NWLink Overview

NWLink IPX/SPX is the Microsoft implementation of Novell’s NetWare Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) protocol. NWLink IPX/SPX is simply called NWLink. NWLink is used in Novell NetWare, and can be considered IPX for Windows. NWLink is an IPX/SPX compatible transport protocol that was developed to enable Windows 2000 computers to communicate with NetWare services. It is therefore used when clients running Microsoft operating systems (OSs) need to access resources on NetWare servers. It is also used where clients running NetWare need to access resources on computers running Microsoft operating systems. Clients that connect to NetWare servers must use the NWLink.

NWLink must be installed if you want to use Gateway Service for NetWare or Client Service for NetWare to connect to NetWare servers. The NWLink protocol provides the network and transport protocols that enable communication with NetWare servers.

The networking application programming interfaces (APIs) supported by NWLink are:

  • NetBIOS
  • Windows Sockets (WinSock).

If you want to log on to a NetWare network from a Windows 2000 Professional computer, you need to use either of the following:

  • Client Service for NetWare
  • Novell Client for Windows 2000: Novell Client for Windows 2000 is an example of a third-party NetWare client which you can use.
  • Install Gateway Service for NetWare on a Windows 2000 server. This is an example of a gateway technology.

NWLink is Network Driver Interface Specification (NDIS) compliant. This means that a computer can concurrently run another protocol stack. NWLink can also bind to multiple network adapters. Multiple frame types are supported as well.

A few advantages of using NWLink are listed below:

  • Installing, configuring, and managing NWLink is not intricate.
  • NWLink is routable
  • Connecting to installed NetWare servers and clients is fairly simple.
  • The 32-bit Windows 2000 implementation of NWLink offers the following:
    • Enables NetWare clients to access Windows 2000 servers.
    • Includes support for communications with NetWare networks
    • Includes support for sockets and NetBIOS over IPX.

However, NWLink has limited support in Windows Server 2003. NWLink does not include support for network management protocols. While TCP/IP is by default installed and bound to each connection, the NWLink protocol has to be manually installed, configured, and bound to connections.

NWLink Architecture

NWLink includes components and protocols that run at the transport layer and network layer of the Open Systems Interconnection (OSI) model to enable communication with NetWare networks:

  • IPX: This is a peer-to-peer networking protocol. IPX is the connectionless protocol that provides datagram transfer services. IPX also controls packet addressing and packet routing. IPX needs less overhead than connection-oriented transmissions because a session does not need to be established whenever data is transmitted. IPX cannot though provide any guarantee that packets arrive at their destinations. IPX only assumes that each packet has been delivered. IPX does not also provide flow control. IPX enables the following:
    • NetBIOS
    • RPC over NetBIOS
    • Mailslots
    • Named Pipes
    • Network Dynamic Data Exchange (NetDDE) service
    • RPC over Named Pipes programming over NetBIOS over IPX (NBIPX)
  • SPX: SPX is a connection-oriented transport protocol. While initial overhead is realized when establishing the connection, once it is established, no extra overhead is needed to pass data. SPX provides the following features:
    • Reliable data delivery: Sequencing and acknowledgments enable reliable data delivery. SPX tracks data sending via acknowledgment requests.
    • Verification that the data packet arrived at the destination in one piece.
    • Verification that the destination received the packet.
    • SPX includes the packet burst feature: Packet burst is the mechanism that enables multiple data packets to be transmitted, and acknowledged only once. Each packet does not need to be individually acknowledged.
    • Packet burst monitors for dropped packets, and then only retransmits those packets which were dropped.
  • SPXII: SPXII an improved version of SPX, is a connection-oriented transport protocol. SPXII improves on SPX in a number of ways:
    • With SPXII, the maximum packet size supported is the maximum packet size of the underlying LAN. SPX only supported a maximum packet size of 576 bytes.
    • SPXII has no set outstanding unacknowledged packet number. SPX could only support one outstanding unacknowledged packet at any point in time. With SPXII, the number of outstanding packets allowed is negotiated between the peers when the connection is established.
  • NetBIOS: NetBIOS over IPX provides the following NetBIOS services:
    • NetBIOS Datagram Services: Used by applications, user authentication and mailslots. Applications use NetBIOS Datagram Services for connectionless communications.
    • NetBIOS Session Services: Used by file and print sharing. NetBIOS Session Services enables connection-oriented communication between applications.
    • NetBIOS Name Service: Provides registering and releasing NetBIOS names.
  • Service Advising Protocol (SAP): IPX clients distribute the names and addresses of services running on IPX nodes through Service Advertising Protocol (SAP). The types of messages used by SAP clients are:
    • A SAP GetNearestServer is broadcast to request the name and addresses of the closest server of a particular type.
    • A SAP general service request is broadcast to request the names and addresses of services.
  • Router Information Protocol (RIP): RIP is supported by NWLink for Windows based clients and Windows 2000 computers that do not have the Routing and Remote Access Service (RRAS) installed. Router Information Protocol (RIP) over IPX (RIPX) is used for route and router discovery services.
  • Forwarder kernel mode component: The Forwarder is automatically installed when you install NWLink. It is used when a Windows 2000 based server runs as an IPX router via the Routing and Remote Access Service. To forward packets, the Forwarder interacts with the IPX Router Manager and the filtering component.

How to install Client Service for NetWare

Installing Client Service for NetWare on Windows 2000 Professional, automatically installs the NWLink IPX/SPX/NetBIOS Compatible Transport Protocol.

