Network Working Group                                           Y. Cheng
Internet-Draft                                              China Unicom
Intended status: Informational                              JF. Tremblay
Expires: November 9, 2015                                       Viagenie
                                                                   J. Bi
                                                     Tsinghua University
                                                         L. M. Contreras
                                                          Telefonica I+D
                                                             May 8, 2015


              Use Case for Distributed Data Center in SUPA
                   draft-cheng-supa-ddc-use-cases-07

Abstract

   Large scale Distributed Data Centers (DDCs) can provide various
   services and usually consist of a lot of internal and external links
   where various VPNs are built upon.  The Service provisioning and
   network connectivity configurations could be complex and dynamic, for
   which manual configuration is not onerous and error-prone.  This
   draft analyzes the use cases in DDCs, in which some VPN scenarios are
   covered, and the applicability of Simplified Use of Policy
   Abstractions (SUPA) data models which can be used for better and
   automated resource usage and easy service/network deployment/
   configuration.

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 November 9, 2015.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   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
   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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Requirements Language  . . . . . . . . . . . . . . . . . . . .  3
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Challenges Faced by Data Center ISPs . . . . . . . . . . . . .  4
   5.  SUPA Benefits  . . . . . . . . . . . . . . . . . . . . . . . .  5
   6.  Scenarios  . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     6.1.  Scenario:Inter DC Connectivity . . . . . . . . . . . . . .  6
     6.2.  Scenario:vDC Connectivity  . . . . . . . . . . . . . . . .  8
     6.3.  Scenario:Dynamic Link Configuration for DC . . . . . . . . 11
     6.4.  Scenario:DC Connectivity for Virtual Private Clouds
           (VPC)  . . . . . . . . . . . . . . . . . . . . . . . . . . 13
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
   10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 15
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 15
     11.2. informative References . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15



















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1.  Introduction

   The SUPA (Simplified Use of Policy Abstractions) work aims at
   providing data models, including network service data models, policy
   data models, to easily, accurately, and efficiently select and use
   the available communication network capabilities.  An example of the
   data model can be found in
   [I-D.zaalouk-supa-vpn-service-management-model].  Service Manager
   (SM) is used by an a communications service provider and/or operator
   to deploy and manage services on top of network facilities.  An
   example of SM is a set of applications used by an Operational Support
   System (OSS) entity to perform network configuration.  Several SUPA
   use cases have been introduced in the problem statement document.
   This document reviews various scenarios for Distributed Data Center
   (DDC) use case.

   Take a large-scale Distributed Data Center (DDC) operator as an
   example, it provides server hosting, leased line, value-added
   services to enterprises and ISPs, and has more than 10 data centers
   using over one Tbps of bandwidth in a capital city.  In this IDC
   network, traffic at each site is routed via configuring policy routes
   and adjusting routes prioritization to choose an outgoing link.  This
   type of static provisioning comes with high costs and poor
   operability.  Furthermore, the link bandwidth resources in the data
   centers are not efficiently utilized.

   In quite some of the scenarios, the links between DCs are VPNs,
   including L2VPN, L3VPN, etc.  SUPA will be mainly used for those VPN
   configurations.  Although there may be some cases where physical
   links are used, but those are out of the scope of this draft.

   DC and network may belong to different operators.  If a DC operator
   needs to configure network connectivity for DCs, it may need to
   cooperate with network operators providing such connectivity.
   Network operators can define and provide data models to enable this.

   This document illustrates several distributed datacenter (DDC)
   applications and explains how an operator could use SUPA to provide
   these applications.


2.  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 [RFC2119].





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3.  Terminology

   The terminology used in the SUPA problem statement draft
   [I-D.zhou-supa-framework] and
   [I-D.karagiannis-supa-problem-statement] apply also to this draft.

   DC        Data Center

   DDC       Distributed Data Center

   ECA       Event Condition Action

   NM/NC     Network Manager / Controller

   OSS       Operational Support System

   SM        Service Manager

   SUPA      Simplified Use of Policy Abstractions

   TTM       Time to Market

   VAS       Value Added Service

   vDC       virtual Data Center

   VPC       Virtual Private Cloud (PC)


4.  Challenges Faced by Data Center ISPs

   There are many challenges in traditional data centers:

   1) infrastructure and network link is usually leased, depending on
   manual planning and design, which leads to low resource usage and
   high cost.  In consequence, the operator that rent these resources
   has to offer SUPA data models for facilitating control of them (for
   instance, by the DC operator).

