Topology, Architecture, Standards

1
Topology, Architecture, Standards

• IACT 302
• Corporate Network Planning

2
Topology

• Definition
• science of place
• The way in which constituent parts are
  interrelated or arranged (OED)
• Largely an OSI level 1 definition
• Physical layout

3
Topology

• Bus
• All devices are connected to a central line,
  called the bus or backbone

4
Topology

• Ring
• All devices are connected to one another in the
  shape of a closed loop, so that each device is
  connected directly to two other devices, one on
  either side of it

5
Topology

• Star
• All devices are connected to a central hub.
  Nodes communicate across the network by passing
  data through the hub

6
Topology

• Mesh
• Devices are connected with many redundant
  interconnections between network nodes. In a true
  mesh topology every node has a connection to
  every other node in the network

7
Topology

• Tree
• A hybrid topology
• Groups of star-configured networks connected to a
  bus backbone

8
Network Architectures

• Definition
• The conceptual structure and overall logical
  organization of a computer or computer-based
  system from the point of view of its use or
  design a particular realization of this.
• Architecture
• The art and science of designing and constructing
• The discipline of dealing with the principles of
  design and building
• An understanding of the relationships between
  architectural components of the network

9
Network Architectures

• Both the process and the overall structure,
  logical components, and the logical
  interrelationships of a network
• An architecture is a design, but most designs are
  not architectures
• A single component or a new function has a design
  that has to fit within the overall architecture
• A similar term, framework, can be thought of as
  the structural part of an architecture.

10
Evolving Architectures

• Stand alone mainframes
• Networked mainframes
• Stand alone workstations
• Local area networking
• LAN internetworking
• Internet commercialisation
• Application driven networks
• Remote-access workers
• Home area networking
• Distributed Network Processing
• Grid/Meta computing

11
Component Architectures

• Description of how and where each function of a
  network is applied within that network
• A set of mechanisms
• Internal relationships

12
Component Architectures

• Function
• Major capability of network
• Mechanisms
• Hardware and software that help a network achieve
  each capability

13
Component Architectures

• Function
• Major capability of network
• Mechanisms
• Hardware and software that help a network achieve
  each capability

14
Component Architectures

• Network functions have a common basis in flows
  and this can be used to divide the network
• Commonly used regions include
• Access (edge)
• Distribution
• Core (backbone)
• Demilitarised zones
• External interfaces

15
Component Architectures

• Component architectures include
• Addressing/Routing
• Network management
• Performance
• Security

16
Reference Architectures

• A description of the complete network
  architecture
• Contains
• All component architectures being considered
• Compilation of all internal and external
  relationships

17
Reference Architectures

• Component architectures define internal
  relationships within a function
• Reference architectures combine these components
  and define external relationships between
  components

18
Telecommunications Standards

• A standard can be a set of specifications, or it
  may describe a formula, a physical requirement, a
  protocol or recipe
• Eg. telephones are manufactured with nos.
  0,1.9 and optionally or keys.

19
Standards Categories

• There are 2 categories of standards
• de facto
• (Latin for from the fact ... a matter of fact)
  eg. IBM PC which happened without formal plans
• de jure
• (Latin for by law from the jury) made by
  authorised standards organisationsor by treaty
  among governments

20
International Telecommunications Union (ITU)

• Formed in 1865 when representatives from many
  European countries met.
• The main role of the ITU is standardising
  international telecommunications.
• The UN member countries contribute to the costs

21
ITU continued

• In 1947 ITU became an agency of the United
  Nations (UN) with 3 main sectors
• 1. Radiocommunications Sector (ITU-R)
• 2. Telecommunications Standardisation
  Sector (ITU-T)
• 3. Development Sector (ITU-D)

22
The ITU

• From 1956 to 1993, the ITU-T was known as CCITT
• Comite Consultatif International Telegraphique et
  Telephonique
• Before 1993 recommendations were published in
  hardcopy every 4 years

