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Network Working Group Daniele Ceccarelli
Internet Draft Ericsson
Intended status: Informational Luyuan Fang
Expires: July 2014 Microsoft
Young Lee
Huawei
Diego Lopez
Telefonica
January 3, 2014
Framework for Abstraction and Control of Transport Networks
draft-ceccarelli-actn-framework-00.txt
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Copyright Notice
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Copyright (c) 2013 IETF Trust and the persons identified as the
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Abstract
This draft provides a framework for abstraction and control of
transport networks.
Table of Contents
1. Terminology....................................................3
2. Introduction...................................................3
3. Business Model of ACTN.........................................5
3.1. Consumers.................................................6
3.2. Service Providers.........................................6
3.3. Network Providers.........................................7
4. Computation Model of ACTN......................................7
4.1. Request Processing........................................7
4.2. Types of Network Resources................................8
4.3. Accuracy of Network Resource Representation...............8
4.4. Resource Efficiency.......................................8
4.5. Guarantee of Client Isolation.............................8
4.6. Computing Time............................................8
4.7. Admission Control.........................................8
4.8. Path Constraints..........................................9
5. Control and Interface Model for ACTN...........................9
5.1. A High-level ACTN Control Architecture....................9
5.2. Consumer Controller......................................11
5.3. Abstracted Topology......................................12
5.4. Workflows of ACTN Control Modules........................15
5.5. Programmability of the ACTN Interfaces...................17
6. Design Principles of ACTN.....................................17
6.1. Network Security.........................................17
6.2. Privacy and Isolation....................................17
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6.3. Scalability..............................................18
6.4. Manageability and Orchestration..........................18
6.5. Programmability..........................................18
6.6. Network Stability........................................18
7. References....................................................19
7.1. Informative References...................................19
8. Contributors..................................................19
Authors' Addresses...............................................20
Intellectual Property Statement..................................20
Disclaimer of Validity...........................................21
1. Terminology
This document uses the terminology defined in [RFC4655], and
[RFC5440].
CVI Consumer-VNC Interface
PNC Physical Network Controller
VL Virtual Link
VNM Virtual Network Mapping
VNC Virtual Network Controller
VNE Virtual Network Element
VNS Virtual Network Service
VPI VNC-PNC Interface
2. Introduction
Transport networks have a variety of mechanisms to facilitate
separation of data plane and control plane including distributed
signaling for path setup and protection, centralized path
computation for planning and traffic engineering, and a range of
management and provisioning protocols to configure and activate
network resources. These mechanisms represent key technologies for
enabling flexible and dynamic networking.
Transport networks in this draft refer to a set of different type of
connection-oriented networks, primarily Connection-Oriented Circuit
Switched (CO-CS) networks and Connection-Oriented Packet Switched
(CO-PS) networks. This implies that at least the following transport
networks are in scope of the discussion of this draft: L1 optical
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networks (e.g., OTN and WSON), MPLS-TP, MPLS-TE, as well as other
emerging connection-oriented networks such as Segment Routing (SR).
One of the characteristics of these network types is the ability of
dynamic provisioning and traffic engineering such that resource
guarantee can be provided to their clients.
One of the main drivers for Software Defined Networking (SDN) is a
physical separation of the network control plane from the data
plane. This separation of the network control plane from the data
plane has been already achieved for with the development of
MPLS/GMPLS [GMPLS] and PCE [PCE] for TE-based transport networks. In
fact, in transport networks such separation of data and control
plane was dictated at the onset due to the very different natures of
the data plane (circuit switched TDM or wavelength) and a packet
switched control plane. The physical separation of the control plane
and the data plane is a major step toward allowing operators to gain
the full control for optimized network design and operation.
Moreover, another advantage of SDN is its logically centralized
control regime that allows a global view of the underlying network
under its control. Centralized control in SDN helps improve network
resource utilization from a distributed network control. For TE-
based transport network control, PCE is essentially equivalent to a
logically centralized control for path computation function.
As transport networks evolve, the need to provide network
abstraction has emerged as a key requirement for operators; this
implies in effect the virtualization of network resources so that
the network is "sliced" for different uses, applications, services,
and consumers each being given a different partial view of the total
topology and each considering that it is operating with or on a
single, stand-alone and consistent network.
