Topology, Architecture, Standards

IACT 302

Corporate Network Planning

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Topology

• Definition

– ‘science of place’

– The way in which constituent parts are interrelated or arranged (OED)

• Largely an OSI level 1 definition

– Physical layout

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Topology

• Bus– All devices are connected to a central line,

called the bus or backbone

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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

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Topology

• Star– All devices are connected to a central hub.

Nodes communicate across the network by passing data through the hub

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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

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Topology

• Tree– A hybrid topology

– Groups of star-configured networks connected to a bus backbone

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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

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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.

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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

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Component Architectures

• Description of how and where each function of a network is applied within that network

– A set of mechanisms

– Internal relationships

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Component Architectures

• Function

– Major capability of network

• Mechanisms

– Hardware and software that help a network achieve each capability

Function Description of capability Example subset of mechanism

Addressing/Routing Provides robust and flexible connectivity between devices

Addressing: ways to allocate and aggregate address space

Routing: routers, routing protocols, ways to manipulate routing flows

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Component Architectures

• Function

– Major capability of network

• Mechanisms

– Hardware and software that help a network achieve each capability

Function Description of capability Example subset of mechanism

Addressing/Routing Provides robust and flexible connectivity between devices

Addressing: ways to allocate and aggregate address space

Routing: routers, routing protocols, ways to manipulate routing flows

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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

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Component Architectures

• Component architectures include

– Addressing/Routing

– Network management

– Performance

– Security

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Reference Architectures

• A description of the complete network architecture

• Contains

– All component architectures being considered

– Compilation of all internal and external relationships

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Reference Architectures

• Component architectures define internal relationships within a function

• Reference architectures combine these components and define external relationships between components

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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.

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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

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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

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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)

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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

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The ITU

• Recommendations since 1993 bear the ITU-T label

• The ITU-T’s 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

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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)

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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 IAB’s 10 members headed a task force to provide feedback

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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/

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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)

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The Internet

• Later, the Internet Society (IS) was created

• The idea was to have the IRTF concentrate on long-term research

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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

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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

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EM Spectrum

Radio Microwave Infrared UV Xray Gamma ray

F(Hz) 104 107 1010 1014 1016 1022 1024

SatelliteFiber optics

Terrestrial microwave

FMAM

TV

Coax

C = f

VLF LF MW SW VHF UHF SHF EHF IR VL UV

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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

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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

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Common Bandwidths• Sometimes called T1 and T3

carrier systems. These are relatively old technologies based on copper transmission media

– DS1=24 digital voice circuits of 64 Kbps each. DS3=30 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.

Service

DS1

DS3

STS-1

STS-3

STS-12

STS-24

STS-48

Bandwidth

1.5 Mbps

45 Mbps

52 Mbps

155 Mbps

622 Mbps

1.2 Gbps

2.5 Gbps

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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

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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

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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: Don’t use the backbone to join a finance workstation to the finance printer!

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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