   2) Service expansion is limited in a single physical DC.  Each DC
   resource is isolated, so service and resource can only be deployed in
   one single DC.

   3) VAS (Value Added Service) is provisioned via static configuration,
   which brings complex training, long service TTM time and poor
   flexibility.  This could not meet the requirements of complex use
   cases, e.g., lot of VAS devices, significant differences between
   various services.



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5.  SUPA Benefits

   In quite some cases, DC oprators need to optimize and automate
   service deployment for them serlfves or for customers.  While in some
   cases, DC tenants also need to perform some optimization, e.g. a vDC
   tennant may want traffic steering to make full use of links.  To
   solve the above challenges for data center oerators and tenants, SUPA
   could be applied in the following ways:

   o  SUPA supports an open network architecture: standardizaed data
      models enable an open architecture and make it possible for
      unified service / network planning, which can interconnect with
      third party cloud platform, supporting fast service innovation.

   o  SUPA supports overall DC resource integration: SUPA data models
      can be used for network resource virtualization; inter-DC
      resource, virtual DC (vDC) resource, etc, can be integrated and
      controlled by a centralized functional entity.

   o  SUPA supports automatic E2E service delivery: Network (including
      virtual network), computing, inter-DC management of storage
      resource, automatic service delivery, automatic VPN connection
      configurations between DCs, which improves operation efficiency.

   o  SUPA contributes to improve DDC network usage by means of
      Intelligent scheduling of DDC traffic, improving link usage.

   o  SUPA supports VAS service on-demand provisioning automatically:
      Create or delete VAS nodes on-demand, based on various service
      requirements; network forwarding policy based on the VAS routing,
      to achieve automatic draining and automatic configuration of VAS
      device policy.

   Please refer to [I-D.zhou-supa-framework] and other SUPA related
   documents for more details of SUPA features.

   The following sections will illustrate three typical cases in
   distributed data center which could benefit from SUPA architecture.


6.  Scenarios

   In the following uses, Service Manager (SM) is used for service and
   policy definition; and Network Manager (Controller) is used for
   network topology maintenance and mapping data models to detail
   network configruations, as defined in [I-D.zhou-supa-framework].





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6.1.  Scenario:Inter DC Connectivity

                   +---------------------------+
                   |    Service Manager        |
                   |                           |
                   | +----------+ +----------+ |
                   | |Service   | |Policy    | |
                   | |Data Model| |Data Model| |
                   | +----------+ +----------+ |
                   |                           |
                   +---------------------------+
                               ^
                               |
                               |
                               |
                               v
                   +--------------------------+
                   |          Network         |
                   |  Manager / Controller    |
                   +--------------------------+
                      /                   \
                     /                     \
              +---------+                   \
             /|  DC1    |\                   \
            / +---------+ \              +-----------+
           |      | d1     \___a1________|   DC-A    |
           |      |                      |           |
           |  +---------+                +-----------+
        d3 |  |  DC2    |\
           |  +---------+ \              +-----------+
           |      | d2     \___a2________|   DC-B    |
           |      |        ____a3________|           |
            \ +---------+ /              +-----------+
             \|  DC3    |/
              +---------+


                      Figure 1: Inter DC Connectivity

   There can be a lot of links between data centers.  Configuration of
   these links is complex.  As shown in Figure 1, service data models
   and policy data models can be defined to automate the configuration
   procedures.  The service data model for connectivity will specify
   attributes of (virtual) links, e.g. the end points of links,
   bandwidth, QoS and availability parameters, etc.  The policy model
   can specify some high level requirements to the links, like routing
   strategy (via and not via) and price/cost strategy.  The policy data
   model can also define the policy rules that drive the security



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   requirements.

   An application example is, the links interconnecting two DCs together
   should guarantee a minimum bandwidth, certain QoS parameters, and
   provide availability guarantees.

   Anothe service policy example in Figure 1, for traffic from DC2 to
   DC-B, if the load on a link exceeds a threshold (e.g., 90%), some
   (new) traffic can be redirect to another link.

