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Contemporary and Emerging Telecommunications Technologies. BAD 64046 29 January 2003. The Telecommunications Revolution. Development of telecommunications services have lagged development of the end devices

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The Telecommunications Revolution

  • Development of telecommunications services have lagged development of the end devices

  • Improvements in connectivity are imperative because data has exceeded voice volume (end of 1990s)

  • Volume of traffic on the Internet doubles every 100 days


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The Analog Network Must Go

  • Has been the staple technology for over 100 years

  • Huge investment in slow, analog, switched voice circuits

  • Present use of the analog network for data is a jury-rig

  • MODEMS are a gross way to adapt to the POTS voice network


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Problems with the POTS Network

  • Analog only

  • Limited (without tricks) to 33.6 Kbps

  • Oriented toward connections that persist for a period of minutes

  • Inefficient for burst traffic patterns

  • All of the network intelligence is centralized at the switches

  • The local loop bottleneck


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Incremental Workarounds to POTS

  • DSL -- uses existing Cu twisted pair, but sophisticated end electronics, to net much higher rates

  • Voice and data on cable TV coax network

  • Wireless local loop technologies


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Evolution of Billing Methods

  • Historically by minute or call count

  • Unmetered flat rate

  • Long distance: time and distance

  • These old methods did not reflect accurate cost accounting

  • New techniques will include:

    • Bandwidth based

    • Traffic based

    • Timed usage

    • Flat rate


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Telecommunications Service Offerings - Overview (1)

  • ATM (Asynchronous Transfer Mode)

    • Connection oriented, packet switching

    • 155Mbps - 2.5 Gbps

  • CLASS (Custom Area Local Signaling Services)

    • Enhanced POTS services

    • Caller ID, call waiting, call forwarding, conference calling


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Telecommunications Service Offerings - Overview (2)

  • Frame Relay

    • Packet switched for city and wide area networking

    • 56/64 Kbps, T1 (1.544Mbps), T3 (44.736Mbps), E1 (2.048Mbps), E3 (34.368Mbps)

  • Personal Communication Services

    • Digital mobile wireless comm systems

    • Use the PCS spectrum allocation


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Telecommunications Service Offerings - Overview (3)

  • POTS (Plain Old Telephone Service)

  • SMDS (Switched Megabit Data Service)

    • Connectionless, provided by LECs to interconnect metropolitan LANs

  • VoIP (Voice Over IP)

    • Digital voice on packet switched networks using the Internet Protocol


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Bandwidth Definitions (1)

  • Broadband

    • Allows rates of 1.544 Mbps or higher

    • Circuits are usually multiplexed

  • Narrowband

    • 64 Kbps or less

  • Wideband

    • 64 Kbps < wideband < 1.5 Mbps


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Bandwidth Definitions (2)

  • Downstream

    • Transmission away from the core network

  • Upstream

    • Transmission toward the core network


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Network Terminology (1)

  • CO (Central Office)

    • The location at which all the circuits in the local loop are switched

  • Circuit Switched Network

    • Dedicated connection established from end to end for the duration of their ”call”

  • Connection-Oriented network

    • Pre-established connection is required

    • All data follows the same path

    • All data is received in same order as transmitted

    • (ATM, for example)


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Network Terminology (2)

  • Digital Subscriber Line (DSL)

    • Uses traditional POTS Cu pairs

    • Voice over the data is sometimes supported

  • Local Loop

    • From the exchange switch (brick building) to your phone

    • Cu twisted pair


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Network Terminology (3)

  • Packet Switched Network

    • Decomposes the bit stream into addressed packets

    • Packets transmitted independently

    • Bit stream is reassembled at the receiving end, into the proper order

    • Utilize bandwidth very efficiently


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Network Terminology (4)

  • PSTN (Public Switched Telephone Network)

    • The existing worldwide circuit-switched telephone network

    • Underlying technology is switching to digital, but the architecture is unchanged

  • Router

    • Store and forward device

    • Connects multiple packet-switched networks running the same protocol


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Network Terminology (5)

  • Switch

    • In packet-switched network: forwards packets to network segments based on hardware addresses of network interfaces

    • In circuit-switched network: establishes a network path between source and destination for the duration of call

    • In PSTN: the central office switch which contains all of the intelligence for the whole network


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Network Terminology (6)

  • SONET (Synchronous Optical Network)

    • An interface standard

    • For fibre optic internetworking of transmission schemes from various vendors

    • Base rate for optical line is OC-1, 51.84 Mbps

    • OC-3 supports 155.52 Mbps


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Network Terminology (7)

  • T-carrier System

    • Aggregates the bandwidth of voice circuits that have been converted for digital

    • Bandwidth is multiples of 64Kbps

    • T1, for example consists of 23 64Kbps channels); T3 has 672 channels

  • Virtual Circuit

    • Predefined path from node to node

    • Supported by a connection-oriented packet-switched network

    • Packets received in order sent


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Telecom Industry Players (1)

  • CLEC (Competitive Local Exchange Carrier)

    • Compete against the incumbents

    • Sometimes have their own local loop infrastructure

  • ILEC (Incumbent Local Exchange Carrier)

    • Still service the majority of local users in the U.S.


