Contents of the X25RUL.TXT file
RULES OF THUMB
Link/X.25 is part of the NetWare Link family of internetworking products.
The Link product family provides transparent and reliable LAN-to-LAN
connectivity for NetWare networks using asynchronous, X.25 and high-speed
synchronous communications lines. Each product takes maximum advantage of
the reliability, security, performance and routing features of the NetWare
operating system. Link/X.25 is Novell's multi-point member of the Link
family which connects multiple NetWare LANs through a private or Public
Data Network (PDN). To aid you in configuring Link/X.25 for optimal
performance, reliability and ease of use, we asked our engineers to
recommend components for the router installation. We have also included
some helpful general information regarding LAN-to-LAN links in a wide area
networking environment. Here is what the experts have to say:
WIDE AREA NETWORK CONFIGURATIONS
The optimal LAN-to-LAN configuration is a blend of products that best serve
the economic and performance requirements of the organization. Many
organizations will require a combination of several NetWare Link products
to meet specific needs. Studies show that users typically need to perform
a number of activities over the internetwork, including:
FILE TRANSFER - Uploading and downloading files, for example, between
ELECTRONIC MAIL - An increasingly used tool for communications in large,
geographically distributed organizations.
HOST ACCESS - Most large organizations need to be able to provide users
with access to key applications on mini or mainframe based systems.
DIRECT FILE ACCESS - Real-time manipulation of data on a remote
workstation, file server or mainframe; for example, accessing a centrally
NETWORK MANAGEMENT - The ability to monitor the activity of separate local
area networks and to distribute software and other LAN utilities from a
NETWARE LINK PERFORMANCE CONSIDERATIONS
Each type of data access across the link must be analyzed carefully to
determine the numbers of users transferring data and/or accessing files, as
well as the number of links that must be crossed in order to get the data.
These issues must also be weighed against performance requirements and cost
considerations. These topics are discussed in the Novell report,
Internetworking Your NetWare LANs (479-000046-002), available from your
NetWare reseller, Novell sales office, or by calling the Product
Information Center for Communication Products (800-221-6402 x4410).
GENERAL NETWARE LINK REQUIREMENTS
Link products require a number of separate components for establishing the
LAN-to-LAN link, including the router software, communication adapter, data
communications equipment (such as modems, CSU/DSUs, or data switches) and
the telecommunications service (such as a standard phone line, X.25 line or
leased line). The correct evaluation of user needs and selection of the
above components is necessary for cost-effective and optimal data
Customers purchasing NetWare Link products should work closely with the
telecommunications and/or MIS personnel to identify the types of services
already available in the organization to determine if new services or
devices are required.
THE LINK/X.25 ROUTER
As a general rule of thumb, NetWare Link/X.25 is ideal for organizations
with existing connections to X.25 private or public data networks, or where
X.25 is needed for international access. Electronic mail, host access,
centralized network management and occasional file transfer applications
work well over Link/X.25. Intensive applications that require availability
of high data bandwidth, such as direct file access (including all database
applications) and large file transfers, will require faster wide area
network connections such as T1.
The X.25 protocol overhead used by Link/X.25 and the delay introduced by
the PDN can slow response time. At any given data rate, a point-to-point
connection such as Link/64 or Link/T1 provide higher throughput.
> External Router Only
Link/X.25 operates as a real mode NetWare external router, so you will need
a workstation separate from the NetWare file server to act as the router
PC. The router attaches to either a CSU/DSU or full-duplex synchronous
modem, which in turn connects to the X.25 line.
> Nondedicated or Dedicated Router?
While there are good reasons to run a non-dedicated router (one that
combines the router with a regular user workstation), we do not recommend
this configuration. If, for any reason, the user should reboot the system
or hang the system while running a particular DOS application, all of the
users dependent upon the link could lose important information and hours of
productivity. Used properly, however, a non-dedicated router can be useful
for running network management programs, such as the ECSTATUS program
provided with Link/X.25, which provides information on router status.
Recommendation: If running the router as a non-dedicated router, leave
it in 'console' mode except when running a network management application.
> NetWare Version
Link/X.25 works with NetWare version 2.10 and higher. Note that a router
created from one version of NetWare 2.10 or higher (including NetWare 386)
can accommodate SPX/IPX packets from any other router running NetWare v2.0a
and above, including NetWare 386 v3.x. However, print services may be
disrupted if you mix NetWare v2.0a with later releases of NetWare.
> DOS Version
Link/X.25 is designed to use PC-DOS 3.x.
