Comparison of Windows NT Network ProtocolsLast reviewed: March 18, 1997Article ID: Q128233 |
The information in this article applies to:
SUMMARYThe following article on Windows NT protocols is a copy of an article published in Microsoft's "Premier Showing" newsletter.
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Comparison of Windows NT Network Protocols OverviewMicrosoft provides three transport drivers (i.e., protocols) with Windows NT 3.5: TCP/IP, NWLink, and NBF. Windows NT 3.5 also ships with the DLC protocol, which does not provide transport layer services. In this article the terms TCP/IP, NWLink and NBF refer to the Windows NT transport drivers that implement the Internet TCP/IP, Novell SPX/IPX and IBM NetBEUI network protocol suites, respectively. This article compares these protocols as implemented in the Windows NT 3.5 transport drivers, to assist users in selecting the appropriate protocol(s) for their network. Since each customer will be concerned with a different set of protocol characteristics, this article does not recommend which protocol customers should use. Instead, it discusses the merits of each, thereby enabling customers to make the best choice for their environment. Microsoft will continue to support these three protocols, today and in the long term. Windows NT installs NWLink by default, primarily because IPX is the most common protocol in PC networks and it has relatively simple configuration requirements. However, administrators can modify setup.inf files to install other protocols by default. This default setting does not imply preference of NWLink over TCP/IP or NBF. NOTE: In the Windows NT 3.51 release, TCP/IP is now installed by default. Customers should generally use the minimum protocols necessary, because multiple protocols usually result in the following:
Windows NT Transport Driver ArchitectureThe Network Basic Input/Output System (NetBIOS) standard, which was originally developed for IBM by Sytek in 1983 defines two entities:
Unlike the 16 bit Windows, MS DOS and OS/2 versions of Microsoft Network software, Windows NT transport drivers do not expose the NetBIOS interface; instead, they expose the more flexible Transport Driver Interface (TDI). Windows NT includes a NetBIOS Emulator to map NetBIOS commands to TDI commands and events. Internal Windows NT network components use TDI commands and events, rather than NetBIOS commands, to communicate with underlying transport drivers. The TDI clients require support for NetBIOS address format and message mode data transfer. NBF supports this natively through NBFP. Transports that do not include NBFP implement a NetBIOS compatibility layer to resolve NetBIOS format addresses to the transport's native address format, and to implement message mode data transfer over the transport's native data transfer protocol. Windows NT transport drivers provide the services defined in several layers of the OSI Reference Model: Some Session Layer services; all Transport and Network Layer services; and the services of the LLC sub layer of the Data Link Layer. This constitutes all services between the TDI and the Network Driver Interface Specification 3.0 (NDIS) interface. All Windows NT transport drivers except DLC export the TDI interface at their upper edge for communication with TDI client applications, such as the Windows NT redirector and server. They export the NDIS interface at the lower edge for communication with the underlying network interface card (NIC) driver.
Background on Windows NT Transport DriversNBF (NetBEUI) IBM first introduced the NetBIOS Extended User Interface (NetBEUI) protocol specification in 1985. It is optimized for departmental LANs or LAN segments. The Windows NT NetBEUI Frame (NBF) transport driver implements the IBM NetBEUI 3.0 specification, and is completely compatible with the NetBEUI shipped with past Microsoft networking products. NBF implements NBFP, and therefore requires no NetBIOS compatibility layer. TCP/IP Windows NT includes an implementation of the Transmission Control Protocol/Internet Protocol (TCP/IP). In general usage, the term TCP/IP refers to a suite of protocols that includes TCP, UDP, IP, ICMP, and ARP. Since TCP/IP is available for many diverse operating systems such as UNIX, MVS, VM, VMS, NetWare and OS/2, Windows NT can use TCP/IP to communicate with these different operating systems. TCP/IP also provides compatibility with the global Internet. TCP/IP is Microsoft's strategic protocol for scaleable Windows-based networking. The Windows NT TCP/IP transport driver includes TCP, UDP, IP, ICMP, ARP and NBT. Microsoft completely redesigned the TCP/IP transport driver in Windows NT 3.5, providing many enhancements over the Streams based TCP/IP transport driver in Windows NT 3.1. The NetBIOS compatibility layer for TCP/IP is NetBIOS over TCP/IP (NetBT in Windows NT 3.5; NBT in Windows NT 3.1). NWLink (IPX) Novell NetWare currently has the largest market share among PC based network operating systems. NetWare's native Network Layer protocol is IPX, a Novell proprietary descendant of the Xerox XNS protocol. Microsoft implements the lower level NetWare protocols in the NWLink transport driver, which includes IPX, SPX, RIPX and NBIPX. The NetBIOS compatibility layer for NWLink is NetBIOS over IPX, also known as NBIPX (NwLnkNb in Windows NT 3.5; NWNBLink in Windows NT 3.1).
