Transcript ACCESS NETWORKING - CERN | Accelerating science
Dr. Prakash D. Vyavahare Dept. of Electronics & Telecomm.Engg.
S. G. S. Inst. Of Tech. And Science, 23 Park Road, INDORE 452 003 [email protected]
• Introduction • PSTN access • ISDN access • VOIP • Emergence of packet switching networks • BB Access Technologies • ADSL • Conclusions • Bibliography
Introduction Telecomm. Tech. Devp
(chronology) • Telecomm. With Morse code • First Telegraph in India (Cal.) • • ITU established with 20 European countries • Trans-Atlantic cable (US - France) (London - Bombay) • Invention of Telephone by Bell • First manual exchange in India (50 lines, Cal.) • Indian Telegraph Act • Sir J. C. Bose transmits on wireless • Marconi demonstrates wireless (UK - France) • Beginning of Bell company • Lee Deforest develops vaccume tube ampl.
• PABX 1847-1845 1852 1865 1866 1870 1876 1882 1885 1895 1899 1903 1906 1910
• Under ground cable in US • Baird develops picture tube and picture tx. • Hartley introduces concept of information • as a measure of quantity of data in a message • Marconi discovers Microwaves • First co-axial cable manufactured • First SPC computer (ENIAC) • Transistor invented • Shannon’s theorem on channel capacity • Electronic switching • First artificial satellite (USSR Sputnik) 1915 1926 1927 1932 1936 1946 1947 1949 1955 1957
• Kilby at TI invents IC 1958 • Paul Baran of Rand Corp. proposes packet switching 1960 • STD in India (Kanpur - Lucknow) • Paging system, Telstar satellite 1960 1962 • ARPANET using packet switching (TCP/IP) 1964 - 69 • First email on ARPANET • Cellular telephone in Tokyo • IBM - PC + Microsoft - DOS • Portable cellular (Motorola) 1971 1979 1981 1984 • GSM in 13 European countries 1988
• Tim Burner Lee at CERN proposes Hyper-text info. System (Birth of WWW) • Digital mobile network in USA • Indian Telecom. Policy opens for private sec.
1990 1993 1994 • Internet service launched in India • Telecomm. Reg. Authority of India set-up 1995 1997 • GMPCS (Iridium) starts 1998 • Long distance telephony opened for competition in India Lucent, Motorola, Microsoft opens office in India • IT bill passed 2000 • Wireless in Local Loop makes its presence in India 2001 • Net Telephones legally introduced in INDIA 1999 1 April 2002
Brief History of Internet • 1965 • 1969 • 1972 • 1974 • 1979 • 1982 • 1989 • 1992 • 1995 • 2000 • 2002 Packet switching proposed (D. Davis UK, P. Baran US) ARPANET Launched Beginning of E-mail (Tomlinson USA) First article on TCP/IP (Cerf/Kahn) First research lab. Comp. Network (NSF, Univ. of wis) Internet defined as TCP/IP connected n/w No. of internet users reach 100,000 and IETF formed WWW released, No. of nodes hits 1 Million VOIP comes to market No. of hosts break 300 M, voice traffic crosses over data VOIP takes 13 % of long haul telephone traffic
Digital Divide • In Africa • In India • USA 1 phone per 100 persons 4 phones per 100 persons 2 phones per persons • Email Growth : 1999 2003 3.3 Billion, 11 Billion • 5 Billion people in the world but Only 5 to 6 % of world population has access to internet and percent of them are in industrial world • Africa and middle east has only 1 % of internet users 90
Technology Development (Services)
• Principles of wire/wireless comm., for point to point (or multi-point) developed (modulation, line, source and channel coding) • First stage of switching technology (FDMA, TDMA, Time and space switch) • Second stage of switching technology (packet switching, Network management, optical fibers multiple services (Multi-media - voice, data, fax, video) • Selection of the appropriate technology for accessing the core network by end user for multiple services with economy and QOS becomes main issue)
• Core Network : Combination of switching centers and transmission systems connecting switching centers.
