Networking

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Networking Communication POTS, TDM ISDN
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Telephone Industry

• Optimized for Voice (low delays)
• Digital voice between exchanges
• Analog voice on local loop (95)
• Connection oriented using Circuit Switching
  (point-to-point)
• Full duplex (i.e., bi-directional)
• World-wide standards (top-down)
• Mature industry with its own jargons

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T1 Channel Bank
Analog Voice Lines
Each analog voice line (Channel) issampled
8,000/s (resolution is 8 bits)
125 micro sec.
1 2 3 . . 24
TDM
24 23 22 . . . 3 2 1 F
24 Digital Channelswith Framing bit F.
Channel Bank for 24 AnalogLines with Analog to
Digital Conversion
Local Loop
DS0 8,000x864 kb/s DS1 24 DS0 8 kb/s DS1
1,5368 1.544 kb/s TDM Time Division
Multiplexing
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Digital Switching

• T1 or DS-1 Transmission Frame (US)
• Bit 193 (F) is framing bit, used for
  synchronization
• Voice channels 7-bit PCM, bit 8 is a signaling
  bit
• Data channels bit 8 of Ch 24 is used for
  control(8 kb/s) reducing capacity to 56 kb/s.

125 micro seconds
Channel 1
Channel 2
Channel 24
......
1 2 3 4 5 6 7 8
1 2 3 4 5 6 7 8
F 1 2 3 4 5 6 7 8
193 bits
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Digital Hierarchy (US, EU)

• Carrier Channels Data Rate
• DS-0 1 .064 Mb/s
• DS-1 T1 24 1.544 Mb/s
• DS-2 T2 96 6.312 Mb/s
• DS-3 T3 672 44.736 Mb/s
• E1 30 2.048 Mb/s
• E2 120 8.448 Mb/s
• E3 480 34.368 Mb/s

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Optical Hierarchy

• Optical Electrical Rate
• OC-1 STS-1 51 Mb/s
• OC-3 3 x STS-1 3 x 51 Mb/s
• OC-3c STS-3 155 Mb/s
• OC-12 STS-12 622 Mb/s
• OC-24 STS-24 1.2 Gb/s
• OC-48 STS-48 2.5 Gb/s
• OC-192 STS-192 10 Gb/s
• Note OC and STS circuits are usually used with
  SONET (Synchronous Optical NETwork)

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Signaling

• Signaling is a technical term used the by the
  telephone industry.
• Signaling is a set of protocols and associated
  data exchange for managing the telephone network
• A signal to indicate Off- and On-Hook condition
  of the telephone set
• Transmission of dial tones, busy tones, ringing
  signal, Caller ID service, etc.
• Transmission of inter-exchange data for rerouting
  calls, diagnostics information, etc.
• Transmission business information for billing and
  accounting.

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Inband Signaling

• Inband (or inchannel) signaling transmits control
  signals in the same channel used by the customer
  voice (or data) signals
• Simple but exposed to fraud (red blue boxes)

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Inband Signaling

• Call Set Up
• 20 seconds set-up time
• Less efficient trunk occupancy
• More vulnerable to fraud on the network
• Call Processing Overhead
• Fixed Routing Patterns

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ISDN

• Integrated Services
• Digital Network

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ISDN

• ITU-T Definition
• A network evolved from the telephony Integrated
  Digital Network (IDN) that provides end-to-end
  digital connectivity to support a wide variety of
  services, to which users have access by a limited
  set of standard multipurpose customer
  interfaces.

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ISDN

• BASIS of ISDN
• Total digital communications
• Digital switching (Time Division Multiplexing or
  TDM)
• Out-of-band signaling, common channel interoffice
  signaling (CCIS)
• World-wide acceptance of ISDN standards

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Digital Communications

• Sampling of voice at 8,000 samples/s using Pulse
  Code Modulation (8 bits)
• 64,000 bits/s for each voice channel
• Standard hierarchies of basic voice channels
• Worldwide acceptance of this basic voice channel
  (DS-0)

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Out-of-Band Signaling

• Transmits control signals using the same
  facilities as the voice but a different part of
  the frequency band
• Provides for continuous supervision (less fraud)

Sig
Sig
Office A
Office B
Sig
Sig
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Common Channel Signaling
Office A
Trunks for Voice
Office B
STP
STP
Signal Transfer Points
SP
SP
Signal Point
SS7

• Transmits control signals over dedicated
  signaling links that are common to a number of
  voice channels. Signaling System 7 (SS7) is a
  standard that provides internal control and
  network intelligence for circuit switched
  networks.