Comparing Transport Driver CharacteristicsThis section compares the Windows NT transport drivers in each of the following areas:
The more popular protocols have a larger based of experienced support and design engineers. In late 1994 Sage Research, Inc. performed a study of router based LAN backbones with at least 250 nodes in Fortune 500 companies. Their study concluded that TCP/IP is used on 95% of all such networks, while SPX/IPX is used on 87%.
Open protocol specifications enable programmers to obtain all the information necessary to develop their own protocol drivers without paying license fees.
The availability of a protocol on a variety of operating systems and hardware platforms provides the advantage of interoperability. Windows NT provides native support for NetBEUI, TCP/IP and SPX/IPX through the NBF, TCP/IP and NWLink transport drivers.
Administrators of any size network desire simplicity of client configuration and network administration. Large sites have many clients to configure, while small sites may not have sufficient support personnel. All three protocols are self tuning in their Windows NT 3.5 implementation. However, Microsoft exposes certain tuning parameters for manual configuration in special situations.
Administrators of large networks desire the ability to differentiate between multiple interconnected networks. Hierarchical network addresses provide the ability to manage a hierarchy of subnetworks within networks, allowing smarter forwarding and security. Creating smaller segments with fewer stations produces more manageable networks with reduced traffic levels. This ability may not be critical for small networks.
Multi location networks require routing capabilities, while single location networks have little use for such capabilities. Routable protocols do not generally allow broadcast packets to traverse routers, thereby reducing network congestion. Both IP and IPX are natively routable; they do not require encapsulation for routing. Both employ interior gateway protocols (IGPs) to exchange routing information among routers within an autonomous network (i.e., a group of nodes controlled by a single administrative authority). One of the most common IGPs is the Routing Information Protocol (RIP), which uses a vector distance algorithm to determine optimum routes. The RIP implementations used in IP and IPX are based upon the XNS RIP developed by Xerox Corporation's Palo Alto Research Center (PARC).
Name resolution requirements impact the simplicity of client configuration and network administration. The methods of name registration and resolution impact the amount of broadcast or multicast activity present on the network, discussed later in the section on network traffic. NetBIOS Name Registration All transport drivers must register NetBIOS names to ensure that each name is unique. NetBIOS Name Resolution Application Layer names (NetBIOS and Sockets host names) must ultimately resolve to Data Link Layer (MAC) addresses. Transport drivers that do not process NetBIOS names natively have an intermediate name resolution step at the Network Layer, where the NetBIOS names resolve to the transport's native address format.
For Windows Sockets applications, TCP/IP resolves host names to IP addresses, which then resolve to MAC addresses. Network Traffic The method of name registration and resolution often impacts the amount of broadcast or multicast (limited broadcast) activity present on the network. Broadcast and multicast activity uses network bandwidth on the local segment and on all bridged segments, and consumes processing cycles on every network station the same protocol. Protocols with a high level of broadcast or multicast activity are not generally well suited for large networks. Name Registration Broadcasts NetBIOS names must be registered to ensure that each name is unique. All transport drivers use broadcast, with one exception. In TCP/IP, WINS clients send directed name registration request to the WINS server. Non WINS clients may use WINS proxy agent for name resolution, but rely on broadcast for name registration. The MS DOS WINS clients send directed name resolution requests to the WINS server, but rely on broadcast for name registration. Name Resolution Broadcasts Name resolution may be accomplished by broadcast, cached mappings, lookup in a local mapping file or query a name service.
