ch08.htm

this describes managing multivendor networks

is aware of any change in the enterprise.</P>
<P>There are a number of solutions for establishing a global directory:

<UL>
	<LI><I>StreetTalk.</I> One of the earliest directories, StreetTalk is part of the
	Banyan Systems VINES network operating system. The Universal StreetTalk directory
	service is being incorporated in equipment from a number of hardware and software
	vendors, including Cisco Systems, Oracle Corp., and SAP AG. However, until recently,
	Universal StreetTalk required a Vines server; but in order to compete in an increasingly
	tough market, Banyan has decided to unbundle its network services from Vines and
	offer them separately.<BR>
	<BR>
	
	<LI><I>NDS.</I> Novell has now added the same facility for NetWare networks, in the
	NetWare Directory Service (NDS) product.<BR>
	<BR>
	
	<LI><I>Windows NT 5.0.</I> Microsoft joined the fray late in the game, but plans
	to add global directory services in the newest release of Windows NT.<BR>
	<BR>
	
	<LI><I>NIS+.</I> Sun's Network Information Services Plus (NIS+), bundled with several
	different UNIX operating systems, also competes in the global directory market. NIS+
	is based on Sun's older NIS product, which was known as Yellow Pages. NIS+ uses a
	tree-based hierarchical directory, and keeps directories synchronized by transmitting
	only changes. The older version sent the entire directory map in the process of synchronization.
</UL>

<P>Although each of these vendor solutions has proprietary components, they are all
moving toward supporting X.500 as a means of exchanging directory information between
them.</P>
<P><B>X.500 Lite</B> X.500 Lite, also known as <I>Lightweight Directory Access Protocol
(LDAP),</I> presents users with a faster way to get data out of an X.500 directory.
The full X.500 <I>Directory Access Protocol (DAP)</I> is much too processor-intensive
to run on a standard desktop PC. Like DAP, LDAP takes information out of the X.500
directory service in response to queries. However, there are a few differences between
DAP and LDAP that make LDAP much more bandwidth-conscious. With LDAP, there is a
limit on the number of replies that can be returned in response to a query. LDAP
also differs from DAP in that no referrals are allowed. Under DAP, if a server is
unable to fulfill a query, a referral technique enables the search to continue on
other servers. LDAP is easier to implement and use, and several vendors have announced
plans to support the new standard, including Novell, Banyan Systems, Lotus Development
and Netscape Communications.</P>
<P>LDAP supports these operations: search, add, delete, modify, modify RDN, bind,
unbind, and abandon. It does not include the list and read functions found in the
full X.500 implementation; rather, list and read are approximated with the LDAP search
function.</P>
<P>An LDAP database record includes basic information, such as name and e-mail address,
but can also include additional fields, such as address, phone, and public encryption
key. LDAP was created at the University of Michigan under an NSF grant. A consortium
of 40 companies have announced support for LDAP. If this type of support continues,
the dream of an Internet-wide directory might eventually become a reality.


<BLOCKQUOTE>
	<P>
<HR>
<B><font color=#000077>ON THE WEB:</font>http://www.umich.edu/~rsug/ldap/</B>&#160;&#160;LDAP clients
	for several platforms are readily available from the University of Michigan Web site.
	
<HR>


</BLOCKQUOTE>

<H3><A NAME="Heading14"></A><FONT COLOR="#000077">Emulation</FONT></H3>
<P><I>Emulation</I> is a software layer that enables one type of system to run applications
meant for another type of system. Emulation software can display a PC window on a
UNIX workstation screen, enabling the UNIX user to work as if she was working on
a standard PC. Software that does the reverse (that is, it enables a PC to emulate
UNIX) is also available. However, most emulation solutions suffer from sluggish performance
and limited compatibility. There are several commercial emulation packages available.
Some of the popular ones are the Macintosh Application Environment, which is a Motorola
68K emulator; Wabi (Windows application binary interface) from SunSoft (Chelmsford,
Massachusetts); and Insignia Solutions Inc.'s (Inglewood, California) SoftWindows.
Wabi and SoftWindows are x86 emulators that run on UNIX workstations.
<H3><A NAME="Heading15"></A><FONT COLOR="#000077">Middleware</FONT></H3>
<P>Application-to-application communications in a multivendor network can often be
achieved through a new type of software, termed <I>middleware,</I> that sits between
the application and the operating system. Developers can use it to accommodate multiple
protocols, platforms, and languages, and exchange messages between applications.
The goal of middleware is to give users seamless access to applications and data,
regardless of platform or operating system. There are several types of middleware,
including network gateways, Message-Oriented Middleware (MOM), remote procedure calls
(RPCs), object request brokers (ORBs), and transaction processing (TP) monitors.</P>
<P>With <I>RPCs</I>, a client process calls a function on a remote server, waits
for the result, then continues processing after the result is received. This synchronous
model contrasts with the asynchronous techniques used with MOM and TP products, which
queue messages. Synchronous middleware products are used in situations where bi-directional,
real-time communications is essential; asynchronous communications are used where
near-real-time is acceptable and high volume and speed are important.</P>
<P><I>MOM</I> products handle message queuing in one of three ways:

<UL>
	<LI><I>Nonpersistent queuing</I> stores queue data in volatile memory, which increases
	performance, but is at risk of being lost in the event of network failure.<BR>
	<BR>
	
