Subject: Re: [ppsp] initial proposal of PPSP component architecture

From: Gonzalo Camarillo <[email-masked]>
Date: Sun, 05 Jul 2009 19:27:16 +0300

Hi,

having an architecture picture is a good start. Thanks for putting that 
diagram together.

The next step is to draw a network diagram with the different types of 
nodes and the protocols between them. The important thing is to explain 
which protocols we would need to develop. For each of those protocols, 
we need to explain its expected functionality and the entities that 
would be using it.

The IETF standardizes protocols and, if we want to charter a WG at some 
point, we need to explain clearly what protocols we want to standardize.

Cheers,

Gonzalo

zhangyunfei wrote:
> Dear all,
>     As Gonzalo suggested,PPSP problem statement draft is better to include a figure to express the component architecture.I propose the following layer architecture as the initial input.The components architecuture is as follows:
>     
>    +=================================================================+
>    | +-------------------------------------------------------------+ |
>    | |                       Application Layer                     | |
>    | +-------------------------------------------------------------+ |
>    |=================================================================|
>    |  Play-out Layer                                                 |
>    |  +----------------+    +---------------+    +-----------------+ |
>    |  |     start      |    |      Pause    |    |       Stop      | |
>    |  +----------------+    +---------------+    +-----------------+ |
>    |=================================================================|
>    |  Information Layer                                              |
>    |  +----------------+    +---------------+    +-----------------+ |
>    |  |  Registration  |    |     Report    |    |    Statistics   | |
>    |  +----------------+    +---------------+    +-----------------+ |
>    |=================================================================|
>    |  Communication Layer                                            |
>    | +------------------------+   +--------------------------------+ |
>    | |    Topology Creation   |   |Head Node/Tracker Communication | |
>    | +------------------------+   +--------------------------------+ |
>    | +------------------------+   +--------------------------------+ |
>    | | Neighbor Communication |   |          Bootstrap             | |
>    | +------------------------+   +--------------------------------+ |
>    |=================================================================|
>    | +-------------------------------------------------------------+ |
>    | |                       Transport Layer                       | |
>    | +-------------------------------------------------------------+ |
>    |=================================================================|
> 
> It can be divided into 5 layers:
> 1)Transport Layer is responsible for data transmission between peers, UDP,TCP or other protocols can be used;
> 2)Communicaton layer is the key layer in PPSP, including four components:
>       1)Topology creation is a component each peer has to request to join the overlay,like tree or    mesh;
>       2)Head Node/Tracker Communication is a component each peer continually to get peer list or peer info report to the tracker or head node.
>       3)Neighbor Communication is a component that peers exchange bitmap or other neigbor availability information for loop avoidance(in tree).
>       4)Bootstrap is a component to introduce a newly joined node to get the tracker or head node information.It keeps monitoring the trackers and head nodes.
> 3)Information layer is a layer that nodes register to the system,publish their contents,report their useful inforamation beyond those in the peer tracker reporting for peer selection and give statistics to the trackers.The tracker itself also use statistic and report module for global control in upload bandwidth consumption,overhead consumption and other regards.
> 4)Play-out layer is a layer to control the action of the media brower.RTSP is in this scope.
> 5)Application layer is the top layer in the ISO/OSI model,where PPSP application exists.
> 
> We are planning to add this part in the Problem statement draft.Any comments are welcome.
> 
>         BR
> 
>       yunfei
>     2009-06-23
> 
> _______________________________________________
> ppsp mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/ppsp
>

---

From: "zhangyunfei" <[email-masked]>
Date: Tue, 7 Jul 2009 15:25:29 +0800

Hi,Gonzalo,
   Thanks for your advice.I am trying to add the architecture picture and the network diagram in the PS draft.

zhangyunfei
2009-07-07

发件人： Gonzalo Camarillo
发送时间： 2009-07-06 00:27:47
收件人： zhangyunfei
抄送： [email-masked]
主题： Re: [ppsp] initial proposal of PPSP component architecture

