Path Computation Element Communication Protocol (PCEP) extensions for Circuit Style Policies
draft-ietf-pce-circuit-style-pcep-extensions-07

PCE Working Group                                               S. Sidor
Internet-Draft                                       Cisco Systems, Inc.
Intended status: Standards Track                           P. Maheshwari
Expires: 9 May 2025                                         Airtel India
                                                                A. Stone
                                                                   Nokia
                                                                L. Jalil
                                                                 Verizon
                                                                 S. Peng
                                                     Huawei Technologies
                                                         5 November 2024

 Path Computation Element Communication Protocol (PCEP) extensions for
                         Circuit Style Policies
            draft-ietf-pce-circuit-style-pcep-extensions-07

Abstract

   Segment Routing (SR) enables a node to steer packet flows along a
   specified path without the need for intermediate per-path states, due
   to the utilization of source routing.  An SR Policy comprises a
   sequence of segments, which are essentially instructions that define
   a source-routed policy

   This document proposes a set of extensions to the Path Computation
   Element Communication Protocol (PCEP) for Segment Routing Policies
   that are designed to satisfy requirements for connection-oriented
   transport services (Circuit-Style SR policies).  They include the
   ability to control path recomputation and the option to request path
   with strict hops only and are also applicable for generic SR policy
   use cases where controlling path recomputation or distinct hop
   requirements are applicable.

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 https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

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   This Internet-Draft will expire on 9 May 2025.

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 (https://trustee.ietf.org/
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Overview of Extensions to PCEP  . . . . . . . . . . . . . . .   4
     3.1.  New flags in STATEFUL-PCE-CAPABILITY TLV  . . . . . . . .   4
     3.2.  New flag in the LSP-EXTENDED-FLAG TLV . . . . . . . . . .   4
     3.3.  PATH-RECOMPUTATION TLV  . . . . . . . . . . . . . . . . .   5
   4.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Strict Path Enforcement . . . . . . . . . . . . . . . . .   6
     4.2.  Path Recomputation  . . . . . . . . . . . . . . . . . . .   6
   5.  Manageability Considerations  . . . . . . . . . . . . . . . .   7
     5.1.  Control of Function and Policy  . . . . . . . . . . . . .   7
     5.2.  Information and Data Models . . . . . . . . . . . . . . .   7
     5.3.  Liveness Detection and Monitoring . . . . . . . . . . . .   8
     5.4.  Verify Correct Operations . . . . . . . . . . . . . . . .   8
     5.5.  Requirements On Other Protocols . . . . . . . . . . . . .   8
     5.6.  Impact On Network Operations  . . . . . . . . . . . . . .   8
   6.  Implementation Status . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Cisco . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  STATEFUL-PCE-CAPABILITY . . . . . . . . . . . . . . . . .   9
     8.2.  LSP-EXTENDED-FLAG TLV . . . . . . . . . . . . . . . . . .  10
     8.3.  PATH-RECOMPUTATION TLV  . . . . . . . . . . . . . . . . .  10
     8.4.  PATH-RECOMPUTATION TLV Flag Field . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

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1.  Introduction

   Segment Routing (SR) leverages the source routing paradigm, where the
   sender of a packet can define the path that the packet takes through
   the network.  This is achieved by encoding the path information as a
   sequence of segments within the packet header.  SR can be applied to
   both MPLS and IPv6 data planes, providing a flexible and scalable
   method for traffic engineering.

   The Path Computation Element (PCE) is a network component,
   application, or node that is capable of computing a network path or
   route based on a network graph and applying computational
   constraints.  The PCE Communication Protocol (PCEP) enables
   communication between a PCE and Path Computation Clients (PCCs),
   facilitating the computation of optimal paths for traffic flows.

   [RFC8664] introduces the concept of Segment Routing Policy (SR
   Policy), which is a set of candidate paths that can be used to steer
   traffic through a network.  Each candidate path is represented by a
   list of segments, and the path can be dynamically adjusted based on
   network conditions and requirements.

   In connection-oriented transport services, such as those defined in
   [I-D.ietf-spring-cs-sr-policy], there is a need for path persistency
   and per-hop behavior for PCE-computed paths.  This ensures that the
   paths remain stable and predictable, which is crucial for services
   that require high reliability and performance guarantees.

