protocols. Systems Application Architecture (SAA) is an IBM standard for developing
distributed applications.
The IBM 3172 cluster controller is invisible to the Token Ring attached PCs and the SNA host.
Therefore, every node must be defined in VTAM, creating an SSCP session to every node type
2 on the ring. This creates a lot of overhead on the host. Also, another drawback is that PCs are
usually turned off at 5 p.m. When they are powered up in the morning, they are all visible to the
IBM 3172, creating much explorer traffic in the network.
an application that runs on the device performs session functions. For example, suppose you
take a Novell Server and load Novell's SAA Gateway software on it, as depicted in Figure
12-16. You would also load some type of client 3270 emulation software on the users' PCs,
which would allow them to connect to the SAA gateway server. LU gateways reduce overhead
on the host because the SSCP is only in session with the PU in the SAA gateway. The SAA
gateway is in session with the terminals. This reduces the required definition on the host. Notice
that the PCs are connected via Ethernet and use NetBIOS over IPX as the transport protocol.
The SAA gateway converts the Ethernet frames into Token Ring LLC2 frames.
improve manageability. Token Ring network interface cards are assigned a 12-digit burned-in
universally administered address (UAA) by the vendor. It is set in the card's ROM memory and
is commonly referred to as its burned-in address (BIA). This UAA can be overridden with an
LAA. The LAA is an assigned address given to LAN administrators from the design team. This
will now be the 12-digit number that will be the hardware address for the physical device on the
LAN. LAAs begin with a hex of 40 to identify them as LAAs. This gives the CCDP several
benefits and one major drawback.
in the second octet. In the Payroll department, the PCs have been administered an LAA of 1111
in the second octet. This helps with troubleshooting because you can identify addresses with
departments and their location in the network hierarchy. Another benefit is that the network
interface cards on the PCs can be swapped out without changing any definitions or purging any