A.T.M - AUTOMATIC TELLER MACHINE

ATM  does  not  stand  for  automatic  teller  machine. In the telecommunication,  it stands  for  Asynchronous  Transfer  Mode,  in   which  data  sends  asynchronously.  This  mode  is  another  fast packet  switching  mode.

ATM  is  regarded  as  the  technology  of  the  21st  century  and  its impact  is  expected  to  be  similar  to  PCM  (pulse  code  modulation) which  is  used  widely  around  the  world  in  telecommunication.

Asynchronous  transfer  mode  (ATM)  is  a  technology  that  has  his  its  history  in  the  development  of  broadband  ISDN  in  the  1970s  and  980s.  Technically,  it  can  be  viewed  as  an  evolution  of  pocket switching.  Like  packet  switching  for  data , ATM integrates  the  multiplexing  and  switching  functions,  is  well  suited  for bursty  traffic  and  allows communications  between  devices  that  operate  at  different  speeds . Unlike  packet  switching , ATM  is  designed  for  high-performance multimedia  networking.

ATM  is  also  a  set  of  international  interface  and  signaling standards  defined  by  the  International  Telecommunication  Union- Telecommunications  (ITU-T)  Standards  Sector  (formerly  the  CCITT). The  ATM  forum  has  played  a  pivotal  role  in  the  ATM  market  since its  formulation  in  1991.

The  ATM  forum  is  an  international  voluntary  organization composed  of  vendors ,  service  providers,  research  organization,  and users.  Its  purpose  is  to  accelerate  the  use  of  ATM  products  and services  through  the  rapid  convergence  of  interoperability  specifications,  promotion  of  industry  cooperation ,  and  other  activities. Developing  multivendor  implementation  agreements  also  furthers  this goal.

What is ATM ?
Asynchronous  transfer  mode  is  a  high  speed;  packet  based multiplexing  technique  in  which  information  flow  is  organized   in   short  fixed  length  cells. 
         
The  cells  are  generated  when  there  is  new  data  to  send, which  allows  an  element  of  data  compression  (e.g  there  is  no need  to  send  the  pauses  that  occurs  in  speech).  It  also  means that  cells  with  different  bandwidth  in  each  direction  are  possible- a  fax  connection,  for  example  uses  little  bandwidth  in  return direction.  This  allows  more  efficient  use  of  the  network resources.

ATM  provides  a  way  of  multiplexing  many  sources  of data  onto  a  common  cells  stream.  Regardless  of  speed  of  the inputs.  This  greatly  improves   flexibility,  enabling  provision  of bandwidth  on  demand.

Benefits  of   ATM
The  benefits  of  ATM  are  the  following:
High   performance  via   hardware  switching
Dynamic  bandwidth  for  busty  traffic
Class- of  –service  support  for  media
Scalability  in  speed  and  network  size
Common  LAN / WAN  architecture
Opportunity  for  simplification  via  VC  architecture
International  standard  compliance

CONCLUSION
ATM  is  a  technology  that  can  handle  all  types  of traffic  ( voice,  video  and  data)  multiplexed  on  the  same  network  . in  an  ATM  network  band  width  can  be  reassigned  in  real  time  to different  traffic  based  on  demand.  ATM  is  the  only  technology  common   to  all  environments   from  LAN  to  GAN .  The  main  reason for  ATM’s  popularly  is  its  selection  as  switch  technology  for  future BISDEN  service  and  can  handle  future  unknown  service .  ATM combines  both  circuit  and  packet - switching  modes  and  thus  able  to  handle  traffic  with  characters  ties  on  the  same  network.

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