Maryanne Morrison

1
Group 10

• Maryanne Morrison
• Amit Ahuja
• Jeff Brown
• Heather Harrison

2
Chapter 15 WAN Implementations

• Discuss the components and workings of IBMs
  Systems Network Architecture
• Describe the problems inherent in international
  networks.

3
Vendor WANs

• Vendor offerings play a major role in network
  implementation and configuration with almost
  every major computer vendor offering networking
  capabilities.
• IBMs Systems Network Architecture has become the
  industry standard

4
Vendor WANs

• Most networks currently being designed on IBM
  mainframe systems use SNA.
• If another vendors equipment interfaces with an
  IBM network it will probably do so via SNA
  interface.
• Most computer manufactures have implemented the
  ability to attach to an SNA network as a type of
  node.

5
Why SNA?

• Before 1974 the implementation f communication
  systems had been somewhat random If a new
  terminal was developed, a new or modified access
  method and data link protocol were likely to
  accompany it.

6
Why SNA?

• Since the 60s IBM has been the leader in
  computer sales and installations.
• By 1974 IBM was offering more than 200 different
  models of communication hardware, 35 different
  device access methods, and more than a dozen data
  link protocols.

7
Why SNA?

• Users in SNA are either people working at a
  terminal or operators console or applications
  that provide services for other programs or
  terminal users.
• SNA was developed to provide communication paths
  and dialogue rules between users. This
  architecture is similar to the OSI reference
  model.

8
SNA Layers

• The early releases of SNA referenced either six
  or four functional layers.
• The discrepancy between a six-layer and a four
  layer definition is explained but the fact that
  layers three through five are sometimes called a
  single layer.

9
SNA

• There are also four distinct hardware groupings
  called physical units.
• The four physical units are numbered 1,2,4,and 5
  with no physical unit currently assigned to
  number 3.
• The hardware configuration consists of IBM or
  IBM-compatible central processing unit,
  communication controllers, terminal cluster
  controllers, and terminals, printers or
  workstations.

10
Logical Units and Sessions

• A logical unit is usually implemented as a
  software function in a device with some
  intelligence such as a central processing unit or
  controller.
• The dialog between the two system users is known
  as a session.

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Logical Unit

• Because a logical unit is the agent of a user,
  when one user wants to establish a session with
  another user, the logical units are involved in
  establishing the communication path between the
  two.

12
Session Types

• Types include a terminal, program to program, or
  terminal to terminal.
• If a terminal wants to retrieve a record from a
  database, the terminal must use the services of
  an application program to obtain the record.

13
Logical Unit Types

• These types are numbered from 0-7 with the
  definition for LU type 5 omitted.
• LU Types refer to session types and not to a
  specific LU.
• Of the 7 LU types all but type 0 and 6 address
  sessions with hardware devices such as printers
  and terminals.

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LU Type 6

• It is defined for program-to-program
  communication. It has evolved through two
  definitions, LU 6.0 and LU 6.1 to its current
  definition LU 6.2 which is a key SNA capability.
  This type is more general and can have wider uses
  than hardware-oriented interfaces.It provides a
  communication path for applications distributed
  over multiple nodes.

15
LU Type 6

• A Program-to-Program interface is more generic
  than a session type involving specific hardware
  devices. In other words other vendors equipment
  can enter into SNA sessions with an application
  process running in an IBM processor as long as
  the communicating program in the vendors
  processor adheres to the session rules.

16
Vendors

• Most vendors have implemented an LU 6.2
  capability for their SNA interface because such
  an interface can be made device independent.
• The International Standards Organization also has
  agreed on a transaction interface that is
  compatible with IBMs LU 6.2 session

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System services control point (SSCP)

• Session - A dialog between 2 users within the
  SNA environment.
• System services control point (SSCP) - A
  supervisor or intermediary is involved in
  establishing a session. In SNA this extremely
  important entity is known as the SSCCP. It
  basically resides in a host processor, which is a
  physical unit type 5. The SSCP is the software
  controlling its host's portion of the network.The
  devices controlled by the host and its SSCP
  represent a domain.

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• Within a given domain the SSCP is the controlling
  entity. It is responsible for the physical and
  logical units within its domain. In fulfilling
  this obligation the SSCP manages its units,
  including unit initialization, maintaining the
  status of individual units, placing units online
  and offline as necessary, and serving as mediator
  in the establishment of sessions.

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• Physical units subordinate to an SSCP must be
  able to carry on a dialogue with the SSCP. To
  accomplish this, a subset of the SSCP
  functionality, called a Physical Unit Control
  Point, resides in SNA nodes that do not contain
  an SSCP.
• A PUCP is responsible for connecting the node to
  and disconnecting the node from the SNA network.

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• Addressing
• For one user to communicate with another , an
  address is required because messages are send to
  a specific unit using its address.
• SNA's addressable unit is known as Network
  Addressable Unit (NAU)
• 2 important properties of NAUs
• Hierarchal in nature
• Can be an SSCP, LU or a PU
• Sub areas - The parts of a domain, consisting of
  a communication controller and all its NAUs or of
  a host /SSCP together with all locally attached
  NAUs.

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• Extended addressing - The 23 bit address
  representing the combination of sub area address
  and unit address that uniquely identifies an NAU
  and allows for a larger number of NAUs in a
  network.

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WAN Implementations

• Communication Between Users
• end-to-end routing is routing for which at least
  one of the nodes must be a type 5 physical unit
  or terminal and the path is determined and
  maintained through the entire session.
• virtual routing has no permanently established
  path each node consults its routing table to
  determine which node should receive the message
  next.