Hi,

Cheers,

Gonzalo

---

From: "zhangyunfei" <[email-masked]>
Date: Tue, 7 Jul 2009 15:51:21 +0800

Hi Mr Oh,
   Registration module in information layer deals with content publishing/updating/deleting actions operated by owner (that may be a peer) .

zhangyunfei
2009-07-07

发件人： 오승훈_2009
发送时间： 2009-07-01 09:38:47
收件人： 'zhangyunfei'; 'Alex Kyungho KIM'
抄送： [email-masked]
主题： RE: RE: [ppsp] ***SPAM*** 5.979 (5) RE: ***SPAM*** 7.949(5)RE:initialproposal of PPSP component architecture

Hello Yunfei,
 
Could you elaborate on ‘Registration’ in ‘Information Layer’? 
Thanks in advance.
 
Seung-Hun Oh
 
From: zhangyunfei [mailto:[email-masked]] 
Sent: Tuesday, June 30, 2009 7:01 PM
To: [email-masked]; 'Alex Kyungho KIM'
Cc: [email-masked]
Subject: Re: RE: [ppsp] ***SPAM*** 5.979 (5) RE: ***SPAM*** 7.949 (5)RE:initialproposal of PPSP component architecture
 
I have the same question with Mr.Ｏｈ．In my point of view, authentication is a kind of action a telecom system must have.However in most of current p2p streaming systems,such an action is not the basic functionality they have while regirstation is an action the publishing node(server)must take.
Another question:What does the session module mean?I think most of the process related to "session"is included in the communication layer.
 
                         Yunfei

zhangyunfei
2009-06-30

发件人： ???_2009
发送时间： 2009-06-29 15:02:14
收件人： 'Alex Kyungho KIM'; 'zhangyunfei'
抄送： [email-masked]
主题： RE: [ppsp] ***SPAM*** 5.979 (5) RE: ***SPAM*** 7.949 (5)RE:initialproposal of PPSP component architecture
 
Hello  Alex,  
 
Now  I  can  see  your  figure  properly.  Thanks  for  your  re-drawing.  
One  question  about  figure  below:
The  components  in  "Information  Layer"  are  a  little  different  from  the  original  one.
Registration  is  changed  into  'Auth'.  Is  there  any  reason?  
 
Regards,
Seung-Hun  Oh
 
-----Original  Message-----
From:  [email-masked]  [mailto:[email-masked]]  On  Behalf  Of  Alex  Kyungho  KIM
Sent:  Friday,  June  26,  2009  8:43  PM
To:  zhangyunfei
Cc:  [email-masked];  [email-masked]
Subject:  Re:  [ppsp]  ***SPAM***  5.979  (5)  RE:  ***SPAM***  7.949  (5)  RE:initialproposal  of  PPSP  component  architecture
 
Dear  all,
 
There  is  a  missing  line.
 
+=================================================================+
|  +-------------------------------------------------------------+  |
|  |                                              Application  Layer                                          |  |
|  |-------------------------------------------------------------+  |
+=================================================================+
|  +-----------------------------+  +-----------------------------+  |
|  |  Play-out  Layer                            |  |  Information  Layer                      |  |
|  |  +-------------------------+  |  |  +----+-------+------------+  |  |
|  |  |Playback(Play,Pause,Stop)|  |  |  |Auth|Session|Report/Stats|  |  |
|  |  +-------------------------+  |  |  +----+-------+------------+  |  |
|  +-----------------------------+  +-----------------------------+  |
|=================================================================|
|    Communication  Layer                                                                                        |
|  +------------------------+      +--------------------------------+  |
|  |        Topology  Creation      |      |Head  Node/Tracker  Communication  |  |
|  +------------------------+      +--------------------------------+  |
|  +------------------------+      +--------------------------------+  |
|  |  Neighbor  Communication  |      |                    Bootstrap                          |  |
|  +------------------------+      +--------------------------------+  |
|=================================================================|
|  +-------------------------------------------------------------+  |
|  |                                            Transport  Layer                                                |  |
|  +-------------------------------------------------------------+  |
|=================================================================|
|  +-------------------------------------------------------------+  |
|  |                                            Physical  Layer                                                  |  |
|  +-------------------------------------------------------------+  |
+=================================================================+

