Operations, Administration, and Maintenance (OAM) in Segment Routing Networks with IPv6 Dataplane (SRv6)
draft-ali-6man-srv6-oam-00

The information below is for an old version of the document
Document Type Active Internet-Draft (individual)
Authors Zafar Ali  , Clarence Filsfils  , Nagendra Nainar  , faiqbal@cisco.com  , Robert Raszuk  , Bart Peirens  , Gaurav Naik 
Last updated 2017-07-03
Replaced by draft-ali-spring-srv6-oam
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6MAN                                                             Z. Ali 
     Internet Draft                                              C. Filsfils 
     Intended status: Informational                                 N. Kumar 
     Expires: January 2, 2018                                       F. Iqbal 
                                                         Cisco Systems, Inc. 
                                                                   R. Raszuk 
                                                                Bloomberg LP 
                                                                  B. Peirens 
                                                                    Proximus 
                                                                     G. Naik 
                                                           Drexel University 
                                                                 July 2, 2017 
                                         
      
                                           
        Operations, Administration, and Maintenance (OAM) in Segment Routing 
                         Networks with IPv6 Dataplane (SRv6) 
                           draft-ali-6man-srv6-oam-00.txt 

     Status of this Memo 

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

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        This Internet-Draft will expire on January 2, 2018. 

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        Copyright (c) 2017 IETF Trust and the persons identified as the 
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     Abstract 

        This document outlines various use-cases for Operations, 
        Administration, and Maintenance (OAM) in Segment Routing with the 
        IPv6 data plane (SRv6) network. It also describes how the existing 
        OAM mechanisms can be used to address SRv6 OAM requirements.   

     Table of Contents 

        1. Introduction...................................................2 
           1.1. Terminology and Reference Topology........................3 
        2. Use-cases......................................................4 
           2.1. Connectivity Verification.................................4 
           2.2. Monitoring A Specific Flow................................5 
           2.3. Monitoring all ECMP/ UCMP Paths...........................5 
           2.4. Proof of Transit..........................................5 
           2.5. Detecting Path Divergence.................................6 
           2.6. Fault Isolation...........................................6 
           2.7. Centralized OAM...........................................6 
        3. OAM Mechanisms.................................................6 
           3.1. ICMPv6 Applicability......................................6 
              3.1.1. Ping.................................................7 
              3.1.2. Error Reporting......................................8 
              3.1.3. Traceroute...........................................8 
           3.2. In-situ OAM..............................................10 
           3.3. Seamless BFD Applicability...............................10 
           3.4. Controller based OAM.....................................11 
        4. Security Considerations.......................................12 
        5. IANA Considerations...........................................12 
        6. References....................................................12 
           6.1. Normative References.....................................12 
           6.2. Informative References...................................12 
        7. Acknowledgments...............................................12 
         
     1. Introduction 

        This document outlines various SRv6 OAM use-cases. It also describes 
        how the existing OAM mechanisms can be used to address SRv6 OAM 
        requirements. 

        Additional OAM use-cases and mechanisms will be added in a future 
        revision of the document.  

      
      
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     1.1. Terminology and Reference Topology 

        This document uses the terminology defined in [I-D.filsfils-
        spring-srv6-network-programming]. The readers are expected to be 
        familiar with the same. 

        Throughout the document, the following simple topology is used for 
        illustration.  

                    |--------------------| N100 |------------------| 
                    |                                              | 
                 ====== link1====== link3------ link5====== link9------      
                 ||N1||======||N2||======| N3 |======||N4||======| N5 | 
                 ||  ||------||  ||------|    |------||  ||------|    |   
                 ====== link2====== link4------ link6======link10------   
                                |                      | 
                                |       ------         | 
                                +-------| N6 |---------+ 
                                  link7 |    | link8   
                                        ------ 
         

                                      Reference Topology 

        In the reference topology:  
        All nodes are internal nodes within a single SRv6 domain of trust
        Nodes N1, N2, and N4 are SRv6 capable nodes.  

        Nodes N3, N5 and N6 are classic IPv6 nodes.     

        Node 100 is an SRv6 capable node that acts as controller.

        Node Nk has a classic IPv6 loopback address Bk::/128 

        Node Nk has Ak::/48 for its local SID space from which Local SIDs 
        are explicitly allocated. 

