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BASIC TELECOMMUNICATIONS

BASIC TELECOMMUNICATIONS . LAN topologies. BASIC TELECOMMUNICATIONS . What is a LAN (Local Area Network): it is a computer network that interconnects computers in a limited area such as a home, school , or office building using network media

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BASIC TELECOMMUNICATIONS

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  1. BASIC TELECOMMUNICATIONS LAN topologies

  2. BASIC TELECOMMUNICATIONS What is a LAN (Local Area Network): it is a computer network that interconnects computers in a limited area such as a home, school, or office building using network media • The defining characteristics of LANs, in contrast to wide area networks (WANs), include their usually higher data-transfer rates, smaller geographic area, and lack of a need for leased telecommunication lines

  3. BASIC TELECOMMUNICATIONS • The network media is the cabling used to support the LAN and makes up the topology • The topology is the physical layout of the cabling infrastructure • There are three basic cabling infrastructures that are utilized to build a LAN, though today there is only one de-facto standard topology for networks

  4. BASIC TELECOMMUNICATIONS • In terms of the historical hierarchy the three basic LAN topologies are; the bus, ring and star • The cable medium used to build these topologies have changed and evolved significantly to support higher transmission speeds as newer technologies are implemented over LANs

  5. BASIC TELECOMMUNICATIONS Bus topologies are the oldest of the three and use a thick coax cable (RG-62, 93 Ω) that network devices tap into N-TYPE connectors VAMPIRE T-TAP

  6. BASIC TELECOMMUNICATIONS The ring topology uses coax cable as well (RG-58, 50Ω) RG-58 with BNC connectors

  7. BASIC TELECOMMUNICATIONS Looking at the bus and ring topologies what do you think is the biggest disadvantage that applies to both of these networks?

  8. BASIC TELECOMMUNICATIONS The star topology uses twisted pair cable and supports telephones, the coax networks don’t support phones

  9. BASIC TELECOMMUNICATIONS • The first cable capable of high speed data transmission with adequately low loss was a coax cable • That is why coax cable was used in the first network topologies • The problem with coax is that it creates a lot of noise that affects the transmitted signal, especially at the higher frequencies needed to support the bandwidth needs of todays networks

  10. BASIC TELECOMMUNICATIONS • Below is a diagram showing the 4 parts of a coax • All of the signal travels down the center conductor which causes high inductance fields (noise), the shielding is used to contain the noise

  11. BASIC TELECOMMUNICATIONS • Because all of the signal travels down the center conductor in a coax cable we call it unbalanced transmission • One significant way to eliminate noise is to use twisted pair cabling, the twists off set the inductance fields and helps to reduce capacitance on the cable

  12. BASIC TELECOMMUNICATIONS • Twisted pair cabling is balanced transmission, two equal but opposite signals, the output is the sum of both signals

  13. BASIC TELECOMMUNICATIONS • Today the TIA/EIA (Telecommunications Industry Association/Electronics Industry Alliance) has developed standards that have been established to ensure optimum network performance that will support future growth and ease of MACs (Moves, Adds and Changes) • The standard that addresses network topology media is the TIA/EIA 568-C; Commercial Building Telecommunications Wiring Standard

  14. BASIC TELECOMMUNICATIONS • TIA/EIA 568-C specifies CAT 5e or CAT 6 UTP or ScTP cable and a star topology, which means all cabling goes back to a central point called the TC (Telecommunications Closet) • In the TC cables are patched to a hub or network switch that performs the traffic control of all the users on the network

  15. BASIC TELECOMMUNICATIONS • The network switch directs users to the central computer in the network called the server, or users are directed to the WAN (Wide Area Network) • The server is where the shared network files are located that all users on the network can access • If users are directed to the WAN, then they’re typically surfing the World Wide Web (WWW)

  16. BASIC TELECOMMUNICATIONS • All of the network topologies that we’ve looked at can be bridged together to build hybrid networks • By now you should be able to identify the 3 different networks in this diagram

  17. BASIC TELECOMMUNICATIONS The star topology not only supports the use of both telephones and computers but can also support any device that can be networked such as: • Scanners • Printers • Wireless access points • CCTV cameras and DVRs • Copiers • VoIP implementations • Smart phones and laptops • Video conferencing

  18. BASIC TELECOMMUNICATIONS • Another network topology that is a hybrid topology is the mesh network • Mesh networks are typically associated with wireless communications and and wide area networks

  19. BASIC TELECOMMUNICATIONS • A Mesh topology Provides each device with a point-to-point connection to every other device in the network • Mesh topologies use routers to determine the best path • Mesh networks provide redundancy, in the event of a link failure, meshed networks enable data to be routed through any other site connected to the network

  20. BASIC TELECOMMUNICATIONS • Because each device has a point-to-point connection to every other device, mesh topologies are the most expensive and difficult to maintain • The PSTN is considered a mesh network on a very large scale and incorporates both wired and wireless communication links for fault tolerant networking

  21. BASIC TELECOMMUNICATIONS • The hierarchal star (tree branch) networks are yet another reiteration of a bus type network Tree/branch or Hierarchal Star

  22. BASIC TELECOMMUNICATIONS • Another topology that was prominent in the mid 80s and into the 90s was the token ring network, which was a theoretical star, physical ring Hermaphroditic connector Type-1 cable

  23. BASIC TELECOMMUNICATIONS • The token ring network developed by IBM and was proprietary was the first step to a star topology using twisted pair cable • In the token ring cables are run back to a central closet like in a star, but they are connected in a ring through token ring MAUs (Multi-Access Units) • It used a twisted pair cable called type-1, which is a two pair, STP, 22AWG cable with an overall braided shield

  24. BASIC TELECOMMUNICATIONS • A fiber optic network used in the WAN is FDDI (Fiber Distributed Data Interface) • FDDI is the standard network topology that utilizes dual counter rotating rings with dual attached stations and dual attached concentrators for fault tolerant networking FDDI Fiber Connector

  25. BASIC TELECOMMUNICATIONS • Here is a FDDI topology with the dual attached concentrators and stations (DAC-DAS) as well as the single attached stations (SAS)

  26. BASIC TELECOMMUNICATIONS • In LANs fiber is used as a backbone cable to support each individual star network as opposed to being a dual ring network This is the preferred network design per TIA/EIA 568-C

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