Regards,
Alex

On  Fri,  Jun  26,  2009  at  8:04  PM,  Alex  Kyungho  KIM <[email-masked] >  wrote:
>  Dear  Yunfei,
> 
>  I  didn't  know  my  drawing  are  disruptive.  :)
> 
>  |  |-------------------------------------------------------------+  |
>  |  +-----------------------------+  +-------------------------------+
>  |  |  Play-out  Layer                            |  |  Information  Layer                          |
>  |  |  +-------------------------+  |  |  +------+-------+------------+  |
>  |  |  |Playback(Play,Pause,Stop)|  |  |  |  Auth  |Session|Report/Stats|  |
>  |  |  +-------------------------+  |  |  +------+-------+------------+  |
>  |  +-----------------------------+  +-------------------------------+
>  |  |                                            Physical  Layer                                                  |  |
>  If  you  have  same  trouble,  Please  look  into  the  enclosed  TEXT  file.
> 
>  My  recommendation  is  to  seperate  the  application  layer  and  any  lower
>  layer.  that  is  the  best  way  to  archive  the  flexiblity  and  more
>  extendible.
> 
>  Regards,
>  Alex
> 
> 
> 
>  2009/6/25  zhangyunfei   <[email-masked] >:
> >  Sorry,Alex,
> >        The  figure  cannot  display  rightly  in  the  email.Would  you  please  send  it
> >  again  for  clarification?Thanks  in  advance.
> >
> >                              Yunfei
> >
> >  ________________________________
> >  zhangyunfei
> >  2009-06-25
> >  ________________________________
> >  发件人：  Alex  Kyungho  KIM
> >  发送时间：  2009-06-23  21:58:34
> >  收件人：  [email-masked];  [email-masked]
> >  抄送：
> >  主题：  Re:  [ppsp]  ***SPAM***  5.979  (5)  RE:  ***SPAM***  7.949  (5)
> >  RE:initialproposal  of  PPSP  component  architecture
> >
> >  Dear  my  colleagues,
> >  ?
> >  Thank  you  your?quick  response  on  my  question
> >  ?
> >  So,  I  am  not  sure  what  you  concern  the  role  of  'Application  Layer'  is.  we
> >  agree  on  the  core  of  PPSP?would  be  the?communication  layer  in  the  OSI  7
> >  Layer  apsect.
> >  ?
> >  What  would  you  expect?any  problems  happening  if  'Application  layer'  is  not
> >  face?on  'Communication  layer'???
> >  ?
> >  Let's  say  'Application  Layer'?is  able  to  access?the  'Play-out  layer;  and
> >  'Information  layer'  but  don't  'touch'  the  'Communication  layer'.  We  may
> >  extend  the  role  of  'Information  layer'  to  cover  some  functionality  of  what
> >  osh93  want.  It  could  be  'session  management'  which  is  relavant  to
> >  'Communication  layer'.
> >  ?
> >  How?do  you  think  of  this?
> >  ?
> >  ?  |  +-------------------------------------------------------------+  |
> >  ?  |  |  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  Application  Layer  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  |  |
> >  ?  |  |---------------------------------------------------------------+  |
> >  ?  |?+==================================================|
> >  ?  |?+-----------------------------+--------------------------------+
> >  ???  |  ?  ?  Play-out  Layer  ?  ?  |  ?  ?Information  Layer  ?  ?|
> >  ?  |?+-----------------------------+--------------------------------+
> >  ?  |=================================================================|
> >  ?  |  ?Communication  Layer  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?|
> >  ?  |  +------------------------+  ?  +--------------------------------+  |
> >  ?  |  |  ?  ?Topology  Creation  ?  |  ?  |Head  Node/Tracker  Communication  |  |
