Normally, signing on to the AS/400 involves no more thought on your part than double-clicking a desktop icon and then grabbing a cup of coffee while your connection is being made. You’re probably presented with a sign-on panel asking for your AS/400 user ID and password, and, within a few moments, your connection is made. Unless you have problems, you probably don’t think twice about what enables a PC to connect to the AS/400. However, when something goes wrong with your connection, the first place you look is the Client Access/400 router program. What is NS/Router? How does it work? What are the options for this important component of IBM’s Client Access/400 product?

The Most Commonly Used Router in the Industry

NetManage NS/Router is undoubtedly the most widely used router in the PC-to- AS/400 communications industry. The NS/Router is the standard by which other AS/400 router programs are judged. NS/Router is used by most of the popular emulation packages, including Client Access/400, Rally!, and WinAPPC. In fact, NS/Router is supported by over 80 independent software vendors (ISVs) and is the only router that is supported by IBM’s Client Access Support Center and comes bundled with Client Access/400. Introduced in 1993, NS/Router was the first native Advanced Program-to-Program Communications (APPC) engine for Windows-to-AS/400 connectivity. When Windows 95 was released, NetManage also released its 32-bit version of the NS/Router. NS/Router is a binary adapter handler that replaced the old PC Support adapter handler, EHNAPPC.DLL—a DOS-based router and a terrible memory manager. By contrast, NS/Router works with the Windows memory manager and supports Windows 3.1, and Windows 95, and Windows NT.

Let’s Dig a Little Deeper

NetManage has made life easier for all of us who must delve into the world of computer-to-computer communications by providing us with a product that demands very

little from us in the way of setup or support. However, don’t you wonder what’s really going on when a connection is being made? Are you even sure of what a router is?

A router is a protocol engine that takes your request—in this case your request to log on to the AS/400—and determines the path or route to deliver it. The routing process is simply one step in a seven-tier layer known as the Open Systems Interconnection (OSI) model, which ties together the pieces that let one computer communicate with another.

The OSI model was developed in 1974 by the International Organization for Standardization (ISO). The OSI model defines the standard for connectivity, but not the hardware or software needed to make it a reality. The model is divided into seven layers, with each layer performing a specific function that allows application software on disparate systems to talk to each other as if they both resided on the same system. These seven layers are as follows:

1. Application Layer—The application layer includes such familiar interfaces as 5250 emulation, FTP, Simple Mail Transfer Protocol (SMTP), Multi-purpose Internet Mail Extension (MIME), and Simple Network Management Protocol (SNMP).

2. Presentation Layer—The presentation layer handles data formatting, character code conversion, and data encryption.

3. Session Layer—The session layer is where the negotiation and establishment of a connection between nodes is made. An example of this would be the “handshake” between two modems.

4. Transport Layer—The transport layer provides the mechanism for reliable endto-end delivery of data.

5. Network Layer—The network layer is responsible for the routing of packets of information across multiple networks. NS/Router operates at this layer.

6. Data Link Layer—The data link layer handles the transfer of addressable units of information, frames, and error checking. Serial Line Internet Protocol (SLIP) and Point-to- Point Protocol (PPP) operate in this layer.

7. Physical Layer—The physical layer is responsible for the transmission of binary data over a communications network. IEEE 802.2 is an example of this type of throughput.

For the sake of brevity, these layers are often referred to by numbers, with the Application Layer being referred to as Layer 1 and the Physical Layer often called Layer 7. The NetManage NS/Router operates at the Network Layer, or Layer 5. It is at this layer that the configuration of a router is defined.

This configuration can take many forms. Once again, these different configurations are merely sets of instructions defining the process. Seven different protocols, or instruction sets, can be used by a router: Internet Protocol (IP), Address Resolution Protocol (ARP), Reverse Address Resolution Protocol (RARP), Internet Control Message Protocol (ICMP), Open Shortest Path First Protocol (OSPF), Border Gateway Protocol (BGP), and Internet Group Management Protocol (IGMP).

