Hybrid Networks Running Multiple Platforms


Multiple Platforms.  In this web page the word platform is used to describe different computing architectures or hardware platforms.  It is also important to remember that different platforms are also likely to run different operating systems.

Presently, we outline some issues of intercommunication across platforms.

  • PC and Macintosh intercommunication
    • this has already been dealt with under the multiple OSs
  • PC and mainframe
    • acquiring software to allow the PC to act as a terminal or terminal emulation software
    • also may need to make use of protocol gateway software
    • it is also important to upload/download between the PC acting as a terminal and the PC - this feature is present in man y terminal emulation packages
  • PC and PDA - Personal Digital Assistants
    • usually connect through the USB port
    • make use of synchronization software
      • Microsoft's ActiveSynch
        • Windows desktop - - Windows CE

Gateways.  Now we look at making use of gateways, particularly software based gateways between networks to ensure connectivity.  These discussions will focus on the following.

  • Windows to NetWare redirectors
    • called redirectors because they intercept a request for a resource and translate it to the appropriate protocol and then redirect it to the appropriate resource server
    • FPNW - File and Print Service for NetWare
      • allows NetWare clients to access Microsoft services
    • NWLink - NetWare Link
      • included with Windows software allows Microsoft clients to access resources on NetWare servers
    • GSNW - Gateway Service for NetWare
      • operates without Microsoft client software
  • Cross platform solutions for Macintosh to PCs

SNA.  SNA was developed by IBM in the 1970s to allow interconnection of incompatible systems with a layered architecture.  In particular, they were motivated to get their own variety of systems, such as PCs and mainframes to interact.

The main components of SNA include the following.

  • Nodes - this is the collection of computers on the SNA network
  • NAU - Network Addressable Unit - this represents the origin or destination of the data being transmitted
    • physical unit
    • logical unit
    • SSCP - system services control point
  • LU - Logical Unit - the port to be used by the network users to access the SNA network
  • PU - Physical Unit - manages the resources of a node
  • SSCP - System Services Control Point - the point on the network used to manage services for the users\

Current implementations are called APPN - Advanced Peer to Peer.  APPN supports two types of nodes.

  • Network Nodes
    • routers
    • network management systems
    • client programs
    • server programs
  • End Nodes
    • client programs
    • server programs

SNA architecture requires that a session between a client and a server is established  before any data can be transferred.  SNA is a more complex protocol than TCP/IP.

It can also be implemented as Communications Manager for OS/2 and SNA Server for Microsoft's Windows NT or Windows 2000.  SNA Server can als obe configured for dial in connections and VPN - Virtual Private Networking.  This has been recently renamed Host Integration Server by Microsoft.  There is also a Linux SNA.

Samba.  Samba has been developed for Windows and UNIX/Linux interconnectivity and interaction.  Samba was created by reverse engineering Microsoft's SMB protocol which has been their so called core protocol for file sharing.  The goal was to make a UNIX server look like a Windows server to Microsoft clients.  This goal is attained to greater and greater extents with each new release.

Samba allows UNIX/Linux and Microsoft systems to intercommunicate through the CIFS - Common Internet File System which is based on SMB.  CIFS provides the following four services.

  • authentication and authorization
  • name resolution
  • file and print sharing services
  • network browsing services

Shared resources can be password protected.  NetBIOS name resolution can be provided  either by broadcast messages or by using a NetBIOS name server such as WINS.

Samba is made up of several programs.  There are two main components or daemons that provide the services listed above.

  • SMB daemon (SMBd)
    • authentication and authorization
    • file and print sharing services
  • NMB daemon (NMBd)
    • name resolution
    • network browsing services