   Requirements and configurations derived from above application
   scenarios can be described by service data model and policy data
   model.


      module: ietf-supa-ddc
         +--rw ddc-services
            +--rw ......                 other possible attributes
            +--rw ddc-service* [name]
            |  +--rw name                string
            |  +--rw connection-type?    enumeration
            |  +--rw connection-name     string
            |  +--rw bandwidth           uint32
            |  +--rw latency             uint32
            +--rw ......                 other possible attributes


          Figure 2: Service Data Model for Inter DC Connectivity

   The above service data model can be used to describe links attributes
   for a VPN, including bandwidth , latency, etc.


   module: ietf-supa-policy
      +--rw supa-policy
         +--rw ......                         other possible attributes
         +--rw supa-policy-atomic
         |  +--rw supa-ECA-policy-rule
         |     +--rw policy-rule-name?        string
         |     +--rw has-policy-events?       boolean
         |     +--rw has-policy-conditions?   boolean
         |     +--rw has-policy-actions?      boolean
         +--rw ......                         other possible attributes


                      Figure 3: ECA Policy Data Model

   The above policy data model can be used to describe the requirement



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   that when the load on a link exceed a threashold.  In this case,
   "event" is the bandwidth of a link, "condition" is "load >= 80%",
   "action" is "redirect some traffic to another link".


   module: ietf-supa-policy
      +--rw policy-set
         +--rw ......                          other possible attributes
         +--rw policy-rule
            +--rw rule-name?                   string
            +--rw rule-type?                   enumeration
            +--rw policy-rule-priority?        uint8
            +--rw intent-policy-rule
            |  +--rw desired-state
            |  |  +--rw constraint?            string
            |  |  +--rw constraint-priority?   uint8
            |  +--rw behavior-constraint
            |     +--rw constraint?            string
            |     +--rw constraint-priority?   uint8
            +--rw ......                       other possible attributes


          Figure 4: Policy Data Model for high level requirements

   The policy model shown above can be used to express some high level
   requirements, e.g. the number of hop of any link should be less than
   5, or any links should not share any network nodes in between and
   should be completely independent to each other so as to achieve high
   availablity in case of network node failure.

   Inter DC connections can be classified into two types: connections
   within a single administrative domain and connections across multiple
   administrative domains.  Links d1, d2 and d3 are within an
   administrative domain; and links a1, a2 and 3 are across domains.
   The difference between them is that connections across multiple
   administrative domain require extra negotiation and authentication/
   authorization, which can be achieved via communications between SMs.
   Data models for this purpose should also be defined.

6.2.  Scenario:vDC Connectivity











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                 +---------------------------+
                 |    Service Manager        |
                 |                           |
                 | +----------+ +----------+ |
                 | |Service   | |Policy    | |
                 | |Data Model| |Data Model| |
                 | +----------+ +----------+ |
                 |                           |
                 +---------------------------+
                               ^
                               |
                               |
                               |
                               v
                   +--------------------------+
                   |          Network         |
                   |  Manager / Controller    |
                   +--------------------------+
                      /         |           \
                     /          |            \
                    /           |             \
                   /   +-------------------+   \
                  /    | DC2               |    \
                 /     | +---------------+ |     \
                /      | |Tenant1 (vDC)  | |      \
               /       | +---------------+ |       \
              /        |                   |        \
             /         | +---------------+ |         \
            /          | | Tenantn (vDC) | |          \
            |          | +---------------+ |          |
            |          +-------------------+          |
            |                     |vDC link           |
            |               +-------------+           |
            |               |             |           |
            |              /|  Cloud      |\          |
            |             / +-------------+ \         |
            |  vDC link  /                   \vDC link|
            |           /                     \       |
    +-------------------+               +-------------------+
    | DC1               |               | DC3               |
    | +---------------+ |               | +---------------+ |
    | | Tenant1 (vDC) | |               | | Tenant1 (vDC) | |
    | +---------------+ |               | +---------------+ |
    |                   |               |                   |
    | +---------------+ |               | +---------------+ |
    | | TenantK (VDC) | |               | | TenantN (vDC) | |
    | +---------------+ |               | +---------------+ |
    +-------------------+               +-------------------+



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                        Figure 5: vDC Connectivity

   A DC tenant may have resources, e.g. network, computing, storage,
   etc, in multiple physical DCs.  DC operators will provide internal
   network connectivity for these distributed resources, and make it
   look like one seamless entity, which can be called as virtual DC
   (vDC).

   The internal links for vDC can be implemented via tunneling overlay
   technologies, e.g.  VPN or VxLAN, etc.  The tunnels need to be
   dynamically established, managed and released.