        The IPv6 address of the nth Link between node X and Y at the X side 
        is represented as 99:X:Y::Xn. e.g.,the IPv6 address of link6 (the 
        2nd link) between N3 and N4 at N3 in Figure 1 is 99:3:4:32. 
        Similarly, the IPv6 address of link5 (the 1st link between N3 and 
        N4) at node 3 is 99:3:4:31. 

        Ak::0 is explicitly allocated as the END function at Node k.  

        Ak::Cij is explicitly allocated as the END.X function at node k 
        towards neighbor node i via jth Link between node i and node j. 
      
      
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        e.g., A2::C31 represents END.X at N2 towards N3 via link3 (the 1st 
        link between N2 and N3). Similarly, A4::C52 represents the END.X at 
        N4 towards N5 via link10.  

        SRH is the abbreviation for the Segment Routing Header. 

        SL is the abbreviation for the Segment Left. 

        SID is the abbreviation for the Segment ID.  

        <S1, S2, S3> represents a SID list where S1 is the first SID and S3 
        is the last SID. (S3, S2, S1; SL) represents the same SID list but 
        encoded in the SRH format where the rightmost SID (S1) in the SRH is 
        the first SID and the leftmost SID (S3) in the SRH is the last SID. 

        ECMP is the abbreviation for the Equal Cost Multi-Path.  

        UCMP is the abbreviation for the Unequal Cost Multi-Path.  

     2. Use-cases 

        This section outlines some for the basic OAM use-cases in an SRv6 
        network. Additional use-cases will be added in a future revision of 
        the document.  

     2.1. Connectivity Verification 

        One of the basic OAM use-cases for any network is the capability to 
        perform path monitoring between different end points over any 
        possible shortest path without any path preference. Such essential 
        path monitoring helps to monitor the path availability and the 
        liveliness of the remote end point.  

        The shortest path monitoring can be done continuously or can be 
        triggered on demand basis using an external event like a script or a 
        CLI trigger. It may be required to perform the connectivity 
        verification in the order of milliseconds, or at a slower pace.  

        In the reference topology in Figure 1, N1 can send OAM probe packet 
        destined to loopback address of N5 (B5::) to monitor the path 
        liveliness between N1 and N5. N1 optionally may include any relevant 
        segment list in SRH. N1 is not concerned about which route is taken 
        by the probe between N1 and N5 as long as N1 receives the response 
        back from N5. All transit nodes treat the probe packet as like other 
        data packet and forward it based on the Destination Address (DA). N5 
        looks into the payload of probe packet and respond back to the 
        source address of the probe packet (N1).  
      
      
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     2.2. Monitoring A Specific Flow 

        The network OAM needs to have the ability to monitor a particular 
        path from the available ECMP paths. For example, in the reference 
        topology in figure 1, there are many ECMP paths between N1 and N5. 
        However, the service provider may like to monitor a flow that 
        follows [N1]<link1>[N2]<link7>[N6]<link8>[N4]<link9>[N5].  

        The flow monitoring can be done continuously or can be triggered on 
        demand basis. It may be required to perform the connectivity 
        verification in the order of milliseconds, or at a slower pace.  

     2.3. Monitoring all ECMP/ UCMP Paths 

        In any network, it is common to see multiple ECMP paths between end 
        points that are used for load balancing or redundancy. While 
        monitoring, the shortest path helps to monitor the path and 
        liveliness of remote node, it may not be sufficient to detect any 
        failure in one of the ECMP paths. In our reference topology in 
        figure 1, N6 has 2 ECMP paths to reach N5 as below: 

        N6--<link8>--N4--<link9>--N5 

        N6--<link8>--N4--<link10>--N5 

        If the probe packet from N6 to N5 uses link10, it may not detect any 
        failure on link9. It is critical and beneficial to discover and 
        monitor all ECMP/ UCMP paths. Monitoring of all ECMP/ UCMP paths can 
        be done by probing the candidate paths from end-to-end or by each 
        node by monitoring its data plane.  

     2.4. Proof of Transit  

        Various scenarios require the packet to be steered over a particular 
        links or nodes. For example: 

        -    Voice traffic in a SLA constrained network needs to traverse a 
        low latency path between endpoints which may not be the shortest 
        path, i.e. the voice traffic needs to be traffic engineered and 
        steered over the specified segment list that satisfies the SLA 
        constraint. 

        -    In a service chaining environment, the traffic may need to 
        traverse over an ordered list of service functions.  

