
   1.25 Gbit/s and 2.5 Gbit/s tributary slot types. 

   [G709-E6.5] introduces new type of ODU tributary slot, i.e., the 
   fine grain tributary slot with a bit rate of approximately 10 
   Mbit/s.  

   The fgOTN control plane routing protocols need to support the 
   discovery and distribution of fgOTN node and link resource 
   information and capability information, including: 

   -  support of fine grain tributary slot, as well as the fine grain 
      tributary slot resource information; 

   -  fgODUflex multiplexing capabilities; 

   -  fgODUflex switching capabilities.  

    

6.2. Scalability Consideration 

   The typical scenarios for fgOTN is to provide low bit rate private 
   line or private network services for more customers. This implies 
   that the OTN network will cover a larger scope of networks, which 
   may include the backbone network, metro core, metro aggregation, 
   metro access, and even the OTN CPE in the customers' networks. 

   Routing protocols such as OSPF-TE and ISIS-TE use flooding 
   mechanisms to distribute the routing information. The route 
   convergence time may increase when if the scale of the network 
   becomes larger. Therefore, the scalability of the fgOTN routing 
   protocols needs to be considered, which is for further study. 

    

7. fgOTN Link Management Consideration 

   For further study. 

    

8. Manageability Considerations 

    For further study. 

 
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9. Security Considerations 

   For further study. 

    

10. IANA Considerations 

   This document requires no IANA actions. 

    

11. References 

11.1. Normative References 

   None. 

11.2.  Informative References 

   [RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label 
             Switching (GMPLS) Architecture", RFC 3945, October 2004. 

   [RFC7138] Ceccarelli, D., Ed., Zhang, F., Belotti, S., Rao, R., and 
             J. Drake, "Traffic Engineering Extensions to OSPF for 
             GMPLS Control of Evolving G.709 Optical Transport 
             Networks", RFC 7138, March 2014. 

   [RFC7139] Zhang, F., Ed., Zhang, G., Belotti, S., Ceccarelli, D., 
             and K. Pithewan, "GMPLS Signaling Extensions for Control 
             of Evolving G.709 Optical Transport Networks", RFC 7139, 
             March 2014. 

   [G709-E6.5] ITU-T, "Interfaces for the optical transport network", 
             G.709 E6.5 (2023). 

   [G709.20] ITU-T, "Overview of fine grain OTN", G.709.20 (2023). 

   [F5G-UC]  ETSI GR F5G 008 (V1.1.1), "Fifth Generation Fixed Network 
             (F5G); F5G Use Cases Release #2", 2022.06. 

   [opt2cloud] S. Liu, H. Zhang, A. Guo, Y. Zhao, and D. King, "draft-
             liu-ccamp-optical2cloud-problem-statement". 

   [PCE-fg]  L. Han, H. Zheng, M. Wang, and Y. Zhao, "draft-han-pce-
             path-computation-fg-transport". 

    
 
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12. Authors' Addresses 

   Yi Lin 
   Huawei France 
   Marco Polo A2, 790 Avenue Maurice Donat 
   Mougins France 
   Email: yi.lin@huawei.com 
    
   Liuyan Han 
   China Mobile 
   No.32 Xuanwumen west street 
   Beijing, 100053 
   China 
   Email: hanliuyan@chinamobile.com 
    
   Yang Zhao 
   China Mobile 
   No.32 Xuanwumen west street 
   Beijing, 100053 
   China 
   Email: zhaoyangyj@chinamobile.com 
    
   Raul Munoz 
   Centre Tecnologic de Telecomunicacions de Catalunya (CTTC) 
   Av. Carl Friedrich Gauss, 7 - Building B4 
   08860 - Castelldefels, Spain 
   Email: raul.munoz@cttc.es 






















 
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