Transcript File - JNNCE ECE Manjunath

Unit - 1
Overview
Layered tasks
OSI Model
Layers in OSI model
TCP/IP Suite
Addressing
Telephone and cable networks for data transmission,
Telephone networks
Dial up modem
DSL
Cable TV for data transmission.
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Telephone and cable networks for data transmission,
Telephone networks
Dial up modem
DSL
Cable TV for data transmission.
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TELEPHONE NETWORK
Telephone networks use circuit switching. The
telephone network had its beginnings in the late
1800s. The entire network, which is referred to as the
plain old telephone system (POTS), was originally an
analog system using analog signals to transmit voice.
PSTN: Public Switched Telephone Network
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Point-to-Point Network Switching
Circuit Switching
Message Switching
Packet Switching.
Connection-Oriented versus Connectionless
Virtual Circuit versus Datagram Networks
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Point-to-Point Switching
Circuit Switching
Store-and -Forward Networks
• Message Switching
• Packet Switching
• connection-oriented vs connectionless
• virtual circuit vs datagram
Circuit Switching:
Seeking out and establishing a physical copper path from
end-to-end [historic definition] .
Circuit switching implies the need to first set up a
dedicated, end-to-end path for the connection before the
information transfer takes place.
Once the connection is made the only delay is propagation
time.
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Circuit Switching
(a) Circuit switching. (b) Packet switching.
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Store-and-Forward Networks
Intermediate processors (IMPS, nodes, routers, gateways,
switches) along the path store the incoming block of data.
Each block is received in its entirety, inspected for errors,
and retransmitted along the path to the destination. This
implies buffering at the router and one transmission time per
hop.
A store-and-forward network where the block of transfer is a
complete message.
Since messages can be quite large, this can cause:
• Buffering problems
• High mean delay times
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Packet Switching
A store-and-forward network where the block of transfer
is a complete packet. A packet is a variable length block
of data with a tight upper bound.
 Using packets improves mean message delay.
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Packet Switched Networks
Connection-oriented Protocols
• A setup stage is used to determine the end-to-end path
before a connection is established.
• Data flow streams are identified by some type of
connection indicator .
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Packet Switched Networks
Connectionless Protocols
• No set up is needed.
• Each packet contains information which allows the
packet to be individually routed hop-by-hop through the
network.
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Datagram v/s Virtual Circuit
Datagram
• Each datagram packet may be individually routed.
Virtual Circuit
• Virtual circuit set up is required.
• All packets in a virtual circuit follow the same path.
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Event Timing
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Telephone and cable networks for
data transmission
Telephone networks
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Major components of a telephone system
LOOPS, TRUNKS, SWITCHING OFFICES
The connection between end or local central office and the
customer is the “local loop”
The first 3 digits of local telephone number define the office and
the last 4 digits define the local loop number.
Trunks: are transmission media that handle the communication
between offices.
To avoid permanent physical link between any two subscribers
telephone company has switches located in a switching office.
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POTS advantages and disadvantages
Advantages
• Available everywhere
• Reliable connectivity
• Low cost
• Easy setup
Disadvantages
• Only one session per circuit
• FCC limited transmission speed at 53 Kbps
• Most circuits will only reach 44 Kbps due to line
noise
• Analog transmissions only
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Local Access Transport Areas (LATA)
Local Access Transport Areas (LATA): A LATA can be small or
metropolitan area.
Small state have one single LATA and a large state may
have several LATAs
The services offered by common carriers inside a LATA
are called intra-LATA services.
The carrier that handles these services is called a local
exchange carrier (LEC)
Intra-LATA services are provided by local exchange
carriers.
Since 1996, there are two types of LECs: incumbent local
exchange carriers and competitive
local exchange carriers.
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Switching offices in a LATA
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Point of presences (POPs)
The services between LATAs are handled by
interexchange carriers (IXCs)
The connection between Tandem office and IXCs are
point of presence (POP).
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Signaling
The tasks of data transfer and signaling
are separated in modern telephone
networks: data transfer is done by one
network, signaling by another.
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Data transfer and signaling networks
Signal Point: Telephone or computer is connected to SP.
Signaling Network uses nodes called signal transport
points (STPs).
SCP: Service Control Point controls the whole operation
of the signaling network
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Signaling System No.7 (SS7)
Signaling System No.7 (SS7) is a set of telephony
signaling protocols which are used to set up most of the
world’s public switched telephone network (signaling
network) telephone calls.
The main purpose is to set up and tear down telephone
calls.
Other uses include number translation, prepaid billing
mechanisms, short messages service(SMS), and a
variety of other mass market services.