23
The ITU

• Recommendations since 1993 bear the ITU-T label
• The ITU-Ts task is to make technical
  recommendations about telephone and data
  communications interfaces
• The ITU-T recommendations are technically only
  suggestions that governments can adopt or ignore

24
Internet Standards

• When the Advanced Research Project Agency Network
  (ARPANET) was set up, the US Department of
  Defense (DoD) created an informal standards
  committee to oversee its development (ICCB)
• In September 1984 the committee was renamed the
  Internet Advisory Board (IAB)

25
Internet Standards

• The goal was to keep the Internet moving more or
  less in the same direction
• The name IAB was later changed to be Internet
  Architecture Board
• Each of the IABs 10 members headed a task force
  to provide feedback

26
The Internet

• When a new standard was needed (eg. a new routing
  algorithm) the IAB members would announce the
  change for implementation
• Communication was done by a series of technical
  reports called RFCs (Request For Comments)
• RFCs are stored online and numbered
  chronologically in the order they were created
• http//www.rfc-editor.org/

27
The Internet

• Internet growth has meant that this informal
  process is no longer adequate
• In 1989, the IAB re-organised again
• Researchers were moved into the Internet
  Research Task Force (IRTF)
• Engineers were moved into the Internet
  Engineering Task Force (IETF)

28
The Internet

• Later, the Internet Society (IS) was created
• The idea was to have the IRTF concentrate on
  long-term research

29
The Internet

• The IETF dealt with short-term engineering issues
• IETF issues included OSI integration, new
  applications, security etc
• A more formal standardisation process was also
  adopted - similar to that of the ISO
• See RFC 3160 for some guiding principles
• http//www.ietf.org/rfc/rfc3160.txt

30
Other Telecommunications Standards Organisations

• ECMA - European Computer Manufacturers
  Association
• ETSI - European Telecommunications Standards
  Institute
• ANSI - American National Standards Institute
• NIST - National Institute of Standards and
  Technology
• IEEE - Electronic Industries Association
• CCIR - International Radio Consultative Committee

31
EM Spectrum
C l f
VLF LF MW SW VHF UHF SHF EHF IR VL UV
32
EM Spectrum

• Frequency bands are agreed upon by the ITU, in
  Europe they are handled by the European
  Radiofrequency Office (ERO)
• All frequencies are registered by the
  International Frequency Registration Board
  (IRFB)
• Reflection and interference of radio frequency
  waves used in mobile communications is similar to
  light waves

33
EM Spectrum

• Growth in long wave radio use and the limited
  number of low frequency channels that exist is
  very limited
• Short wave radio signals are reflected by the
  ionosphere and enable a signal to make several
  hops (a multi-hop connection)
• Higher frequencies are not reflected in the
  ionosphere and therefore need to depend on line
  of sight limits

34
Common Bandwidths

• Sometimes called T1 and T3 carrier systems. These
  are relatively old technologies based on copper
  transmission media
• DS124 digital voice circuits of 64 Kbps each.
  DS330 x DS1 links.
• All synchronous transport signal STS-N are for
  optical fiber and has N times the bandwidth of an
  STS-1. STS-N sometimes referred to as an Optical
  Carrier OC-N.

35
Traffic

• Backbone
• Line(s) connecting a LAN to a WAN, or within a
  LAN to span distances efficiently
• Normally a high-speed link
• To carry larger
• Joins workgroup areas together
• A relative term backbone with respect to
  network scale

36
Traffic

• Segmentation
• One way to share resources is across areas that
  define a network or subnetwork
• Separate part of a larger network, represents a
  limited number of host computers, hosts in a
  building or geographic area, or the hosts on an
  individual LAN

37
Traffic

• The goal is to keep backbone traffic to a minimum
  to avoid congesting its capacity
• Keep network load between associated nodes within
  a segmented area
• Eg Dont use the backbone to join a finance
  workstation to the finance printer!

38
Traffic

• Aim for a collection of autonomous systemsthat
  can operateindependently
• eg if the backbone is down you may lose access
  to the Internet, but the staff in a particular
  area can still do local work
• Requires an organisational understanding of the
  company