[Docs] [txt|pdf] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02

Network Working Group                                              Z. Li
Internet-Draft                                                   Q. Zhao
Intended status: Informational                       Huawei Technologies
Expires: August 18, 2014                                         T. Yang
                                                            China Mobile
                                                       February 14, 2014


                    A Framework of MPLS Global Label
                draft-li-mpls-global-label-framework-01

Abstract

   The document defines the framework of MPLS global label including:
   representation of MPLS global label, process of control plane for
   MPLS global label, and process of data plane for MPLS global label.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://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."

   This Internet-Draft will expire on August 18, 2014.

Copyright Notice

   Copyright (c) 2014 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
   (http://trustee.ietf.org/license-info) in effect on the date of



Li, et al.               Expires August 18, 2014                [Page 1]


Internet-Draft      A Framework of MPLS Global Label       February 2014


   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Representation of MPLS Global Label . . . . . . . . . . . . .   3
     3.1.  Option A  -- Traditional MPLS Label . . . . . . . . . . .   3
     3.2.  Option B -- Expansions of MPLS Label  . . . . . . . . . .   3
   4.  Control Plane . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .   4
       4.1.1.  Shared MPLS Global Label Range Calculation  . . . . .   4
       4.1.2.  MPLS Global Label Allocation  . . . . . . . . . . . .   4
       4.1.3.  MPLS Global Label Withdraw  . . . . . . . . . . . . .   5
       4.1.4.  Error Process . . . . . . . . . . . . . . . . . . . .   5
       4.1.5.  Redundancy  . . . . . . . . . . . . . . . . . . . . .   5
     4.2.  BGP-Based Control Plane . . . . . . . . . . . . . . . . .   6
     4.3.  IGP-Based Control Plane . . . . . . . . . . . . . . . . .   6
     4.4.  PCE-Based Control Plane . . . . . . . . . . . . . . . . .   8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   [I-D.li-mpls-global-label-usecases] proposes possible usecases of
   MPLS global label.  MPLS global label can be used for identification
   of the location, the service and the network in different application
   scenarios.  The new solutions based on MPLS global label can gain
   advantage over the existing solutions to facilitate service
   provisions.

   This document defines the framework for MPLS global label.  The
   framework includes the representation of MPLS global label, the
   process of control plane and data plane for MPLS global label.








Li, et al.               Expires August 18, 2014                [Page 2]


Internet-Draft      A Framework of MPLS Global Label       February 2014


2.  Terminology

   BDR: Backup Designated Router

   DR: Designated Router

   FEC: Forward Equivalence Class

   MVPN: Multicast VPN

   NBMA: Non-broadcast multi-access

   PCE: Path Computation Element

   PCC: Path Computation Client

   RR: Route Reflector

3.  Representation of MPLS Global Label

3.1.  Option A -- Traditional MPLS Label

   Current MPLS label uses 20 bits to represent the label range from 0
   to 2^20 - 1.  Since the existing MPLS label is always allocated
   locally, in order to guarantee a specific label is allocated
   globally, the available label values of the network nodes should be
   reported to a central control point.  The central control point can
   calculate the COMMON label space which is available for all network
   nodes.  Then the network nodes must reserve the common label space
   for the global label.  When the global label is requested to allocate
   for specific service, the central control point can allocate the
   label from the common label space.

3.2.  Option B -- Expansions of MPLS Label

   [I-D.mpls-big-label-ucase-req] proposes the usecases and requirements
   for MPLS big label.  It could also be a reasonable way to define a
   new label range or segment for MPLS global label which is independent
   from the existing MPLS label range.  The label stack mechanism can be
   introduced to expand the MPLS label range.  For example, the MPLS
   global label can be represented as the following figure.  The global
   label value is achieved by adding the actual base label value
   indicated by the base label and the remainder label value.








Li, et al.               Expires August 18, 2014                [Page 3]


Internet-Draft      A Framework of MPLS Global Label       February 2014


0                                     32                                   64
+-------------------+----+-+---------+-------------------+----+-+---------+
|    Base    Label  | TC |S|   TTL   |  Remainder Label  | TC |S|   TTL   |
+-------------------+----+-+---------+-------------------+----+-+---------+

              Figure 1 Representation of MPLS Global Label

   If the new label range is used for the global label, it can reduce
   the possible confliction with the existing label range.

