Q128233: Comparison of Windows NT Network Protocols
Article: Q128233
Product(s): Microsoft Windows NT
Version(s): 3.1 3.5
Operating System(s):
Keyword(s): kbnetwork
Last Modified: 08-AUG-2001
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The information in this article applies to:
- Microsoft Windows NT Server version 3.1
- Microsoft Windows NT Workstation version 3.1
- Microsoft Windows NT Advanced Server, version 3.1
- Microsoft Windows NT Workstation version 3.5
- Microsoft Windows NT Server version 3.5
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SUMMARY
=======
The following article on Windows NT protocols is a copy of an article published
in Microsoft's "Premier Showing" newsletter.
MORE INFORMATION
================
Comparison of Windows NT Network Protocols
Overview
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Microsoft 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:
- Higher memory requirement for clients.
- More complex client configuration and network administration.
- Higher support and software license costs.
Windows NT Transport Driver Architecture
----------------------------------------
The Network Basic Input/Output System (NetBIOS) standard, which was originally
developed for IBM by Sytek in 1983 defines two entities:
- A Session Layer interface that is a standard API for user applications to
submit network I/O and control directives to underlying network protocol
software. NetBIOS commands are submitted via Network Control Blocks (NCBs).
- A session management/data transport protocol called NetBIOS Frames Protocol
(NBFP). NBFP functions at the Session and Transport Layers to perform the
network I/O to accommodate the NetBIOS interface command set.
An application program that uses the NetBIOS interface API for network
communication can operate on any transport driver that exposes the NetBIOS
interface. Transport drivers that do not implement NBFP (e.g., TCP/IP and IPX)
must expose the NetBIOS interface and have a means of mapping each NetBIOS
interface command to some sequence of their own native network frames and
protocols.
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 Drivers
------------------------------------------
NBF (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 Characteristics
------------------------------------------
This section compares the Windows NT transport drivers in each of the following
areas:
- Industry acceptance and experience
- Open or proprietary specifications
- Interoperability
- Simplicity of configuration and administration
- Network segmentation
- Routing capabilities
- Name registration and resolution requirements
- Network traffic
- Network status reporting
- Memory requirements
- Performance
- Application programming support
As mentioned previously, the customer's computing environment will determine
which protocol characteristics are desired, and which are most important. The
applicability and importance of the foregoing characteristics will be dependent
upon factors such as the following:
- Size of the network
- Single or multiple locations
- Homogeneous or heterogeneous nodes
- Internet connectivity requirements
- Application programming requirements
- Size and expertise of support staff
Industry Acceptance and Experience
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%.
- NetBEUI usage is limited primarily to Microsoft and IBM PC network
environments.
- TCP/IP is widely accepted, established and understood, especially in UNIX and
non PC networks. It is the protocol of the global Internet.
- SPX/IPX is the most popular protocol in PC network environments.
Open or Proprietary Specifications
Open protocol specifications enable programmers to obtain all the information
necessary to develop their own protocol drivers without paying license fees.
- NetBEUI is a proprietary specification owned by IBM. However, IBM makes this
specification available to developers.
- TCP/IP is an open specification. Anyone can easily obtain RFCs for
implementing the TCP/IP protocols. Anyone can also submit RFCs to the
Internet Engineering Task Force (IETF) for consideration.
- SPX/IPX is a proprietary specification owned by Novell, which can make it
difficult to obtain specifications for the upper layers like NCP. However,
Novell has made the new SPX II specification available.
Interoperability
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.
- NetBEUI is limited almost exclusively to Microsoft and IBM PC networks:
Microsoft LAN Manager, Windows NT, Windows for Workgroups; LAN Manager for
UNIX; and IBM PCLAN and LAN Server environments.
- TCP/IP is available on a wide variety of operating systems such as Windows
NT, UNIX, NetWare, VMS, VM, MVS, MS DOS, Macintosh, and OS/2. It is the
protocol of the global Internet. NetWare/IP will enable NetWare customers to
run TCP/IP-only networks, accessing NetWare services without requiring
SPX/IPX. However, NetWare/IP is not native IP for NetWare; it emulates the
IPX stack to NCP, which still requires an underlying IPX (or emulated IPX)
layer. In comparison, Windows NT provides true protocol independent
networking, running SMBs over its transport drivers without emulation
requirements.