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Types of Signaling
Signaling in Telecommunications Network
Channel Associated Signaling (CAS)
Common Channel Signaling (CCS)
Signaling System Number (SS7) is a form of Common
Channel Signaling.
Channel Associated Signaling (CAS)
Used for In-Band Signaling
Signaling is transmitted in the same frequency band as used
by voice.
Voice path is established when the call setup is complete,
using the same path that the call setup signals used.
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Common Channel Signaling
Out of Band signaling
Employs separate, dedicated path for
signaling.
Voice trunks are used only when a
connection is established, not before.
Faster Call Setup.
Voice Trunks
Switch
Switch
A
B
Signaling Link
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Advantage of CCS over CAS
Faster call setup
No interference between signaling tones by
network and frequency of human speech
pattern.
Greater Trunking Efficiency:- CCS has
shorter call set up and tear down times that
result in less call holding time, thereby
reducing the traffic on the network.
Information Transfer:- CCS allows the
transfer of additional information along with
the signaling traffic providing facilities such as
caller identification and voice or data
identification
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SS7 Principle
Out of band Signaling
Higher Signaling data rates (56Kbps & 64 Kbps)
Signaling traffic is bursty and of short duration,
hence operates in connectionless mode using
packet switching
Variable length signal units with maximum size
limitation
Optimum use of bandwidth
Reliability and flexibility
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SS7 Protocol Stack
OSI
SS7
MTP: Message transport level
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Protocols
Message Transfer Part (MTP Level 1) Physical
• Provides an interface to the actual physical channel over
which communication takes place
• CCITT (Consultative Committee for International Telegraphy and Telephony) recommends
64Kbps transmission whereas ANSI recommends 56 Kbps
MTP Level 2 (Data Link)
• Ensures accurate end-to-end transmission of a message
across a signaling link
• Variable Length Packet Messages are defined here
• Implements flow control, message sequence validation,
error checking and message retransmission
• Monitor links and reports their status
• Test links before allowing their use
• Provides sequence numbers for outgoing messages
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Layers in SS7
Similar to Internet model, is signaling system seven(SS7)
Physical Layer: uses several physical layer specifications
such as T-1 (1.544 Mbps) and DC0 (64kbps)
Data link Layer: provides service such packetizing, packet
header and CRC
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Protocols
MTP Level 3 (Network)
• Message routing between signaling points in the SS7 network
• Signaling network management that provides traffic, links and
routing management, as well as congestion (flow) control
• Re-routes traffic away from failed links and signaling points,
controls traffic when congestion occurs
Signaling Connection Control Part (SCCP)
• Provides connectionless and connection-oriented network
services
• Provides more detailed addressing information than MTPs
• Used as transport layer for TCAP (Transaction capabilities
applications part) based services
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Protocols
Transaction Capabilities Applications Part (TCAP)
Exchange of non-circuit related data
• Between applications across the SS#7 network
• Using the SCCP service
Queries and responses sent between Signaling Switching
Point (SSPs) and Signaling Control Point (SCPs)
Sends and receives database information
• Credit card validation
• Routing information
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Layers in SS7
Network Layer: Provides end to end connectivity by
using the datagram approach to switching .
Routers and switches route the signal packets from the
source to destination
Transport Layer: Signaling connection control points is
used for special services such as 800 call processing
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Layers in SS7
Upper Layers: TUP, TCAP and ISUP. 3 protocols
Telephone User Port (TUP) is responsible for setting up voice calls,
receives the dialed digits and routes the calls.
Transaction capabilities application port (TCAP) provides remote
calls that let an application program on a computer invoke
procedure on another computer
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Services provided by Telephone Networks
Telephone companies provide two types of services:
Analog and Digital
Analog Services
Analog Switched Services
Analog Leased Services
Digital Services
Switched 56/ Service
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Services provided by Telephone Networks
Analog Switched Services:
This is dial up service, signal is of analog and the
bandwidth is of between 0 to 4000 Hz.
Service is normally provided for a flat monthly rate or
charged for each call or a set of call.
800 service: If a subscriber needs to provide free
connections for other subscribers (customers) it request
the 800 service. The call is free for the caller, but is paid
by the callee (Tollfree).
Wide area telephone service (WATS): Outbound call (to
the customer) paid by the organization, charges are
based on the number of calls.
900 Service: Inbound service, call is paid by the caller
and is normally more expensive than a normal call.
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Services provided by Telephone Networks
Analog Leased Service:
Customer can use leased line called a dedicated line.
Permanently connected to another customer. Although
connection passes through the switches in the network,
but switch is always closed, no dialing is needed.