        In these scenarios, the SRH contains the list of SID functions that 
        the packet should execute before reaching the destination. It is 
      
      
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        possible, due to an error, that the packet may reach the destination 
        without visiting all the segments in the segment list. It is, 
        therefore, important to have the ability to verify that all the 
        function SIDs have been executed correctly before the packet is 
        delivered to the destination. It is also important to ensure that 
        the order of execution of the SID function has been consistent with 
        the SRH contents.  

     2.5. Detecting Path Divergence 

        Path divergence occurs when network traffic diverges from the 
        expected path that packet was supposed to take. Path divergence may 
        result in congestion, delay, or breakage of strict SLAs promised to 
        customers. It is, therefore, important to exercise mechanisms that 
        can detect path divergence in the SRv6 network.  

     2.6. Fault Isolation  

        In the cases where a monitoring technique discovers an issue, it is 
        required to have the ability to pinpoint the failure location. The 
        fault isolation mechanisms are required to help service providers 
        troubleshoot failure in an SRv6 network.   

     2.7. Centralized OAM   

        In the recent past, network operators are interested in performing 
        network operations, administration, and maintenance configuration in 
        a centralized manner. In this use-case, one of the requirements is 
        to implement centralized OAM functionality without any control plane 
        intervention at the monitored nodes.  

        Additional OAM use-cases will be included in a future revision of 
        the document. 

     3. OAM Mechanisms 

        This section describes how existing OAM mechanisms can be used in an 
        SRv6 network. Additional OAM mechanisms will be added in a future 
        revision of the document.  

     3.1. ICMPv6 Applicability 

        [RFC4443] describes Internet Control Message Protocol for IPv6 
        (ICMPv6) that is used by IPv6 devices for network diagnostic and 
        error reporting purposes. As Segment Routing with IPv6 data plane 
        (SRv6) simply adds a new type of Routing Extension Header, existing 
        ICMPv6 mechanisms can be used in an SRv6 network. This section 
      
      
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        describes the applicability of ICMPv6 in the SRv6 network and how 
        the existing ICMPv6 mechanisms can be used for basic OAM 
        functionality to address many use-cases outlined in Section 2.  

        Throughout this document, unless otherwise specified, the acronym 
        ICMPv6 refers to multi-part ICMPv6 messages [RFC4884]. The document 
        does not propose any changes to the standard ICMPv6 [RFC4443], 
        [RFC4884] or standard ICMPv4 [RFC792].   

     3.1.1. Ping 

        There is no change required for ping operation at the classic IPv6. 
        Similarly, the existing ping mechanism works along the IGP shortest 
        paths at an SRv6 capable node. However, if an SRv6 capable ingress 
        node wants to ping an IPv6 prefix via an arbitrary segment list <S1, 
        S2, S3>, it needs to initiate ICMPv6 ping with an SR header 
        containing the SID list <S1, S2, S3>. The originator can 
        appropriately set the flow-label field in the IPv6 header of the 
        echo request to influence Equal-Cost Multi-Path (ECMP).  

        Figure 2 contains sample output for a ping request initiated at node 
        N1 to the loopback address of node N5 via a segment list <A2::C31, 
        A4::C52>.  

        > ping B5:: via segment-list A2::C31, A4::C52  

        Sending 5, 100-byte ICMP Echos to B5::, timeout is 2 seconds: 
        !!!!! 
        Success rate is 100 percent (5/5), round-trip min/avg/max = 0.625 
        /0.749/0.931 ms 
                         A sample ping output at an SRv6 capable node 

        All transit nodes process the echo request message like any other 
        data packet carrying SR header and hence do not require any change. 
        Similarly, the egress node (IPv6 classic or SRv6 capable) does not 
        require any change to process the ICMPv6 echo request. For example, 
        in the ping example of Figure 2: 

        - Node N2, which is an SRv6 capable node, performs the standard SRH 
          processing. Specifically, it executes the END.X function (A2::C31) 
          on the echo request packet.  
        - Node N3, which is a classic IPv6 node, performs the standard IPv6 
          processing. Specifically, it forwards the echo request based on DA 
          A4::C52 in the IPv6 header.  
        - Node N4, which is an SRv6 capable node, performs the standard SRH 
          processing. Specifically, it observes the END.X function 
          (A4::C52)with PSP (Penultimate Segment POP) on the echo request 
      
      
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          packet and removes the SRH and forwards the packet across link10 
          to N5.  
        - The echo request packet at N5 arrives as an IPv6 packet without a 
          SRH. If the SRH arrives at classic N5, with SL=0, it should ignore 
          the routing header and process normally. Node N5, which is a 
          classic IPv6 node, performs the standard IPv6/ ICMPv6 processing 
          on the echo request.  

