Unit 1 Overview Layered tasks OSI Model Layers

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. 04820 Unit-I introduction 1

Telephone and cable networks for data transmission, Telephone networks Dial up modem DSL Cable TV for data transmission. 04820 Unit-I introduction 2

TELEPHONE NETWORK Telephone networks use circuit switching. The telephone network had its beginnings in the late 1800 s. 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 04820 Unit-I introduction 3

Point-to-Point Network Switching Circuit Switching Message Switching Packet Switching. Connection-Oriented versus Connectionless Virtual Circuit versus Datagram Networks 04820 Unit-I introduction 4

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. 04820 Unit-I introduction 5

Circuit Switching (a) Circuit switching. (b) Packet switching. 04820 Unit-I introduction 6

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 04820 Unit-I introduction 7

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. ð Using packets improves mean message delay. 04820 Unit-I introduction 8

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. 04820 Unit-I introduction 9

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. 04820 Unit-I introduction 10

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. 04820 Unit-I introduction 11

Event Timing 04820 Unit-I introduction 12

Telephone and cable networks for data transmission Telephone networks 04820 Unit-I introduction 13

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. 04820 Unit-I introduction 14

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 04820 Unit-I introduction 15

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. 04820 Unit-I introduction 16

Switching offices in a LATA 04820 Unit-I introduction 17

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). 04820 Unit-I introduction 18

Signaling The tasks of data transfer and signaling are separated in modern telephone networks: data transfer is done by one network, signaling by another. 04820 Unit-I introduction 19

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 04820 Unit-I introduction 20

Signaling System No. 7 (SS 7) 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. 04820 Unit-I introduction 21

Types of Signaling in Telecommunications Network Channel Associated Signaling (CAS) Common Channel Signaling (CCS) Signaling System Number (SS 7) is a form of Common Channel Signaling. Channel Associated Signaling (CAS) Used for In-Band 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. 04820 Unit-I introduction 22

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 A B Signaling Link 04820 Unit-I introduction 23

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 04820 Unit-I introduction 24

SS 7 Principle Out of band Signaling Higher Signaling data rates (56 Kbps & 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 04820 Unit-I introduction 25

SS 7 Protocol Stack OSI SS 7 MTP: Message transport level 04820 Unit-I introduction 26

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 64 Kbps 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 04820 Unit-I introduction 27

Layers in SS 7 Similar to Internet model, is signaling system seven(SS 7) Physical Layer: uses several physical layer specifications such as T-1 (1. 544 Mbps) and DC 0 (64 kbps) Data link Layer: provides service such packetizing, packet header and CRC 04820 Unit-I introduction 28

Protocols MTP Level 3 (Network) Message routing between signaling points in the SS 7 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 04820 Unit-I introduction 29

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 04820 Unit-I introduction 30

Layers in SS 7 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 04820 Unit-I introduction 31

Layers in SS 7 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 04820 Unit-I introduction 32

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 04820 Unit-I introduction 33

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. 04820 Unit-I introduction 34

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 56 kbps. 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. 04820 Unit-I introduction 35

Dial up modem 04820 Unit-I introduction 36

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. 04820 Unit-I introduction 37

Telephone line bandwidth 04820 Unit-I introduction 38

Modems (a) A binary signal (b) Amplitude modulation 04820 (c) Frequency modulation (d) Phase modulation Unit-I introduction 39

Modems (a) QPSK. (b) QAM-16. (c) QAM-64. 04820 Unit-I introduction 40

Modems (a) (b) (a) V. 32 for 9600 bps. (b) V 32 bis for 14, 400 bps. 04820 Unit-I introduction 41

Modulation/demodulation 04820 Unit-I introduction 42

Modem Standards V series standards V. 32 and 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 04820 Unit-I introduction 43

The V. 32 and V. 32 bis 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=9600 bps V. 32 bis uses 128 QAM : 7 bits/baud with 1 bit for error detection 2400*6=14400 bps 04820 Unit-I introduction 44

Uploading and downloading in 56 K 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=56 kbps 04820 Unit-I introduction 45

DIGITAL SUBSCRIBER LINE (DSL) 04820 Unit-I introduction 46

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. 04820 Unit-I introduction 47

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. 04820 Unit-I introduction 48

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 k. Hz 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 24 X 4000(Hz)X 15(bits)=1. 44 Mbps (Normally below 500 kbps, some channels are deleted ) Downstream: 31 to 255 (225 Ch) 1 Ch for Contr, 224 X 4000 X 15=13. 4 Mbps (Normally below 8 Mbps) 04820 Unit-I introduction 49

Discrete multitone technique 04820 Unit-I introduction 50

Bandwidth division in ADSL 04820 Unit-I introduction 51

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. 04820 Unit-I introduction 52

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) 04820 Unit-I introduction 53

ADSL Lite: (Splitterless ADSL), Downstream is of 1. 5 Mbps and downstream of 512 kbps Symmetric Digital Subscriber Line (SDSL) is a Digital Subscriber Line (DSL) variant with T 1/E 1 -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. 04820 Unit-I introduction 54

HDSL (High bit-rate Digital Subscriber Line: • Single wire of twisted-pair cable as can be carried on a T 1 line (up to 1. 544 Mbps) in North America or an E 1 line (up to 2. 048 Mbps) in Europe over a somewhat longer range and is considered an alternative to a T 1 or E 1 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 04820 Unit-I introduction 55

Summary of DSL technologies 04820 Unit-I introduction 56

CABLE TV NETWORKS 04820 Unit-I introduction 57

CABLE TV NETWORKS The cable TV network started as a video service provider, but it has moved to the business of Internet access. 04820 Unit-I introduction 58

Traditional cable TV network HDSL (High bit-rate Digital Subscriber Line), Head end receives video signals feeds signal to coaxial cables. 04820 Unit-I introduction 59

Hybrid fiber-coaxial (HFC) network RCH: Regional cable head 400, 000 subscribers. Communication in an HFC cable TV network can be bidirectional. 04820 Unit-I introduction 60

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 04820 Unit-I introduction 61

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 04820 Unit-I introduction 62

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 128 Kbps-3 Mbps upstream Maximum Distance from provider customer site: 30 miles 04820 Unit-I introduction to 63

Cable Modems 04820 Unit-I introduction 64

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 04820 Unit-I introduction 65

Cable modem transmission system (CMTS) 04820 Unit-I introduction 66

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 ) 04820 Unit-I introduction 67

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. 04820 Unit-I introduction 68

Questions December 09/Jan 10 Show the layer representation in the TCP/IP and the OSI model and explain. Give a brief overview of SS 7 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 04820 Unit-I introduction 69