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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
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
the analog network must go
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
problems with the pots network
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
incremental workarounds to pots
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
evolution of billing methods
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
telecommunications service offerings overview 1
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
telecommunications service offerings overview 2
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
telecommunications service offerings overview 3
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
bandwidth definitions 1
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
bandwidth definitions 2
Bandwidth Definitions (2)
  • Downstream
    • Transmission away from the core network
  • Upstream
    • Transmission toward the core network
network terminology 1
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)
network terminology 2
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
network terminology 3
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
network terminology 4
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
network terminology 5
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
network terminology 6
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
network terminology 7
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
telecom industry players 1
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.

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
telecom industry players 3
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
telecom industry players 4
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 for example
telecom industry players 6
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
data communications services 1
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
data communications services 2
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
data communications services 3
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
more about frame relay
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
still more
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
frame relay vpn features
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
frame relay standards
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
data communications services 4
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
atm details
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
atm advantages
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
service level agreements
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
atm and lans
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”)
data communications services 5
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
data communications services 6
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
data communications services 7
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