Network virtualization, in general, refers to allowing the consumers
to utilize a certain amount of network resources as if they own them
and thus control their allocated resources in a way most optimal
with higher layer or application processes. This empowerment of
consumer control facilitates introduction of new services and
applications as the consumers are given to create, modify, and
delete their virtual network services. The level of virtual control
given to the consumers can vary from a tunnel connecting two end-
points to virtual network elements that consist of a set of virtual
nodes and virtual links in a mesh network topology. More flexible,
dynamic consumer control capabilities are added to the traditional
VPN along with a consumer specific virtual network view. Consumers
control a view of virtual network resources, specifically allocated
to each one of them. This view is called an abstracted network
topology. Such a view may be specific to the set of consumed
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services as well as to the particular consumer. As the consumer
controller is envisioned to support a plethora of distinct
applications, there would be another level of virtualization from
the consumer to individual applications.
The virtualization framework described in this draft is named
Abstraction and Control of Transport Network (ACTN) and facilitates:
- Abstraction of the underlying network resources to higher-layer
applications and users (consumers);
- Sharing of network resources, to meet specific application and
users requirements;
- A computation scheme, via an information model, to serve
various consumers that request network connectivity and
properties associated with it;
- A virtual network controller that adapts consumer requests to
the virtual resources allocated to them to the supporting
physical network control and performs the necessary mapping,
translation, isolation and security/policy enforcement, etc.;
- The coordination of the underlying transport topology,
presenting it as an abstracted topology to consumervia open and
programmable interfaces.
The organization of this draft is as follows. Section 3 provides a
discussion for a Business Model, Section 4 a Computation Model,
Section 5 a Control and Interface model and Section 6 Design
Principles.
3. Business Model of ACTN
The traditional Virtual Private Network (VPN) and Overlay Network
(ON) models are built on the premise that one single network
provider provides all virtual private or overlay networks to its
consumers. This model is simple to operate but has some
disadvantages in accommodating the increasing need for flexible and
dynamic network virtualization capabilities.
The ACTN model is built upon entities that reflect the current
landscape of network virtualization environments. There are three
key entities in the ACTN model:
- Consumers
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- Network Providers
- Service Providers
3.1. Consumers
Consumers are the users of virtual network services. As consumers
are geographically spread over multiple network provider domains,
the necessary control and data interfaces to support such consumer
needs is no longer a single interface between the consumer and one
single network provider. With this premise, consumers have to
interface multiple providers to get their end-to-end network
connectivity servjce and the associated topology information.
Consumers may have to support multiple virtual network services with
differing service objectives and QoS requirements. For flexible and
dynamic applications, consumers may want to control their allocated
virtual network resources in a dynamic fashion. To allow that,
consumers should be given an abstracted view of topology on which
they can perform the necessary control decisions and take the
corresponding actions.
3.2. Service Providers
Service providers are the providers of virtual network services to
their consumers. Service providers may or may not own physical
network resources. When a service provider is the same as the
network provider, this is similar to traditional VPN models. This
model works well when the consumer maintains a single interface with
a single provider. When consumer location spans across multiple
independent network provider domains, then it becomes hard to
facilitate the creation of end-to-end virtual network services with
this model.
A more interesting case arises when network providers only provide
infrastructure while service providers directly interface their
consumers. In this case, service providers themselves are consumers
of the network infrastructure providers. One service provider may
need to keep multiple independent network providers as its end-users
span geographically across multiple network provider domains. The
ACTN network model is predicated upon this three tier model.
There can be multiple types of service providers. Data Center
providers can be viewed as a service provider type as they own and
operate data center resources to various WAN clients, they can lease
physical network resources from network providers. Internet Service
Providers (ISP) can be a service provider of internet services to
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their customers while leasing physical network resources from
network providers. There may be other types of service providers
such as mobile virtual network operators (MVNO) that provide mobile
services to their end-users without owning the physical network
infrastructure.
3.3. Network Providers
Network Providers are the infrastructure providers that own the
physical network resources and provide network resources to their
consumers. The layered model proposed by this draft separates the
concerns of network providers and consumers, with service providers
acting as aggregators of consumer requests.
4. Computation Model of ACTN
This section discusses ACTN from a computational point of view. As
multiple consumers run their virtualized network on a shared
infrastructure, making efficient use of the underlying resources
requires effective computational models and algorithms. This general
problem space is known as Virtual Network Mapping or Embedding (VNM
or VNE). (Put some reference).