	<LI><I>Persistent queuing</I> is slower than nonpersistent, but more secure. This
	type of queue data is stored on disk.<BR>
	<BR>
	
	<LI><I>Transactional queuing</I> is also disk-based, but includes a mechanism for
	verifying that messages have been received.
</UL>

<P><I>TP</I> monitors can maintain transactions over multiple servers, and are used
in high-volume, critical environments.</P>
<P>Middleware is a vague term, and can have different meanings depending on the situation.
Generally, middleware sits between the client and server, but it can also sit between
the application and the database. Some middleware is based on messaging, while others
are replication-oriented or transaction-oriented.</P>
<P><I>Object request brokers (ORBs)</I> are not strictly middleware, but they might
have a significant impact on the middleware market as the <I>Common Object Request
Broker (CORBA)</I> architecture matures. One limitation of the ORB model is its limitations
in connecting legacy systems to new architectures. Middleware is largely a custom
business, with little available in terms of off-the-shelf, ready-to-run products.
For more about CORBA and object technology, refer to Chapter 13, &quot;Software Considerations.&quot;</P>
<P>Advances in middleware technology are permitting more end users to share information,
regardless of the underlying network and operating system platform. For example,
Teknekron Software Systems, Inc.'s Rendezvous Software Bus works as a communications
software layer, which is able to translate data from different applications into
a common format. Applications wanting to access data from a different application
merely plug into the bus to access data from any source. With tools such as Rendezvous,
it is no longer necessary to establish individual point-to-point links between many
applications.</P>
<P>IBM's MQSeries middleware, a messaging and queuing technology, lets users establish
links between client/server applications and legacy data. IBM has added object-oriented
technology and asynchronous communications features to the middleware, which offers
direct links to legacy TSO, IMS, and CICS packages. It is used to simplify the process
of establishing application-to-application communications links, and permits applications
to communicate asynchronously.</P>
<P>Novell's Tuxedo transaction processing monitor is being positioned as a key middleware
tool for connecting Windows NT, UNIX, and mainframe systems into NetWare networks.
With Tuxedo, developers can create distributed applications that are operating system-independent.


<BLOCKQUOTE>
	<P>
<HR>
<FONT COLOR="#000077"><B>Fitting NetWare for a Tuxedo</B></FONT><BR>
	Novell has established a partnership with BEA Systems (Sunnyvale, California) for
	future development of Tuxedo. The partnership will focus on integrating Tuxedo with
	NetWare. Tuxedo's namespace will be replaced with NetWare Directory Services (NDS),
	which will give NetWare users easy access to dozens of applications and processes
	running on multiple platforms. Under this scenario, a NetWare user could merely click
	an object in the NDS tree that represents a process or application running on any
	server. Consequently, users would no longer have to run live sessions in UNIX, NT,
	and NetWare simultaneously. Tuxedo would instead monitor calls to specific applications.
	
<HR>


</BLOCKQUOTE>

<H3><A NAME="Heading16"></A><FONT COLOR="#000077">SNA-LAN Internetworking</FONT></H3>
<P>As internetworks grow in size and complexity, many corporations are recognizing
the need to integrate legacy data and applications with their LANs. Simply eliminating
mainframes completely in favor of a distributed, client/server environment might
initially sound attractive at first, but can be an enormously complex and costly
procedure, especially if several mission-critical programs and datasets reside on
a mainframe or midrange platform.</P>
<P>IBM has embraced the necessity for integration by enabling NetWare to be integrated
with the AS/400. A new board-level file server for the AS/400 adds NetWare support
to the platform. Previously, the AS/400 could only run IBM's own OS/2 LAN Server
network operating system. Although LAN Server is faster than NetWare, NetWare integration
is an important step because of NetWare's large presence. The addition of NetWare
support will let the AS/400 run business applications perform file and print sharing,
and eliminate costs by cutting out the need for additional PC servers.</P>
<P>There are a number of software options for connecting 32-bit Windows desktops
to mainframe and midrange platforms. Vendors such as Wall Data, NetSoft, and Walker
Richer &amp; Quinn are offering connectivity software for this purpose. Wall Data
is planning Windows 95 and Windows NT versions of the Rumba Office product; IBM is
also getting into the game with the Personal Communications product family, available
for Windows 95. Others include Attachmate's Extra Personal Client 6.0, NetSoft's
NS/Elite and NS/Router, and WRQ's Reflection 3270 and Reflection AS/400. Many of
these products offer much more than plain terminal emulation. Many support OLE 2.0
technology, and offer Windows users direct access to legacy databases.</P>
<P>IBM's 3172 Interconnect Controller Model 390 for the Network Control Program-Multinetwork
Server (3172-390) attaches to a 3745 front-end processor, and is used to off-load
SNA and TCP/IP session establishment routines from the mainframe. This can significantly
decrease WAN traffic, because administrative traffic no longer has to be sent across
the WAN. The 3172-390 can be used as a tool to migrate to APPN. It supports TCP/IP
routing as well as APPN, although this support can also be achieved with IBM's 3746-950.</P>
<P>IBM's front-end processor family, the 3746 Nways Multinetwork Controllers, can
help you with the task of running SNA, AP