   As show in Figure 5, service data model and policy data model can be
   defined to automate the links configuration for vDCs.  A service data
   model should specify the attributes of the tunnels, e.g., bandwidth,
   QoS and availability parameters.  Policy systems can dynamically
   scale the DC resources assigned to a tenant, and the policy rules
   that drive the prioritization of resource assignments.  The
   networking resources assigned to a tenant should scale proportionally
   to the compute resources assigned to a tenant.  The traffic should be
   prioritized to resources owned by tenants that offer interactive
   services according to the time zone the DC is located in.  Because a
   DC serving enterprise may require higher priority in working hour,
   and a DC providing entertainment service may need higher network
   priority in non-working hours.


   module: ietf-supa-policy
      +--rw supa-policy
         +--rw ......                         other possible attributes
         +--rw supa-policy-validity-period
         |  +--rw start?                      yang:date-and-time
         |  +--rw end?                        yang:date-and-time
         |  +--rw duration?                   uint32
         |  +--rw periodicity?                enumeration
         +--rw supa-policy-atomic
         |  +--rw supa-ECA-policy-rule
         |     +--rw policy-rule-name?        string
         |     +--rw has-policy-events?       boolean
         |     +--rw has-policy-conditions?   boolean
         |     +--rw has-policy-actions?      boolean
         +--rw ......                         other possible attributes


             Figure 6: Policy Data Model for vDC Connectivity

   In the above policy data model, events and conditions may not be
   necessary; the actions will be based on the time; and two actions



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   will be required: set the VPN priority to low or high.

6.3.  Scenario:Dynamic Link Configuration for DC

   Static and over provisioning for DC links is not always a good
   solution.  Sometimes dynamic configuration is necessary.


                  +---------------------------+
                  |    Service Manager        |
                  |                           |
                  | +----------+ +----------+ |
                  | |Service   | |Policy    | |
                  | |Data Model| |Data Model| |
                  | +----------+ +----------+ |
                  |                           |
                  +---------------------------+
                               ^
                               |
                               |
                               |
                               v
                   +--------------------------+
                   |          Network         |
                   |  Manager / Controller    |______________
                   +--------------------------+              \
                      /                    \                  \
                     /                      \                  \
                    /                        \                 |
        +--------------+                +-------------------+  |
        |              |                |                   |  |
        |              |                |  DC2              |
        |              |--------------- |                   |  |
        |   DC1        |                +-------------------+  |
        |              |                                       |
        |              |  \                                    |
        |              |   \            +-------------------+  |
        |              |    \           |                   | /
        |              |     \__________|  DC2              |/
        +--------------|                |                   |
                                        +-------------------+


                Figure 7: Dynamic Link Configuration for DC

   One case is virtual machine migration and large amount of data
   transfer between DCs.  But this kind of activity does not happen
   frequently.  A dedicated link with constant bandwidth for this



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   purpose is too expensive.  The network operator should allow the DC
   operator to create a link on demand when necessary.  This link may
   have large bandwidth but last for a limited time period.  An
   alternative is to create short-term dedicated links for backups and
   migrations.

   As shown in Figure 7, data models can help to automate these kind of
   configurations.  In the data models, the attributes of links
   (bandwidth, QoS and availability parameters) should be specified.
   The policy concerning strict and soft bounds on the lifetime of such
   links, and the policy concerning the scheduling of dedicated links
   (e.g., based on the current load) and the services using the
   dedicated links can also be specified.

   When the traffic volume between DCs exceeds a certain threshold, the
   policy-driven service manager requests that traffic schedules may be
   adjusted within bounds in order to balance load on the links (e.g.,
   delay backups and migrations until the network has the necessary
   capacity).

   In this case, the ECA policy model will apply, but the action is
   different -- change the bandwidth of link(s) with time period
   constraints, as shown in Figure 6.




























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6.4.  Scenario:DC Connectivity for Virtual Private Clouds (VPC)

                  +---------------------------+
                  |    Service Manager        |
                  |                           |
                  | +----------+ +----------+ |
                  | |Service   | |Policy    | |
                  | |Data Model| |Data Model| |
                  | +----------+ +----------+ |
                  |                           |
                  +---------------------------+
                               ^
                               |
                               |
                               |
                               v
                   +--------------------------+
                   |          Network         |
                   |  Manager / Controller    |______________
                   +--------------------------+              \
                      /                    \                  \
                     /                      \                  \
                    /                        \                 |
    +-------------------+               +-------------------+  |
    | Cloud for VPCs    |               |                   |  |
    | +---------------+ |   VPC link    |  DC1 (Database)   |  |
    | |     VPC1      |-----------------|                   |  |
    | +---------------+ \               +-------------------+  |
    | +---------------+ |\                                     |
    | |     VPC2      | | \                                    |
    | +---------------+ |  \            +-------------------+  |
    | +---------------+ |   \  VPC link |                   | /
    | |    ......     | |    \__________|  DC2 (Storage)    |/
    | +---------------+ |               |                   |
    +-------------------+               +-------------------+