     3.1.2. Error Reporting 

        Any IPv6 node can use ICMPv6 control messages to report packet 
        processing errors to the host that originated the datagram packet. 
        To name a few such scenarios: 

        - If the router receives an undeliverable IP datagram, or 
        - If the router receives a packet with a Hop Limit of zero, or  
        - If the router receives a packet such that if the router decrements 
          the packet's Hop Limit it becomes zero, or 
        - If the router receives a packet with problem with a field in the 
          IPv6 header or the extension headers such that it cannot complete 
          processing the packet, or  
        - If the router cannot forward a packet because the packet is larger 
          than the MTU of the outgoing link.  

        In the scenarios listed above, the ICMPv6 response also contains the 
        IP header, IP extension headers and leading payload octets of the 
        "original datagram" to which the ICMPv6 message is a response. 
        Specifically, the Destination Unreachable Message, Time Exceeded 
        Message, Packet Too Big Message and Parameter Problem Message
        ICMPV6 messages can contain as much of the invoking packet as 
        possible without the ICMPv6 packet exceeding the minimum IPv6 MTU 
        [RFC4443], [RFC4884]. In an SRv6 network, the copy of the invoking 
        packet contains the SR header. The packet originator can use this 
        information for diagnostic purposes. For example, traceroute can use 
        this information as detailed in the following.  

     3.1.3. Traceroute 

        There is no change required for traceroute operation at the classic 
        IPv6. Similarly, the existing ping mechanism works along the IGP 
        shortest paths at an SRv6 capable node. However, if an SRv6 capable 
        ingress node wants to traceroute to IPv6 prefix via an arbitrary 
        segment list <S1, S2, S3>, it needs to initiate traceroute probe 
        with an SR header containing the SID list <S1, S2, S3>. The 
        originator can appropriately set the flow-label field in the IPv6 
        header of the traceroute probe to influence Equal-Cost Multi-Path 
        (ECMP).  
      
      
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        Figure 3 contains sample output for a traceroute request initiated 
        at node N1 to the loopback address of node N5 via a segment list < 
        A2::C31, A4::C52>.  

        > traceroute B5:: via segment-list A2::C31, A4::C52 

        Tracing the route to B5:: 

         1  99:1:2::21 0.512 msec 0.425 msec 0.374 msec 
            SRH: (B5::, A4::C52, A2::C31, SL=2) 
         
         2  99:2:3::31 0.721 msec 0.810 msec 0.795 msec 
            SRH: (B5::, A4::C52, A2::C31, SL=1) 
         
         3  99:3:4::41 0.921 msec 0.816 msec 0.759 msec 
            SRH: (B5::, A4::C52, A2::C31, SL=1) 

         5  99:4:5::52 0.879 msec 0.916 msec 1.024 msec 

                      A sample traceroute output at an SRv6 capable node 

        Please note that information for hop2 is returned by N3, which is a 
        classic IPv6 node. Nonetheless, the ingress node is able to display 
        SR header contents as the packet travels through the IPv6 classic 
        node. This is because the "Time Exceeded Message" ICMPv6 message can 
        contain as much of the invoking packet as possible without the 
        ICMPv6 packet exceeding the minimum IPv6 MTU [RFC4443]. The SR 
        header is also included in these ICMPv6 messages initiated by the 
        classic IPv6 transit nodes that are not running SRv6 software. 
        Specifically, a node generating ICMPv6 message containing a copy of 
        the invoking packet does not need to understand the extension 
        header(s) in the invoking packet.  

        The segment list information returned for hop1 is returned by N2, 
        which is an SRv6 capable node. Just like for hop2, the ingress node 
        is able to display SR header contents for hop1.  

        There is no difference in processing of the traceroute probe at an 
        IPv6 classic node and an SRv6 capable node. Similarly, both IPv6 
        classic and SRv6 capable nodes use the address of the interface on 
        which probe was received as the source address in the ICMPv6 
        response. ICMP extensions defined in [RFC5837] can be used to also 
        display information about the IP interface through which the 
        datagram would have been forwarded had it been forwardable, and the 
        IP next hop to which the datagram would have been forwarded, the IP 
        interface upon which a datagram arrived, the sub-IP component of an 
        IP interface upon which a datagram arrived. 
      