   To support the requirements of connection-oriented transport
   services, this document specifies extensions to PCEP that enable the
   use of Circuit Style Policies.  These extensions allow for the
   request of strict paths from the PCE, the encoding of information to
   disable path recomputation for specific paths, and the clarification
   of the usage of existing flags within PCEP messages.

   The PCEP extensions described in this document are designed to be
   compatible with any Path Setup Type and are not limited to Circuit
   Style SR policies, ensuring broad applicability across different
   network environments and use cases.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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2.  Terminology

   The following terminologies are used in this document:

   ERO:  Explicit Route Object

   IGP:  Interior Gateway Protocol

   LSP:  Label Switched Path.

   LSPA:  Label Switched Path Attributes.

   OTN:  Optical Transport Network.

   PCC:  Path Computation Client

   PCE:  Path Computation Element

   PCEP:  Path Computation Element Protocol.

   SID:  Segment Identifier

   SR:  Segment Routing.

   SR-TE:  Segment Routing Traffic Engineering.

3.  Overview of Extensions to PCEP

3.1.  New flags in STATEFUL-PCE-CAPABILITY TLV

   The STATEFUL-PCE-CAPABILITY TLV is an optional TLV introduced in
   [RFC8231] in the OPEN object for stateful PCEP peer capability
   advertisement.  This document defines the following new flags in that
   TLV:

   *  STRICT-PATH-CAPABILITY - 1 bit (Bit Position 18) - If set to 1, it
      indicates support for Strict-Path flag in LSP-EXTENDED-FLAG TLV.
      See Section 4.1 for details.

   *  PATH-RECOMPUTATION-CAPABILITY - 1 bit (Bit Position 19) - If set
      to 1, it indicates support for PATH-RECOMPUTATION TLV.  See
      Section 4.2 for details.

3.2.  New flag in the LSP-EXTENDED-FLAG TLV

   O-flag is proposed in the LSP-EXTENDED-FLAG TLV, which was introduced
   in 3.1 of [RFC9357].

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   O (Strict-Path) - 1 bit (Bit Position 4): If set to 1, this indicates
   to the PCE that a path exclusively made of strict hops is required.
   Strict hop definition is described in Section 4.1

3.3.  PATH-RECOMPUTATION TLV

   This document defines new TLV for the LSPA Object for encoding
   information whether path recomputation is allowed for delegated LSP.
   The TLV is optional.  If the TLV is included in LSPA object, the PCE
   MUST NOT recompute path in cases specified by flags in the TLV.  Only
   the first instance of this TLV MUST be processed, subsequent
   instances MUST be ignored.

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           Type = 72          |             Length = 4         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |             Reserved         |      Flags                 |P|F|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type: the value is 72

   Length: 4 octets

   Reserved:  MUST be set to zero by the sender and MUST be ignored by
      the receiver.

   Flags:  This document defines the following flag bits.  The other
      bits MUST be set to zero by the sender and MUST be ignored by the
      receiver.

      *  P (Permanent): If set to 1, the PCE MUST NOT recompute path
         even if current path is not satisfying path computation
         constraints.  If this flag is cleared, then the PCE SHOULD
         recompute path if original path is invalidated.

      *  F (Force): If set to 1, the PCE MUST NOT update path
         (exceptions description in Section 4.2).  If flag is cleared,
         the PCE MAY update path based on explicit request from
         operator.

4.  Operation

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4.1.  Strict Path Enforcement

   PCC MAY set the O flag in LSP-EXTENDED-FLAG TLV in PCRpt message sent
   to the PCE to indicate that a path exclusively made of strict hops is
   required.  It MUST NOT be set to 1 if one or both PCEP speakers have
   not set STRICT-PATH-CAPABILITY to 1 in STATEFUL-PCE-CAPABILITY TLV.
   If PCEP peer received LSP-EXTENDED-FLAG TLV with O flag set, but it
   does not support that flag, it MUST send PCErr with Error-Type = 2
   (Capability not supported).

   O flag cleared or LSP-EXTENDED-FLAG TLV not included indicates that a
   loose path is acceptable.

   In PCUpd or PCInitiate messages, PCE MAY set O bit if strict path is
   provided.