4.  Control Plane

4.1.  Overview

   MPLS global label should be allocated concentratedly to guarantee all
   nodes can understand the same meaning for a specific global label.
   It should adopt a server/client model in the control plane for MPLS
   global label allocation.  The procedures for the global label are
   described as follows.

4.1.1.  Shared MPLS Global Label Range Calculation

   1.  Clients nodes should report MPLS global label capability to the
   central controller.

   2.  The central controller collects MPLS global label capability and
   MPLS global label range of all nodes.  Then it can calculate the
   shared MPLS global label range for all nodes.

   3.  The centralized controller should notify the shared global label
   range to all client nodes.  Client nodes reserve the shared global
   label range.

4.1.2.  MPLS Global Label Allocation

   1.  The client node should send the global label request for specific
   usage to the central controller.  FEC(Forward Equivalence Class)
   should be incorporated in the MPLS global label request message.

   2.  When the central controllers receives the MPLS global label
   request, it should allocate the label from the shared MPLS global
   label segment of all nodes.

   3.  The central controller sends the MPLS global label mapping
   message to all client nodes.  Thus the MPLS global label for specific
   usage can be understood by all client nodes.





Li, et al.               Expires August 18, 2014                [Page 4]


Internet-Draft      A Framework of MPLS Global Label       February 2014


   4.  The client node receives the MPLS global label mapping message
   and installs the corresponding MPLS forwarding entry for the global
   label.

4.1.2.1.  Process of Duplicate MPLS Global Label Request

   Since MPLS global label is used for specific usage globally, it is
   possible that multiple MPLS global label requests for the same usage
   are sent by different client nodes to the central controller.  The
   controller needs to count the MPLS global label requests for the same
   usage.  It can send multiple global label mapping messages to respond
   these requests.  It can also send only one copy of the global label
   mapping message to all nodes in order to reduce the unnecessary
   protocol operation.  If the controller sends multiple copies of the
   global label mapping message to respond each label request, client
   nodes need to ignore the subsequent messages.

4.1.3.  MPLS Global Label Withdraw

   TBD.

4.1.4.  Error Process

   TBD.

4.1.5.  Redundancy

   Since MPLS global label is allocated concentratedly, it is important
   to guarantee the high availability of the central controller.
   Redundant backup needs to be introduced for the high availability.
   The backup central controller needs to learn global label requests
   sent by client nodes and corresponding label mapping sent by the
   primary central controller.  The backup central controller will not
   send any global label mapping to client nodes until failure happens
   for the primary central controller.

   The primary role and the backup role of the central controllers can
   be specified administratively.  They can also be elected dynamically
   based on auto-discovery of these controllers.

   The failure detection mechanism also needs to be introduced between
   the primary controller and the backup controller.  It can be the
   keepalive-like mechanism, the fast detection mechanism like BFD, or
   mixing use of both mechanisms.







Li, et al.               Expires August 18, 2014                [Page 5]


Internet-Draft      A Framework of MPLS Global Label       February 2014


4.2.  BGP-Based Control Plane

                     +---------------------+
                     |      IP/MPLS        |
                     |      Network        |
   +----+     +----+ |                     | +----+     +----+
   | CE1|-----|    | |                     | |    |-----| CE2|
   +----+\    | PE1|\|     +----------+    |/| PE3|     +----+
          \   +----+ \_____|    BGP   |    / +----+
           \               |Controller|___/|
            \ +----+ /-----|  (RR+)   |    |
             \|    |/|     +----------+    |
              | PE2| |                     |
              +----+ |                     |
                     +---------------------+

                Figure 2: BGP-based Control Plane

   Many types of services such as VPLS[RFC4761], Multicast VPN[RFC6514]
   and E-VPN[I-D.ietf-l2vpn-evpn] are based on MP-BGP.  If new solutions
   based on MPLS global label are introduced for such services, the
   architecture shown in the figure 2 can be applied.