As VNM/VNE issues impose some additional compute models and
algorithms for virtual network path computation, this section
discusses key issues and constraints for virtual network path
computation.
4.1. Request Processing
This is concerned about whether a set of consumer requests for VN
creation can be dealt with simultaneously or not. This depends on
the nature of applications the consumer support. If the consumer
does not require real-time instantiation of VN creation, the
computation engine can process a set of VN creation requests
simultaneously to improve network efficiency.
4.2. Types of Network Resources
When a consumer makes a VN creation request to the substrate
network, what kind of network resources is consumed is of concern of
both the consumer and network providers. For transport network
virtualization, the network resource consumed is primarily network
bandwidth that the required paths would occupy on the physical
link(s). However, there may be other resource types such as CPU and
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memory that need to be considered for certain applications. These
resource types shall be part of the VN request made by the consumer.
4.3. Accuracy of Network Resource Representation
As the underlying transport network in itself may consist of a
layered structure, it is a challenge how to represent these
underlying physical network resources and topology into a form that
can be reliably used by the computation engine that assigns consumer
requests into the physical network resource and topology.
4.4. Resource Efficiency
Related to the accuracy of network resource representation is
resource efficiency. As a set of independent consumer VN is created
and mapped onto physical network resources, the overall network
resource utilization is the primary concern of the network provider.
4.5. Guarantee of Client Isolation
While network resource sharing across a set of consumers for
efficient utilization is an important aspect of network
virtualization, consumer isolation has to be guaranteed. Admissions
of new consumer requests or any changes of other existing consumer
VNs must not affect any particular consumer in terms of resource
guarantee, security constraints, and other performance constraints.
4.6. Computing Time
Depending on the nature of applications, how quickly a VN is
instantiated from the time of request is an important factor. For
dynamic applications that require instantaneous VN creation, the
computation model/algorithm should support this constraint.
4.7. Admission Control
To coordinate the request process of multiple consumers, an
admission control will help maximize an overall efficiency.
4.8. Path Constraints
There may be some factors of path constraints that can affect the
overall efficiency. Path Split can lower VN request blocking if the
underlying network can support such capability. A packet-based TE
network can support path split while circuit-based transport may
have limitations.
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Path migration is a technique that allows changes of nodes or link
assignments of the established paths in an effort to accommodate new
requests that would not be accepted without such path migration(s).
This can improve overall efficiency, yet additional care needs to be
applied to avoid any adverse impacts associated with changing the
existing paths.
Re-optimization is a global process to re-shuffle all existing path
assignments to minimize network resource fragmentation. Again, an
extra care needs to be applied for re-optimization.
5. Control and Interface Model for ACTN
This section provides a high-level control and interface model of
ACTN.
5.1. A High-level ACTN Control Architecture
To allow virtualization, the network has to provide open,
programmable interfaces in which consumer applications can create,
replace and modify virtual network resources in an interactive,
flexible and dynamic fashion while having no impact on other network
consumers. Direct consumer control of transport network elements
over existing interfaces (control or management plane) is not
perceived as a viable proposition for transport network providers
due to security and policy concerns among other reasons. In
addition, as discussed in the previous section, the network control
plane for transport networks has been separated from data plane and
as such it is not viable for the consumer to directly interface with
transport network elements.
While the current network control plane is well suited for control
of physical network resources via dynamic provisioning, path
computation, etc., a virtual network controller needs to be built on
top of physical network controller to support network
virtualization. On a high-level, virtual network control refers to a
mediation layer that performs several functions:
- Computation of consumer resource requests into virtual network
paths based on the global network-wide abstracted topology;
- Mapping and translation of consumer virtual network slices into
physical network resources;
- Creation of an abstracted view of network slices allocated to each
consumer, according to consumer-specific objective functions, and
to the consumer traffic profile.
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In order to facilitate the above-mentioned virtual control
functions, the virtual network controller (aka., "virtualizer")
needs to maintain two interfaces:
- One interface with the physical network controller functions
assumed by MPLS/GMPLS and PCE, which is termed as the VNC-PNC
Interface (VPI);
- Another interface with the consumer controller for the virtual
network, which is termed as Client-VNC Interface (CVI).
