6TiSCH                                               MR. Palattella, Ed.
Internet-Draft                                   SnT/Univ. of Luxembourg
Intended status: Informational                                P. Thubert
Expires: January 7, 2016                                           cisco
                                                             T. Watteyne
                                       Linear Technology / Dust Networks
                                                                 Q. Wang
                                         Univ. of Sci. and Tech. Beijing
                                                            July 6, 2015


        Terminology in IPv6 over the TSCH mode of IEEE 802.15.4e
                    draft-ietf-6tisch-terminology-05

Abstract

   6TiSCH proposes an architecture for an IPv6 multi-link subnet that is
   composed of a high speed powered backbone and a number of
   IEEE802.15.4e TSCH wireless networks attached and synchronized by
   backbone routers.  This document extends existing terminology
   documents available for Low-power and Lossy Networks to provide
   additional terminology elements.

Requirements Language

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

Status of This Memo

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

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

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

   This Internet-Draft will expire on January 7, 2016.





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Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   5.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  11
     6.3.  External Informative References . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   The IEEE802.15.4 Medium Access Control (MAC) has evolved with
   IEEE802.15.4e which provides in particular the Time Slotted Channel
   Hopping (TSCH) mode for industrial-type applications.  It provides
   deterministic capabilities to the point that a packet that pertains
   to a certain flow crosses the network from node to node following a
   very precise schedule, like a train leaves intermediate stations at
   precise times along its path.

   This document provides additional terminology elements to cover terms
   that are new to the context of TSCH wireless networks and other
   deterministic networks.

2.  Terminology

   The draft extends [I-D.ietf-roll-terminology] and use terms from RFC
   6550 [RFC6550] and RFC 6552 [RFC6552], which are all included here by
   reference.




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   The draft does not reuse terms from IEEE802.15.4e such as "path" or
   "link" which bear a meaning that is quite different from classical
   IETF parlance.

   This document adds the following terms:

   6TiSCH:     IPv6 over the Timeslotted Channel Hopping (TSCH) mode of
               IEEE802.15.4e.  It defines (i)the 6top sublayer; (ii) a
               set of protocols for setting up a TSCH schedule with a
               centralized and/or distributed approach, for managing the
               allocation of resources; and (iii) the architecture to
               bind them together, for use in IPv6 TSCH based networks.

   6F:         IPv6 Forwarding.  One of the three forwarding models
               supported by 6TiSCH.  Packets are routed at layer 3,
               where Quality of Service (QoS) and Active Queue
               Management (e.g., Random Early Detection, RED, [RFC2309])
               operations are expected to prioritize flows with
               differentiated services.

   6top:       6top is the adaptation sublayer between TSCH and upper
               layers like IPv6 over Low-Power Wireless Personal Area
               Networks (6LoWPANs) and IPv6 Routing Protocol for Low-
               Power and Lossy Networks (RPL).  It is defined in
               [I-D.wang-6tisch-6top-sublayer].

   6top Data Convey Model:  Model describing how the 6top adaptation
               layer feeds the data flow coming from upper layers into
               TSCH.  It is composed by an I-MUX module, a MUX module, a
               set of priority queues, and a PDU (Payload Data Unit).
               See [I-D.wang-6tisch-6top-sublayer].

   ARO:        [RFC6775] defines a number of new Neighbor Discovery
               options including the Address Registration Option (ARO).

   ASN:        Absolute Slot Number, the total number of timeslots that
               has elapsed since the PAN coordinator has started the
               TSCH network.  It is incremented by one at each timeslot.
               It is wide enough to not roll over in practice.  See
               [IEEE802154e].

   Blacklist of Frequencies:  Simply defined Blacklist in [IEEE802154e],
               it is the set of frequencies among the 16 available ones,
               which should not be used for communication.

   BBR:        Backbone Router.  In the 6TiSCH architecture, it is an
               LBR and also a IPv6 ND-efficiency-aware Router (NEAR)
               [I-D.chakrabarti-nordmark-6man-efficient-nd].  It



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               performs ND proxy operations between registered devices
               and classical ND devices that are located over the
               backbone.

   Broadcast Cell:  A scheduled cell used for broadcast transmission.

