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Versions: (RFC 2917) 00

Internet Engineering Task Force           Karthik Muthukrishnan
INTERNET-DRAFT                          Chandrasekar Kathirvelu
                                        Tom Walsh
Expires January 2002                    Lucent Technologies

Andrew Malis                                        Fred Ammann
Vivace Networks, Inc.               COMMCARE telecommunications

Jing Ming Xiao                          Junichi Sumimoto
China UNICOM                            NTT Information Sharing Platform Labs




                                                  July 2001


                    A Core MPLS IP VPN Architecture

                  <draft-ietf-ppvpn-rfc2917bis-00.txt>


1. Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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 draft is not a product of any working group and was written and
   presented to the IETF well before the formation of any working group
   related to Core VPNs.

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

Abstract This memo presents an approach for building core Virtual



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   Private Network (VPN) services in a service provider's MPLS backbone.
   This approach uses Multiprotocol Label Switching (MPLS) running in
   the backbone to provide premium services in addition to best effort
   services. The central vision is for the service provider to provide a
   virtual router service to their customers. The keystones of this
   architecture are ease of configuration, user security, network
   security, dynamic neighbor discovery, scaling and the use of existing
   routing protocols as they exist today without any modifications.

1.0. Acronyms

      ARP     Address Resolution Protocol
      CE      Customer Edge router
      LSP     Label Switched Path
      PNA     Private Network Administrator
      SLA     Service Level Agreement
      SP      Service Provider
      PE      Service Provider Edge Device
      SPNA    SP Network Administrator
      VMA     VPN Multicast Address
      VPNID   VPN Identifier
      VR      Virtual Router
      VRC     Virtual Router Console
      P       Provider Device
      DSCP    DiffServ Code Point
      OUI     Organizationally Unique Identifier

2.0. Introduction

      This draft describes an approach for building IP VPN services out
      of the backbone of the SP's network. Broadly speaking, two
      possible approaches present themselves: the piggyback model and
      the virtual router approach. The piggyback model is based on
      overloading some semantic(s) of existing routing protocols to
      carry reachability information.  In this document, we focus on the
      virtual router service.

      The approach presented here does not depend on any modifications
      of any existing routing protocols. This draft makes a concerted
      effort to draw the line between the SP and the PNA: the SP owns
      and manages layer 1 and layer 2 services while layer 3 services
      belong to and are manageable by the PNA. By the provisioning of
      fully logically independent routing domains, the PNA has been
      given the flexibility to use private and unregistered addresses.
      Due to the use of private LSPs and the use of VPNID encapsulation
      using label stacks over shared LSPs, data security is not an
      issue.




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      The approach espoused in this draft differs from that described in
      [Rosen1] in that no specific routing protocol has been overloaded
      to carry VPN routes.  [Rosen1] specifies a way to modify BGP to
      carry VPN unicast routes across the SP's backbone. To carry
      multicast routes, further architectural work will be necessary.

3.0. Virtual Routers

      A virtual router is a collection of threads, either static or
      dynamic, in a routing device, that provides routing and forwarding
      services much like physical routers. A virtual router need not be
      a separate operating system process (although it could be); it
      simply has to provide the illusion that a dedicated router is
      available to satisfy the needs of the network(s) to which it is
      connected. A virtual router, like its physical counterpart, is an
      element in a IP domain. The other routers in this domain could be
      physical or virtual routers themselves. Given that the virtual
      router connects to a specific (logically discrete) routing domain
      and that a physical router can support multiple virtual routers,
      it follows that a physical router supports multiple (logically
      discreet) routing domains.

      From the user (VPN customer) standpoint, it is imperative that the
      virtual router be as equivalent to a physical router as possible.
      In other words, with very minor and very few exceptions, the
      virtual router should appear for all purposes (configuration,
      management, monitoring and troubleshooting) like a dedicated
      physical router. The main motivation behind this requirement is to
      avoid upgrading or re-configuring the large installed base of
      routers and to avoid retraining of network administrators.