Figure 1 depicts a high-level control and interface architecture for
ACTN.
------------------------------------------
| Application Layer |
------------------------------------------
/|\ /|\ /|\
| | \|/ Northbound API
| | ---------------
| \|/ | Consumer |
| --------------- Controller |
\|/ | Consumer |------------
-------------- Controller | /|\
| Consumer |----------- |
| Controller | /|\ |
-------------- | |
/|\ | | Consumer-VNC
| | | Interface (CVI)
\|/ \|/ \|/
-----------------------------------
| Virtual Network Controller (VNC) |
-----------------------------------
/|\
| VNC-PNC Interface (VPI)
\|/
-----------------------------------
| Physical Network Controller (PNC) |
-----------------------------------
/|\
| Control Interface to NEs
\|/
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Physical Network Infrastructure
Figure 1: Control and Interface Architecture for ACTN.
Figure 1 shows that there are multiple consumer controllers, which
are independent to one another, and that each consumer supports
various business applications over its NB API. There are layered
client-server relationships in this architecture. As various
applications are clients to the consumer controller, it also becomes
itself a client to the virtual network controller. Likewise, the
virtual network controller is also a client to the physical network
controller. This layered relationship is important in the protocol
definition work on the NB API, the CVI and VPI interfaces as this
allows third-party software developers to program client controllers
and virtual network controllers independently.
5.2. Consumer Controller
A Virtual Network Service is instantiated by the consumer controller
via the CVI. As the consumer controller directly interfaces the
application stratum, it understands multiple application
requirements and their service needs. It is assumed that the
consumer controller and the VNC have a common knowledge on the end-
point interfaces based on their business negotiation prior to
service instantiation. End-point interfaces refer to consumer-
network physical interfaces that connect consumer premise equipment
to network provider equipment. Figure 2 shows an example physical
network topology that supports multiple consumers. In this example,
consumer A has three end-points A.1, A.2 and A.3. The interfaces
between consumers and transport networks are assumed to be 40G OTU
links. For simplicity's sake, all network interfaces are assumed to
be 40G OTU links and all network ports support ODU switching and
grooming on the level of ODU1 and ODU2. Consumer controller for A
provides its traffic demand matrix that describes bandwidth
requirements and other optional QoS parameters (e.g., latency,
diversity requirement, etc.) for each pair of end-point connections.
5.3. Abstracted Topology
There are two levels of abstracted topology that needs to be
maintained and supported for ACTN. Consumer-specific Abstracted
Topology refers to the abstracted view of network resources
allocated to the consumer. The granularity of this abstraction
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varies depending on the nature of consumer applications. Figure 2
illustrates this.
Figure 2 shows how three independent consumers A, B and C provide
its respective traffic demand matrices to the VNC. The physical
network topology shown in Figure 2 is the provider's network
topology generated by the PNC topology creation engine such as the
link state database (LSDB) and Traffic Engineering DB (TEDB) based
on control plane discovery function. This topology is internal to
PNC and not available to consumers. What is available to them is an
abstracted network topology (a virtual network topology) based on
the negotiated level of abstraction. This is a part of VNS
instantiation between a client control and VNC.
+------+ +------+ +------+
A.1 ------o o-----------o o----------o o------- A.2
B.1 ------o 1 | | 2 | | 3 |
C.1 ------o o-----------o o----------o o------- B.2
+-o--o-+ +-o--o-+ +-o--o-+
| | | | | |
| | | | | |
| | | | | |
| | +-o--o-+ +-o--o-+
| `-------------o o----------o o------- B.3
| | 4 | | 5 |
`----------------o o----------o o------- C.3
+-o--o-+ +------+
| |
| |
C.2 A.3
Traffic Matrix Traffic Matrix Traffic Matrix
for Consumer A for Consumer B for Consumer C
A.1 A.2 A.3 B.1 B.2 B.3 C.1 C.2 C.3
------------------- ------------------ -----------------
A.1 - 20G 20G B.1 - 40G 40G C.1 - 20G 20G
A.2 20G - 10G B.2 40G - 20G C.2 20G - 10G
A.3 20G 10G - B.3 40G 20G - C.3 20G 10G -
Figure 2: Physical network topology shared with multiple consumers
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Figure 3 depicts illustrative examples of different level of
topology abstractions that can be provided by the VNC topology
abstraction engine based on the physical topology base maintained by
the PNC. The level of topology abstraction is expressed in terms of
the number of virtual network elements (VNEs) and virtual links
(VLs). For example, the abstracted topology for consumer A shows
there are 5 VNEs and 10 VLs. This is by far the most detailed
topology abstraction with a minimal link hiding compared to other
abstracted topologies in Figure 3.