> >  ?  |  +------------------------+  ?  +--------------------------------+  |
> >  ?  |  +------------------------+  ?  +--------------------------------+  |
> >  ?  |  |  Neighbor  Communication  |  ?  |  ?  ?  ?  ?  ?Bootstrap  ?  ?  ?  ?  ?  ?  |  |
> >  ?  |  +------------------------+  ?  +--------------------------------+  |
> >  ?  |=================================================================|
> >  ?  |  +-------------------------------------------------------------+  |
> >  ?  |  |  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  Transport  Layer  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  |  |
> >  ?  |  +-------------------------------------------------------------+  |
> >  ?  |=================================================================|
> >  ?
> >  Regards,
> >  Alex
> >  ?
> >  2009/6/23  ???_2009   <[email-masked] >
> > >
> > >  Dear  Alex
> > >
> > >  ?
> > >
> > >  Sorry  for  my  ambiguous  expression.
> > >
> > >  That  means  that  ‘Application  Layer’  and  ‘Communication  Layer’  are
> > >  adjacent.
> > >
> > >  Is  that  clear  now?
> > >
> > >  ?
> > >
> > >  Best  Regards,
> > >
> > >  Seung-Hun  Oh
> > >
> > >  ?
> > >
> > >  From:  [email-masked]  [mailto:[email-masked]]  On  Behalf  Of  Alex
> > >  Kyungho  KIM
> > >  Sent:  Tuesday,  June  23,  2009  10:17  PM
> > >  To:  [email-masked]
> > >  Subject:  Re:  [ppsp]  ***SPAM***  7.949  (5)  RE:  initial  proposal  of  PPSP
> > >  component  architecture
> > >
> > >  ?
> > >
> > >  Dear  osh93,
> > >
> > >  ?
> > >
> > >  This  is  high  level  diagram  to  make  someone  understand  our  work  or  what  we
> > >  are  doing.  You  have  several  modifications  but  I  should  ask  you  a
> > >  question?about  your  proposal.
> > >
> > >  ?
> > >
> > >  I  am  not  clear  "touch  each  other"  in  your  comment.  What  does  it  mean?
> > >
> > >  ?
> > >
> > >  Regards,
> > >
> > >  Alex
> > >
> > >  2009/6/23  ???_2009   <[email-masked] >
> > >
> > >  Dear  yunfei
> > >
> > >  I  think  it  is  good  idea  to  in  insert  this  figure  into  the  PPSP  problem
> > >  statement  draft.
> > >  But  I  think  it  needs  more  clarification.
> > >
> > >  I  think  that  the  word,  'layer',  is  not  appropriate  for  'Play-out  Layer'
> > >  and
> > >  'Information  Layer',  or  the  position  of  them  need  to  be  a  little  bit
> > >  modified.
> > >  As  you  know,  each  layer  must  be  vertically  related  in  communication  world,
> > >  as  far  as  I  know.
> > >  Here  is  my  minor  proposal:
> > >  ?  +=================================================================+
> > >  ?  |  +-------------------------------------------------------------+  |
> > >  ?  |  |  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  Application  Layer  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  |  |
> > >  ?  |  |  ?  ?  ?  ?  ?+--------------------------------------------------+  |
> > >  ?  |  |  ?  ?  ?  ?  ?|  +==================================================|
> > >  ?  |  |  ?  ?  ?  ?  ?|  |  ?  ?  Play-out  Layer  ?  ?  |  ?  ?Information  Layer  ?  ?|
> > >  ?  |  |  ?  ?  ?  ?  ?|  |  ?+----+  ?+----+  ?+---+  |  ?  +----+  ?+----+  ?+---+  |
> > >  ?  |  |  ?  ?  ?  ?  ?|  |  ?|  ?  ?|  ?|  ?  ?|  ?|  ?  |  |  ?  |  ?  ?|  ?|  ?  ?|  ?|  ?  |  |
> > >  ?  |  +----------+  |  ?+----+  ?+----+  ?+---+  |  ?  +----+  ?+----+  ?+---+  |
> > >  ?  |=================================================================|
> > >  ?  |  ?Communication  Layer  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?|
