UTP-based Ethernet LANs may use an Extended Star topology. Clearly explain what such a topology is.

Authors Avatar

CCM 2071 – Network Install and Programming                                 05/04/02

Question 1

UTP-based Ethernet LANs may use an Extended Star topology. Clearly explain what such a topology is. [5 marks]

The star topology is a type of network where a central node performs all switching and routing functions. There are a few problems with this topology in which if the host goes down the whole network does and if there is a large building in which you want to install a network the star topology is not suited as it cannot provide enough coverage for the area to be networked. A solution to this problem is to extend the network by using repeaters in order to avoid the problem of signal attenuation. This topology is known as extended star topology, this consists of more than one star topology connected together by linking the hubs and switches, this will extend the length and size of the network.

This topology is specified by the EIA/TIA – 568 standard which specifies a number of networking media that can be used for backbone cabling. Backbone cabling is cabling that provides interconnections between wiring closets and between buildings that are part of the same LAN and acts as the primary path for traffic that is sent and received from other networks. When repeaters and hubs are used to extend networks they are located in wiring closets. The most centrally located wiring closet is designated as the main distribution facility (MDF), and all other wiring referred to as intermediate distribution facility (IDFs).

Question 2

With reference to 100BaseT using Extended Star topology, investigate what recommendations have to be followed in:

  1. installing cabling.
  2. Connecting nodes and networking equipment such as hubs and switches

Your answer should consider general rules for installing cable, cable lengths, etc. Equipment should include what may, and may not, be connected to segments.  [30 marks]

The 100BaseT is the latest edition to the IEEE 802.3 standard and runs at a data rate of 100Mbps, this option is used where network load is high e.g. systems using multimedia. This is unshielded twisted pair medium, which uses Baseband (Manchester) encoding signalling technique. The properties of this cable resemble 10BaseT, it has the same 0.4 – 0.6mm diameter, and the maximum segment length is 100 metres and by using 4 repeaters the network span of this wire reaches 500 metres.

I’m going to install an extended star topology network in a building with several floors, and each room being 50 metres squared and I will refer my answer to this analogy. When installing an Extended Star network, different cabling is used depending on the type of connection to be made. Wiring closets which contain repeaters or hubs connected together in an extended star topology is known as backbone cabling, this is also given the name, vertical cabling. The backbone cabling consists of backbone cabling runs, intermediate and main cross connects, mechanical terminations and path cords for backbone-to-backbone cross-connections. Horizontal cabling is that which runs from the telecommunications outlet to the IDF, this includes the mechanical terminations in the wiring closet, the patch cords or jumpers in the wiring closet. Other cabling requirements include the media wiring closets on different floors (if we are installing an extended star topology in a building), networking media between the MDF and POP, and networking media used between different buildings if we are making a large network situated in campus.

Join now!

To install horizontal cabling we have two run two cables, for one voice and the other for data, one must be four pair UTP for voice (100BaseT4) they will be connected to two telecommunications outlets or connectors at each work area, I chose 100BaseT4 (100ohm) because it can be segmented up till 100 metres. The second network media could be a 2 pair Cat 5 STP 150 ohm (100BaseTX) with its appropriate connector.  This uses a single Cat 5 pair in each direction, which also minimises EMI from nearby signal pairs (voice) and environmental noise. Also connected to the ...

This is a preview of the whole essay