(a) Abstracted Topology for Consumer A (5 VNEs and 10 VLs)
+------+ +------+ +------+
A.1 ------o o-----------o o----------o o------- A.2
| 1 | | 2 | | 3 |
| | | | | |
+-o----+ +-o----+ +-o----+
| | |
| | |
| | |
| +-o----+ +-o--o-+
| | | | |
| | 4 | | 5 |
`----------------o o----------o |
+----o-+ +------+
|
|
A.3
(b) Abstracted Topology for Consumer B (3 VNEs and 6 VLs)
+------+ +------+
B.1 ------o o-----------------------------o o------ B.2
| 1 | | 3 |
| | | |
+-o----+ +-o----+
\ |
\ |
\ |
`------------------- |
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` +-o----+
\ | o------ B.3
\ | 5 |
`-------o |
+------+
(c) Abstracted Topology for Consumer C (1 VNE and 3 VLs)
+-------------------------------------------+
| |
| |
C.1 ------o |
| |
| |
| |
| o--------C.3
| |
+--------------------o----------------------+
|
|
|
|
C.2
Figure 3: Topology Abstraction Examples for Consumers
As different consumers have different control/application needs,
abstracted topologies for consumers B and C, respectively show a
much higher degree of abstraction. The level of abstraction is
determined by the policy (e.g., the granularity level) placed for
the consumer and/or the path computation results by the PCE operated
by the PNC. The more granular the abstraction topology is, the more
control is given to the consumer controller. If the consumer
controller has applications that require more granular control of
virtual network resources, then the abstracted topology shown for
consumer A may be the right abstraction level for such controller.
For instance, if the consumer is a third-party virtual service
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broker/provider, then it would desire much more sophisticated
control of virtual network resources to support different
application needs. On the other hand, if the consumer were only to
support simple tunnel services to its applications, then the
abstracted topology shown for consumer C (one VNE and three VLs)
would suffice.
5.4. Workflows of ACTN Control Modules
Figure 4 shows workflows across the consumer controller, VNC and PNC
for the VNS instantiation, topology exchange, and VNS setup.
The consumer controller "owns" a VNS and initiates it by providing
the instantiation identifier with a traffic demand matrix that
includes path selection constraints for that instance. This VNS
instantiation request from the Consumer Controller triggers a path
computation request by the virtual PCE (vPCE) agent in the VNC after
VNC's proxy's interlay of this request to the vPCE. vPCE sends a
concurrent path computation request that is converted according to
the traffic demand matrix as part of the VNS instantiation request
from the Consumer Controller. Upon receipt of this path computation
request, the PCE in the PNC block computes paths and updates network
topology DB and informs the vPCE agent of the VNC of the paths and
topology updates.
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------------------------------------------------------------------
| Consumer ----------------------------------------------- |
| Controller | VNS Control | |
| ----------------------------------------------- |
------------------------------------------------------------------
1.VNS | /|\ 4. Abstracted | /|\
Instantiation | | Topology | |
(instance id, | | | |
Traffic Matr.) | | | | 8. VNS
| | 5. VNS | | Set-up
\|/ | Set-up \|/ | Confirm
------------------------------------------------------------------
| Virtual ----------------------------------------------- |
| Network | VNS Proxy | |
| Controller ----------------------------------------------- |
| ----------------------- ----------------------- |
| | vPCE Agent | | vConnection Agent | |
| ----------------------- ----------------------- |
------------------------------------------------------------------
2. Path | /|\ 3. PC Reply | /|\
Computation | | with updated | |
Request | | topology | |
| | 6. Network | |8.Network
| | Provisioning | |Provisioning
\|/ | Request \|/ |Confirm
------------------------------------------------------------------
| Physical ------------- -------------------------- |
| Network | PCE | | Network Provisioning ||
| Controller ------------- -------------------------- |
------------------------------------------------------------------
Figure 4. Workflows across Consumer Controller, VNC and PNC
It is assumed that the PCE in PNC is a stateful PCE [PCE-S]. vPCE
agent abstracts the network topology into an abstracted topology for
the consumer based on the agreed-upon granularity level. The
abstracted topology is then passed to the VNS control of the
Consumer Controller. This controller computes and assigns virtual
network resources for its applications based on the abstracted
topology and creates VNS setup command to the VNC. The VNC
vConnection module turns this VN setup command into network
provisioning requests over the network elements using control plane
messages such as GMPLS, etc.
