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Outline. API definition What an API is What an API is not Examples of APIs in other industries Examples of APIs in the wireless industry APIs as applied to wireless core networks Summary. Application Programmers’ Interface (API) Definitions. An API is:

hiram-griffith
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  1. Outline • API definition • What an API is • What an API is not • Examples of APIs in other industries • Examples of APIs in the wireless industry • APIs as applied to wireless core networks • Summary

  2. Application Programmers’ Interface (API) Definitions • An API is: • a specification of how one layer presents its services to the layer above, • a sublayer between layers of a protocol stack, • an aid to application developers, • often provided in a Software Developers’ Kit (SDK) • An API is not: • a protocol between peer entities in a network, • implementation language dependent • APIs hide the complexities of what lies behind them, e.g. • memory allocation, • communications protocol state machine, • architecture and functional elements, • transport technology, etc.

  3. Layer n+1 API Layer n+1 API Layer n+1 services Layer n+1 services Layer n API Layer n API Layer n Services Layer n Services Layer n-1 API Layer n-1 API Layer n-1 Services Layer n-1 Services Layers, Protocols, Services, and APIs Layer n+1 protocols Layer n protocols Layer n-1 protocols

  4. Service Primitives as OSI API Model • OSI model describes API at each layer in terms of service primitives • Request (1): layer n requests service from layer n-1 • Indication (2): layer n-1 delivers information packet to layer n • Response (3): layer n responds to the indication from layer n-1 • Confirm (4): layer n-1 delivers the response to the service request Response (3) Indication (2) Request (1) Confirm (4) Layer n Layer n-1

  5. API Examples • To create a window in Microsoft Windows: Declare FunctionCreateWindowExLib "user32.dll" Alias "CreateWindowExA" (ByVal dwExStyle As Long, ByVal lpClassName As String, ByVal lpWindowName As String, ByVal dwStyle As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hWndParent As Long, ByVal hMenu As Long, ByVal hInstance As Long, lpParam As Any) As Long • To create a socket for TCP/IP communications: socket(PF_INET, SOCK_STREAM, 0)

  6. APIs in the Wireless Network • The goals of wireless APIs should be to: • simplify interactions with the network and clients, • hide the topology of the network from the application, and • hide the complexity of the underlying protocols from the application • standardize the interface presented to application developers so that applications are developed independent of the network • APIs control access to the wireless network • Access is controlled by content of API specification • Determines what can and can’t be done by the layer above • Not every interface needs an API • Only those capabilities presented to the outside world benefit from an API • APIs to internal interfaces are implementation matters and left to the manufacturer

  7. OSA as an API • To register a service using OSA: registerService(serviceTypeName : in TpServiceTypeName, servicePropertyList : in TpServicePropertyList, serviceID : out TpServiceIDRef) : TpResult • To place a call using OSA: routeReq(callSessionID : in TpSessionID , responseRequested : in TpCallReportRequestSet , targetAddress : in TpAddress , originatingAddress : in TpAddress , originalDestinationAddress : in TpAddress , redirectingAddress : in TpAddress , appInfo : in TpCallAppInfoSet , callLegSessionID : out TpSessionIDRef ) : TpResult

  8. Advantages of APIs for WNOs • APIs make telecom functionality accessible to a larger development community • This developer community will have the benefit of one common set of APIs • WNOs will thus be able to more easily extend their service portfolios • Standard APIs simplify integration of applications with the wireless network • APIs would include appropriate levels of security to protect the WNO's network

  9. Summary • APIs are specifications of how a layer in a protocol stack offers its service(s) • They hide the topology of the network and the complexities of the protocols • They simplify interactions between clients and servers • They might be offered in a Software Developers’ Kit (SDK), e.g. from the NCG vendor

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