> > >  ?  |  +------------------------+  ?  +--------------------------------+  |
> > >  ?  |  |  ?  ?Topology  Creation  ?  |  ?  |Head  Node/Tracker  Communication  |  |
> > >  ?  |  +------------------------+  ?  +--------------------------------+  |
> > >  ?  |  +------------------------+  ?  +--------------------------------+  |
> > >  ?  |  |  Neighbor  Communication  |  ?  |  ?  ?  ?  ?  ?Bootstrap  ?  ?  ?  ?  ?  ?  |  |
> > >  ?  |  +------------------------+  ?  +--------------------------------+  |
> > >  ?  |=================================================================|
> > >  ?  |  +-------------------------------------------------------------+  |
> > >  ?  |  |  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  Transport  Layer  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  |  |
> > >  ?  |  +-------------------------------------------------------------+  |
> > >  ?  |=================================================================|
> > >
> > >  I  try  to  locate  both  'Play-out  Layer'  and  'Info.  Layer'  parallely  and
> > >  'Application  Layer'  and  'Communication  Layer'  try  to  be  located  to  touch
> > >  each  other.
> > >
> > >  These  are  just  my  opinion.
> > >
> > >  Best  Regards,
> > >
> > >  Seung-Hun  Oh
> > >
> > >
> > >  -----Original  Message-----
> > >  From:  [email-masked]  [mailto:[email-masked]]  On  Behalf  Of
> > >  zhangyunfei
> > >  Sent:  Tuesday,  June  23,  2009  7:01  PM
> > >  To:  [email-masked]
> > >  Subject:  [ppsp]  initial  proposal  of  PPSP  component  architecture
> > >
> > >
> > >  Dear  all,
> > >  ?  ?As  Gonzalo  suggested,PPSP  problem  statement  draft  is  better  to  include
> > >  a  figure  to  express  the  component  architecture.I  propose  the  following
> > >  layer  architecture  as  the  initial  input.The  components  architecuture  is  as
> > >  follows:
> > >
> > >  ?  +=================================================================+
> > >  ?  |  +-------------------------------------------------------------+  |
> > >  ?  |  |  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  Application  Layer  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  |  |
> > >  ?  |  +-------------------------------------------------------------+  |
> > >  ?  |=================================================================|
> > >  ?  |  ?Play-out  Layer  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  |
> > >  ?  |  ?+----------------+  ?  ?+---------------+  ?  ?+-----------------+  |
> > >  ?  |  ?|  ?  ?  start  ?  ?  ?|  ?  ?|  ?  ?  ?Pause  ?  ?|  ?  ?|  ?  ?  ?  Stop  ?  ?  ?|  |
> > >  ?  |  ?+----------------+  ?  ?+---------------+  ?  ?+-----------------+  |
> > >  ?  |=================================================================|
> > >  ?  |  ?Information  Layer  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?|
> > >  ?  |  ?+----------------+  ?  ?+---------------+  ?  ?+-----------------+  |
> > >  ?  |  ?|  ?Registration  ?|  ?  ?|  ?  ?  Report  ?  ?|  ?  ?|  ?  ?Statistics  ?  |  |
> > >  ?  |  ?+----------------+  ?  ?+---------------+  ?  ?+-----------------+  |
> > >  ?  |=================================================================|
> > >  ?  |  ?Communication  Layer  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?|
> > >  ?  |  +------------------------+  ?  +--------------------------------+  |
> > >  ?  |  |  ?  ?Topology  Creation  ?  |  ?  |Head  Node/Tracker  Communication  |  |
> > >  ?  |  +------------------------+  ?  +--------------------------------+  |