Digital Services:
Switched /56 Service: Digital version of an analog
switched line. Provides data rate up to 56kbps.
Subscribers do not need modems need a device called a
digital service unit (DSU).
Digital Data Service: DDS is the digital version of an
analog leased line, with a maximum data rate of 64 kbps.
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Dial up modem
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DIAL-UP MODEMS
Traditional telephone lines can carry frequencies
between 300 and 3300 Hz, giving them a bandwidth of
3000 Hz. All this range is used for transmitting voice,
where a great deal of interference and distortion can
be accepted without loss of intelligibility.
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Telephone line bandwidth
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Modems
(a) A binary signal
(b) Amplitude modulation
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(c) Frequency modulation
(d) Phase modulation
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Modems
(a) QPSK.
(b) QAM-16.
(c) QAM-64.
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Modems
(a)
(b)
(a) V.32 for 9600 bps.
(b) V32 bis for 14,400 bps.
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Modulation/demodulation
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Modem Standards
V series standards
V.32 and V.32 bis
V.32 bis
V.90
V. 34 bit : Bit rate of 28,800 bps with a 960 point
constellation and a bit rate of 33,600 bps with a 1664
point
V. 90 : Bit rate of 56,000 bps
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The V.32 and V.32bis constellation and bandwidth
V.32 uses
combined
modulation and
coding technique:
Trellis coded
modulation
4 bit and 1 extra
bit for error
detection
32 QAM with baud
rate of 2400.
4*2400=9600bps
V.32 bis uses 128QAM :7 bits/baud
with 1 bit for error
detection
2400*6=14400bps
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Uploading and downloading in 56K modems
In uploading
quantization noise
limits the data rate
to 33.6 kbps
In downloading
data rate is 56
kbps
Sampling rate
8000 and 8 bits
per sample, one
bit is used for
control purpose
8000*7=56kbps
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DIGITAL SUBSCRIBER LINE (DSL)
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DIGITAL SUBSCRIBER LINE
After traditional modems reached their peak data rate,
telephone companies developed another technology, DSL,
to provide higher-speed access to the Internet. Digital
subscriber line (DSL) technology is one of the most
promising
for
supporting
high-speed
digital
communication over the existing local loops.
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DIGITAL SUBSCRIBER LINE
ADSL is an adaptive asymmetric communication
technology designed for residential users; it is not
suitable for businesses.
The existing local loops can handle bandwidths up to 1.1
MHz.
The system uses a data rate based on the condition of
the local loop line.
Twisted pair cable is capable of handling BW up to 1.1
MHz, but filter installed at the end office of the telephone
company which limits BW to 4 Khz, If the filter is
removed entire 1.1 Mhz BW is available.
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ADSL
Asymmetric DSL: provides higher speed (bit rate) in the
downstream direction than in the upstream direction.
Discrete Multitone Technique (DMT): Modulation technique
used in ADSL is called the discrete multitone technique
which combines QAM and FDM.
Available bandwidth is 1.104 MHz is divided into 256
channels, each channel of 4.312 kHz
Voice: Channel 0 is reserved for Voice
Idle: 1 to 5
Upstream: 6 to 30(25 Channels), one for control channel
and 24 channels for data transfer
24X4000(Hz)X15(bits)=1.44 Mbps (Normally below 500
kbps, some channels are deleted )
Downstream: 31 to 255 (225 Ch) 1 Ch for Contr,
224 X4000X15=13.4 Mbps (Normally below 8 Mbps)
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Discrete multitone technique
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Bandwidth division in ADSL
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Customer site: ADSL modem
At the customer site, device is called a digital subscriber
line access multiplexer (ADSL).
ADSL modem modulates and demodulates the data
using DMT, and creates downstream and upstream
channels.
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Telephone Company Site: DSLAM
At the telephone company site, device is called a digital
subscriber line access multiplexer (DSLAM).
Its function is similar to ADSL modem, and in addition it
packetizes the data to be sent to the Internet (ISP server)
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ADSL Lite: (Splitterless ADSL), Downstream is of
1.5Mbps and downstream of 512 kbps
Symmetric Digital Subscriber Line (SDSL)
is a Digital Subscriber Line (DSL) variant with T1/E1-like
data rates (72 to 2320 kbit/s).
It runs over one pair of copper wires, with a maximum
range of about 3 kilometers or 1.86 miles.
The main difference between ADSL and SDSL is that
SDSL has the same upstream data rate as downstream
(symmetrical), whereas ADSL always has smaller
upstream bandwidth (asymmetrical).
However, unlike ADSL, it can't co-exist with a
conventional voice service on the same pair as it takes
over the entire bandwidth.