Each of these protocols uniquely defines a method of routing a datagram, the smallest unit in which data is sent. Without getting too much deeper here, suffice it to say that the NS/Router will choose the correct protocol based upon which connection method is defined in the NS/Administrator.

Configuring the NS/Router Couldn’t Be Easier

If you are using Client Access/400, you configure the NS/Router while creating a new Client Access connection using the NetManage Administrator. There are several ways to do this. You can start the NetManage Administrator from the panel shown in Figure 1. You can also choose to start NetManage Administrator from the NetManage folder inside

the Client Access folder. Or, you can manually run the NS ADMIN.EXE program from the Start/Run prompt of Windows 95. The NSADMIN.EXE program can be found in directory C:Program FilesIBMClient Access. Once NetManage Administrator is started, you are presented with the Administrator panel (shown in Figure 2). From here, you can add a new router configuration to existing workspaces or create new workspaces. A workspace is a grouping of collected router configurations. You might want to create separate workspaces when you want the same PC to connect to multiple systems. Each workspace can have one or more router configurations defined within it.

To define a router configuration, click on the Properties button in the toolbar (or right-click on the router icon and select Properties). You will be presented with a Properties panel like the one shown in Figure 3. The first thing you must do is choose the Link type. This is the method you want the NS/Router to use to physically connect to another computer. The link type works in concert with the definition of the CA/400 connection type to set the protocol the NS/Router will use to communicate with the AS/400.

A Chain Is Only as Strong as Its Weakest Link

Using Client Access/400, you can choose to connect your PC to the AS/400 through six different connection links:

• 8022—Used to communicate directly with your token-ring or Ethernet adapter
• AnyNet—Uses TCP/IP to communicate to an AS/400 with the IBM AnyNet protocol

• Asynch—Used to communicate with a host through the PC serial port
• NetWare for SAA—Used to communicate with a host using Novell NetWare for SAA Server

• SDLC—Used to communicate with a host using a supported SDLC adapter
• Twinax—Used to communicate with a host using a twinax adapter The NetManage NS/Router is flexible enough to allow a PC to use any or all of these connections simultaneously, provided the PC has all the requisite hardware and software installed. For example, you might have a 5250 emulation card and an Ethernet adapter card installed in your PC. The 5250 card would allow you to communicate to one system through that AS/400’s twinax controller while the Ethernet card would allow you to access other AS/400s in the network. All of these connections could be active at the same time, orchestrated by the NS/Router.

Pick a System, Any System

The Systems panel (shown in Figure 4) allows you to define the name of the connected AS/400 system. You add a new system by clicking on the Add button and entering the system’s name and network ID. This ID must correspond to the NETID parameter of the connected AS/400. You can find this NETID by keying the Display Network Attributes (DSPNETA) command on the AS/400. You may also enter the AS/400 user ID and password you want NS/Router to use to connect to the AS/400. If a user ID and password are not entered here, the NS/Router will automatically use the user ID and password from the Common properties tab shown in Figure 5. If the user ID and password are left blank in both tab boxes, the user will be prompted to enter them before he or she is allowed to connect to the AS/400.

Now, here is something to note: This user ID/password pair may not necessarily be the same values required to actually sign on to an AS/400 workstation session. They may be defined differently, and are actually stored separately. The second user ID/password pair is actually configured in a separate CA/400 configuration panel outside of NetManage Administrator and is stored in the Windows 95 password cache. That

second pair can be set by clicking on the Windows 95 Passwords icon in Control Panel. The NS/Router user ID and password are only used by the NS/Router program itself to route commands to the AS/400.

Who Says Redundancy Is a Bad Thing?

Looking back at the Systems tab (Figure 4), you will see you can also set the Router Redundancy List. Use this feature if you have more than one router configuration defined to connect to the same AS/400. This can be very handy. For example, you might have three phone numbers set up to dial for an asynchronous connection. One phone number might be used if you’re dialing from an office that requires a 9 to get an outside line. Another phone number might use an 8 to get an outside line; most hotel phone systems require this. The third configuration might not require any extra digits to access an outside line. The Router Redundancy List will also let you synchronize the order in which the different router configurations will be executed. This parameter only affects those routers defined within the same workspace.