NetBEUI is not routable, and therefore has no impact on router broadcasts. Dynamic IP and IPX routers maintain routing tables by issuing a RIP broadcast on every port at regular intervals. IP broadcasts every 30 seconds; IPX, every 60 seconds. All NetWare file servers are inherently routers, and therefore issue RIP broadcasts. IP RIP allows for active or passive participants. Active participants issue RIP broadcasts; passive or silent participants only listen. IP routers are active whereas IP hosts are typically passive. Unfortunately, IP RIP does not communicate with IPX RIP, resulting in redundant RIP broadcasts on networks running both IP and IPX. SAP Broadcasts IPX servers use the Service Advertising Protocol (SAP) to automatically notify other IPX nodes of their presence and the services they provide. IPX servers, but not routers, issue SAP broadcasts every 60 seconds. Clients use SAP to determine what network resources are available. These SAP broadcasts may cause congestion on networks with numerous services, especially over WAN links. NWLink does not issue SAP broadcasts. To address this problem on NetWare, Novell implemented SAP filters and the NetWare Link Service Protocol (NLSP) in its Multiprotocol Router (MPR) with NetWare 4.x. NLSP couples OSPF-based route information with Novell's SAP functions, substantially reducing the overhead traffic commonly generated by RIP and SAP. DHCP Broadcasts DHCP will greatly simply IP client configuration. However, DHCP will slightly increase network traffic. DHCP accomplishes client configuration negotiation through broadcast. Once the client accepts the IP address offered by the DHCP server, all activity is by directed packets. Since DHCP servers act autonomously, there is no replication traffic between DHCP servers. WINS Replication WINS can significantly reduce name query broadcasts. However, WINS will introduce network traffic for replication among multiple WINS servers. If configured properly, this replication traffic will be minimal and the net effect will be reduced network traffic. Network Status Reporting
Network administrators generally desire a small memory footprint, especially on clients. Protocol memory requirements are typically a characteristic of the transport driver implementation rather than the protocol itself.
Protocol performance is typically dependent upon the efficiency and tuning of the transport driver implementation rather than the protocol itself.
Users who wish to connect to the global Internet must obtain a network ID from InterNIC. The supply of unallocated IP addresses on the global Internet is rapidly declining. In an effort to address this problem the Internet Engineering Task Force (IETF) has formed IP Version 4 Address Lifetime Estimation (IPv4 ALE) working group to determine how much longer IPv4 can last. The IETF is also developing IP Version 6 (IPv6), also known as IP Next Generation (IPng), to replace the current IPv4. IPng increases the IPv4 addresses from four bytes (32 bits) to sixteen bytes (128 bits). However, there is much controversy over IPng.
Summary
Characteristic TCP/IP NWLink NBF Industry Acceptance Most popular, Primary protocol Limited to IBM
and Experience especially in in PC networks & Microsoft PC
non PC networks networks
Open vs. Proprietary Open Proprietary Proprietary, Specification but published Interoperability Available on Available on Limited to IBM
nearly every many platforms & Microsoft PC
platform networks
Simplicity of Client Can be Simple Simple Configuration difficult Simplicity of Can be Simple Simple Administration difficultNetwork Segmentation: ------------------------------------------------------------------------ Differentiates Yes No No Between Networks ------------------------------------------------------------------------ Hierarchy of Subnets Yes Yes No within Networks Routing Capabilities Native Native NoName Resolution Requirements: ------------------------------------------------------------------------
Application Layer to Resolves host Resolves Uses NetBIOS
Network Layer or NetBIOS name NetBIOS name names natively
to IP address to IPX address
------------------------------------------------------------------------
Network Layer to Resolves IP IPX address Resolves
Data Link Layer address to MAC contains MAC NetBIOS name
address address to MAC address
Network Traffic:
------------------------------------------------------------------------
NetBIOS Name WINS, Broadcast Broadcast Broadcast
Registration
------------------------------------------------------------------------
NetBIOS Name Cache, WINS, Cache, Multicast
Resolution WINS Proxy, Broadcast
LMHOSTS,
Broadcast,
HOSTS, DNS
------------------------------------------------------------------------
Router Broadcasts Dynamic routers Dynamic routers N/A
issue RIP & NetWare file
broadcasts servers issue
every 30 RIP broadcasts
seconds every 60 seconds
------------------------------------------------------------------------
SAP Broadcasts N/A IPX servers N/A
issue SAP
broadcasts every
60 seconds.
------------------------------------------------------------------------
DHCP Broadcasts Client IP N/A N/A
configuration
negotiated via
broadcast.
------------------------------------------------------------------------
WINS Replication Replication N/A N/A
traffic when
using multiple
WINS servers
Network Status Reporting Yes No NoPerformance: ------------------------------------------------------------------------ Small LANs Fast Fast Fastest ------------------------------------------------------------------------ File and Print Fast Fastest Fast Operations ------------------------------------------------------------------------ Application Services Fastest Fast Fast
References
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