Network protocol support is one of the most critical low-level features of a network operating system. It alone determines the types of clients supported by the server software as well as the types of other computer systems with which the network operating system can communicate. For the purpose of this document, each operating system will be reviewed based on its ability to provide core networking services and functionality over the TCP/IP protocol, the most dominant protocol in use today. Additionally, each network operating system will be reviewed based on its ability to support other popular network protocols, such as IPX/SPX, NetBEUI, AppleTalk, or DLC.
Built on and around the TCP/IP protocol, Solaris deserves its reputation as the operating system on which the Internet runs. With a robust and mature TCP/IP implementation, Solaris 7 boasts IP connectivity that is second to none. Support for Streams is also part of the base operating system. However, other protocols are not well integrated with the operating system.
Support for NetBEUI, NetBIOS, IPX/SPX, and AppleTalk is available via the TotalNET Advanced Server 5.2 application. Services are configured in three Realms. NetBEUI and NetBIOS support are provided via the Services for LM-NT-OS/2 Realm, IPX support via the Services for NetWare Realm, and AppleTalk via the Services for AppleTalk realm.
Once the various protocols are installed, the services can be started and stopped dynamically and do not require a reboot to handle configuration changes.
Windows NT Server 4.0 Implementation Details
Windows NT Server 4.0 was designed to be protocol independent. Rather than having support for specific protocols built into the operating system, a modular driver architecture has been used to provide protocol support. Drivers for many popular protocols are shipped with the operating system. The protocols include:
Additionally, as modular driver architecture has been used, additional protocol support can be added easily to the operating system. However, not all protocols under Windows NT offer full networking and operating system functionality such as file and printer sharing, directory services, browsing/service location, or network name resolution. Instead, full networking functionality is offered only with the TCP/IP, NetBEUI, and IPX/SPX protocols. A subset of networking functionality is offered with the AppleTalk protocol for connectivity to client systems running Apple MacOS. DLC and Streams Environment have been provided for specialized connectivity purposes only. Point-to-Point Tunneling protocol is used extensively as a transport to carry traffic from other protocols securely over a public network as part of the Windows NT Server 4.0 Remote Access/VPN functionality, which will be discussed elsewhere in this document. Connectivity is transparent and automatic to the end user over both local and wide area network environments (with the noted exception of NetBEUI over a WAN, as it is a non-routable protocol).
Configuration at the time of installation and post-installation is GUI-based via the Network application in the Windows NT Server 4.0 control panel. Protocols can be added or deleted and selectively bound to all network interfaces present in the server. Protocol binding order is determined by the order in which the protocols were initially installed. The order can be changed at any time for each interface, allowing a greater detail of control than Solaris 7 allows. For example, the first interface could have TCP/IP and IPX/SPX both bound, with TCP/IP having precedence whereas the second interface could still have both protocols bound, but the IPX/SPX protocol could have precedence.
Additionally, network services can be selectively enabled or disabled on a per adapter or per protocol basis, or any combination thereof. This will provide extremely fine control over networking configuration. And it will allow extremely secure configurations to be constructed with a minimum of difficulty. Such configurations might include disabling all network services on public interfaces connected directly to the Internet. The only downside to this configuration is that most configuration changes require the server be rebooted.
Windows 2000 Server Implementation Details
Windows 2000 Server builds on the already strong protocol support in Windows NT Server 4.0. Basic network protocol support remains the same, although the user interface to manage network configuration has been totally revamped.
The Network application in Control Panel has been replaced with the new Network Connections folder. This allows all physical and remote access interfaces to be managed using the same user interface. It greatly simplifies network configuration for Remote Access Service (RAS). All configuration changes can now take place dynamically, eliminating the need for any server reboots to add, remove, or change network protocol support. Additionally, entire network interfaces and all associated bindings can be enabled or disabled at the click of a mouse –button without a server reboot.
Basic TCP/IP protocol support has been greatly enhanced in Windows 2000 Server with the addition of several key performance improvements for networking in high-bandwidth LAN and WAN environments. Specifically, these improvements include:
Large Window Support greatly improves the performance of TCP/IP when a large amount of data is present on the physical network that remains unacknowledged between two connected hosts over a long period of time. In TCP-based communications, the window size is typically fixed and negotiated at the onset of a session between two hosts. With Large Window Support, window size can be dynamically recalculated and increased as appropriate during longer sessions when large amounts of data need to be interchanged. This provides for additional data packets to be in transit on the network at one time, thereby increasing effective bandwidth.
Selective Acknowledgement provides for quick and effective recovery from a state of network congestion caused by temporary interference on the physical media. Selective Acknowledgement is a TCP option that allows the receiver to selectively notify and request from the sender only those packets that were missing or corrupted during initial delivery. In prior implementations of TCP/IP, if a receiving host failed to receive a single TCP packet, the sender would be required to retransmit not only the corrupt packet, but also all packets transmitted after the missing one. With Selective Acknowledgement, only those packets actually corrupted or missing must be retransmitted.
RTT Estimation improves TCP/IP performance by accurately assessing the round-trip time (RTT) interval between hosts on the network. Because performance is dependent on knowing how long to wait for a missing packet, improving the accuracy of RTT estimation results in improved timeout values being set on each host. Consequently, hosts cannot submit requests for packets to be retransmitted until the requisite time interval expires. Better timing will improve performance over long round-trip network links, such as WANs spanning large distances using wireless or satellite links.
Network Protocol Support Summary
Windows 2000 Server ties with Windows NT Server 4.0 in providing support for the greatest number of protocols (TCP/IP, IPX/SPX, NetBEUI, AppleTalk, DLC, and Streams). In Windows 2000, unlike Windows NT Server 4.0, protocol configuration can be performed dynamically, allowing settings to be changed without reboots. Additionally, for TCP/IP-based environments, Windows 2000 Server offers several performance enhancements unmatched by the other operating systems.
Basic protocol support is identical in Windows NT Server 4.0 and Windows 2000 Server. However, two key differences make Windows NT Server 4.0 a less ideal solution. Windows NT Server 4.0 does not support Windows 2000 TCP/IP performance enhancements and requires a reboot for certain configuration changes.
Solaris 7 offers excellent TCP/IP support. TCP/IP is, and always has been, the native protocol for the Sun operating system and the support for TCP/IP in the current product is a very mature and stable implementation. The TotalNET Advanced Server component of the Solaris 7 package adds support for NetBIOS, NetBEUI, AppleTalk, and IPX/SPX clients.