      The aspects of a router that a virtual router needs to emulate
      are:

      - Configuration of any combination of routing protocols

      - Transport of  Unicast and Multicast IP traffic with
      differentiated or with absolute Qos.

      - Monitoring of the network

      - Troubleshooting.

      Every VPN has a logically independent routing domain. This
      enhances the SP's ability to offer a fully flexible virtual router
      service that can fully serve the SP's customer without requiring
      physical per-VPN routers. This means that the SP's "hardware"
      investments, namely routers and links between them, can be re-used



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      by multiple customers.

4.0. Objectives

      4.1. Easy, scaleable configuration of VPN endpoints in the service
      provider network. At most, one piece of configuration should be
      necessary when a CE is added.

      4.2. No use of SP resources that are globally unique and hard to
      get such as IP addresses and subnets.

      4.3. Dynamic discovery of VRs (Virtual Routers) in the SP's cloud.
      This is an optional, but extremely valuable "keep it simple" goal.

      4.4. Virtual Routers should be fully configurable and monitorable
      by the VPN network administrator. This provides the PNA with the
      flexibility to either configure the VPN themselves or outsource
      configuration tasks to the SP.

      4.5. Quality of data forwarding should be configurable on a VPN-
      by-VPN basis.  This should translate to continuous (but perhaps
      discrete) grades of service.  Some examples include best effort,
      dedicated bandwidth, QOS, and policy based forwarding services.

      4.6. Differentiated services should be configurable on a VPN-by-
      VPN basis, perhaps based on LSPs set up for exclusive use for
      forwarding data traffic in the VPN.

      4.7. Security of internet routers extended to virtual routers.
      This means that the virtual router's data forwarding and routing
      functions should be as secure as a dedicated, private physical
      router. There should be no unintended leak of information (user
      data and reachability information) from one routing domain to
      another.

      4.8. Specific routing protocols should not be mandated between
      virtual routers. This is critical to ensuring the VPN customer can
      setup the network and policies as the customer sees fit. For
      example, some protocols are strong in filtering, while others are
      strong in traffic engineering. The VPN customer might want to
      exploit both to achieve "best of breed" network quality.

      4.9. No special extensions to existing routing protocols such as
      BGP, RIP, OSPF, ISIS etc. This is critical to allowing the future
      addition of other services such as NHRP and multicast. In
      addition, as advances and addenda are made to existing protocols
      (such as traffic engineering extensions to ISIS and OSPF), they
      can be easily incorporated into the VPN implementation.



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5.0. Architectural Outline

      5.1. Every VPN is assigned a VPNID which is unique within the SP's
      network.i.e., local to the SP's network.

      By definition there can be different VPNIDs for the same OUI in
      different VPN clouds.

      These different VPN Clouds are separated by one or more IP/MPLS
      links.

      This identifier unambiguously identifies the VPN with which a
      packet or connection is associated. The VPNID of zero is reserved;
      it is associated with and represents the public internet.

      5.2. The VPN service is offered in the form of a Virtual Router
      service.  These VRs reside in the PE and are as such confined to
      the edge of the SP's cloud. The VRs will use the SP's network for
      data and control packet forwarding but are otherwise invisible
      outside the PEs.

      5.3. The "size" of the VR contracted to the VPN in a given PE is
      expressed by the quantity of IP resources such as routing
      interfaces, route filters, routing entries etc. This is entirely
      under the control of the SP and provides the fine granularity that
      the SP requires to offer virtually infinite grades of VR service
      on a per-PE level. [Example:  one PE may be the aggregating point
      (say headquarters of the corporation) for a given VPN and a number
      of other PE may be access points (branch offices). In this case,
      the PE connected to the headquarters may be contracted to provide
      a large VR while the PE connected to the branch offices may house
      small, perhaps stub VRs]. This provision also allows the SP to
      design the network with an end goal of distributing the load among
      the routers in the network.