   Bundle:     A group of equivalent scheduled cells, i.e. cells
               identified by different [slotOffset, channelOffset],
               which are scheduled for a same purpose, with the same
               neighbor, with the same flags, and the same slotframe.
               The size of the bundle refers to the number of cells it
               contains.  Given the length of the slotframe, the size of
               the bundle translates directly into bandwidth.  A bundle
               represents a half-duplex link between nodes, one
               transmitter and one or more receivers, with a bandwidth
               that amount to the sum of the cells in the bundle.  A
               bundle is globally identified by (source MAC, destination
               MAC, TrackID).  At Layer 3 a pair of bundles forms a
               link.  By usining a well-known constant, NULLT, as
               TrackId for a L3 link, the IP link between adjacent nodes
               A and B comprises 2 bundles: (macA, macB, NULLT) and
               (macB, macA, NULLT).  At L2 a pair of bundles forms a
               switching state.  Considered a segment A-B-C along a
               track, there are two bundles in node B, one incoming =
               (macA, macB, trackId) and one outgoing = (macB, macC,
               trackId).

   Cell:       A single element in the TSCH schedule, identified by a
               slotOffset, a channelOffset, a slotframeHandle.  A cell
               can be scheduled or unscheduled.

   Centralized Cell Reservation:  A reservation of a cell done by a
               centralized entity (e.g., a PCE) in the network.

   Centralized Track Reservation:  A reservation of a track done by a
               centralized entity (e.g., a PCE) in the network.

   ChannelOffset:  Identifies a row in the TSCH schedule.  The number of
               available channelOffsets is equal to the number of
               available frequencies.  The channelOffset translates into
               a frequency when the communication takes place, resulting
               in channel hopping, as detailed in [RFC7554].

   Channel Distribution/Usage (CDU) matrix:  : Matrix of cells (i,j)
               representing the spectrum (channel) distribution among
               the different nodes in the 6TiSCH network.  The CDU
               matrix has width in timeslots, equal to the period of the
               network scheduling operation, and height equal to the



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               number of available channels.  Every cell (i,j) in the
               CDU, identified by (slotOffset, channelOffset), belongs
               to a specific chunk.  It has to be noticed that such a
               matrix which includes all the cells grouped in chunks,
               belonging to different slotframes, is different from the
               TSCH schedule.

   Chunk:      A well-known list of cells, distributed in time and
               frequency, within a CDU matrix; a chunk represents a
               portion of a CDU matrix.  The partition of the CDU in
               chunks is globally known by all the nodes in the network
               to support the appropriation process, which is a
               negotiation between nodes within an interference domain.
               A node that manages to appropriate a chunk gets to decide
               which transmissions will occur over the cells in the
               chunk within its interference domain (i.e., a parent node
               will decide when the cells within the appropriated chunk
               are used and by which node, among its children.

   Communication Paradigm:  It is Associated with the Information Model
               [RFC3444] of the state that is exchanged, and indicates:
               the location of that state (e.g., centralized vs.
               distributed, RESTful, etc.), the numbers of parties
               (e.g., point to point, P2P, vs. point to multi-point,
               P2MP) and the relationship between parties (e.g., master/
               slave vs. peers) at a high level of protocol abstraction.
               Layer 5 client/server REST is a typical communication
               paradigm, but industrial protocols also use publish/
               subscribe which is P2MP and source/sink which is multi-
               point to multi-point (MP2MP) and primarily used for
               alarms and alerts at the application layer.  At layer 3,
               basic flooding, P2P synchronization and path-marking
               (RSVP-like) are commonly used paradigms, whereas at layer
               2, master/slave polling and peer-to-peer forwarding are
               classical examples.

   DAR/DAC:    [RFC6775] defines the Duplicate Address Request (DAR) and
               Duplicate Address Confirmation (DAC) options to turn the
               multicast Duplicate Address Detection protocol into a
               unicast-based multi-hop process between routers and the
               backbone router.

   Dedicated Cell:  A cell that is reserved for a given node to transmit
               to a specific neighbor.

   Deterministic Network:  A Deterministic Network supports traffic
               flows with communication patterns that are known a
               priori.  Thus, routing paths and communication schedules



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               can be computed in advance, in a fashion similar to a
               railway system, to avoid losses due to packet collisions,
               and to perform global optimizations across multiple
               flows.  A deterministic network can allocates the
               required resources (buffers, processors, medium access)
               along the multi-hop routing path at the precise moment
               the resources are needed.