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5.5. Programmability of the ACTN Interfaces
From Figures 1 and 4, we have identified several interfaces that are
of interest of the ACTN model. More precisely, ACTN concerns the
following interfaces:
- Consumer-VNC Interface (CVI): an interface between a consumer
controller and a virtual network controller.
- VNC-PNC Interface (VPI): an interface between a virtual network
controller and a physical network controller.
The NBI interfaces and direct control interfaces to NEs are outside
of the scope of ACTN.
The CVI interface should allow programmability, first of all, to the
consumer so they can create, modify and delete virtual service
instances. This interface should also support open standard
information and data models that can transport abstracted topology.
The VPI interface should allow programmability to service
provider(s) (through VNCs) in such ways that control functions such
as path computation, provisioning, and restoration can be
facilitated. Seamless mapping and translation between physical
resources and virtual resources should also be facilitated via this
interface.
6. Design Principles of ACTN
6.1. Network Security
Network security concerns are always one of the primary principles
of any network design. ACTN is no exception. Due to the nature of
heterogeneous VNs that are to be created, maintained and deleted
flexibly and dynamically and the anticipated interaction with
physical network control components, secure programming models and
interfaces have to be available beyond secured tunnels, encryption
and other network security tools.
6.2. Privacy and Isolation
As physical network resources are shared with and controlled by
multiple independent consumers, isolation and privacy for each
consumer has to be guaranteed.
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Policy should be applied per client.
6.3. Scalability
As multiple VNs need to be supported seamlessly, there are
potentially several scaling issues associated with ACTN. The VN
Controller system should be scalable in supporting multiple parallel
computation requests from multiple consumers. New VN request should
not affect the control and maintenance of the existing VNs. Any VN
request should also be satisfied within a time-bound of the consumer
application request.
Interfaces should also be scalable as a large amount of data needs
to be transported across consumers to virtual network controllers
and across virtual network controllers and physical network
controllers.
6.4. Manageability and Orchestration
As there are multiple entities participating in network
virtualization, seamless manageability has to be provided across
every layer of network virtualization. Orchestration is an important
aspect of manageability as the ACTN design should allow
orchestration capability.
ACTN orchestration should encompass network provider multi-domains,
relationships between service provider(s) and network provider(s),
and relationships between consumers and service/network providers.
Ease of deploying end-to-end virtual network services across
heterogeneous network environments is a challenge.
6.5. Programmability
As discussed earlier in Section 5.5, the ACTN interfaces should
support open standard interfaces to allow flexible and dynamic
virtual service creation environments.
6.6. Network Stability
As multiple VNs are envisioned to share the same physical network
resources, combining many resources into one should not cause any
network instability. Provider network oscillation can affect readily
both on virtual networks and the end-users.
Part of network instability can be caused when virtual network
mapping is done on an inaccurate or unreliable resource data. Data
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base synchronization is one of the key issues that need to be
ensured in ACTN design.
7. References
7.1. Informative References
[PCE] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", IETF RFC
4655, August 2006.
[PCE-S] Crabbe, E, et. al., "PCEP extension for stateful
PCE",draft-ietf-pce-stateful-pce, work in progress.
[GMPLS] Manning, E., et al., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945, October 2004.
[NFV-AF] "Network Functions Virtualization (NFV); Architectural
Framework", ETSI GS NFV 002 v1.1.1, October 2013.
8. Contributors
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Authors' Addresses
Daniel Ceccarelli
Email: daniele.ceccarelli@ericsson.com
Luyuan Fang
Email: luyuanf@gmail.com
Young Lee
Huawei Technologies
5340 Legacy Drive
Plano, TX 75023, USA
Phone: (469)277-5838
Email: leeyoung@huawei.com
Diego Lopez
Telefonica I+D
Don Ramon de la Cruz, 82
28006 Madrid, Spain
Email: diego@tid.es
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