Chapter 8: LAN System Software

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Chapter 8 LAN System Software

• MIS 3523 Business Data Communications
• Fall 2001
• Dr. Segall

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LAN Software

• 2 Classes of LAN Software (See Figure 8-1,
  p.210)
• 1. Workstation System Software
• 2. Server System Software
• Purpose of System Software
• to insulate applications from hardware details
  (e.g. I/O and memory management).
• Provides an interface through which the
  applications can request hardware services.

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LAN System Software

• 1. Components for Workstation
• Application Programs
• Operating System
• Network Redirector
• Medium Interface Software
• 2. Components for Server
• Server Operating System
• Server System Software
• Medium Interface Software

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LAN System Software in Server and Workstation
Application Program A1
Server Operating System
Network Redirector
Server System Software
Operating System
Disk Drive
Disk Drive
Medium Interface Software
Medium Interface Software
LAN Medium
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System Software Functions

• Hardware
• provides the PHYSICAL connection between
  workstation and server.
• Software
• provides the LOGICAL connection between
  workstation and server.
• Redirector (See Figure 8-2 on pg. 212.)
• The software that reroutes I/O requests before
  they get to the workstations OS.

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System Software Functions

• Multithreading
• the capacity of a server to work on MULTIPLE
  request at once.
• Client/Server Protocol

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LAN Redirector Functions
Application Program A1
Redirector intercepts I/O request and routes
to appropriate software module.
Network Redirector
Operating System
Disk
Medium Interface Software
Network Request
LAN Medium
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LAN Server Request Queue
Server Operating System
Server Disk
LAN System Software
Database Read Write to Printer Download
Application Database Read Write to Printer Write
to Printer
Queue of Waiting Requests
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LAN Workstation Software

• 3 Classes of LAN Workstation Software
• 1. Application Software
• 2. Workstation System Software
• 3. LAN System Software

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Workstation System Software

• 2 Parts of Interface
• 1. With the applications and OS.
• 2. With the network hardware.
• Medium-interface portion of LAN workstation
  software has 2 basic functions
• 1. Placing data onto the network.
• 2. Receiving data from the network.

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SPECIFICS OF SERVER SOFTWARE

• 1. Server OS
• Server software is more complex than workstation
  software because
• Server software is usually multithreaded
• Server software must work well with the hardware.
• INTEGRATED SOFTWARE
• Examples Novell Netware and MS Windows NT
• Advantage can optimize the software for LAN
  operation
• Disadvantage requires writing more complex
  software.

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SPECIFICS OF SERVER SOFTWARE

• 1. Server OS (Continued)
• LAN software that can run under existing OS
• Examples Banyan Vines which runs under UNIX and
• IBM Warp Server which runs under OS/2.
• 2. LAN OS Functions
• I. I/O Optimization
• 1. Disk caching
• 2. Disk seek enhancement (See Figure 8-2 on p.217)

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SPECIFICS OF SERVER SOFTWARE

• II. Fault Tolerance Techniques
• 1. Read-after-write
• 2. Mirrored Disks See Figure 8-4(a) on p. 218
• 3. Redundant Arrays of Independent Disks (RAID)
  See Figure 8-4(b) on p. 218
• 4. Duplex Servers See Figure 8-5 on p. 219
• 5. Clustering

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PRINT SPOOLER

• SPOOL stands for Simultaneous Peripheral
  Operation Online.
• Allows several users to logically write to one
  printer at the same time.
• Redirector directs the request to the server.
• See Table 8-3 for Spooler Options.

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BACKUP SOFTWARE

• See Table 8-4 for Backup Software Capabilities.

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SOFTWARE REQUIREMENTS FOR SHARED USAGE

• 1. Hardware Configuration
• See Table 8-5 for User Configuration Options
• 2. Application Settings
• User sets own application settings to meet
  personal preferences.
• 3. Contention
• Devices compete for control of network medium.
• LAN Software can prevent contention

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User Configuration Options
Default disk drive Default disk directory Disk
drive mappings
Disk drive/directory search paths Printer
mappings Initial program/menu
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SOFTWARE REQUIREMENTS FOR SHARED USAGE

• 3. Contention (Continued)
• One method of preventing contention is the way
  application program opens a file.
• 3 Basic file open modes
• Exclusive open mode only one user has exclusive
  right to open file
• Protected open mode user has secure entry
  procedure to access file
• Shared open mode allows multiple users to have
  file open concurrently.

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SOFTWARE REQUIREMENTS FOR SHARED USAGE

• 3. Contention (Continued)
• See Table 8-6 for Comparison of Open Modes.
• Record Locking and Accessibility See Figure 8-7
  on p. 225.
• Deadlock See Figure 8-8 on p.226.
• 4. Access Security
• LAN Software must provide protection through
  security.

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A Contention Problem
Karen's Application
Karen reads Record A with lock Juan issues a
read request for Record A Record A is locked
by Karen so Juan must wait
Record A
Record A
Juan's Application
Read Record A
Database
Pending Request
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Exclusive, Protected, and Shared Open Combinations
Currently Opened As
Shared Update
Open Mode Requested
Exclusive
Protected
Shared Read-only
Exclusive Protected Shared, update Shared,
read-only
Denied Denied Denied Denied
Denied Denied Denied Granted
Denied Denied Granted Granted
Denied Granted Granted Granted
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Waiting for Lock Release
Application 1
Application 1 reads Record A with
lock Application 2 issues a read request to
Record A Record A is locked by Application 1, so
Application 2 must wait
Record A
Record A
Application 2
Read Record A
Database
Pending Request
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Deadlock Situation
Application 1 has read and locked Record
A Application 2 has read and locked Record
B Application 1 is waiting for Application 2 to
release Record B Application 2 is waiting for
Application 1 to release Record A Application 1
and 2 are deadlocked and will wait forever
Application 1
Record A Record B Locked by A2
Record A
Application 2
Record B
Read Record A
Database
Pending Request
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SOFTWARE LICENSE AGREEMENTS (pp. 227-232)