   The flag is applicable only for stateful messages.  Existing O flag
   in RP object MAY be used to indicate similar behavior in PCReq and
   PCRep messages as described in as described in Section 7.4.1 of
   [RFC5440].

   If O flag is set to 1 for both stateful and stateless messages for SR
   paths introduced in [RFC8664], PCE MUST use only SIDs that explicitly
   specify adjacencies for packet forwarding.  For example Adjacency
   SIDs MAY be used, but Prefix SIDs MUST NOT be used (even if there is
   only one adjacency).

4.2.  Path Recomputation

   PCC MAY set flags in PATH-RECOMPUTATION TLV to control path
   computation behavior on PCE side.  If TLV is not included, then the
   PCE MAY use local policy to trigger path-computation or LSP path
   update.

   If a PCEP speaker does not recognize the PATH-RECOMPUTATION TLV, it
   MUST ignore the TLV based on Section 7.1 of [RFC5440].  If a PCEP
   speaker recognizes the TLV but does not support the TLV, it MUST send
   PCErr with Error-Type = 2 (Capability not supported).

   The presence of the TLV is blocking path recomputation based on
   various triggers like topology update, any periodic update or changed
   state of other LSPs in the network.  LSP path MAY be modified if
   forwarded packets will still use same path - for example if same path
   can be encoded using Adjacency, Binding, Prefix or other SIDs, then
   PCE MAY switch between various representations of same path.

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   If P flag is cleared, the PCE MAY recompute if current path is not
   considered valid, for example after topology update resulting in path
   not satisfying LSP's path constraints, but it MUST NOT recompute path
   if current path is not optimal.

   If P flag is set, the PCE MUST NOT recompute path during LSP lifetime
   even if path is invalidated.  Only exception is explicit request from
   operator to recompute path

   If F flag is cleared, path update triggered manually by operator or
   any northbound interface of PCE MAY be done.  If flag is set then PCE
   can update path only to tear down LSP by sending PCUpd message with
   empty ERO ERO or to bring it up again with path, which was used
   before LSP was tore down.

   TLV MAY be included in PCInitiate and PCUpd messages to indicate,
   which triggers will be disabled on the PCE.  PCC should reflect flag
   values in PCRpt messages to forward requirement to other PCEs in the
   network.

5.  Manageability Considerations

   All manageability requirements and considerations listed in
   [RFC5440], [RFC8231] and [RFC8281] apply to PCEP protocol extensions
   defined in this document.  In addition, requirements and
   considerations listed in this section apply.

5.1.  Control of Function and Policy

   A PCE or PCC implementation MAY allow the capability of supporting
   PCEP extensions introduced in this document to be enabled/disabled as
   part of the global configuration.

5.2.  Information and Data Models

   An implementation SHOULD allow the operator to view the PCEP peer
   capability defined in this document.  Section 4.1 and 4.1.1 of
   [I-D.ietf-pce-pcep-yang] should be extended to include that
   capability for PCEP peer.

   Section 4.2 of [I-D.ietf-pce-pcep-yang] module should be extended to
   add notification for blocked recomputation satisfying specified
   constraints if recomputation is blocked using PATH-RECOMPUTATION TLV.

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5.3.  Liveness Detection and Monitoring

   Circuit-Style Policy draft [I-D.ietf-spring-cs-sr-policy] is already
   describing connectivity verification and path validity considerations
   for Circuit Style Policies.

5.4.  Verify Correct Operations

   A PCE implementation SHOULD notify operator in case blocked
   recomputation for LSP, which is no longer satisfying specified
   constraints and it SHOULD allow the operator to view LSPs on PCE,
   which are not satisfying specified constraints.

5.5.  Requirements On Other Protocols

   The PCEP extensions defined in this document do not imply any new
   requirements on other protocols.  Overall concept of Circuit Style
   policies requires interaction with other protocols, but those
   requirements are already described in [I-D.ietf-spring-cs-sr-policy].

5.6.  Impact On Network Operations

   The mechanisms defined in [RFC5440], [RFC8231], and [RFC8281] also
   apply to the PCEP extensions defined in this document.

6.  Implementation Status

   [Note to the RFC Editor - remove this section before publication, as
   well as remove the reference to RFC 7942.]