      
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        The information about the IP address of the incoming interface on 
        which the traceroute probe was received by the reporting node is 
        very useful. This information can also be used to verify if SID 
        functions A2::C31 and A4::C52 are executed correctly by N2 and N4, 
        respectively. Specifically, the information displayed for hop2 
        contains the incoming interface address 99:2:3::31 at N3. This 
        matches with the expected interface bound to END.X function A2::C31 
        (link3). Similarly, the information displayed for hop5 contains the 
        incoming interface address 99:4:5::52 at N5. This matches with the 
        expected interface bound to the END.X function A4::C52 (link10).   

     3.2. In-situ OAM    

        [I-D.brockners-inband-oam-requirements] describes motivation 
        and requirements for In-situ OAM (iOAM). iOAM records operational 
        and telemetry information in the data packet while the packet 
        traverses the network of telemetry domain. iOAM complements out-of-
        band probe based OAM mechanisms such ICMP ping and traceroute by 
        directly encoding tracing and the other kind of telemetry 
        information to the regular data traffic.  

        [I-D.brockners-inband-oam-transport] describes transport mechanisms 
        for iOAM data including IPv6 and Segment Routing traffic. 
        furthermore, [I-D.brockners-inband-oam-data] defines information 
        encoding for iOAM data.  
        
        One of the applications of iOAM is to provide the Proof of Transit 
        (POT). Among other features of iOAM, SRv6 networks can use the POT 
        feature of iOAM to verify that all the function SIDs in SRH have 
        been executed before the packet is delivered to the destination. It 
        can also ensure that the order of execution of the SID function has 
        been consistent with the SRH contents.   

        More details on various applications of iOAM in SRv6 networks will 
        be included in future versions of this document. 

     3.3. Seamless BFD Applicability 

        [RFC7880] defines Seamless BFD (S-BFD) architecture that simplifies 
        BFD mechanism and enables it to perform path monitoring in a 
        controlled and scalable manner. [RFC7881] describes the procedure to 
        perform continuity check using S-BFD in different environments 
        including IPv6 networks. Section 5.1 of [RFC7881] explains the 
        SBFDInitiator specification and procedure to initiate S-BFD control 
        packet in IP and MPLS network. The specification described for IP-
        routed S-BFD control packet is also directly applicable to the SRv6 
        network.  
      
      
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        S-BFD has a fast bootstrapping capability. Furthermore, in S-BFD, 
        only the ingress is required to keep BFD states; the egress and 
        transit node does not have any knowledge of the BFD session. These 
        attributes of S-BFD makes it an excellent candidate for rapid 
        failure detection in the SRv6 network. More details on various S-BFD 
        usage on the SRv6 network will be included in a future version. 

     3.4. Controller based OAM 

        In the recent past, network operators are interested in performing 
        network operations, administration, and maintenance configuration in 
        a centralized manner. Various data models like YANG are available to 
        collect data from the network and manage it from a centralized 
        entity.  

        SR technology enables a centralized OAM entity to perform path 
        monitoring from centralized OAM entity without control plane 
        intervention on monitored nodes. [I.D-draft-ietf-spring-oam-usecase] 
        describes such a centralized OAM mechanism. Specifically, the draft 
        describes a procedure that can be used to perform path continuity 
        check between any nodes within an SR domain from a centralized 
        monitoring system, with minimal or no control plane intervene on the 
        nodes. However, the draft focuses on SR networks with MPLS data 
        plane. The same concept applies to the SRv6 networks. This document 
        describes how the concept can be used to perform path monitoring in 
        an SRv6 network. 

        In the above reference topology, N100 is the centralized monitoring 
        system implementing an END function A100::. In order to verify a 
        segment list <A2::C31, A4::C52>, N100 generates a probe packet with 
        SRH set to (A100::, A4::C52, A2::C31, SL=2). The controller routes 
        the probe packet towards the first segment, which is A2::C31. N2 
        performs the standard SRH processing and forward it over link3 with 
        the DA of IPv6 packet set to A4::C52. N4 also performs the normal 
        SRH processing and forward it over link10 with the DA of IPv6 packet 
        set to A100::. This makes the probe loops back to the centralized 
        monitoring system. Please note that there is no control plane 
        intervention at the monitored nodes. The entire data plane is exercised
        at the monitored nodes. 