      5.4. As per the traffic requirement we can incrementally add the
      PEs.

      5.5. One indicator of the VPN size is the number of PE in the SP's
      network that have connections to CPE routers in that VPN.  In this
      respect, a VPN with many sites that need to be connected is a
      "large" VPN whereas one with a few sites is a "small" VPN. Also,
      it is conceivable that a VPN grows or shrinks in size over time.
      VPNs may even merge due to corporate mergers, acquisitions and
      partnering agreements. These changes are easy to accommodate in
      this architecture, as globally unique IP resources do not have to
      be dedicated or assigned to VPNs. The number of PE is not limited
      by any artificial configuration limits.



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      5.6. The SP owns and manages Layer 1 and Layer 2 entities. To be
      specific, the SP controls physical switches or routers, physical
      links, logical layer 2 connections (such as DLCI in Frame Relay
      and VPI/VCI in ATM) and LSPs (and their assignment to specific
      VPNs). In the context of VPNs, it is the SP's responsibility to
      contract and assign layer 2 entities to specific VPNs.

      5.7. Layer 3 entities belong to and are manageable by the PNA.
      Examples of these entities include IP interfaces, choice of
      dynamic routing protocols or static routes, and routing
      interfaces. Note that although Layer 3 configuration logically
      falls under the PNA's area of responsibility, it is not necessary
      for the PNA to execute it. It is quite viable for the PNA to
      outsource the IP administration of the virtual routers to the
      Service Provider.  Regardless of who assumes responsibility for
      configuration and monitoring, this approach provides a full
      routing domain view to the PNA and empowers the PNA to design the
      network to achieve intranet, extranet and traffic engineering
      goals.

      5.8. The VPNs can be managed as if physical routers rather than
      VRs were deployed.  Therefore, management may be performed using
      SNMP or other similar methods or directly at the VR console (VRC).

      5.9. Industry-standard troubleshooting tools such as 'ping,'
      'traceroute,' etc., are available in a routing domain exclusively
      of dedicated physical routers.  Therefore, monitoring and
      troubleshooting may be performed using SNMP or similar methods,
      but may also include the use of these standard tools. Again, the
      VRC may be used for these purposes just like any physical router.

      5.10. Since the VRC is visible to the user, router specific
      security checks need to be put in place to make sure the VPN user
      is allowed access to Layer 3 resources in that VPN only and is
      disallowed from accessing physical resources in the router.  Most
      routers achieve this through the use of database views.

      5.11. The VRC is available to the SP as well. If configuration and
      monitoring has been outsourced to the SP, the SP may use the VRC
      to accomplish these tasks as if it were the PNA.

      5.12.  The VRs in the PE form the VPN in the SP's network.
      Together, they represent a virtual routing domain. They
      dynamically discover each other by utilizing variety of technics.

      5.13. If SPs network supports multicast then routing protocols
      which uses multicast like OSPF, RIPV2 can be easily supported in
      VPN.



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      5.14. User data forwarding may be done in one of several ways:

      5.14.1. An LSP with best-effort characteristics that all VPNS can
      use.

      5.14.2. An LSP dedicated to a VPN and traffic engineered by the
      VPN customer.

      5.14.3. A private LSP with differentiated characteristics.

      5.14.4. Policy based forwarding on a dedicated L2 Virtual Circuit

   The choice of the preferred method is negotiable between the SP and
   the VPN customer, perhaps constituting part of the SLA between them.
   This allows the SP to offer different grades of service to different
   VPN customers.

   Of course, hop-by-hop forwarding is also available to forward routing
   packets and to forward user data packets during periods of LSP
   establishment and failure.

   5.15. This approach does not mandate that separate operating system
   tasks for each of the routing protocols be run for each VR that the
   PE houses. Specific implementations may be tailored to the particular
   PE in use. Maintaining separate routing databases and forwarding
   tables, one per VR, is one way to get the highest performance for a
   given PE.

6.0. Scaleable Configuration

   A typical VPN is expected to have 100s to 1000s of endpoints within
   the SP cloud.  Therefore, configuration should scale (at most)
   linearly with the number of end points. To be specific, the
   administrator should have to add a couple of configuration items when
   a new customer site joins the set of VRs constituting a specific VPN.
   Anything worse will make this task too daunting for the service
   provider.  In this architecture, all that the service provider needs
   to allocate and configure is the ingress/egress physical link (e.g.
   Frame Relay DLCI or ATM VPI/VCI) and the virtual connection between
   the VR and the Service Provider Core.