                     Figure 8: VPC to DC Connectivity

   In practice, a public cloud operator can virtualize its cloud
   resources into different isolated private clouds and provided them
   for different tenants.  Such a virtualized private cloud is referred
   to as a VPC.  In a typical VPC provided by, e.g., Alibaba or Amazon,
   through the control portal, a tenant can establish and manage its
   network easily, for instance, deploying or removing virtualized
   network devices (e.g., virtualized routers and virtualized switches),
   adjusting network topologies, specifying packet forwarding policies,
   and deploying or un-deploying virtual services (e.g., load balancers,
   firewalls, databases, DNS, etc.).  The network functionalities that



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   the tenant can accessed are virtualized and actually performed by the
   VMs located on the servers connected through physical or overlay
   networks.  Note that the servers may be located in different data
   centers which are geographically distributed.

   The manipulation of the virtualized VPC network may also affect the
   configuration of physical networks.  For instance, when a tenant
   newly deployes two VMs in its VPC which are located in different DCs,
   the VPC control mechanism may have to generate a VPN between two DCs
   for the internal VPC communciaiton.  Therefore, the control mechanism
   for a VPC should be able to adjust the underlying network when a
   tenant changes the network or service deployment of the virtual VPC
   network.

   In another example, a university, sometimes provides database
   services for VMs in certain VPCs.  The VMs and the database services
   could be located in different DCs, or even provided by different
   vendors.  VPNs are configured for the VPCs to provide connection to
   the internal services, and to create and manage VPNs to internal
   services.  The access of VMs to data resources should be controlled.
   For instance, the VMs in a VPC can access the database services only
   when the tennant has deployed database into its VPC through the
   control protal.

   As shown in figure 4, service data models and policy data models can
   be defined to automate the configurations of links between VPC and DC
   where service is located.  The data models should specify the policy
   controlling authentication and authorization concerning access to
   data residing in internal services.


7.  Security Considerations

   Security is a key aspect of any protocol that allows state
   installation and extracting of detailed configuration states.  More
   investigation remains to fully define the security requirements, such
   as authorization and authentication levels.


8.  IANA Considerations

   Not applicable.


9.  Acknowledgements

   The authors of this draft would like to thank the following persons
   for review, discussion, and valuable comments: Cathy Zhou, Georgios



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   Karagiannis, Scott O. Bradner, James Huang, Bob Natale.


10.  Contributors

   The following persons contribute use case and text to this draft, and
   are listed below:

           Scott O. Bradner
           sob@sobco.com

           Dacheng Zhang
           dacheng.zdc@alibaba-inc.com


11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

11.2.  informative References

   [I-D.karagiannis-supa-problem-statement]
              Karagiannis, G., Qiong, Q., Contreras, L., Yegani, P., and
              J. Bi, "Problem Statement for Simplified Use of Policy
              Abstractions (SUPA)",
              draft-karagiannis-supa-problem-statement-06 (work in
              progress), March 2015.

   [I-D.zaalouk-supa-vpn-service-management-model]
              Zhang, D., Zaalouk, A., Pentikousis, K., and Y. Cheng,
              "VPN Service Management YANG Data Model",
              draft-zaalouk-supa-vpn-service-management-model-03 (work
              in progress), April 2015.

   [I-D.zhou-supa-framework]
              Zhou, C., Contreras, L., Qiong, Q., and P. Yegani, "The
              Framework of Simplified Use of Policy Abstractions
              (SUPA)", draft-zhou-supa-framework-01 (work in progress),
              February 2015.









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Internet-Draft   Use cases for DDC Applications in SUPA         May 2015


Authors' Addresses

   Ying Cheng
   China Unicom
   P.R. China

   Email: chengying10@chinaunicom.cn


   JF Tremblay
   Viagenie


   Email: jean-francois.tremblay@viagenie.ca


   Jun Bi
   Tsinghua University
   Bei Jing
   China

   Email: junbi@cernet.edu.cn


   Luis M. Contreras
   Telefonica I+D
   Ronda de la Comunicacion, Sur-3 building, 3rd floor
   Madrid  28050
   Spain

   Email: luismiguel.contrerasmurillo@telefonica.com




















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