(In India core network, till now, extended up to national boundaries, now the core networks of various TELCOs will be connected by the inter-exchange networks) • Access Networks : The portion of public switched network that connects access node (edge of access n/w) to the individual subscriber Access network in India is predominantly twisted copper wire (approx. 750 million of copper lines in the world)
• Access Nodes (Access Network Interface or ANI) • Concentrators of individual lines to T1/E1 • Cellular antenna sites • PBX • Optical Network Units • Cable TV
Various Access Options
• Narrow band – PSTN based access – ISDN based access – Cellular based (Cellular digital packet data) – PLCC based • Broad band – xDSL – Cable modems – Fixed wireless – FTTx (PON)
Traditional Local Loops
• In 1970’s – Residence to CO by copper line carrying analog voice/data (CO interconnected by T1/E1 or microwaves) – Business Premises PABX connected to CO by number of lines for carrying analog voice/data • In 1980’s – Residence to RLU by copper wire carrying analog voice/data or Digital voice (ISDN), RLU to CO by OFC – Business premises PABX to MUX on digital trunk lines like T1/E1 (Mux to CO by T3/E3) – Some business houses also use satellite links
Local Loops (cont.)
• Residence to power line company center on electric wire • Fiber to the home or cabinet (FTTH/FTTC) – Residence to ONU on twisted pair/ co-axial/fiber – ONU then connects to optical MUX/DEMUX • Business PABX connects to a MUX switch by trunk lines which connects to the SDH/SONET optical ring
Digital transmission Hierarchy
US A Na me Call s Rat e DS0 1 ( Mbps) . 064 DS1 24 1. 544 DS2* DS3 DS4* 96 6. 312 Na me Eur ope/Indi a Call s Rat e CEPT1 30 CEPT2 120 672 44. 736 CEPT3 480 2. 048 8. 448 34. 368 4032 274. 176 CEPT4 1920 139. 264
SDH/SONET Multiplexing Hierarchy
• Multiplexing Level • 1 2 3 4 5 6 8 9 10 Data Rate (MBPS) 51.84
USA Name OC-1 OC-3 OC-9 OC-12 OC-18 OC-24 OC-36 OC-48 OC-192 European Name Undefined STM-1 STM-3 STM-4 STM-6 STM-8 STM-12 STM-16 STM-64
Internet Access to Home (PSTN Modems)
• The Client work station connects to modem which is connected through the PSTN twisted pair to CO and finally to the modem pool at the server • PSTN MODEM STANDARDS – V.21/Bell - 301 – V.32
– V.90, V.92
300 baud, FSK, 2-wire, async 9600 baud, QAM with trallis FEC and Echo cancellation 28000 baud ISDN 64/128 Kbps With error correction and compression 56 Kbps voice band modem 100 Kbps leased line baseband modem 2 wire and 4 wire
Shannon’s theorem on channel capacity
• C <
log (1 + S/N) . 2 • For B = 4 KHz and S/N = 30 dB C = 40 KBps approx.
• • Assumption AWGN, • Modulation Technique and Coding technique not defined • Cross talk and ISI are major issues in PSTN lines
Issues in PSTN based access to Internet
• Slow connect time to server (via local switch) (Not suitable for on-line transaction processing) • Low band width • Cost of connect time on PSTN even when not being used for data transmission • Not suitable for many high BW applications like video conferencing, Bulk file transfer etc.
Accessing Network using ISDN
• Digital Network Access – Networks are digital – Services are integrated – Two types of access • (One for home and another for business (PABX)) – Considerable economy in terms of access time and ease in operation and maintenance
• Uses two wires (basic access) or 4 wires (primary access) for getting connected to the central office digital switc • ISDN based equipment (TE!) can be directly connected to the network Terminator • Non-ISDN based equipment (TE2) can be connected via Terminal Adapter (TA) • Network Terminator - 2 (NT2) can connect multiple number of equipments • Various ISDN reference interfaces R, S, T, U for interfacing between NT1/2, TA and TE1/2
ISDN Services & Access Network Interface (ANI) structure
Int erface St r uct ure Us er dat a rat e Tot al bit rat e Basi c Access BRI 2B + D( 16) 144 Kbps 192 Kbps Pri mar y Access PRI ( USA) PRI ( Eur ope) 23B + D( 64) 1. 536 Mbps 1. 544 Mbps 30B + D( 64) 1. 984 Mbps 2. 048 Mbps
• Simultaneous voice and data transmission • 128 Kbps delivery rate • Integration of multiple services on single line • cost effective than PSTN • Most local loops can be used without modification • Lower error rate • Faster connect time to server
Voice Over IP (VOIP)
• VOIP is the fastest growing area in comm. Today • Carries voice traffic as data packets over packet switched data networks instead of as asynchronous stream of binary data over a circuit switched TDM voice network • Address and control info of IP packet carries voice to dest.