- IPX is the native protocol of Novell NetWare. However, SPX/IPX is also
available on other operating systems: Microsoft provides NWLink for Windows
NT; TGV provides IPX for DEC VMS; Novell offers IPX on UnixWare.
Simplicity of Configuration and Administration
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.
- NBF requires little or no initial configuration or network administration.
- TCP/IP is potentially difficult to configure due to the relative complexity
of its multi part naming scheme, and the fact that a default gateway (router)
must be identified for each station. To reduce the client configuration
burden, Windows NT 3.5 supports the Dynamic Host Configuration Protocol
(DHCP), an open standard that transparently provides dynamic negotiation of
client configuration. DHCP clients require no manual IP configuration, and
administrators do not have to manually assign IP addresses. However, DHCP
does require proper planning and administration of DHCP servers.
- NWLink requires little or no initial client configuration on small non routed
networks. The node ID component of the IPX address is simply the six byte MAC
address of the NIC. This simple node ID eliminates the need for manual client
configuration. Configuring a server's external and internal networks is more
complex, however.
Network Segmentation
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.
- NetBEUI uses a single part naming scheme, and therefore has no facility for
differentiating between multiple interconnected networks.
- TCP/IP uses a multi part naming scheme that allows very large multi location
networks to be logically segmented into multiple levels of subnets. Network
administrators can use the network ID component of the IP address in
conjunction with a subnet mask to configure and manage subnetworks within
subnetworks. IP uses subnetworks to logically segment large networks into
separate, smaller interconnected subnetworks.
- IPX uses a simple two part naming scheme that allows large multi location
networks to be logically segmented into multiple subnets. However, the IPX
network ID is not hierarchical; it does not divide into subcomponents.
Routing Capabilities
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).
- NetBEUI is not routable. NBF does support a simple form of routing known as
Token ring Source Routing, offered only on Token Ring networks. However,
source routing is not actually implemented at the OSI Network Layer.
- TCP/IP packets are routeable by third-party routers that use RIP, IGPs such
as Cisco Systems' Interior Gateway Routing Protocol (IGRP), or IETF's Open
Shortest Path First (OSPF) protocol, even though Windows NT itself does not
understand these protocols. However, if MPR is installed, Windows NT uses
RIP. You may configure Windows NT as a static TCP/IP router by checking the
Enable IP Routing check box in Control Panel. Dynamic routing must be
implemented with third party routers.
- Windows NT cannot act as an IPX router, but IPX provides full inter network
routing support. NWLink uses Routing Information Protocol over IPX (RIPX) to
implement route and router discovery services used by SPX and NBIPX. When
NWLink loads, it sends out a RIPX request for a network number to be used for
addressing at the IPX level. NetWare servers respond with a RIP packet
containing the network number of the local network. If there is no RIPX
response, NWLink uses 0 for the network number and indicates that the IPX
packet is for the local subnet.
Name Registration and Resolution Requirements
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.
- NBF uses NetBIOS names natively, then resolves them to MAC addresses.
- In TCP/IP, NetBT resolves NetBIOS names to IP addresses, which then resolve
to MAC addresses via ARP cache or broadcast.
- In NWLink, NBIPX resolves NetBIOS names to IPX addresses. IPX addresses
contain the MAC address as the host ID, so IPX requires no further
resolution.
Sockets Host Name Resolution
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.
- NBF does not cache NetBIOS names that have already been resolved to MAC
addresses. NBF also does not use a mapping file or name service. Therefore,
NBF will generate multicast activity each time a link to another station is
re established.
- TCP/IP in Windows NT 3.5 provides many options for name resolution, resulting
in few broadcasts if configured properly. For NetBIOS name resolution, TCP/IP
can use cache, LMHOSTS lookup, WINS query, broadcast, DNS query and HOSTS
lookup. For host name resolution, TCP/IP can use all of these methods except
cache. Regardless of the method used for resolving NetBIOS and host names, IP
must resolve IP addresses to MAC addresses. This final resolution stage is
accomplished by ARP cache or ARP broadcast.
- NWLink uses broadcast to resolve names to addresses. However, NWLink reduces
name resolution broadcast activity by caching NetBIOS name to IPX address
mappings. NWLink does not use an address mapping file or name service. A
future version may implement a name service similar to WINS or DNS.
Router Broadcasts
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
- NBF does not provide any information about the state of the network.
- TCP/IP routers use ICMP to notify the source that errors have been
encountered, such as Destination Unreachable, Source Quench, etc.
