Topology, Architecture, Standards

Topology, Architecture, Standards IACT 302 Corporate Network Planning

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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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.

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

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

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)

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

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

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)

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

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/

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)

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

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

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

F(Hz) 104107 1010 1014 1016 1022 1024 • Radio Microwave Infrared UV Xray Gamma ray Satellite Fiber optics Coax Terrestrial microwave AM FM TV EM Spectrum C = l f VLF LF MW SW VHF UHF SHF EHF IR VL UV

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

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

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 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.

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

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

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!

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

Topology, Architecture, Standards