• License agreement
• an agreement that covers the rules under which
  you are allowed to use a product.
• Types of License Agreements
• Single User, Single Workstation
• Restricted Number of Concurrent Users
• Site License
• Single User, Multiple Workstation
• Server License
• Corporate License

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Software License Agreements

• The license agreement states the conditions under
  which you are allowed to use the product.
• In general, license agreements take one of the
  following forms
• Single-user, single-workstation licenses
• A single-user, single-workstation license
  agreement is the most restrictive. It specifies
  that the software is to be used on one
  workstation only and by only one person at a
  time.
• Single-user, multiple-workstation licenses
• The constraints of the single-user,
  single-workstation agreement are relaxed by the
  single-user, multiple-workstation license
  agreement. It usually relies on the honor system
  for enforcement. The purchase of a single copy
  of the software allows the owner to install it on
  several systems.

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Software License Agreements (cont.)

• Restricted number of concurrent users licenses
• Most LAN-compatible software is designed for
  multiple users however, some software vendors
  limit the number of concurrent users with a
  restricted number of concurrent users license
  agreement. The main idea behind this strategy is
  to charge by the number of users.
• Server licenses
• A server license allows an application to be
  installed on one server. All users attached to
  that server may use the application. If a company
  has several servers, say three, and wants to use
  the application on each of them, the company must
  purchase three licenses or three copies of the
  software.,

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Software License Agreements (cont.)

• Site licenses
• A site license gives the user unlimited rights to
  use the software at a given site. The site may
  be a single LAN or multiple LANs at one location.
• Corporate licenses
• A corporate license gives the corporation
  unlimited use of the software at all locations.
  Some companies restrict a corporate license to
  all locations within one country. Sometimes, the
  right to reproduce documentation is also granted.

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NOVELL OPERATING SYSTEMS (NOS)

• Three Basic Systems
• 1. NetWare 3.x
• Formerly known as NetWare 386
• Uses Sever-oriented bindery
• 2. NetWare 4.x
• Uses Network-oriented Directory
• 3. Personal NetWare (PNW) for small networks

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NetWare 3.x

• Network information database is called the
  bindery.
• Bindery consists of 3 files
• 1. Names of objects
• 2. Properties of objects
• 3. Values associated with properties.
• Supports a Transaction Tracking System (TSS)
  which restores data files of unsuccessfully
  completed transactions.

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NetWare 3.x (Continued)

• Lacks network directory
• Better security capabilities than previous
  version of NetWare 2.x
• Includes Message Handling Services (MHS)

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NetWare 4.x

• Distinguishing feature is network directory
  called Novell Directory Services (NDS). See
  Figure 8-10 for sample directory tree.
• Container Objects are objects that can have
  subordinate objects.
• Leaf Objects are objects that can NOT have
  subordinate objects.

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NetWare 4.x (Continued)

• Partitions distributed portions of directory
• Root Object or Top Unique top level object
  of directory tree.
• Application Program Interface (API) Can be
  used to add new objects or properties to the
  existing objects.

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NetWare 4.x (Continued)

• See Table 8-7 on page 237 for a list of some of
  the available objects and a partial list of their
  properties.
• Security capabilities of NetWare 4.x includes
  those of NetWare 3.x plus
• 1. Ability to audit network activities
• 2. Extension of security to Novell Directory
  Services (NDS)

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NetWare 4.x (Continued)

• Remote Management Facility (RMF) allows an
  administrator to execute console commmands, load
  and unload NetWare Loadable Modules (NLMs).
• NetWare LANalyzer
• an NLM that monitors packets sent to and
  transmitted by a server.
• allows a network administrator identify the type
  and source of protocol problems.

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NetWare 4.x (Continued)

• NetWare 4.x provides interfaces to a variety of
  other networks and protocols. See page 239 for a
  partial list.
• IntraNetWare 4.11 allows Novell servers to
  provide services to both the Internet and
  Intranets.

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MICROSOFTS NETWORK OPERATING SYSTEMS (NOSs)

• OS/2 LAN Manager by Microsoft is similar to
  IBM OS/2 LAN Server.
• Windows NT Server (NTS) a LAN OS software
  which functions as an application server.
• Expected to have a global distributed network
  directory by 2000.
• Prior to introduction of above NTS provided a
  limited directory service called a domain.

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MS NETWORK OPERATING SYSTEMS (NOSs)

• Windows NT Server (NTS) (Continued)
• In the fault tolerance area, NTS supports
• 1. Disk Mirroring
• 2. RAID disk arrays
• Can be installed in High Performance File
  System (HPFS) formats.

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BANYAN VINES

• LAN Software that runs on UNIX-based servers.
• Advantage because many WANs contain nodes running
  the UNIX OS.
• This makes it easier for Banyan Vines systems to
  connect to the WAN nodes.
• One major strength is global naming strategy
  called Street Talk.

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BANYAN VINES

• Street Talk is database that provides Network
  Directory Services (NDS).
• NDS includes identifying network resources

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INTEROPERABILITY OF SERVER SOFTWARE

• Interoperability means the ability of all
  network components to connect to the network and
  to communicate with shared network resources.
• See Table 8-9 on p. 242 for Possible
  Complications of Having Two Network Operating
  Systems (NOSs) in one LAN.

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CHAPTER 8 LAN System Software

• THE END!!!