   This section records the status of known implementations of the
   protocol defined by this specification at the time of posting of this
   Internet-Draft, and is based on a proposal described in [RFC7942].
   The description of implementations in this section is intended to
   assist the IETF in its decision processes in progressing drafts to
   RFCs.  Please note that the listing of any individual implementation
   here does not imply endorsement by the IETF.  Furthermore, no effort
   has been spent to verify the information presented here that was
   supplied by IETF contributors.  This is not intended as, and must not
   be construed to be, a catalog of available implementations or their
   features.  Readers are advised to note that other implementations may
   exist.

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   According to [RFC7942], "this will allow reviewers and working groups
   to assign due consideration to documents that have the benefit of
   running code, which may serve as evidence of valuable experimentation
   and feedback that have made the implemented protocols more mature.
   It is up to the individual working groups to use this information as
   they see fit".

6.1.  Cisco

   *  Organization: Cisco Systems

   *  Implementation: IOS-XR PCC and PCE.

   *  Description: PCEP extensions supported using VENDOR-INFORMATION
      Object.

   *  Maturity Level: Production.

   *  Coverage: Partial.

   *  Contact: ssidor@cisco.com

7.  Security Considerations

   The security considerations described in [RFC5440], [RFC8231],
   [RFC8253],[RFC8281] and [RFC8664] in itself.

   Note that this specification introduces possibility to block path
   recomputation after various topology events.  This creates an
   additional vulnerability if the security mechanisms of [RFC5440],
   [RFC8231], and [RFC8281] are not used.  If there is no integrity
   protection on the session, then an attacker could block path updates
   from PCE potentially resulting in traffic drop.

   As per [RFC8231] it is RECOMMENDED that these PCEP extensions only be
   activated on authenticated and encrypted sessions across PCEs and
   PCCs using Transport Layer Security (TLS) [RFC8253], as per the
   recommendations and best current practices in RFC 9325 [BCP195]
   (unless explicitly set aside in [RFC8253]).

8.  IANA Considerations

8.1.  STATEFUL-PCE-CAPABILITY

   [RFC8231] defines the STATEFUL-PCE-CAPABILITY.  IANA is requested to
   make the following assignment from the "STATEFUL-PCE-CAPABILITY TLV
   Flag Field" registry:

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          +=====+===============================+===============+
          | Bit | Description                   | Reference     |
          +=====+===============================+===============+
          |  18 | STRICT-PATH-CAPABILITY        | This document |
          +-----+-------------------------------+---------------+
          |  19 | PATH-RECOMPUTATION-CAPABILITY | This document |
          +-----+-------------------------------+---------------+

                                  Table 1

8.2.  LSP-EXTENDED-FLAG TLV

   [RFC9357] defines the LSP-EXTENDED-FLAG TLV.  IANA is requested to
   make the following assignment from the "LSP-EXTENDED-FLAG TLV Flag
   Field" registry:

              +=====+======================+===============+
              | Bit | Description          | Reference     |
              +=====+======================+===============+
              |  4  | Strict-Path Flag (O) | This document |
              +-----+----------------------+---------------+

                                 Table 2

8.3.  PATH-RECOMPUTATION TLV

   IANA is requested to make the assignment of a new value for the
   existing "PCEP TLV Type Indicators" registry as follows:

           +==========+========================+===============+
           | TLV Type | TLV Name               | Reference     |
           +==========+========================+===============+
           |    72    | PATH-RECOMPUTATION TLV | This document |
           +----------+------------------------+---------------+

                                  Table 3

8.4.  PATH-RECOMPUTATION TLV Flag Field

   IANA has created a new registry named "PATH-RECOMPUTATION TLV Flag
   Field" within the "Path Computation Element Protocol (PCEP) Numbers"
   registry group.  New values are to be assigned by "IETF Review"
   [RFC8126].  Each bit should be tracked with the following qualities:

   *  Bit number (count from 0 as the most significant bit)

   *  Description

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   *  Reference

   The registry contains the following codepoints, with initial values,
   to be assigned by IANA with the reference set to this document:

                  +======+=============+===============+
                  | Bit  | Description | Reference     |
                  +======+=============+===============+
                  | 0-13 | Unassigned  |               |
                  +------+-------------+---------------+
                  |  14  | Permanent   | This document |
                  +------+-------------+---------------+
                  |  15  | Force       | This document |
                  +------+-------------+---------------+

                                 Table 4

9.  References

9.1.  Normative References

   [BCP195]   Best Current Practice 195,
              <https://www.rfc-editor.org/info/bcp195>.
              At the time of writing, this BCP comprises the following:

              Moriarty, K. and S. Farrell, "Deprecating TLS 1.0 and TLS
              1.1", BCP 195, RFC 8996, DOI 10.17487/RFC8996, March 2021,
              <https://www.rfc-editor.org/info/rfc8996>.