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HDSL (High bit-rate Digital Subscriber Line:
• Single wire of twisted-pair cable as can be carried on a T1
line (up to 1.544 Mbps) in North America or an E1 line (up
to 2.048 Mbps) in Europe over a somewhat longer range
and is considered an alternative to a T1 or E1 connection.
SDSL (Symmetric Digital Subscriber Line:)
• One twisted pair version of HDSL
• Full duplex symmetric communication upto 768 kbps in
each direction
VDSL (Very High bit-rate Digital Subscriber Line)
• Uses coaxial, fiber optic, or twisted pair cable for short
distances.
• DMT modulation technique is used
• 25 to 55 Mbps for downstream and 3.2 mbps for upstream
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Summary of DSL technologies
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CABLE TV NETWORKS
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CABLE TV NETWORKS
The cable TV network started as a video service
provider, but it has moved to the business of Internet
access.
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Traditional cable TV network
HDSL (High bit-rate Digital Subscriber Line), Head end
receives video signals feeds signal to coaxial cables.
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Hybrid fiber-coaxial (HFC) network
RCH: Regional cable head 400,000 subscribers.
Communication in an HFC cable TV network can be
bidirectional.
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CABLE TV FOR DATA TRANSFER
Cable companies are now competing with telephone
companies for the residential customer who wants highspeed data transfer.
Bandwidth: Coax BW is of 5 to 750 MHz
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Division of coaxial cable band by CATV
Downstream Video Band: 54 to 550 Mhz , Each TV
Channel occupies 6 MHz this can accommodate more
than 80 channels
Downstream Data Band: Occupies upper band, from 550
to 750 MHz, this band is divided into 6-Mhz channels,
64-QAM modulation technique.
Data rate: 6 bits/baud in 64 QAM. 1 bit is used for error
detection 5 bits of data per baud. 5 bits/Hz* 6 Mhz=30
Mbps.
Upstream Data Band: Occupies upper band, from 5 to 42
MHz, this band is divided into 6-Mhz channels, QPSK
modulation technique.
Data rate: 2 bits/baud in 64 QAM, 2 bits/Hz* 6 Mhz=12
Mbps. The theoretical upstream data rate is 12 Mbps
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Cable modem (CM)
Cable modems transfer data across local cable TV lines,
toggling between analog and digital signals with data
transfer rates comparable to DSL.
The cable modem connects a computer to the
cable company network through the same
coaxial cabling that feeds cable TV (CATV)
signals to a television set.
Uses Cable Modem at Home End and CMTS
(Cable Modem Termination System) at Head End.
Characteristics:
Shared bandwidth technology
10 Mbps to 30 Mbps downstream
128Kbps-3 Mbps upstream
Maximum Distance from provider
customer site: 30 miles
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Cable Modems
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Cable modem (CM)
Coaxial TV cable
1 to 10 Mbps download speeds
Up to 2 Mbps upload speeds
Cable connects from NIC to a cable modem, which has
an RJ-45 port
Many users connect a router to the cable modem to
provide access to several PC’s or other network
devices
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Cable modem transmission system (CMTS)
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Cable modem transmission system (CMTS)
Cable TV (CATV) Network serves as the Internet Service
Provider (ISP)
Cable Modem modulates/transmits and demodulates/receives
to/from a CATV channel
Downstream: data received at the modem is communicated
to one or more PCs on a LAN via Ethernet, USB, PCI Bus,
etc.
Upstream: data requests from the PC are transmitted through
the modem to the CATV network via coaxial cable, phone line
or wireless.
CATV data service interfaces to the Internet via Cable Modem
Termination System (CMTS )
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Questions
June/July 2011
With a neat diagram, explain the TCP/IP reference model,
giving brief description of the protocols in each layer.
Differentiate between CM and CMTS
Explain the operation of ADSL using discrete muti tone
modulation indicating the different channels, with a neat
diagram
May/June 2010
Explain OSI model, with a neat block diagram. Consider a
source, destination machine and some intermediate nodes for
discussion.
How addresses employed (used) in internet employing
TCP/IP protocol can be classified
What is DSL technology List different DSLs available. Discuss
salient features of ADSL.
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Questions
December 09/Jan 10
Show the layer representation in the TCP/IP and the OSI model
and explain.
Give a brief overview of SS7 signaling
Match the following functions to the appropriate layers in the OSI
model.
• Dividing the transmitted bit stream into frames
• Determining the route to be used through subnet
• Reliable process to process message delivery
• Accessing the World Wide Web
December 2010
What are the levels of addresses that are used in an internet,
employing the TCP/IP protocol
What are different types of services provided by telephone
networks
Name the major components of a telephone network
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