• Convenient to talk with multi-media PC • VOIP on LAN is convenient since no additional resources are needed (PC should be on all the time) • Saves resources as against circuit switched network • Economical and with reduced maintenance cost • Alternatively : voice enabled cable modem, or DSL boxes
Steps Involved in VoIP
• Analog voice digitized at 8 K samples per second generating 64 Kbps bit stream, non-linear ADC, A-law (India) • Digital filtering to remove line echo, remove silence period, time stamping, (add comfort noise at the rx end ) • Voice frame formation and data compression 64 Kbps compressed to 8 Kbps, 10 msec frame (10 byte data) • IP packet preparation, Real-time Transport Protocol (RTP) with 12 byte header, 8 byte UDP header, 20 byte IP header • IP packet transmission on internet (hubs, switches, routers) • Steps 1 to 5 are executed in reverse order at the rx. end
End-to-end VoIP packet latency (Delay)
• Delay source Typical values in msec. Recording (in PC) Encoding (codec) Compression -- 10 - 40 5 - 10 5 - 10 Internet delivery Jitter buffer De-compression Decode 70 - 120 50 - 200 5 - 10 5 - 10 -------------------------------------------------------------- Average delay 150 - 400 msec
PSTN v/s VoIP
• PSTN delay is less than 30 msec across globe, VoIP delay is approx. 150 msec • QOS (delay) and QOV are variable and not guaranteed • PC should be on all the time • Annoying echoes due to larger delays (echo suppression can not be used, complex echo cancellation need to be used) • Larger overhead per packet • Much lower monthly is the main motivating factor
• Application • P, S, T • Network • Data link • Physical
ftp, mail protocols sw, speech coders TCP, UDP, RTP, RTCP, SNMP IP, ICMP, X.25
Ethernet LLC, MAC 10baseT ATM, Frame relay HDLC, LAPB V.34, 90 ISDN U, S, T int.
SLIC codec LAN ISDN, WAN POTS
QOS in Internet networks
• QOS is a measure of how quickly and reliably the data is transferred from source to the destination.
(data : Time sensitive financial transactions, still images, larger data files, voice, video) • How to quantify and measure QOS • Each service may require different types of QOS • Subscriber Lease Agreement (SLA) must mention how QOS will be measured, conveyed to the customer, and what are the compensation clauses if it is not met.
5 Important performance of QOS
• Availability 100 % theoretically, 99.8 (90 minutes down time per month) 99.9999 (2.6 secs/month) • Throughput (is not maximum capacity of the network) – Sharing network lowers throughput – Overhead of extra-bits per packet reduces the effective transfer rate – The service provider must guarantee minimum rate of throughput for an application
• Packet loss Buffered queues get overflow or errors Retransmission adds delay – Normal value of less than 1 % average delay per month • Latency (Delay) – PSTN less than 30 msec, – Internet 150 msec (digitizatin, compression, queuing ) • Jitter – – – Variation in queue length Variation in processing time Time to re-order segmented packets
Sensitivity of data types to QOS on internet • Traffic Type Bandwidth Loss delay Jitter Voice E-commerce (Transactions) Very low Low Med.
High High Med.
High E-mail Telnet Low Low Low Low Serious Browsing Low FTP Video conf.
High High Medium High High High Low Med.
High High High Low Low Low High Med.