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Signaling System 7

• Specified in 1980, updated in 1984 and 1988
• Supports circuit switching and packet switching
  (e.g., X.25 and Frame Relay)
• Conforms to the 7-layer OSI-ISO model
• A very complex piece of software that manages all
  the switches in the telephone network (over 10
  million lines of code)
• Installed in the Signal Point (SP) computer
  network to control the Signal Transfer Point
  (STP) switches which carry all voice and data
  traffic
• Software errors have caused major outages

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Signaling System 7
SP Signal Point STP Signal Transfer Point
STP
SP
SP
SP
SP
STP
SPs are connected to 2 or more STPs STPs are
fully meshed (not drawn)
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Out-of-Band Signaling

• Call Set Up
• 1-3 seconds set-up time
• Maximize trunk utilization
• Highly secure
• Minimal switch overhead
• Flexible design

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ISDN Interfaces

• Basic Rate Interface (BRI)
• 2B D (2x64 kb/s 16 kb/s)
• Primary Rate Interface (PRI)
• 23B D (23x64 kb/s) in the US, Japan
• 30B D ( F) (30x64 kb/s) in Europe
• Broadband ISDN (B-ISDN)
• based on ATM cell switching

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ISDN BRI
2BD Basic Rate Interface
B1 64 Kbps FD Clear
BRI
B2 64 Kbps FD Clear
D 16 Kbps FD Packet
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Basic Rate Service (2BD)

• 2 Independent Bearer Channels (2B)
• Each with a capacity of 64 kbits/s
• Full Duplex (i.e., bi-directional)
• Can be circuit switched and/or packet switched
• Can be combined for 128 kbits/s (if same phone )
• 1 Signaling Channel (D)
• 16 kbits/s for users in packet mode only (e.g.,
  X.25)
• 48 kbits/s for signaling using packet mode
  (LAP-D)
• Full Duplex (i.e., bi-directional)

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ISDN Bearer Services

• Bearer Services
• Interactive Voice, data, or images without
  changing the form of the information (real-time
  communication between two points)
• Bearer services are network transport services,
  used to create, maintain, and close a connection
  and move data
• Teleservices
• Digital telephone, fax, storing voice mail, music
• Security alarm services, telemetry, e-mail,
• Videoconferencing,
• Supplemental Services
• Call transfer, forwarding, call waiting, hold
• Conference calling, third-party service
• Caller Identification and Caller ID blocking
• Credit card calls, reverse charging

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ISDN BRI
Sampling Rate 8,000 per second
8 bit data 64 kb/s
8 bit data 64 kb/s
2 bit packet data 6 bit signaling 16 kb/s packet
data 48 kb/s signaling
Basic Rate Interface
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Basic Rate Usage
Telemedicine
PBX
Resident
Attending Physician
ISDN
PRI
BRI
B1 for Voice B2 for Image D for Data
ISDN LAN Access
Hospital
Home
LAN
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ISDN Primary Rate Interface
B1 64 kb/s FD Clear Channel
B2 64 kb/s FD Clear Channel
Each Primary Rate Interface has 23 B Channels in
the US
PRI
B22 64 kb/s FD Clear Channel
B23 64 kb/s FD Clear Channel
1 D Channel for Signaling no data
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ISDN Primary Rate Interface
23BD 24 Channels 192 bits . . . . . . . . . . .
. . . . . 1,536 Mb/s 1 bit for Framing . . .
. . . . 8 kb/s 193 bits x 8,000 / second
1,544 Mb/s
F Framing Bit
D D Channel (8 bits)
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Primary Rate Service

• USA 23BD
• 23 Independent Bearer Channels (23B)
• Each with a capacity of 64 kbits/s
• Full Duplex (i.e., bi-directional)
• Can be circuit switched and/or packet switched
• can be combined for higher rates
• 1 Signaling Channel (D)
• 64 kbits/s for signaling of all other channels
• Packet mode only (LAP-D)
• Full Duplex (i.e., bi-directional)

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Primary Rate Service in

• Europe 30BDF
• 30 Bearer Channels (30B)
• Each with a capacity of 64 kbits/s
• Full Duplex (i.e., bi-directional)
• Can be circuit switched and/or packet switched
• Can be combined for higher rates (same phone )
• 1 Signaling Channel (D)
• 64 kbits/s for signaling of all other channels
• Packet mode only (LAP-D), Full Duplex
• 1 Framing Channel (F)
• Needed to maintain channel separation and/or
  bonding

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ISDN Addressing

• Country Code (CC) 1 - 3 digits
• National Destination Code (NDC) area code
• ISDN Subscriber Number (SN) depends on country
• NOTE CCNDCSN maximum is 15 digits
• ISDN Sub-address (SA) max 40 digits
• Max digits for CCNDCSNSA is 55 digits
• SA Number could be used to address individual
  devices (or components of larger devices)

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ISDN Architecture
Packets
User
User
Circuits
ISDNSwitch
ISDNSwitch
Permanent Circuits
User-Net Signaling
User-Net Signaling
CC Signaling
User-to-User Signaling