   Distributed Cell Reservation:  A reservation of a cell done by one or
               more in-network entities (typically a connection
               endpoint).

   Distributed Track Reservation:  A reservation of a track done by one
               or more in-network entities (typically a connection
               endpoint).

   EARO:       [I-D.thubert-6lo-rfc6775-update-reqs] extends the ARO
               option to include some additional fields necessary to
               distinguish duplicate addresses from nodes that have
               moved networks when there are mulitple LLNs linked over a
               backbone.

   EB:         Enhanced Beacon frame used by a node to announce the
               presence of the network.  It contains useful information
               (see [IEEE802154e] for details) that allow a new node to
               synhronize and join the network.

   FF:         6LoWPAN Fragment Forwarding.  It is one of the three
               forwarding models supported by 6TiSCH.  The 6LoWPAN
               Fragment is used as a label for switching at the 6LoWPAN
               sublayer, as defined in
               [I-D.thubert-roll-forwarding-frags].

   GMPLS:      Generalized Multi-Protocol Label Switching, a 2.5 layer
               service that is used to forward packets based on the
               concept of generalized labels.

   Hard Cell:  A scheduled cell which the 6top sublayer cannot
               reallocate.  See [I-D.wang-6tisch-6top-sublayer].

   Hopping Sequence:  Ordered sequence of frequencies, identified by a
               Hopping_Sequence_ID, used for channel hopping, when
               translating the channel offset value into a frequency
               (i.e., PHY channel).  See [IEEE802154e] and [RFC7554].

   IE:         Information Elements, a list of Type-Length-Value
               containers placed at the end of the MAC header, used to
               pass data between layers or devices.  A small number of



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               types are defined by [IEEE802154e], but a range of types
               is available for extensions, and thus, is exploitable by
               6TiSCH.  See [IEEE802154e].

   I-MUX module:  Inverse-Multiplexer, a classifier that receives
               6LoWPAN frames and places them into priority queues.  See
               [I-D.wang-6tisch-6top-sublayer].

   Interaction Model:  It is a particular way of implementing a
               communication paradigm.  Defined at a lower level of
               abstraction, it includes protocol-specific details such
               as a particular method (e.g., a REST GET) and a Data
               Model for the state to be exchanged.

   Interference Domain:  The Interference Domain of a given
               (transmitter) node A includes all the nodes in its
               neighbourhood that can generate interference at its
               receiver B, when transmitting on the same channel (i.e.,
               using the same frequency).

   JCE:        The Join Coordination Entity (JCE) is a central entity
               like the Path Computation Element (PCE), that may assist
               in several aspects of the join protocol, such as
               authentication, authorization, and configuration.

   JA:         The Join Assistant (JA) is a one-hop neighbor of a
               joining node that may facilitate it to become meaningful
               part of the network (e.g., by serving as a local
               connectivity point to the remainder of the network).

   Join Protocol:  The protocol which secures initial communication
               between a joining node and the JCE.

   LBR:        Low-power Lossy Network (LLN) Border Router.  It is an
               LLN device, usually powered, that acts as a Border Router
               to the outside within the 6TiSCH architecture.

   Link:       A communication facility or medium over which nodes can
               communicate at the link layer, i.e., the layer
               immediately below IP.  Thus, the IETF parlance for the
               term "Link" is adopted, as opposed to the IEEE802.15.4e
               terminology.  In the context of the 6TiSCH architecture,
               which applies to Low Power Lossy Networks (LLNs), an IPv6
               subnet is usually not congruent to a single link and
               techniques such as IPv6 Neighbor Discovery Proxying are
               used to achieve reachability within the multilink subnet.
               A link is distinct from a track.  In fact, link local
               addresses are not expected to be used over a track for



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               end to end communication.  Finally, from the Layer 3
               perspective (where the inner complexities of TSCH
               operations are hidden to enable classical IP routing and
               forwarding), a single radio interface may be seen as a
               number of Links with different capabilities for unicast
               or multicast services.

   MAC:        Medium Access Control.

   MUX Module: Multiplexer, the entity that dequeues frames from
               priority queues and associates them to a cell for
               transmission.  See [I-D.wang-6tisch-6top-sublayer].

   NEAR:       IPv6 ND-efficiency-aware Router, as defined in
               [I-D.chakrabarti-nordmark-6man-efficient-nd].