Define Common Information

Let’s look closer at the Common properties tab (shown in Figure 5), used to define the user ID and password. The password and user ID pair entered here will be used across all NS/Router configurations within a given workspace. This means you only need to enter this information once for a given router configuration. Within this panel, you can also identify the code page and other advanced session properties that are common to all systems. If you need to, you can specify additional parameters such as Local Transaction Programs to be started when the router session starts, set security by user ID and password for a given transaction program, and add CPI-C Side information such as remote user ID and symbolic destination name.

Local Names Are Important, Too

The Local LU properties panel (shown in Figure 6) is used to define configuration data that is uniquely localized to the defined systems. For instance, you use this panel to specify the network ID of the AS/400 you are connecting to, as well as the PC location name to be used when connecting to the AS/400. The PC location name is a unique name defined for each workstation. If your AS/400 has Auto Configure Virtual Devices turned on in the system value, this will be the name generated when the PC first connects to the AS/400. Otherwise, this value must correspond to an already defined device. This is useful when a particular PC must attach to the AS/400 to a particular device configuration.

Within the NS/Router Properties panel, the Link Type, System Name, and Local LU properties all contain required entries. The Common properties are optional. Once you have configured these tabs, save the data and close the NetManage Administrator. If you started the Administrator while configuring a new Client Access session, you will be returned to the screen shown in Figure 1, and you can continue the remaining Client Access/400 configuration tasks.

Nothing Works Perfectly All the Time

The NS/Router is one of the most reliable routers in the industry. However, even the best of us have bad days. One common problem that many people experience is the infamous CWBSY1000 “A communication error occurred while validating your user ID and password on the specified system” message. This is not really a problem with the NS/Router product, but rather a problem with the way routers must sign on to hosts and their ability to report user validation errors. The CWBSY1000 message appears any time an attempt to connect to an AS/400 fails. Of course, a cursory review of the error message might lead you to believe that the user ID on the AS/400 was invalid. This could be the case, but it could also be caused by any number of situations. More often than not, the real

cause can be traced to a failure of the physical connection that is occurring before the user ID and password are validated. The router itself has no way of communicating back to Client Access/400 what type of error it has received, and Client Access/400 merely interprets NS/Router’s failure as a validation problem.

Other problems can occur when you are using the Run Remote Command (RUNRMTCMD) command from your PC to send instructions between the PC and the AS/400. Errors associated with this APPC function are often cryptic, taking the form of Sense Code or Invalid Parameter errors. Often, they relate to the fact that the NS/Router doesn’t support certain parameter passing, such as the common PCID common control vector, or because NS/Router doesn’t support data compression or session-level encryption.

There are a few other rather esoteric errors that could occur when using NS/Router, but in general, once the software has been properly configured, errors are rare occurrences.

Making the Complex Simple

NetManage NS/Router is a tool that performs very complex steps behind the scenes, while presenting the user with a simple interface. The next time you use your PC to connect to an AS/400, give a little thought to the many events that had to occur to get that 5250 session displayed on your screen. If you do, you’re sure to appreciate what this little piece of the PC-to-AS/400 connection process does to simplify your life.

Figure 1: You can start the NetManage Administrator using this panel

Figure 2: The NetManage Administrator panel

Figure 3: The Properties panel

Figure 4: You can define the name of the connected AS/400 system using the Systems panel

Figure 5: The Common properties tab is used to define the user ID and password

Figure 6: The Local LU properties panel

Shannon O'Donnell has held a variety of positions, most of them as a consultant, in dozens of industries. This breadth of experience gives him insight into multiple aspects of how the AS/400 is used in the real world. Shannon continues to work as a consultant. He is an IBM Certified Professional--AS/400 RPG Programmer and the author of an industry-leading certification test for RPG IV programmers available from ReviewNet.net.

 

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