7.0. VPN IP Domain Configuration









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                                151.0.0.1
                                ################
                               #              #
                              #  ROUTER 'A'  #
                             #              #
                            ################
                                 #       #
                                #         #
                               #           #
                              #             #
                         #############    ###############
                        #           #    #             #
                       # ROUTER 'B'#    # ROUTER 'C'  #
                      #           #    #             #
                     #           #    #             #
                    #############    ###############
                    152.0.0.2         153.0.0.3

                   Figure 1 'Physical Routing Domain'

   The physical domain in the SP's network is shown in Figure.1. In this
   network, physical routers A, B and C are connected together. Each of
   the routers has a 'public' IP address assigned to it. These addresses
   uniquely identify each of the routers in the SP's network.



























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            172.150.0/18                                172.150.128/18
    -----------------------             ---------------------------|
                |                                       |          |
                |                                       |      172.150.128.1
                |               ROUTER 'A' (151.0.0.1)  |       |---------|
                |               #############           |       |Parts DB |
                |           ---#-----------#            |       /---------/
                |    OSPF   | #           #     OSPF    |      /----------/
                ------------|#  VR - A   #|--------------
                            #-------|---#-|
                           #############10.0.0.1/24
                |----|------------#-#---------------|-----|
                     |10.0.0.2/24#   #              |10.0.0.3/24
              |------|-------|  #     #    ---------|-------|
              |  ###############       #   |############### |
              | #  VR - B    |#         #  #    VR - C   #  |
              |#-------------# ROUTER 'B'##|------------#----
   (152.0.0.2)###############            ############### (153.0.0.3)
                    |                               |
                    |                               |
         -------------------------       ROUTER 'C' |
               172.150.64/18                        V
                                         Vendors Extranet

                   Figure 2 'Virtual Routing Domain'

   Each Virtual Router is configurable by the PNA as though it were a
   private physical router. Of course, the SP limits the resources that
   this Virtual Router may consume on a PE-by-PE basis. Each VPN has a
   number of physical connections (to CE routers) and a number of
   logical connections (to the emulated LAN). The emulated LAN (shown
   with IP addresses 10.0.0.x/24) provides the VPN Backbone connecting
   the VRs in Figure 2.  Each connection is IP-capable and can be
   configured to utilize any combination of the standard routing
   protocols and routing policies to achieve specific corporate network
   goals.

   To illustrate, in Figure 2, 3 VRs reside on 3 PE in VPN 1. Router 'A'
   houses VR-A, router 'B' houses VR-B and router 'C' houses VR-C.  VR-C
   and VR-B have a physical connection to CE equipment, while VR-A has 2
   physical connections. Each of the VRs has a fully IP-capable logical
   connection to the emulated LAN.  VR-A has the (physical) connections
   to the headquarters of the company and runs OSPF over those
   connections. Therefore, it can route packets to 172.150.0/18 and
   172.150.128/18. VR-B runs RIP in the branch office (over the physical
   connection) and uses RIP (over the logical connection) to export
   172.150.64/18 to VR-A. VR-A advertises a default route to VR-B over
   the logical connection.  Vendors use VR-C as the extranet connection



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   to connect to the parts database at 172.150.128.1. Hence, VR-C
   advertises a default route to VR-A over the logical connection. VR-A
   exports only 175.150.128.1 to VR-C. This keeps the rest of the
   corporate network from a security problem.

   The network administrator will configure the following:

   7.1. OSPF connections to the 172.150.0/18 and 172.150.128/18  network
   in VR-A.

   7.2. RIP connections to VR-B and VR-C on VR-A.

   7.3. Route policies on VR-A to advertise only the default route to
   VR-B.

   7.4. Route policies on VR-A to advertise only 172.150.128.1 to VR-C.

   7.5. RIP on VR-B to VR-A.

   7.6. RIP on VR-C to advertise a default route to VR-A.

8.0. Forwarding

   As mentioned in the architectural outline, data forwarding may be
   done in one of several ways. In all techniques except the Hop-by-Hop
   technique for forwarding routing/control packets, the actual method
   is configurable. At the high end, policy based forwarding for quick
   service and at the other end best effort forwarding using public LSP
   is used. The order of forwarding preference is as follows:

   - Policy based forwarding.

