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The Telephone Network

The Telephone Network. Chapter 3. Basic Call Processing . Call Request. Call Accepted . Conversation Starts. TALKING. Time. Call Termination. Global Telephone Network. Local Exchg sw. Digital Loop Carrier. Int. Exchg SW. Tandem Sw. Network Basics . Components

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The Telephone Network

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  1. The Telephone Network Chapter 3

  2. Basic Call Processing Call Request Call Accepted Conversation Starts TALKING Time Call Termination

  3. Global Telephone Network Local Exchg sw Digital Loop Carrier Int. Exchg SW Tandem Sw

  4. Network Basics • Components • Trunk: connection between central offices • Local Office/Switch: Receives and route call requests; connected to the customer • Tandem Office/Switch: Receives and routes call requests; connected to another office • Technology: type of the circuit established on the trunk • Analog: FDM • Digital: TDM, T-Carriers • Basic Switching technology • Digital (TDM based) / Analog • Routing: can be Intra or Inter-company • To a customer on the same switch • To another tandem switch

  5. T-Carrier Trunks

  6. Basic Call Routing (Intra/Inter Company) Exchange Switch 214-403-4433 Tandem Switch Local Switch Tandem Office Shared Trunk The local switch can route the request three different ways: Local Office Local Office Customer Customer Customer

  7. Definitions • Tandem Switch • An intermediary switch connected to another switch • Trunk • Connection between two offices - a trunk is often shared between multiple users • LATA • Local Access Transport Area • 161 LATA have been defined covering the US, 1981 • Different companies can have point of present (POP) in different LATAs • LEC • Local Exchange Carrier • ILEC • Incumbent Local Exchange Carrier • Refers to 7 RBOCs companies • CLEC • Competitive Local Exchange Carrier

  8. More Definitions • Telco • short form for telephone company. Sometimes it means a local telephone company, such as a Bell operating company or an independent local telephone company. • FG-D • Featured Group D - A protocol which defines interconnection rules between a local exchange carrier (LEC) and an inter-exchange carrier (IEC) such as MCI or Sprint. • Also known as equal access because it guarantees that all carriers are processed equally. • It is also referred to the trunk connection • Inter-exchange carrier (IEC or IXC) • A telephone company that provides connections between local exchanges in different geographic areas. • They're commonly referred to as "long-distance carriers." IXCs include AT&T, MCI, Sprint, and others.

  9. Inter-Company Routing Long Distance Tandem Switch DLC: Digital Loop Carrier – multiplexing channels Tandem Shared Trunk POT: Plane OLD Telephone/ Or Point of Termination End office Switch All wires belong to ILEC ILEC CLEC DLC POT u

  10. Long Distance Routing Different LATA/Diff. Company Toll/ Tandem SW Tandem Featured Group D Trunk Long Distance Network Trunk IXC LD SW IXC LD SW Local Office ILEC Inter-exchange Long Distance SW IXC: Inter Exchange Carrier – must have a point of presence in LATA DLC u IMT (DS3/SONET) IMT: Inter Machine Trunks provided by IXC

  11. Long Distance Routing Different LATA/Diff. Company Toll/ Tandem SW Tandem Featured Group D Trunk Int/LD Distance Network Trunk IXC LD SW IXC LD SW Local Office ILEC Inter-exchange Long Distance SW IXC: Inter Exchange Carrier – must have a point of presence in LATA DLC u IMT (DS3/SONET) IMT: Inter Machine Trunks provided by IXC

  12. Long Distance Calls • A +1 indicates that the call is going to the tandem switch – long distance call • Sometimes a code is used to indicate the long distance company: • 1323 +1 +area code +local number  MCI • Avoided due to equal access law  using they use Featured Group D Trunks

  13. Featured Group D (FG-D) • The FG-D protocol defines interconnection rules between a local exchange carrier (LEC) and an inter-exchange carrier (IEC) such as MCI or Sprint.

  14. Long Distance (international) Calls IMT Inter-exchange Office Inter-exchange Office Tandem Office Tandem Office Local Office Local Office DLC DLC POT POT Inter Machine Trunks

  15. Putting it all together…. Overseas Switch POP POP Switch Switch Switch POP POP Switch Routing is a major issue! POP POP Switched access provided by LEC (DS3)Inter Machine Trunks provided by IXC (DS3/SONET) Inter Machine Trunks connecting switches (DS3/SONET)

  16. Some interesting stuff!

  17. 24 hour period - calls per minute recorded at an IXC switch

  18. Busy hour - calls per minute recorded at an IXC switch

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