Neon-komputadór

Other Network Protocols: IPX/SPX and NetBEUI

As the popularity of the TCP/IP suite increases the share of the computer networks that use other protocol systems is steadily diminishing. However, two in particular has a large installed base, the IPX/SPX suite by Novell, known by the tradename Novell NetWare and Microsoft non-routable NetBUI. Whilst neither of these protocols are used at the Ministry of Foreign Affairs and Cooperation, and nor are they ever likely to be, it is worth briefly discussing both of them.

Novell Netware was until recently the most popular local area network protocol in the world. Its strength lay in the fact that it worked on a variety of network typologies with a consistent interface, including both Ethernet and Token-Ring networks. The name IPX/SPX, like TCP/IP comes from two layers in the protocol stack. IPX stands for Internetwork Packet Exchange, which is the equivalent of IP, or layer 3 of the OSI model. It provides connectionless communications. SPX stands for Sequenced Packet Exchange and operates on Layer 4 of the OSI model. It is the Novell equivalent of TCP.

With the increased popularity of TCP/IP a solution has been found to combine the two protocols so that IPX/SPX can send through TCP/IP without causing problems with the upper IPX/SPX stack. The solution, called IPX tunneling, basically grafts the IPX/SPX stack onto the UDP protocol in TCP/IP. Data thus passes down from IPX to UDP where it turns itself into a standard TCP/IP datagram and is delivered to the physical networks. Of course, Novell is quite aware of the growing popularity of TCP/IP and recent version of Netware are increasingly supportive of TCP/IP. It is possible in the near future that IPX tunneling will not be necessary.

With the dominance of the Windows operating system and it's almost total usage at the Ministry of Foreign Affairs and Cooperation, no discussion of networking protocols would be complete without mentioning NetBEUI. NetBUI stands for NetBIOS Enhanced User Interface. Basically, NetBIOS is a Session Layer in the OSI model that uses NetBIOS names up to 15 characters in length to address computers on a network. NetBEIU is an extension of this protocol and is used by the various Windows network operating systems (i.e, all versions of Windows after Windows for Workgroups, which was pre-Windows95). Whilst very efficient, NetBEUI has what many to consider a fatal flaw - it's not routable. This means that computers that are not on the same network subnet can't communicate with each other. Of course, there are some cases where for purposes of security this is actually preferred.

Communicating Between Linux and Windows

Windows uses a message format called Server Message Block (SMB) to share files, directories and devices. Samba is an open source implementation of the SMB file sharing protocol that provides file and device services. Although originally developed for UNIX, Samba is available on numerous platforms including Linux.

smbclient -L tlsvr001 -U username

And enter the required password.

This will provide a list of all the file and print shares that the server gives to the Windows Network Neighbourhood.

To access a particular file or print share the following command is used.

smbclient //tlsvr001/share -U username

And enter the requisite password.

Where "share" is the file or print service you want to use.

From there a command prompt access to the files is provided with a series of commands to facilitate file access and print services, including 'get ', 'put ', mget , mput lcd (local change directory), print and so forth. Further information can be obtained by typing "help" at the samba command prompt.