   - Optionally configured private LSP.

   - Best-effort public LSP.

8.1  Private LSP

   This LSP is optionally configured on a per-VPN basis. This LSP is
   usually associated with non-zero bandwidth reservation and/or a
   specific differentiated service or QOS class. If this LSP is
   available, it is used for user data and for VPN private control data
   forwarding.

8.2 Best Effort Public LSP

   VPN data packets are forwarded using this LSP if a private LSP with
   specified bandwidth and/or QOS characteristics is either not



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   configured or not presently available. The LSP used is the one
   destined for the egress router in VPN 0.(i.e., the reserved VPNID
   designating the public Internet). The VPNID in the shim header is
   used to de-multiplex data packets from various VPNs at the egress
   router.

9.0. Differentiated Services

   Configuring private LSPs for VPNs allows the SP to offer
   differentiated services to paying customers. These private LSPs could
   be associated with any available L2 QOS class or Diff-Serv
   codepoints. In a VPN, multiple private LSPs with different service
   classes could be configured with flow profiles for sorting the
   packets among the LSPs. This feature, together with the ability to
   size the virtual routers, allows the SP to offer truly differentiated
   services to the VPN customer.

10.0.  Security Considerations

10.1  Routing Security

   The use of standard routing protocols such as OSPF and BGP in their
   unmodified form means that all the encryption and security methods
   (such as MD5 authentication of neighbors) are fully available in VRs.
   Making sure that routes are not accidentally leaked from one VPN to
   another is an implementation issue. One way to achieve this is to
   maintain separate routing and forwarding databases.


10.2  Data Security

   This allows the SP to assure the VPN customer that data packets in
   one VPN never have the opportunity to wander into another. From a
   routing standpoint, this could be achieved by maintaining separate
   routing databases for each virtual router. From a data forwarding
   standpoint, the use of label stacks in the case of shared LSPs
   [Rosen2] [Callon] or the use of private LSPs guarantees data privacy.
   Packet filters may also be configured to help ease the problem.

10.3  Configuration Security

   Virtual routers appear as physical routers to the PNA. This means
   that they may be configured by the PNA to achieve connectivity
   between offices of a corporation. Obviously, the SP has to guarantee
   that the PNA and the PNA's designees are the only ones who have
   access to the VRs on the PE the private network has connections to.
   Since the virtual router console is functionally equivalent to a
   physical router, all of the authentication methods available on a



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   physical console such as password, RADIUS, etc. are available to the
   PNA.

10.4 Physical Network Security

   When a PNA logs in to a PE to configure or monitor the VPN, the PNA
   is logged into the VR for the VPN. The PNA has only layer 3
   configuration and monitoring privileges for the VR. Specifically, the
   PNA has no configuration privileges for the physical network. This
   provides the guarantee to the SP that a VPN administrator will not be
   able to inadvertently or otherwise adversely affect the SP's network.

11.0.  Virtual Router Monitoring

   All of the router monitoring features available on a physical router
   are available on the virtual router. This includes utilities such as
   "ping" and "traceroute". In addition, the ability to display private
   routing tables, link state databases, etc. are available.

12.0. Performance Considerations

   For the purposes of discussing performance and scaling issues,
   today's routers can be split into two planes: the routing (control)
   plane and the forwarding plane.

   In looking at the routing plane, most modern-day routing protocols
   use some form of optimized calculation methodologies to calculate the
   shortest path(s) to end stations. For instance, OSPF and ISIS use the
   Djikstra algorithm while BGP uses the "Decision Process". These
   algorithms are based on parsing the routing database and computing
   the best paths to end stations. The performance characteristics of
   any of these algorithms is based on either topological
   characteristics (ISIS and OSPF) or the number of ASs in the path to
   the destinations (BGP). But it is important to note that the overhead
   in setting up and beginning these calculations is very little for
   most any modern day router. This is because, although we refer to
   routing calculation input as "databases", these are memory resident
   data structures.