To install Client Service for NetWare,

  1. Right-click My Network Places, and click Properties on the shortcut menu.
  2. In the Network and Dial-Up Connections dialog box, right-click the local area connection that you want to install Client Service for NetWare for, and then click Properties on the shortcut menu.
  3. Click the Install button on the General tab.
  4. When the Select Network Component Type dialog box appears, click Client, and then click Add.
  5. When the Select Network Client dialog box opens, click Client Service For NetWare.
  6. Click OK.

How to install NWLink

While TCP/IP is by default installed and bound to each connection, the NWLink protocol has to be manually installed.

To install the NWLink protocol,

  1. Right-click My Network Places, and click Properties on the shortcut menu.
  2. When the Network And Dial-Up Connections dialog box opens, right-click Local Area Connection, and select Properties on the shortcut menu.
  3. The Local Area Connection Properties dialog box opens.
  4. Click Install.
  5. When the Select Network Component Type dialog box appears, click Protocol, and click Add.
  6. When the Slect Network Protocol dialog box appears, click NWLink IPX/SPX/NetBIOS Compatible Transport Protocol.
  7. Click OK.

Configuring NWLink

Configuring NWLink includes the configuration of the following components:

  • Internal Network Number: The internal network number is used for internal routing, to identify a computer. The number is a hexadecimal number or virtual number, and is made up of 8 digits. The default value of the internal network number is 00000000. The internal network number identifies another virtual network segment in the computer. The NetWare server or a router adds an additional hop in the route to the computer. You have to manually configure a unique internal network number under the following circumstances:
    • The NetWare Service Advertising Protocol (SAP) is being used by an application.
    • When FPNW is installed, and the following statements are true.
      • NWLink is bound to multiple adapters in the computer.
      • Multiple frame types exist on a single adapter
  • Frame Type: The frame type determines how a network adapter card in a computer formats data. This is important because the NWLink frame type has to be the same as the frame type on the NetWare server so that the Windows computer and a NetWare server can communicate. The frame types supported by NWLink are:
    • Ethernet network topology: Ethernet II, 802.2, 802.3, and Subnetwork Access Protocol (SNAP).
    • Token Ring network topology: 802.5 and SNAP
    • Fiber Distributed Data Interface (FDDI): 802.2 and SNAP
  • External Network Number: Each frame type that is defined on the network adapter card must have a network number. This external network number must be unique for each network segment, and all computers on the same network segment using the frame type have to utilize the identical external network number to communicate. The external network number therefore signifies a specific network segment. Both the IPX frame type and network number are configured when NWLink is installed. You can however use the Registry Editor to manually configure the network number.
    The registry subkey that you have to edit to change the network number is: HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesNwlnkipxParametersAdaptersAdapter. The entries that have to be edited are:

    • NetworkNumber: This is the hexadecimal network number for the adapter. A value of 0 means that the network number is obtained from the network. External network numbers are 4 bytes
    • PktType: This is the packet form that should be used. The values that can be set for PktType are:
      • 0, Ethernet_II
      • 1; Ethernet_802.3
      • 2; 802.2
      • 3; SNAP
      • 4; ArcNet
      • FF; Auto-detect

How to change the internal network number

  1. Open Control Panel
  2. Double-click Network And Dial-Up Connections
  3. Right-click the local area connection and select Properties on the shortcut menu.
  4. Select NWLink IPX/SPX/NetBIOS Compatible Transport Protocol, and then click Properties.
  5. When the NWLink IPX/SPX/NetBIOS Compatible Transport Protocol dialog box appears, enter the internal network number in the Internal Network Number box.
  6. Click OK.

How to change the frame type and external network number

  1. Open Control Panel
  2. Double-click Network And Dial-Up Connections
  3. Right-click the local area connection and select Properties on the shortcut menu.
  4. Click NWLink IPX/SPX/NetBIOS Compatible Transport Protocol, and click Properties.
  5. The NWLink IPX/SPX/NetBIOS Compatible Transport Protocol dialog box appears.
  6. Select a frame type from the Frame Type drop-down list box
  7. Enter a network number in the Network Number text box.
  8. Click OK.

How to configure netork bindings

  1. Right-click My Network Places and select Properties on the shortcut menu.
  2. When the Network And Dial-Up Connections dialog box opens, click the Advanced button.
  3. Click Advanced Settings.
  4. The Advanced Settings dialog box opens.
  5. Beneath Client For Microsoft Networks, to bind the NWLink IPX/SPX/NetBIOS Compatible Transport Protocol to the adapter, click to choose the adapter.
  6. If you want to unbind the protocol, click to deselect the adapter.
  7. Click OK.

How to specify the NWLink protocol binding order

  1. Right-click My Network Places and select Properties on the shortcut menu.
  2. When the Network And Dial-Up Connections dialog box opens, click the Advanced button.
  3. Click Advanced Settings.
  4. The Advanced Settings dialog box opens.
  5. Beneath Client For Microsoft Networks, click NWLink IPX/SPX/NetBIOS Compatible Transport Protocol, and use the Up and Down buttons to change the binding order for protocol:
    • Click the Up button to move the NWLink protocol higher in the binding order.
    • Click the Down button to move the NWLink protocol lower in the binding order.
  6. Click OK.

How to uninstall the NWLink protocol

  1. Right-click Local Area Connection in the Network And Dial-Up Connections dialog box, and select Properties on the shortcut menu.
  2. On the Local Area Connection Properties dialog box, click NWLink IPX/SPX/NetBIOS Compatible Transport Protocol, and click Uninstall.
  3. Click Yes to uninstall NWLink IPX/SPX/NetBIOS Compatible Transport Protocol.
  4. Click Close.