> NetWare Link Compatibility
Link/X.25 can coexist in the same router machine with Link/64 and Link/T1
but not with NetWare Link/Async or another Link/X.25 router. Of course,
all NetWare Link products can coexist on the same network or internetwork.
> Optimal X.25 Configuration Parameters
Link/X.25 can accommodate packet sizes from 128 to 1,024. We recommend a
packet size of 1,024 for optimal performance. Setting a window size of 7
is also recommended. These parameters may be defined by the PDN upon
> Accessing IBM SNA Mainframes
With a NetWare SNA Gateway installed on your central LAN, NetWare users can
run the NetWare 3270 LAN Workstation software on remote LANs to access
their SNA host across the X.25 links. This eliminates the need for QLLC or
NPSI (IBM Network Packet-Switching Interface) software.
> Macintosh Connections
NetWare for Macintosh will only work at speeds of 19.2 kbit/s or faster.
AppleTalk timeouts may occur if WAN delays are encountered going through
multiple packet switches. The NetWare router (previously known as a
bridge) routes only SPX/IPX packets. Therefore, a NetWare for Macintosh
Service Protocol Gateway must be installed at the same site as the
Macintosh workstations to convert AppleTalk protocols to SPX/IPX before
crossing the router. The NetWare for Macintosh value-added processes
(VAPs) run in protected mode and Link/X.25 runs in real mode, so the VAPs
need to be installed in another external router or file server in order to
> NetBIOS Support
Link/X.25 does not support NetBIOS emulation packets. NetBIOS is only
suited to bridging and routing over high-speed network links such as those
supported by Link/T1. With Link X.25, timeouts occur when transferring
> NetWare Care
NetWare Care allows a network manager to view the network status for the
local LAN. It does not view sessions across the Link/X.25 router. NetWare
Care only recognizes the local router. At this writing, NetWare Care must
be used only with NetWare 2.1x-based file servers.
For the router PC hardware, we recommend you select from one of the tested
machines listed in this booklet. A fast processor is needed for optimal
performance and we recommend at least an AT-compatible 286-based machine.
Link/X.25 needs at least 512K RAM in the router PC. Link/X.25 will also
work in extended memory, protected mode.
> LAN Adapters
The Link/X.25 router also requires a LAN adapter to connect the router to
the network. A list of tested adapters for Link/X.25 is included in this
NOTE: In a 386-based PC, some 'dumb' LAN adapters actually perform faster
than 'smart' LAN adapters that have on-board processors and memory.
> WAN Adapter
You will also need a Novell X.25 Adapter for PC or a Novell X.25 Adapter
for PS/2 to provide the connection to the X.25 communications line.
> Physical Connection
A CSU/DSU or full duplex synchronous modem is required at each router
location. We have listed only the modems tested and certified in our
Novell laboratories. Note that if the CSU/DSU is equipped with a V.35
interface, an RS-232 to V.35 interface converter is also needed.
NetWare Link/X.25 has been tested or certified with the following PDNs.
Canada (Telecom) Datapac
Canada (CN/CP) Infoswitch
United States Accunet
United States Infonet
United States SpiritNet (Telenet)
United States Tymnet
United States CompuServe
Austria Radaus Data
United Kingdom PSS
Hong Kong Datapak
Hong Kong Intelpak
Japan (NTT) DDX-P
RECOMMENDED HARDWARE ENVIRONMENTS
Personal Computers LAN Adapters Modems
Routers Router LAN Adapters
Novell AT 286 (10 MHz) Novell NE/2 Ethernet (MCA) UDS 2425
Novell 386 (16 MHz) Novell NE1000 Ethernet UDS 224 AT/O
Zenith 386 (20 MHz) Novell NE2000 Ethernet*
IBM PS/2 55 SX (16 MHz) Novell RX-NET Arcnet
IBM PS/2 80 (16 MHz) 3COM 3C505 Ethernet
Compaq Deskpro 386/S (16 MHz) 3COM 3C523 Ethernet (MCA)
Compaq 386/25 IBM Token-Ring 4**
IBM Token-Ring 16/4** Standard Micro RX-NET
* These are 16-bit adapter cards and are recommended for optimal NetWare
** Must use IBM LAN Support Program.
NetWare Link/X.25 883-000896-001
Novell X.25 Adapter for PC 905-301928-001
Novell X.25 Extended Adapter 905-302013-001
Novell X.25 Adapter for PS/2 905-301929-001