Contemporary and Emerging Telecommunications Technologies

1
Contemporary and Emerging Telecommunications
Technologies

• BAD 64046
• 29 January 2003

2
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

3
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

4
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

5
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

6
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

7
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

8
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

9
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

10
Bandwidth Definitions (1)

• Broadband
• Allows rates of 1.544 Mbps or higher
• Circuits are usually multiplexed
• Narrowband
• 64 Kbps or less
• Wideband
• 64 Kbps lt wideband lt 1.5 Mbps

11
Bandwidth Definitions (2)

• Downstream
• Transmission away from the core network
• Upstream
• Transmission toward the core network

12
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)

13
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

14
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

15
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

16
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

17
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

18
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

19
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.

20
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)
• ATT, MCI WorldCom, Sprint
• Carry traffic between telephone central exchanges

21
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

22
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

23
Telecom Industry Players (6)

• RBOC (Regional Bell Operating Company)
• 1982 consent decree broke up ATT
• Seven parent companies formed for the then 22
  existing Bell Operating Companies
• Ours is SBC, formerly Ameritech

24
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

25
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

26
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

27
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

28
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

29
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

30
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

31
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

32
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, ATT, BT, France Telecom
  all have implemented high speed ATM backbones

33
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

34
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

35
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)

36
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

37
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

38
Data Communications Services (7)

• Internet Based Virtual Private Networks
• Used to make tunnels over private networks
• The service providers network and intervening
  protocols are transparent to the VPN users
• A key technology to support Virtual Corporations
• Better SLAs are needed