   Therefore, the following conclusions can be drawn:

   1. Beginning a routing calculation for a routing domain is nothing
   more than setting up some registers to point to the right database
   objects.

   2. Based on 1, the performance of a given algorithm is not
   significantly worsened by the overhead required to set it up.




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   3. Based on 2, it follows that, when a number of routing calculations
   for a number of virtual routers has to be performed by a physical
   router, the complexity of the resulting routing calculation is
   nothing more than the sum of the complexities of the routing
   calculations of the individual virtual routers.

   4. Based on 3, it follows that whether an overlay model is used or a
   virtual routing model is employed, the performance characteristics of
   a router are dependent purely on its hardware capabilities and the
   choice of data structures and algorithms.

   To illustrate, let's say a physical router houses N VPNs, all running
   some routing protocol say RP. Let's also suppose that the average
   performance of RP's routing calculation algorithm is  f(X,Y) where x
   and y are parameters that determine performance of the algorithm for
   that routing protocol. As an example, for Djikstra algorithm users
   such as OSPF, X could be the number of nodes in the area while Y
   could be the number of links. The performance of an arbitrary VPN n
   is f (Xn, Yn). The performance of the (physical) router is the sum of
   f(Xi, Yi) for all values of i in 0 <= i <= N. This conclusion is
   independent of the chosen VPN approach (virtual router or overlay
   model).

   In the usual case, the forwarding plane has two inputs: the
   forwarding table and the packet header. The main performance
   parameter is the lookup algorithm. The very best performance one can
   get for a IP routing table lookup is by organizing the table as some
   form of a tree and use binary search methods to do the actual lookup.
   The performance of this algorithm is O(log n).

   Hence, as long as the virtual routers' routing tables are distinct
   from each other, the lookup cost is constant for finding the routing
   table and O(log n) to find the entry. This is no worse or different
   from any router and no different from a router that employs overlay
   techniques to deliver VPN services. However, when the overlay router
   utilizes integration of multiple VPNs' routing tables, the
   performance is O(log m*n) where 'm' is the number of VPNs that the
   routing table holds routes for.

13.0. Some Applications

   Some typical applications of PPVPN are illustrated here to assist
   better understanding of the PPVPNs.

   13.1. Example 1
    World HQ wants to connect  Regional HQs and  small stationary
   outlet/storage.




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                        (     )      +-+
           (  )        (       )-----| |
          (    )      (         )    +-+ Regional Office 1
         ( C(HQ))-----( SP      )
          (    )      (         )     +-+
            ( )        (       )------| | Regional office 2
                        (     )       +-+


   13.2. Example 2:

   In the similar model as said above the SP's network may differ.  More
   than one SP will be involved in connecting the corporate user.  In
   that case we need a SLA between SPs for the service.


                        (     )       ( )    +-+
           (  )        (       )-----(SP2)---| |
          (    )      (         )     ( )    +-+ Regional Office 1
         ( C(HQ))-----( SP1     )
          (    )      (         )     +-+
            ( )        (       )------| | Regional office 2
                        (     )       +-+

    We need a policy between two SP's VPN for exchange of routes. We
   need VPN id conversion since the VPNs may have different ID in each
   SP.

   13.3. Example 3:  When a Mobile user wants to join the VPN, the
   connection can be made by an LSP tunnel or an IPSec tunnel to the
   nearest VPN PE.




















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                        (     )       ( )    +-+
           (  )        (       )-----(SP2)---| |
          (    )      (         )     ( )    +-+ Regional Office 1  +-+
         ( C(HQ))-----( SP1     )----------//-----------------------| |
          (    )      (         )     +-+                           +-+
            ( )        (       )------| | Regional office 2    Mobile user
                        (     )       +-+

   13.4. Hierarchical VPNs



                                           +-+
                                       +---| | Blue VPN
     +-+  Blue VPN                     |   +-+
     | |                (     )  Y    ( )    +-+
     +-+-- (  )        (       )-----(SP2)---| |
          (    )   Y  (         )     (G)    +-+ Red VPN
         ( SP2B )-----( SP1     )
          (    )      (         ) Y    ( )    +-+
            ( )        (       )------(SP2)---| | Red VPN
  +-+       |           (     )        (F)    +-+
  | |-------+                           |              +-+
  +-+   Red VPN                         +--------------| | Blue VPN
                                                       +-+



    Y - Yellow VPN. Which SP2 gets from SP1.