   In the BGP-based control plane, Route Reflector (RR) of BGP [RFC4456]
   can act as the role of the central controller.  We call this type of
   RR as RR+. For VPLS, Multicast VPN and E-VPN services, auto-discovery
   mechanisms based on MP-BGP are introduced.  So the RR+ can learn the
   necessary membership information through these A-D routes.  RR+ can
   also learn the MPLS label capability information through necessary
   MP-BGP extensions.  When MPLS global label is necessary, the BGP
   client on the PE node can send label request to RR+ and the label
   mapping for the allocated MPLS global label will be advertised to all
   PEs.  Thus all PEs can learn the binding between the service and the
   MPLS global and the forwarding entry for the MPLS global label can be
   installed accordingly.

4.3.  IGP-Based Control Plane














Li, et al.               Expires August 18, 2014                [Page 6]


Internet-Draft      A Framework of MPLS Global Label       February 2014


   +------------------------------+    +------------------------------+
   |         IGP Domain 1         |    |         IGP Domain 2         |
   |         +----------+         |    |         +----------+         |
   |         |   IGP    |         |    |         |   IGP    |         |
   |         |Controller|------------------------|Controller|         |
   |         |  (DR+)   |         |    |         |  (DR+)   |         |
   |         |          |         |    |         |          |         |
   |         +----------+         |    |         +----------+         |
   |         /          \         |    |         /          \         |
   |        /            \        |    |        /            \        |
   |       /              \       |    |       /              \       |
   | +--------+        +--------+ |    | +--------+        +--------+ |
   | | NODE 1 |        | NODE n | |    | | NODE 1 |        | NODE n | |
   | |        | ...... |        | |    | |        | ...... |        | |
   | |  IGP   |        |  IGP   | |    | |  IGP   |        |  IGP   | |
   | | CLIENT |        | CLIENT | |    | | CLIENT |        | CLIENT | |
   | +--------+        +--------+ |    | +--------+        +--------+ |
   |                              |    |                              |
   +------------------------------+    +------------------------------+

                 Figure 3: IGP-based Control Plane

   If the internal nodes of the network support MPLS global label, IGP-
   based control plane can be introduced.  IGP has ever introduced the
   DR(Designated Router) and BDR(Backup Designated Router) concepts for
   broadcast and NBMA network([RFC2328]).  The Designated Router is
   elected in the broadcast or NBMA network to act as a centralized
   control point to advertise adjacencies among DR and DR others.  In
   the IGP-base control plane for MPLS global label, we can adopt the DR
   concept which can act as the central controller for the MPLS global
   label.  We called this type of DR ad DR+. The DR+ can collect the
   MPLS global label capability of all client nodes.  If MPLS global
   label is necessary for specific usage, the MPLS global label will be
   allocated by the DR+ and the corresponding label mapping can be
   advertised to all network nodes through IGP extensions.  Thus all
   network nodes in the IGP area can learn the label binding between the
   specific usage and the MPLS global label and the forwarding entry for
   the MPLS global label can be installed accordingly.

   MPLS global label binding information should be always advertised in
   a specific IGP domains.  There may be multiple IGP domains and nodes
   in other IGP domains may be necessary to learn the MPLS global label
   information.  There are two possible solutions:

   1.  The global label information can be advertised by IGP to span
   multiple domains.  It is like leaking the information from the native
   area to other areas.




Li, et al.               Expires August 18, 2014                [Page 7]


Internet-Draft      A Framework of MPLS Global Label       February 2014


   2.  There can exist direct connections between IGP DR+. The MPLS
   global label information can be advertised from the native IGP DR+ to
   the other IGP DR+ using possible protocol extensions other than
   IGP(e.g. PCEP extensions or BGP extensions).  The other IGP DR+ can
   learn the MPLS global label information and advertise it in its own
   area through IGP extensions.

