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Services for the International Market

Explore a wide range of telecommunication services including PSTN, dedicated analog lines, digital data service, packet-switching networks, and more. Choose the right service based on bandwidth needs, cost, reliability, and connection type. Learn about the limitations of dial-up lines and the advantages of the local loop in the analog network. Discover the strengths and weaknesses of the PSTN and POTS services, as well as dedicated and leased analog line services. Upgrade your communication infrastructure for improved connectivity in the global market.

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Services for the International Market

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  1. Services for the International Market ISOM 591 February 28, 2000

  2. The Players • LEC (local exchange carriers) • SBC http://www.sbc.com/ • Competitive LECs • USLEC http://www.uslec.com/ • IEX (interexchange carriers), long distance carriers AT&T, MCI, Sprint • Worldwide carriers Cable and Wireless, France Telecom, LDDS WorldCom

  3. The Players • Satellite services Hughes Network Systems • VAN providers McDonnell Douglas Network Systems CompanyGeneral Electric Information Systems • International Record Carriers • AT&T, MCI, RCA Global Communications, ITT World Communications • formulated agreements with int’l counterparts to provide end-to-end service • follow the ITU-T guidelines for interconnection

  4. The Players • Public data network services provide end to end communication services regardless of protocols used • Time sharing service providers • Packet switching system services Compuserve offers a packet-based mail service

  5. The Services • Public Switched Telephone Network • dial-up, to 33.3 Kbps, North America • Dedicated (leased) telephone service • to 64 Kbps, North America • Switched/56 Service • 56 Kbps, North America

  6. The Services • Digital Data Service • to 64 kbps, North America • T-DS Carrier Service • to 800 Mbps, Int’l • SMDS (switched multimegabit digital service) • to 655 Mbps, Int’l • Integrated Service Digital Network (ISDN) • to 2,048 Mbps, Int’l

  7. The Services: Carrier Services • SONET • to 13 Gbps, Int’l • FDDI • 100 Mbps, Int’l

  8. The Services • Packet-switching networks • Wireless infrared and radio-wave LANs satellite circuits microwave cellular and PCS

  9. How to Choose? • bandwidth needs • cost • analog or digital • reliability

  10. How to Choose? • wire or wireless • connection-oriented • a logical or physical connection is required before information can be transmitted • ex: voice communication, interative terminal sessions, ATM • connectionless • a logical or physical connection is required before information can be transmitted • ex: file transfer on a network, SMDS

  11. Public Switched Telephone Network (PSTN) • dial-up lines, local loop telephone circuits • CO central office switching • trunk lines • transmission lines

  12. Local Loop • connects the telephone lines from residences or offices to the central switching office (CO) • for a residence, typically an analog line that uses two wires • for a business, typically analog or digital line that uses four or more wires

  13. Local Loop • cablecos now can use coaxial cable as your connection to services • in the future, probably a hybrid of coax (needed to provide power to the telephone) between home and an outside box and fiber from outside box to CO

  14. Why Is Bandwidth Limited on Dial-Up Lines? • twisted pair can support bit rates in excess of 100 Mbps • twisted pair is not the limiting factor, but rather the analog switches originally designed to support 33 Kbps need to transmit analog voice • one solution is upgrade CO switches and handsets to support a digital format like ISDN

  15. Why Is the Local Loop Still Analog? • lower cost • wide availability • digital signals require expensive repeaters when travelling over standard telephone wires • still adequate for voice communication which far exceeds the transmission of data at the current time

  16. Public Switched Telephone Network (PSTN) • Strengths • inexpensive • most widely available • extensive base of installed twisted-pair wiring • Weakness • limited bandwidtth • analog needs a modem to carry digital data • Transmission Medium • two-wire twisted pair, four-wire twisted pair, cable

  17. Public Switched Telephone Service POTS (plain old telephone service) • can be used to move graphics and multimedia if you are willing to wait! • POTS includes the local loop telephone circuits which currently connect customers with central offices • local loops may be replaced with wireless or coax already run by cable companies

  18. Dedicated or Leased Analog Line Service • need for higher speed and more reliable lines • hard-wired dedicated links between customers’ locations • configured to support point-to-point or multipoint service

  19. Dedicated or Leased Analog Line Service • permanent circuit • voiceband (3 Khz), bit rates exceeding 100 Kbps • wideband supports higher bandwidth and bit rates • synchronous transmission • conditioned lines

  20. Dedicated or Leased Analog Line Service • Strengths relatively inexpensive, available more reliable than PSTN allows synchronous and asynchronous transmission • Weaknesses inflexible and upgrades require changes in the central office billed for the entire month

  21. Dedicated Telephone Service • Analog requires modem to convert digital signals • usually four-wire twisted pair, may use fiber optic, satellite and microwave • support full-duplex and dial-in services • reliability guaranteed; conditioned analog lines support speeds up to 64 kbps

  22. Switched/56 Digital Service • digital transmission at 56 Kbps over a leased line or on a dial-up basis AT&T 4ESS and 5ESS, other IEXs, LECs • one time installation charge, monthly service charge, charge for the amount of time the service is used