        In our reference topology in Figure 1, N100 uses an IGP protocol 
        like OSPF or ISIS to get the topology view within the IGP domain. 
        N100 can also use BGP-LS to get the complete view of an inter-domain 
        topology. In other words, the controller leverages the visibility of 
        the topology to monitor the paths between the various endpoints 
        without control plane intervention required at the monitored nodes. 

      
      
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     4. Security Considerations 

        This document does not define any new protocol extensions and relies 
        on existing procedures defined for ICMP. This document does not 
        impose any additional security challenges to be considered beyond 
        security considerations described in [RFC4884], [RFC4443], [RFC792] 
        and RFCs that updates these RFCs.  

     5. IANA Considerations 

        This document does not define any new protocol or any extension to 
        an existing protocol.   

     6. References 

     6.1. Normative References 

        [RFC4884] Extended ICMP to Support Multi-Part Messages. R. Bonica, 
                  D. Gan, D. Tappan, C. Pignataro. April 2007. 

        [RFC4443] Internet Control Message Protocol (ICMPv6) for the 
                  Internet Protocol Version 6 (IPv6) Specification. A. 
                  Conta, S. Deering, M. Gupta, Ed. March 2006.  

        [RFC792] Internet Control Message Protocol. J. Postel. September 
                  1981. 

        [RFC5837] Extending ICMP for Interface and Next-Hop Identification. 
                  A. Atlas, Ed., R. Bonica, Ed., C. Pignataro, Ed., N. Shen, 
                  JR. Rivers. April 2010. 

        [RFC7880] Seamless Bidirectional Forwarding Detection (S-BFD). C.Pignataro,            
                  D.Ward, N.Akiya, M.Bhatia, S.Pallagatti. July 2016.

        [RFC7881] Seamless Bidirectional Forwarding Detection (S-BFD) for IPv4, IPv6, 
                  and MPLS. C.Pignataro, D.Ward, N.Akiya. July 2016.

        [RFC7880] Seamless Bidirectional Forwarding Detection (S-BFD). C.Pignataro, 
                  D.Ward, N.Akiya, M.Bhatia, S.Pallagatti. July 2016.

        [RFC7881] Seamless Bidirectional Forwarding Detection (S-BFD) for IPv4, IPv6, 
                  and MPLS. C.Pignataro, D.Ward, N.Akiya. July 2016.

        [I.D-draft-ietf-spring-oam-usecase] A Scalable and Topology-Aware 
                  MPLS Dataplane Monitoring System. R. Geib, C. Filsfils, C. 
                  Pignataro, N. Kumar. 

        [I-D.brockners-inband-oam-data] Data Formats for In-situ OAM. F.          
                  Brockners, work in progress.

        [I-D.brockners-inband-oam-transport] Encapsulations for In-situ OAM Data, 
                  F.Brockners, work in progress.

     6.2. Informative References 

        [I-D.filsfils-spring-srv6-network-programming] SRv6 Network 
                  Programming, draft-filsfils-spring-srv6-network-
                  programming, C. Fisfils, et al.  

        [I-D.brockners-inband-oam-requirements] Requirements for In-situ OAM, 
                  F.Brockners, work in progress.

     7. Acknowledgments 

        To be added.  

      
      
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     Internet-Draft                 SRv6 OAM                       July 2017 
         

     Authors' Addresses

        Clarence Filsfils 
        <Cisco Systems, Inc.> 
        Email: cfilsfil@cisco.com 

        Zafar Ali 
        Cisco Systems, Inc.  
        Email: zali@cisco.com 
         
        Nagendra Kumar 
        Cisco Systems, Inc.  
        Email: naikumar@cisco.com 

        Faisal Iqbal  
        Cisco Systems, Inc.  
        Email: faiqbal@cisco.com 

        Robert Raszuk 
        Bloomberg LP 
        731 Lexington Ave 
        New York City, NY10022, USA 
        Email: robert@raszuk.net 

        Bart Peirens 
        Proximus 
        Netherlands 
        Email: bart.peirens@proximus.com 

        Gaurav Naik 
        Drexel University 
        United States of America 
        Email: gn@drexel.edu 

         

         

         

         

         

      

      
      
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