   NME:        Network Management Entity, the entity in the network
               managing cells and other device resources.  It may
               cooperate with the PCE.  It interacts with LLN nodes
               through the backbone router.

   Operational Network:  A IEEE802.15.4e network whose encryption/
               authentication keys are determined by some algorithms/
               protocols.  There may be network-wide group keys, or per-
               link keys.

   Operational Network Key:  A Link-layer key known by all authorized
               nodes, used for multicast messages.

   PCE:        Path Computation Element, the entity in the network which
               is responsible for building and maintaining the TSCH
               schedule, when centralized scheduling is used.

   QoS:        Quality of Service.

   (to) Reallocate a Cell:  The action operated by the 6top sublayer of
               changing the slotOffset and/or channelOffset of a soft
               cell.

   (to) Schedule a Cell:  The action of turning an unscheduled cell into
               a scheduled cell.

   Scheduled cell:  A cell which is assigned a neighbor MAC address
               (broadcast address is also possible), and one or more of
               the following flags: TX, RX, shared, timeskeeping.  A
               scheduled cell can be used by the IEEE802.15.4e TSCH
               implementation to communicate.  A scheduled cell can be
               either a hard or a soft cell.



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   Shared Cell:  A cell marked with both the "TX" and "shared" flags.
               This cell can be used by more than one transmitter node.
               A backoff algorithm is used to resolve contention.  See
               [RFC7554].

   SlotOffset: Identifies a column in the TSCH schedule, i.e., the
               number of timeslots since the beginning of the current
               iteration of the slotframe.

   Slotframe:  A MAC-level abstraction that is internal to the node and
               contains a series of timeslots of equal length and
               priority.  It is characterized by a slotframe_ID, and a
               slotframe_size.  Multiple slotframes can coexist in a
               node's schedule, i.e., a node can have multiple
               activities scheduled in different slotframes, based on
               the priority of its packets/traffic flows.  The timeslots
               in the Slotframe are indexed by the SlotOffset; the first
               timeslot is at SlotOffset 0.

   Soft Cell:  A scheduled cell which the 6top sublayer can reallocate,
               as described in [I-D.wang-6tisch-6top-sublayer].

   TF:         Track Forwarding.  It is the simplest and fastest
               forwarding model supported by 6TiSCH.  It is a GMPLS-like
               forwarding model.  The incoming bundle (and thus, the
               input cell) characterizes the flow and indicates the
               outgoing bundle (and output cell).

   Timeslot:   A basic communication unit in TSCH which allows a
               transmitter node to send a frame to a receiver neighbor,
               and that receiver neighbor to optionally send back an
               acknowledgment.

   Time Source Neighbor:  A neighbor that a node uses as its time
               reference, and to which it needs to keep its clock
               synchronized.  A node can have one or more time source
               neighbors.

   Track:      A determined sequence of cells along a multi-hop path.
               It is typically the result of a track reservation.  The
               node that initializes the process for establishing a
               track is the owner of the track.  The latter assigns a
               unique identifier to the track, called TrackID.

   TrackID:    Unique identifier of a track, assigned by the owner of
               the track.





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   TSCH:       Time Slotted Channel Hopping, a medium access mode of the
               [IEEE802154e] standard which uses time synchronization to
               achieve ultra low-power operation and channel hopping to
               enable high reliability.

   TSCH Schedule:  A matrix of cells, each cell indexed by a slotOffset
               and a channelOffset.  The TSCH schedule contains all the
               scheduled cells from all slotframes and is sufficient to
               qualify the communication in the TSCH network.  The
               "width of the matrix is equal to the number of scheduled
               timeslots in all the concurrent active slotframes.  The
               number of channelOffset values (the "height" of the
               matrix) is equal to the number of available frequencies.

   Unscheduled Cell:  A cell which is not used by the IEEE802.15.4e TSCH
               implementation.

3.  IANA Considerations

   This specification does not require IANA action.

4.  Security Considerations

   This specification is not found to introduce new security threats.

5.  Acknowledgments

   Thanks to the IoT6 European Project (STREP) of the 7th Framework
   Program (Grant 288445).