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Telecom Industry Players (2)

  • LATA (Local Access and Transport Area)

    • Area around a major city where RBOCs are allowed to conduct business

    • Modified SMSAs

  • IXC (Interexchange Carrier)

    • AT&T, MCI WorldCom, Sprint

    • Carry traffic between telephone central exchanges


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Telecom Industry Players (3)

  • IntraLATA

    • RBOCs restricted to selling only IntraLATA service unless they open their local service markets to competition

    • Only Bell Atlantic, now Verizon, has done so


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Telecom Industry Players (4)

  • Long Distance Service

    • Generally, service across LATAs

    • Sometimes toll service within a large LATA

  • PTT (Post, Telegraph, and Telephone Administration)

    • Government agency responsible for providing postal and telecom services

    • Usually a monopoly

    • Privatized in most countries

    • See http://www.uts.an for example


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Telecom Industry Players (6)

  • RBOC (Regional Bell Operating Company)

    • 1982 consent decree broke up AT&T

    • Seven parent companies formed for the then 22 existing Bell Operating Companies

    • Ours is SBC, formerly Ameritech


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Data Communications Services (1)

  • Private Line Services

    • End to end non-switched persistent connection

    • Only appropriate when cheaper than a switched circuit

    • T1 is most common

    • Fractional T1 is possible

    • Pricing usually fixed monthly; distance sensitive but not usage sensitive


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Data Communications Services (2)

  • ISDN (Integrated Services Digital Network)

    • Circuit switched narrowband or wideband service

    • Provides a digital local loop to the CO

    • Prices for residential service vary widely in U.S. ($30 to $200/month)

    • Usually two 64Kbps “B” channels and one 16Kbps “D” channel

    • The B channels can be multiplexed for faster throughput

    • Widely used for POS and credit card verification because of the persistent connection


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Data Communications Services (3)

  • Frame Relay

    • Preferred by corporate data network users since mid 1990s

    • Packet switching system that builds variable length frames that are then relayed from node to node

    • Advantage is that it can handle many various protocols because of variable length frames

    • Handles delay sensitive data well, but not as well as ATM


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More About Frame Relay

  • Typical connection speeds of 56Kbps up to 1.5Mbps for LAN to LAN connections

  • Up to 45Mbps is possible

  • CIR - Committed Information Rate can be exceeded in small bursts

  • Frame relay can be transported over SONET

  • Uses a combination of Permanent Virtual Circuits and Switched Virtual Circuits


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Still More...

  • Frame Relay is standard in the U.S. for enterprise networks

    • Greatly reduces the need for in-house network engineers

    • Most of the network intelligence is at the vendor

  • Popularity is growing internationally because of the flexibility of the variable frame sizes


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Frame Relay VPN Features

  • Data Services

    • Wide range of connectivity speeds supported

  • Integration of Voice Over Data

  • Service Separation

    • Facilitates coexistence of voice and data services

  • Integrated Billing


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Frame Relay Standards

  • Developed by the Frame Relay Forum

  • Standards dictate how software will be used to combine low speed frame relay links into one faster link


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Data Communications Services (4)

  • ATM

    • Developed in mid-1980s

    • Intended to be a carrier backbone technology

    • Uses fixed length packets called “cells”

    • Low latency supports synchronous demands

    • Can be implemented across backbones, WANs, LANs


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ATM Details

  • Uses 53 byte cells

  • Can be switched by hardware very fast

  • Cell overhead is approximately 10%

  • Carrier ATM services are as fast as 622Mbps

  • MCI WorldCom, Sprint, AT&T, BT, France Telecom all have implemented high speed ATM backbones


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ATM Advantages

  • Traffic integration

    • Isochronous traffic integrates easily with non delay-sensitive traffic

  • Supports very high bandwidths

  • Virtual networking capabilities ease network administration

  • Not widely used yet, as it is overkill except for high end applications such as CAD/CAM and videoconferencing


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Service Level Agreements

  • Contract between vendor and customer

  • Defines measurement methods

  • Provides for penalties

  • Requires:

    • Baselining

    • Scope definition

    • Definition of measurement parameters

      • Mean Time to Install

      • Mean Time to Repair


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ATM and LANs

  • ATM can be used to interconnect LANs

  • Ethernet and Token Ring packets are encapsulated in ATM packets

  • Standard is LANE 2.0 (“LAN Emulation”)


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Data Communications Services (5)

  • POS (Packet Over SONET)

    • SONET uses time division multiplexing to transport data over fiber optics at very high speeds (~40Gbps)

    • POS allows packet data to be sent over a SONET link without the need for the intervening ATM switching layer

    • POS is 99.5% efficient versus only 88.4% for ATM


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Data Communications Services (6)

  • SMDS (Switched Megabit Data Service)

    • Connectionless service

    • Every packet is sent independently of all others

    • No established virtual circuit is required

    • As fast as 45Mbps

    • Primarily used as a niche technique in companies that need multicasting capabilities


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Data Communications Services (7)

  • Internet Based Virtual Private Networks

    • Used to make “tunnels” over private networks

    • The service provider’s network and intervening protocols are transparent to the VPN users

    • A key technology to support Virtual Corporations

    • Better SLAs are needed


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