Asynchronous transfer mode (ATM) is a switching technique 
used by telecommunication networks that uses asynchronous 
time-division multiplexing to encode data into small, 
fixed-sized cells. 
This is different from Ethernet or the Internet, which use variable packet sizes for data or frames.


https://www.youtube.com/watch?v=LrUrexb_qLA


ATM cell 
An ATM cell consists of a 5-byte header and a 48-byte payload. 
ATM defines two different cell formats: 
   user–network interface (UNI) 
   and network–network interface (NNI). Most ATM links use UNI cell format.


Asynchronous Transfer Mode (ATM) is a flexible network protocol carrying voice, video, and data in fixed length cells.
ATM network has two kinds of interfaces, UNI (Interface between ATM User and Public ATM switch) 
                                     and NNI (Interface between two Public ATM switches). 
Porovnání s OSI 
Similar to the OSI Protocol model, 
  ATM has an ATM Layer as Layer 2, 
  ATM Adaptation Layer (AAL) as Layer 3 
and other higher layers depending on C-Plane, U-Plane or Layer Management Plane.


   
https://www.gl.com/lightspeed1000-atm-analyzer.html
https://www.gl.com/images/lightspeed1000-atm-analyzer-web-uni-nni-format.gif


Docela hezké je to na Wikipedii
https://en.wikipedia.org/wiki/Asynchronous_Transfer_Mode

Použitelné, podobně jako Wikipedie
https://www.tutorialspoint.com/explain-the-atm-cell-structure-in-computer-network



ATM classes
Traffic engineering    ve Wikipedia - 5 tříd   



https://www.geeksforgeeks.org/asynchronous-transfer-mode-atm-in-computer-network/


Working of ATM: 
ATM standard uses two types of connections. i.e., 
Virtual path connections (VPCs) which consist of Virtual channel connections (VCCs)
  bundled together which is a basic unit carrying a single stream of cells from user to user.
   A virtual path can be created end-to-end across an ATM network, 
   as it does not rout the cells to a particular virtual circuit. In case of major failure,
    all cells belonging to a particular virtual path are routed the same way through the ATM network, thus helping in faster recovery. 

Switches connected to subscribers use both VPIs and VCIs to switch the cells which are Virtual Path and Virtual Connection switches that can have different virtual channel connections between them, serving the purpose of creating a virtual trunk between the switches which can be handled as a single entity. Its basic operation is straightforward by looking up the connection value in the local translation table determining the outgoing port of the connection and the new VPI/VCI value of connection on that link. 


    
    Physical Layer     podle OSI 
    It manages the medium-dependent transmission and is divided into two parts physical medium-dependent sublayer and transmission convergence sublayer. The main functions are as follows: 
        It converts cells into a bitstream.
        It controls the transmission and receipt of bits in the physical medium.
        It can track the ATM cell boundaries.
        Look for the packaging of cells into the appropriate type of frames.
        
        
    ATM Layer –   Link lazer podle OSI 
    It handles transmission, switching, congestion control, cell header processing, sequential delivery, etc., and is responsible for simultaneously sharing the virtual circuits over the physical link known as cell multiplexing and passing cells through an ATM network known as cell relay making use of the VPI and VCI information in the cell header. 

   ATM Adaption Layer (AAL) –  síťová  dle OSI 
    It is meant for isolating higher-layer protocols from details of ATM processes and prepares for conversion of user data into cells and segments it into 48-byte cell payloads. AAL protocol excepts transmission from upper-layer services and helps them in mapping applications, e.g., voice, data to ATM cells. 



     

ATM Applications: 
 

    ATM WANs – 
    It can be used as a WAN to send cells over long distances, a router serving as an end-point between ATM network and other networks, which has two stacks of the protocol. 
     
    Multimedia virtual private networks and managed services – 
    It helps in managing ATM, LAN, voice, and video services and is capable of full-service virtual private networking, which includes integrated access to multimedia. 
     
    Frame relay backbone – 
    Frame relay services are used as a networking infrastructure for a range of data services and enabling frame-relay ATM service to Internetworking services. 
     
    Residential broadband networks – 
    ATM is by choice provides the networking infrastructure for the establishment of residential broadband services in the search of highly scalable solutions. 
     
    Carrier infrastructure for telephone and private line networks – 
    To make more effective use of SONET/SDH fiber infrastructures by building the ATM infrastructure for carrying the telephonic and private-line traffic. 
     

 
 
Adresování ATM 
https://naoshad.tripod.com/atmguide/node7.html 
 
 

Popis sítě, i s navázáním azrušením spojení, ale to už je hodně podrobné 
http://www.inrialpes.fr/planete/people/elsayed/msc/ch2.pdf
je tady popsána spousta dalších vrstev, může být užitečné pro 4. ročnák - DSL, ONU a podobně







https://ecomputernotes.com/computernetworkingnotes/switching/atm-cell-structure
a tohleto má na záložce velevo odkazy na mnoho jiných sítí a protoklů