6.  References

6.1.  Normative References

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

   [RFC2309]  Braden, B., Clark, D., Crowcroft, J., Davie, B., Deering,
              S., Estrin, D., Floyd, S., Jacobson, V., Minshall, G.,
              Partridge, C., Peterson, L., Ramakrishnan, K., Shenker,
              S., Wroclawski, J., and L. Zhang, "Recommendations on
              Queue Management and Congestion Avoidance in the
              Internet", RFC 2309, April 1998.

   [RFC3444]  Pras, A. and J. Schoenwaelder, "On the Difference between
              Information Models and Data Models", RFC 3444, January
              2003.




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   [RFC5191]  Forsberg, D., Ohba, Y., Patil, B., Tschofenig, H., and A.
              Yegin, "Protocol for Carrying Authentication for Network
              Access (PANA)", RFC 5191, May 2008.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, January 2012.

   [RFC6550]  Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R.,
              Levis, P., Pister, K., Struik, R., Vasseur, JP., and R.
              Alexander, "RPL: IPv6 Routing Protocol for Low-Power and
              Lossy Networks", RFC 6550, March 2012.

   [RFC6552]  Thubert, P., "Objective Function Zero for the Routing
              Protocol for Low-Power and Lossy Networks (RPL)", RFC
              6552, March 2012.

   [RFC6775]  Shelby, Z., Chakrabarti, S., Nordmark, E., and C. Bormann,
              "Neighbor Discovery Optimization for IPv6 over Low-Power
              Wireless Personal Area Networks (6LoWPANs)", RFC 6775,
              November 2012.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252, June 2014.

   [RFC7554]  Watteyne, T., Palattella, M., and L. Grieco, "Using IEEE
              802.15.4e Time-Slotted Channel Hopping (TSCH) in the
              Internet of Things (IoT): Problem Statement", RFC 7554,
              May 2015.

6.2.  Informative References

   [I-D.chakrabarti-nordmark-6man-efficient-nd]
              Chakrabarti, S., Nordmark, E., Thubert, P., and M.
              Wasserman, "IPv6 Neighbor Discovery Optimizations for
              Wired and Wireless Networks", draft-chakrabarti-nordmark-
              6man-efficient-nd-07 (work in progress), February 2015.

   [I-D.ietf-roll-terminology]
              Vasseur, J., "Terms used in Routing for Low power And
              Lossy Networks", draft-ietf-roll-terminology-13 (work in
              progress), October 2013.

   [I-D.thubert-6lo-rfc6775-update-reqs]
              Thubert, P. and P. Stok, "Requirements for an update to
              6LoWPAN ND", draft-thubert-6lo-rfc6775-update-reqs-06
              (work in progress), January 2015.





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   [I-D.thubert-roll-forwarding-frags]
              Thubert, P. and J. Hui, "LLN Fragment Forwarding and
              Recovery", draft-thubert-roll-forwarding-frags-02 (work in
              progress), September 2013.

   [I-D.wang-6tisch-6top-sublayer]
              Wang, Q., Vilajosana, X., and T. Watteyne, "6TiSCH
              Operation Sublayer (6top)", draft-wang-6tisch-6top-
              sublayer-01 (work in progress), July 2014.

6.3.  External Informative References

   [IEEE802154e]
              IEEE standard for Information Technology, "IEEE std.
              802.15.4e, Part. 15.4: Low-Rate Wireless Personal Area
              Networks (LR-WPANs) Amendment 1: MAC sublayer", April
              2012.

Authors' Addresses

   Maria Rita Palattella (editor)
   University of Luxembourg
   Interdisciplinary Centre for Security, Reliability and Trust
   4, rue Alphonse Weicker
   Luxembourg  L-2721
   Luxembourg

   Phone: (+352) 46 66 44 5841
   Email: maria-rita.palattella@uni.lu


   Pascal Thubert
   Cisco Systems, Inc
   Village d'Entreprises Green Side
   400, Avenue de Roumanille
   Batiment T3
   Biot - Sophia Antipolis  06410
   France

   Phone: +33 497 23 26 34
   Email: pthubert@cisco.com










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   Thomas Watteyne
   Linear Technology / Dust Networks
   30695 Huntwood Avenue
   Hayward, CA  94544
   USA

   Phone: +1 (510) 400-2978
   Email: twatteyne@linear.com


   Qin Wang
   Univ. of Sci. and Tech. Beijing
   30 Xueyuan Road
   Beijing  100083
   China

   Phone: +86 (10) 6233 4781
   Email: wangqin@ies.ustb.edu.cn

































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