IBM Advanced Peer-to-Peer Networking

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Advanced Peer-to-Peer Networking (APPN) is an extension to the Systems Network Architecture (SNA).

It includes features such as these:

  • distributed network control
  • dynamic exchange of network topology information to foster ease of connection, reconfiguration, and route selection
  • dynamic definition of network resources
  • automated resource registration and directory lookup.

APPN was meant to complement IBM's Systems Network Architecture, a legacy from the mainframe era. It was designed as a simplification, but it turned out to be utterly complex, in particular in migration situations. APPN was originally meant to be a "DECNET killer", but DEC actually died before APPN was completed. APPN has been largely superseded by TCP/IP (Internet).

Note that APPN has nothing to do with peer-to-peer file sharing software such as KaZaa or Napster. The designation peer-to-peer in the case of APPN refers to its independence from a central point of control, similar to the way that a FireWire PC connection allows a video camera to talk directly to a disk drive on the FireWire network.

APPN evolved to include a more efficient data routing layer which was called High Performance Routing (HPR). HPR was made available across a range of enterprise corporation networking products in the late 1990s, but today is typically used only within IBM's z/OS environments as a replacement for legacy SNA networks. It seems to be still widely used within UDP tunnels, this technology is known as Enterprise Extender.[1]

APPN should not be confused with the similarly named APPC (Advanced Program-to-Program Communication). APPN manages communication between machines, including routing, and operates at the transport and network layers. By contrast, APPC manages communication between programs, operating at the application and presentation layers.


  1. ^ IBM Corporation. "Enterprise Extender". Retrieved 3 September 2012.