   SP2 bought Yellow VPN from SP1. SP2 has branch offices as SP2B, SP2G
   and SP2F in different locations.  SP2 also provides VPN services and
   Red and Blue VPNs are SP2's customers.

   SP2B CE for VPN Y towards SP1 will have the instance of Blue Red and
   Yellow VPNs.  Relation between  Yellow VPN  and  Blue/Red VPN is
   configured by policy.  Yellow VPN provides separate transport for
   Red/Blue VPNs, it does not participate in routing, which keeps all
   the VPNs separate to each other, but still they can use the upper
   level VPN for transport. In this example Client of SP2B Red VPN can
   peer with RedVPN in SP2G. SP2G will peer with SP2B in Yellow VPN.
   Data from RedVPN in SP2B will use Yellow VPN link from SP2B through
   SP1 to SP2G. Data from BlueVPN will also use the same path or same
   LSP. In SP2G it will be demuxed to reach Red/Blue VPNs. Here
   YellowVPN acts like a LSP tunnel to Red/Blue VPNs.

14.0.  References




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INTERNET-DRAFT                 Core VPNs                       July 2001


   [Callon] Callon R., et al, "A framework for Multiprotocol Label
       Switching", draft-ietf-mpls-framework-05.txt.

   [Fox] Fox B., et al, "Virtual Private Networks Identifier", RFC 2685.

   [Meyer] Meyer D., "Administratively Scoped IP Multicast", RFC 2365.

   [Rosen1] Rosen, E., et al. draft-rosen-rfc2547bis-02.txt

   [Rosen2] Rosen E., et al, "Multiprotocol Label Switching
       Architecture", draft-ietf-mpls-arch-06.txt.

   [muthuk] K.Muthukrishnan, A.Malis "A Core MPLS IP VPN Architecture",
       RFC 2917 September 2000.

       [VPN-FRAME] M.Suzuki, J.Sumimoto, "A Framework for Network-based
       VPNs", <draft-suzuki-nbvpn-framework-01.txt>, October 2000.

15. Authors' addresses

   Karthik Muthukrishnan
   Lucent Technologies
   1 Robbins Road
   Phone: (978) 952-1368
   Westford, MA 01886
   Email: mkarthik@lucent.com

   Andrew Malis
   Vivace Networks, Inc.
   2730 Orchard Parkway
   San Jose, CA 95134
   Phone: (408) 383-7223
   EMail: Andy.Malis@vivacenetworks.com

   Chandrasekar Kathirvelu
   Lucent Technologies
   1 Robbins Road
   Westford, MA 01886
   Phone: (978) 952-7116
   EMail: ck32@lucent.com

   Tom Walsh
   Lucent Technologies
   10 Lyberty Way
   Westford, MA 01886
   Phone: (978) 392-2311
   EMail: tdwalsh@lucent.com




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INTERNET-DRAFT                 Core VPNs                       July 2001


   Fred Ammann
   COMMCARE Telecommunications
   Turmstrasse 8
   CH-8952 Schlieren
   Switzerland
   Phone: +41 1 738 61 11
   Email: fa@commcare.ch

   Jing Ming Xiao
   China UNICOM
   Data & Fixed Communication Department
   6/F Office Tower 3
   Henderson Center
   Beijing, China
   Email: unicomnet@bj.cnuninet.net

   Junichi Sumimoto
   NTT Information Sharing Platform Labs
   3-9-11, Midori-cho
   Musashino-shi, Tokyo 180-8585
   Japan
   Email: sumimoto.junichi@lab.ntt.co.jp





























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