  23. Switched/56 Digital Service • IEX carrier maintains a local point of presence (POP), so gaining access is similar to regular telephone service • switched CSU/DSU (channel service unit/digital service unit) is used to connect a computer to the switched 56 network • dials out, answers, etc. • DSU (digital service unit) converts the parallel output from the computer into serial signal for the digital network

  24. Switched/56 Digital Service • Strengths access to 56 kbps digital lines with dial-up monthly fee plus usage good for intermittent data transmission needs bandwidth on demand (videoconferencing, multimedia, large file transfers, remote backup, connecting LANs) uses any transmission media available

  25. Switched/56 Digital Service • Weaknesses more expensive than dedicated line on a per minute basis requires a DSU which is more expensive than a modem

  26. Digital Data Service (DDS) • originally an AT&T service, now generally describes a digital service provided by LECs and IEXs • leased digital line circuits that provide direct connection synchronous transmission of pure digital sources • available at over 120 LATAs, serving over 400 cities

  27. Digital Data Service (DDS) • requires a DSU/CSU, like a digital modem • can operate over a twisted pair configuration

  28. Digital Data Service (DDS) • Strengths end to end digital service; first digital service to be offered dedicated, allows the use of more efficient synchronous transfer mode offered by RBOCs and AT&T good for applications which do not require more than 56 Kb/s can operate over a twisted pair

  29. Digital Data Service (DDS) • Weaknesses expensive does not provide bandwidth on demand

  30. T-DS Carrier Service • wideband digital and analog service offered by major carriers • refered to as T or DS-x services • digital more expensive but better noise control, higher bit rates, better management featured

  31. T-DS Carrier Service • channel information (data or voice) is carried within data frames, known as DS-1 signal frames • each DS-1 frame carries 192 bits and one frame control bit • 12 DS-1 signal frame are grouped to form a D4 superframe

  32. T-DS Carrier Service • a DS-0 link is the equivalent of one voice circuit of 64 Kbps • DS-1 is a 1.544 Mbps link usually multiplexed into 24 64 Kbps channels

  33. T-Carrier Services • DS-1 T1 1.544 Mbps 24 channels of 64Kbps DS-2 T2 6.312 Mbps 96 channels of 64 Kbps DS-3 T3 44.736 Mbps 672 channels DS-4 T4 274.176 Mbps 4032 channels

  34. E Services • slightly different in Europe E1 2048 Mbps 30 channels E2, E3, E4 also available in some areas • interconnection generally not a problem

  35. T-Carrier Services • designed to handle 24 voice grade lines • increased capacity over DDS and works with both voice and data • digital service over T lines is called DS (T is the circuit itself, DS is the service)

  36. T-Carrier Services • fractional T-1 and T-3 services allow a business to pay for the amount of bandwidth needed • 56,64,128,256,384,512, 768 Kbps supported • available from long distance and local carriers AT&T, ACCUNET offer a spectrum of Digital Services • a multiplexer (MUX) or DSU/CSU (data service unit/channel service unit) used to connect customer to the services

  37. T-DS Carrier Service • Strengths high bit rates allow voice, data, and multimedia to travel over the same circuits

  38. T-DS Carrier Service • Weaknesses T-services in North America differ slightly from E-services offered in other parts of the world will not run on two-wire twisted pairs does not offer bandwidth on demand

  39. Narrowband ISDN • Strengths integrates voice, data, and multimedia handles both analog and digital signals widely available internationally • Weaknesses some incompatibility problems bit rates limited to 1.544 Mbps relatively expensive

  40. Narrowband ISDN • Basic Rate Interface (BRI) • total bandwidth of 1.44 bpbs divided into one data channel and two B-channels that will carry voice or data • a b channel carries voice or data • a d channel carries signalling and control data • Primary Rate Interface (PRI) • total bandwidth of 1.544 Mbps divided into one data channel and 23 B-channels that will carry voice or data

  41. Broadband ISDN • Strengths provides bandwidth up to 2.5 Gpbs based on standards like SONET, FDDI to avoid incompatibility problems

  42. Switched Multimegabit Digital Service (SMDS) • public high-speed data transmission originally developed by AT&T and the RBOCs to support high-speed public LAN networking • customer premise equipment (CPE) gains access to a SMDS located at a central office using twisted pair wiring at the • T1 rate or optical fiber at the T3 rate • supports WANs and the IEEE 802.6 MAN standard

  43. Switched Multimegabit Digital Service (SMDS) • supports the ability to interconnect geographically dispersed LANs operating at speeds up to 16 Mbps • connectionless service

  44. Switched Multimegabit Digital Service (SMDS) • Strengths considered an on-demand high bandwidth service protocol independent service can use either frame relay or ATM frames • Weaknesses does not fully support isochronous traffic needed for voice and video

  45. Packet-Switched Networks • Strengths • inexpensive form of exchanging files and data • readily available • easy access; just dial phone number of network and send • Weaknesses • not good for continuous signals used in voice, multimedia • analog signals must be converted to travel over this service

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