              Sheffer, Y., Saint-Andre, P., and T. Fossati,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC9325, November
              2022, <https://www.rfc-editor.org/info/rfc9325>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

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   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8231]  Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for Stateful PCE", RFC 8231,
              DOI 10.17487/RFC8231, September 2017,
              <https://www.rfc-editor.org/info/rfc8231>.

   [RFC8281]  Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for PCE-Initiated LSP Setup in a Stateful PCE
              Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
              <https://www.rfc-editor.org/info/rfc8281>.

   [RFC8664]  Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
              and J. Hardwick, "Path Computation Element Communication
              Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
              DOI 10.17487/RFC8664, December 2019,
              <https://www.rfc-editor.org/info/rfc8664>.

   [RFC9357]  Xiong, Q., "Label Switched Path (LSP) Object Flag
              Extension for Stateful PCE", RFC 9357,
              DOI 10.17487/RFC9357, February 2023,
              <https://www.rfc-editor.org/info/rfc9357>.

9.2.  Informative References

   [I-D.ietf-pce-pcep-yang]
              Dhody, D., Beeram, V. P., Hardwick, J., and J. Tantsura,
              "A YANG Data Model for Path Computation Element
              Communications Protocol (PCEP)", Work in Progress,
              Internet-Draft, draft-ietf-pce-pcep-yang-26, 19 October
              2024, <https://datatracker.ietf.org/doc/html/draft-ietf-
              pce-pcep-yang-26>.

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   [I-D.ietf-spring-cs-sr-policy]
              Schmutzer, C., Ali, Z., Maheshwari, P., Rokui, R., and A.
              Stone, "Circuit Style Segment Routing Policies", Work in
              Progress, Internet-Draft, draft-ietf-spring-cs-sr-policy-
              03, 18 October 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-spring-
              cs-sr-policy-03>.

   [RFC7942]  Sheffer, Y. and A. Farrel, "Improving Awareness of Running
              Code: The Implementation Status Section", BCP 205,
              RFC 7942, DOI 10.17487/RFC7942, July 2016,
              <https://www.rfc-editor.org/info/rfc7942>.

   [RFC8253]  Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
              "PCEPS: Usage of TLS to Provide a Secure Transport for the
              Path Computation Element Communication Protocol (PCEP)",
              RFC 8253, DOI 10.17487/RFC8253, October 2017,
              <https://www.rfc-editor.org/info/rfc8253>.

Contributors

   Daniel Voyer
   Bell Canada
   Email: daniel.voyer@bell.ca

   Reza Rokui
   Ciena
   Email: rrokui@ciena.com

   Tarek Saad
   Cisco Systems, Inc.
   Email: tsaad.net@gmail.com

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

   Ran Chen
   ZTE Corporation
   Email: chen.ran@zte.com.cn

   Quan Xiong
   ZTE Corporation

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   Email: xiong.quan@zte.com.cn

   Dhruv Dhody
   Huawei
   Email: dhruv.ietf@gmail.com

   Christian Schmutzer
   Cisco Systems, Inc.
   Email: cschmutz@cisco.com

Authors' Addresses

   Samuel Sidor
   Cisco Systems, Inc.
   Eurovea Central 3.
   811 09 Bratislava
   Slovakia
   Email: ssidor@cisco.com

   Praveen Maheshwari
   Airtel India
   Email: Praveen.Maheshwari@airtel.com

   Andrew Stone
   Nokia
   Email: andrew.stone@nokia.com

   Luay Jalil
   Verizon
   Email: luay.jalil@verizon.com

   Shuping Peng
   Huawei Technologies
   Email: pengshuping@huawei.com

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