4.4.  PCE-Based Control Plane

   +------------------------------+    +------------------------------+
   |         PCE DOMAIN 1         |    |         PCE DOMAIN 2         |
   |          +--------+          |    |          +--------+          |
   |          |        |          |    |          |        |          |
   |          |  PCE   |--------------------------|  PCE   |          |
   |          | Server |          |    |          | Server |          |
   |          |        |          |    |          |        |          |
   |          +--------+          |    |          +--------+          |
   |         /          \         |    |         /          \         |
   |        /            \        |    |        /            \        |
   |       /              \       |    |       /              \       |
   | +--------+        +--------+ |    | +--------+        +--------+ |
   | | NODE 1 |        | NODE n | |    | | NODE 1 |        | NODE n | |
   | |        | ...... |        | |    | |        | ...... |        | |
   | |  PCC   |        |  PCC   | |    | |  PCC   |        |  PCC   | |
   | |        |        |        | |    | |        |        |        | |
   | +--------+        +--------+ |    | +--------+        +--------+ |
   |                              |    |                              |
   +------------------------------+    +------------------------------+

                   Figure 4: PCE-based Control Plane

   PCE[RFC4655] is another choice to implement the control plane for
   MPLS global label.  The PCE servers can act as the role of the
   centralized controller and the PCC can act the role of the client for
   process of MPLS global label.  PCE servers can collect the MPLS
   global label capability of all nodes through PCEP extensions.  If
   MPLS global label is necessary for specific usage, the label request
   can be sent from PCC to PCE server.  MPLS global label will be
   allocated by the PCE server and the corresponding label mapping will
   be advertised to all network nodes through PCEP extensions.  Thus all
   network nodes in the domain can learn the label binding between the
   specific usage and the MPLS global label and the forwarding entry for
   the MPLS global label can be installed accordingly.

   If MPLS global label information needs to be advertised in different
   domain, it can be advertised from the native PCE server to other PCE
   servers through PECP extensions.  Then other PCE servers can




Li, et al.               Expires August 18, 2014                [Page 8]


Internet-Draft      A Framework of MPLS Global Label       February 2014


   advertise the MPLS global information to PCC through PCEP in its own
   domain.

5.  IANA Considerations

   This document makes no request of IANA.

6.  Security Considerations

   TBD.

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.

7.2.  Informative References

   [I-D.ietf-l2vpn-evpn]
              Sajassi, A., Aggarwal, R., Henderickx, W., Isaac, A., and
              J. Uttaro, "BGP MPLS Based Ethernet VPN", draft-ietf-
              l2vpn-evpn-05 (work in progress), February 2014.

   [I-D.li-mpls-global-label-usecases]
              Li, Z., Zhao, Q., and T. Yang, "Usecases of MPLS Global
              Label", draft-li-mpls-global-label-usecases-01 (work in
              progress), February 2014.

   [I-D.mpls-big-label-ucase-req]
              Li, R. and K. Zhao, "MPLS Big Label Usecases and
              Requirements", draft-mpls-big-label-ucase-req-00 (work in
              progress), October 2013.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

   [RFC4456]  Bates, T., Chen, E., and R. Chandra, "BGP Route
              Reflection: An Alternative to Full Mesh Internal BGP
              (IBGP)", RFC 4456, April 2006.

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655, August 2006.

   [RFC4761]  Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
              (VPLS) Using BGP for Auto-Discovery and Signaling", RFC
              4761, January 2007.




Li, et al.               Expires August 18, 2014                [Page 9]


Internet-Draft      A Framework of MPLS Global Label       February 2014


   [RFC6514]  Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
              Encodings and Procedures for Multicast in MPLS/BGP IP
              VPNs", RFC 6514, February 2012.

Authors' Addresses

   Zhenbin Li
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: lizhenbin@huawei.com


   Quintin Zhao
   Huawei Technologies
   125 Nagog Technology Park
   Acton, MA  01719
   US

   Email: quintin.zhao@huawei.com


   Tianle Yang
   China Mobile
   32, Xuanwumenxi Ave.
   Beijing  01719
   China

   Email: yangtianle@chinamobile.com




















Li, et al.               Expires August 18, 2014               [Page 10]


Html markup produced by rfcmarkup 1.129b, available from https://tools.ietf.org/tools/rfcmarkup/