23
WAN Implementations

• Additional SNA Elements and Capabilities
• network control program (NCP) is a data
  communication program that helps manage a
  communication network specifically an IBMs 37xx
  line of controllers.
• advanced communications facility (ACF) provides
  inter-domain communication, improved error and
  testing capabilities and dynamic device
  configuration.
• network performance analyzer (NPA) provides
  performance information for the system such
  lines, buffers, errors, queue lengths and data
  rates.

24
WAN Implementations

• Additional SNA Elements and Capabilities
  (Continued)
• network problem determination aid (NPDA)
  collects, maintains, and reports information on
  error conditions within the network.
• netview, netview/PC and netview/6000 is a network
  management package developed by IBM for open
  systems like SNA.
• SNA distribution services (SNADS) is an SNA
  facility that provides asynchronous distribution
  of documents throughout a network.

25
WAN Implementations

• Additional SNA Elements and Capabilities
  (Continued)
• SNA is continually upgraded and has evolved from
  an IBM-only network architecture to a multiple
  platform inter-network architecture. Other SNA
  capabilities include
• TCP/IP support
• multiple LAN interfaces
• advanced peer-to-peer networking
• distributed database support
• internetworking capabilities

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WAN Implementations

• International Networks
• Data communication networks are not confined to
  national boundaries and many companies have an
  international scope. Some of the problems that
  may be encountered include politics, security,
  regulations, hardware and language.
• Politics - On occasion, politics are the problems
  to be resolved rather than technical issues.
• Security It is possible for data to be
  captured, read and even changed. Data should be
  encrypted with a strong encryption algorithm.

27
WAN Implementations

• International Networks (Continued)
• Regulations A countries communication networks
  are controlled by the postal, telephone and
  telegraph (PTT) authority. The PTT often is a
  government agency with exclusive rights to
  provide communication facilities. The
  regulations sometimes impede the establishment of
  international data communication systems.
• Hardware Several countries require that all or
  part of the equipment used within the country be
  manufactured locally or restrict the equipment to
  a selected group of companies. Power supply is a
  big factor as well.

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WAN Implementations

• International Networks (Continued)
• Language Network managers at different
  locations must be able to communicate to resolve
  differences. Several countries and several
  languages may be involved in solving one problem.
  Such translations may be manual or through
  language translation programs.

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Other Issues

• International Networks
• Involves the coordination of several
  communication providers
• One of the easier methods of creating an
  international network is to use the existing X.25
  networks

• Most public 25 network providers have established
  interconnections and the network implementer need
  not worry with PTT interfaces

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Pricing of an International Network Includes

• Collecting tariff information
• Local as well as international tariffs
• Multiple circuit providers with variable rates
• Variations between long-distance and local rates
• Taxes of data movement over a countries borders
• Taxes on imported software

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International Telecommunications Union (ITU)

• Standards implemented by the ITU as well as other
  international organizations
• OSI
• X.25
• X.400 e-mail interface

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General Agreement on Trade and Tariffs (GATT)

• Organization of 97 nations
• Proposed a treaty that will ease the problems of
  international networks
• Treaty set stipulations regarding the use and
  cost of private lines

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Case Study The Syncrasy Corporation pg. 436

• Network requirements are
• Reliability- high among the major centers of New
  York City, Chicago, Kansas City, and Los Angeles
• Low Cost- lowest-cost for the necessary functions
• A Backbone network was decided
• to be the most efficient.

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• TABLE 15-3 Pg. 436
• Expansion Cities
• Seattle
• Denver
• Hong Kong
• Dallas
• Paris
• Detroit
• Oslo
• Miami
• London
• Mexico City

• Rome
• Boston
• Toronto
• Tokyo
• Philadelphia
• Phoenix
• Montreal
• Sydney
• Washington, D.C.
• Frankfurt

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CHI
NY
LA
KC
FIGURE 15-5 Pg. 437
36
Remaining US Network

• Three primary options were considered
• Leased Media
• Switched Media
• Public Data Network (PDN)
• Distance becomes a factor when determining costs
  for leased and switched connections, it is
  usually not a factor with respect to PDN rates.
  Message traffic affects the connect time for
  switched connections and the packet charges for
  PDN.

37
BOS
SEA
DET
FIGURE 15-6 Pg. 438
CHI
NY
SF
PHIL
DEN
WDC
LA
ATL
KC
PHO
DAL
MIA
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Cost Effectiveness of the Different Medias

• Leased -First 100mi _at_ 2.52/mi 710 mi _at_
  0.94/mi 252 667.40 919.40
• Switched- 3 connections _at_0.60/first min. 247
  remaining min. _at_ 0.40/min 1.80 98.80
  100.60 23days 2313.80
• PDN-(2400)(30,000/128)(1.50/1000)23
  800 (235.001523) 800 8.11 808.11

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Breakeven Analysis

• Connection charge per node 400.00 per month
• Packet charge 1.50 per 1000 packets
• Packet size 128 characters
• X breakeven of characters required per day
• (2400) (x/128)0.001523 919.40
• X 442,991 characters per day

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San Francisco to Los Angeles

• A similar analysis was done on page 440 of your
  text to find that leased lines would be the most
  economical in this particular case.
• In the case of the International lines all
  European cities will be connected by a backbone
  network via X.25 networks. The amount of traffic
  between these entities does not warrant the use
  of leased facilities.

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Maryannes Question

• What is Logical Unit Type 6?

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Amit Ahuja's Question

• What is a Sub area and extended addressing?

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Jeffs Question

• What are some of the factors to consider when
  implementing an international network and
  describe any two?

44
Heathers Question

• What were the three types of media considered by
  Syncrasy Corporation when building their networks
  and describe any two?

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The End