- IPX does not provide any information about the state of the network. IPX has
no internet control management protocol, such as TCP/IP's ICMP. An IPX router
has no way to indicate to a sending station that a destination is
unreachable, that it should decrease its transmission rate, etc.
Memory Requirements
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.
- NBF has relatively small memory usage.
- TCP/IP and IPX have similar memory usage requirements, but require more than
NBF.
Performance
Protocol performance is typically dependent upon the efficiency and tuning of the
transport driver implementation rather than the protocol itself.
- NBF is tuned for small LAN communication, and therefore is very fast. Its
performance across WANs is poor.
- TCP/IP is not as fast as NBF on small LANs. The TCP/IP driver in Windows NT
3.1 was significantly slower than NBF on a local area network. However, the
re designed TCP/IP in Windows NT 3.5 is only slightly slower than NBF.
- NWLink is not as fast as NBF on small LANs. The NWLink driver in Windows NT
3.1 was significantly slower than NBF on a local area network. However, the
re designed NWLink in Windows NT 3.5 is only slightly slower than NBF.
- IPX/SPX protocols have some significant performance limitations in a routed
(wide-area) network, which is why Novell has been modifying them with "packet
burst" and "SPX II" changes.
- IPX is only slightly faster than TCP/IP for file and print operations, and
only slightly slower than TCP/IP for application services.
Application Programming Support
- NBF enables NetBIOS, Named Pipes, Mailslot, NetDDE, RPC over NetBIOS, and RPC
over Named Pipes programming using NBFP. NBF does not support Sockets or RPC
over Sockets programming.
- TCP/IP enables Sockets and RPC over Sockets application programming over TCP
and UDP. TCP/IP also enables NetBIOS, Named Pipes, Mailslot, NetDDE, RPC over
NetBIOS and RPC over Named Pipes programming over NBT.
- IPX enables Sockets and RPC over Sockets application programming over SPX and
IPX. IPX also enables NetBIOS, Named Pipes, Mailslot, NetDDE, RPC over
NetBIOS and RPC over Named Pipes programming over NBIPX. IPX supports Socket
IDs for use by Sockets applications and other applications that use IPX
directly. This direct hosting capability allows IPX to realize performance
advantages for small I/O by bypassing NBIPX and calling IPX directly.
API TCP/IP NWLink NBF
-------------------- ------------- ------------- ---
NetBIOS Yes (NBT) Yes (NBIPX) Yes
Named Pipes Yes (NBT) Yes (NBIPX) Yes
Mailslot Yes (NBT) Yes (NBIPX) Yes
NetDDE Yes (NBT) Yes (NBIPX) Yes
Sockets Yes (TCP/UDP) Yes (SPX/IPX) No
RPC over NetBIOS Yes (NBT) Yes (NBIPX) Yes
RPC over Named Pipes Yes (NBT) Yes (NBIPX) Yes
RPC over Sockets Yes (TCP/UDP) Yes (SPX/IPX) No
Other Considerations
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
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Characteristic TCP/IP NWLink NBF
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Industry Acceptance Most popular, Primary protocol Limited to IBM
and Experience especially in in PC networks & Microsoft PC
non PC networks networks
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Open vs. Proprietary Open Proprietary Proprietary,
Specification but published</H3>
Interoperability Available on Available on Limited to IBM
nearly every many platforms & Microsoft PC
platform networks
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Simplicity of Client Can be Simple Simple
Configuration difficult
Simplicity of Can be Simple Simple
Administration difficult
Network Segmentation:
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Differentiates Yes No No
Between Networks
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Hierarchy of Subnets Yes Yes No
within Networks
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Routing Capabilities Native Native No
Name Resolution Requirements:
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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
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Network Traffic:
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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 No
Performance:
------------------------------------------------------------------------
Small LANs Fast Fast Fastest
------------------------------------------------------------------------
File and Print Fast Fastest Fast
Operations
------------------------------------------------------------------------
Application Services Fastest Fast Fast
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References
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- Windows NT 3.5 Concepts and Planning Guide, Chapter 2
- Windows NT Server TCP/IP
- Windows NT Server Solutions for NetWare Networks
- Novell IPX Router Specification, Novell part number 107-000029-001
- IBM LAN Technical Reference, IBM Publications, 39F9353, SC30-3383-03
- Internetworking with TCP/IP, Volumes I and II, by Douglas E. Comer
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Version : 3.1 3.5
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