> > >  ?  |  +------------------------+  ?  +--------------------------------+  |
> > >  ?  |  |  Neighbor  Communication  |  ?  |  ?  ?  ?  ?  ?Bootstrap  ?  ?  ?  ?  ?  ?  |  |
> > >  ?  |  +------------------------+  ?  +--------------------------------+  |
> > >  ?  |=================================================================|
> > >  ?  |  +-------------------------------------------------------------+  |
> > >  ?  |  |  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  Transport  Layer  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  ?  |  |
> > >  ?  |  +-------------------------------------------------------------+  |
> > >  ?  |=================================================================|
> > >
> > >  ?  ?  ?1)Topology  creation  is  a  component  each  peer  has  to  request  to  join
> > >  the  overlay,like  tree  or  ?  ?mesh;
> > >  ?  ?  ?2)Head  Node/Tracker  Communication  is  a  component  each  peer
> > >  continually  to  get  peer  list  or  peer  info  report  to  the  tracker  or  head
> > >  node.
> > >  ?  ?  ?3)Neighbor  Communication  is  a  component  that  peers  exchange  bitmap  or
> > >  other  neigbor  availability  information  for  loop  avoidance(in  tree).
> > >  ?  ?  ?4)Bootstrap  is  a  component  to  introduce  a  newly  joined  node  to  get
> > >  the  tracker  or  head  node  information.It  keeps  monitoring  the  trackers  and
> > >  head  nodes.
> > >  3)Information  layer  is  a  layer  that  nodes  register  to  the  system,publish
> > >  their  contents,report  their  useful  inforamation  beyond  those  in  the  peer
> > >  tracker  reporting  for  peer  selection  and  give  statistics  to  the
> > >  trackers.The  tracker  itself  also  use  statistic  and  report  module  for
> > >  global
> > >  control  in  upload  bandwidth  consumption,overhead  consumption  and  other
> > >  regards.
> > >  ?  ?  ?  ?BR
> > >  ?  ?  ?yunfei
> > >  ?  ?2009-06-23
> > >  --
> > >  Alex  Kyungho  KIM
> > >  LG  Electronics.
> > >  Senior  Research  Engineer
> > >  E-mail  ?:  [email-masked]
> > >  Office  ?:  +82  ?  2  2102  0111
> > >  Mobile  :  +82  10  7917  0406
> > >  FAX  ?  ?  :  +82  ?  2  2102  0140
> > >  DTV  Research  Laboratory,  LG  Electronics.
> > >  Seoul  University  Research  Park
> > >  San  4-1,  BongCheon  7-Dong
> > >  KwanAk-Gu,Seoul,  151-919
> > >  The  Republic  of  Korea.
> > >
> >  --
> >  Alex  Kyungho  KIM
> >  LG  Electronics.
> >  Senior  Research  Engineer
> >  E-mail  ?:  [email-masked]
> >  Office  ?:  +82  ?  2  2102  0111
> >  Mobile  :  +82  10  7917  0406
> >  FAX  ?  ?  :  +82  ?  2  2102  0140
> >  DTV  Research  Laboratory,  LG  Electronics.
> >  Seoul  University  Research  Park
> >  San  4-1,  BongCheon  7-Dong
> >  KwanAk-Gu,Seoul,  151-919
> >  The  Republic  of  Korea.
> >
>  --
>  Alex  Kyungho  KIM
>  LG  Electronics.
>  Senior  Research  Engineer
>  E-mail    :  [email-masked]
>  Office    :  +82      2  2102  0111
>  Mobile  :  +82  10  7917  0406
>  FAX          :  +82      2  2102  0140
>  DTV  Research  Laboratory,  LG  Electronics.
>  Seoul  University  Research  Park
>  San  4-1,  BongCheon  7-Dong
>  KwanAk-Gu,Seoul,  151-919
>  The  Republic  of  Korea.
> 

--  
Alex  Kyungho  KIM
LG  Electronics.
Senior  Research  Engineer
E-mail    :  [email-masked]
Office    :  +82      2  2102  0111
Mobile  :  +82  10  7917  0406
FAX          :  +82      2  2102  0140
DTV  Research  Laboratory,  LG  Electronics.
Seoul  University  Research  Park
San  4-1,  BongCheon  7-Dong
KwanAk-Gu,Seoul,  151-919
The  Republic  of  Korea.