• IP • TCP • UDP • ATM • Soln :
Provisions for QOS
Best effort, no guarantee on delivery or delay Checks for sequence number of rx. Packet and requests for retransmission (slow) Runs faster than TCP Extensive provisions for QOS tags IPV-6, IP over ATM, Edge routers
Broadband Access Technologies
• xDSL Technologies (Digital subscriber line) • CATV Technology • Fiber To The Home/Cabinet (FTTx) Technology • Wireless access • Satellite Technology • Power line Technology
Various DSL Technologies
• IDSL • HDSL • ADSL ISDN based DSL (128 kbps modem banks) High Data rate DSL (T1/E1 speed) earlier DSL Asymmetric DSL (1.5 to 9 Mbps downstream) (16 to 800 Kbps upstream depending on dis.) • UDSL, SDSL • VDSL Unidirectional, Symmetric 12.9 Mbps (4500 ft) - 52.8 (1000 ft) • Uses twisted copper wire, future local loops
• High speed internet access, real-time access on remote LAN • Distance learning (school, colleges, libraries), always on • Video conferencing • Combined voice and high speed data on same line • Video on demand in apartment blocks using VDSL
Advantages of ADSL (over cable or satellite) • Low infra structure investments (shares telephone line) • Can adapt to varying line conditions • As secure as dial-up modem or T1 connection • Asymmetric matches with future internet applications • High dedicated BW (unlike sharing in cable TV) • ADSL switches bypass the telephone switches that are getting overloaded with data traffic • 40 times faster than ISDN and 100 times than 28 K modem
Key features of ADSL
• 4 KHz is reserved for POTS • The high bit rate data is line encoded using efficient and robust line coding techniques like DMT or CAP • Multiplexed at CO by DSLAM (Digital Subscriber Line Access Multiplexor) • Uses DSP techniques for echo-cancellation of Near-End (NEXT) and Far-End (FEXT) cross talk of multi-pair • Line is properly terminated to reduce loading of loop • better UTP category cable used
• CAP - Carrierless Amplitude/phase modulation – a version of QAM in which incoming data modulates a single carrier which is them transmitted, the carrier itself is suppressed • DMT - Discrete Multi-tone – a version of multi-carrier modulation in which incoming data is collected and then distributed over a large number of small individual carriers each of which uses QAM
Wireless Access Techniques
• 2G • 3G 1991 GSM (Digital circuit switched) • 2.5G 2001 HSCSD/EDGE (High Speed Circuit Switched Data) 16 Kbps 192 Kbps 2004 EDGE_2, 3G_IP (ckt + packet) upto 2 Mbps • Broadband wireless access – 13 frequencies allocated by ITU (700 MHz to 40 GHz)
Broadband access in wireless
• Challenges – Spectral allocation and BW limitations – Noise environment and interference • Techniques used – Line coding and error correction coding – Signal processing – Antenna design – TDMA/FDMA/SDMA/CDMA
• Advantages – Bandwidth for large number of users at a site – Growth potential (cost of fiber reducing) – QOS – can directly connect to SDH/SONEt – Topologies : bus, ring or star (Unidirectional) – Access : TDMA, WDMA
• Set-top box interfaces TV at customer premises with cable modem connected by co-axial cable to cable operator • Uses collision resolution protocol (request for mini-slots) • Uses 64 or 256 QAM • 6 MHz channel (30 - 40 Mbps (shared), 450 - 750 MHz • 17 Million cable connections, security is an issue
• Orbit LEO KM Altitude Round 13 trip delay Data rate 1400 MEO 84 nx2 Mbps GEO 10,352 36,000 250 msec 128 Kbps
• The ability to access broadbase contents from internet regardless of physical location is beneficial in increasing productivity through telecommuting • At global level, data comm. Is moving to a single, public networking environment environment with multi-gigabit tx. Rates, optical fiber based SDH (SONET) at physical layer with ease in mux/demux of low data rate traffic in high speed links • (Core networks and transmission between exchanges are capable of carrying high bit rate user data)
• Types of services significantly increased at user premises • Access at high speed from customer premises and QOS is the main issue • Many options : Dial-up, ISDN, cable, ADSL • More options in future : FTTX, satellite, mobile, PLCC • Availability, reliability and economy as deciding factor • No unique solution • Knowledge of access technologies, their QOS and cost and market trends are important in making long term investmens
• `The cost of quality in internet-style networks’ Amitya Dutta-Roy, IEEE spectrum, Sept. 2000 • `Internet Telephony : going like crazy’ Thomsen & Jani, IEEE spectrum, May 2000 • Dr. Dobb’a journal, May 2000 • `An engineering approach to computer networking’ S. Kesav, 1999, Addison wesley • `Telecommunication Transmission systems’ R. G. Winch, 1993, McGraw Hill • `Digital Communications’ Glover and Grant, 1998, prentice Hall
• Telecommunications Network management Aidarous and Plevyak, IEEE press, 2001 • Security for Telecomm. Network Manag.
Rozenblit, IEEE press, 2001 • Fundamentals of Digital Switching McDonald, Plenum press • IP technology: History, current state and prospects Yanovsky, St. Petersburg univ, Russian fed.
• IT and Telecomm. Impact on developing countries W. Luther, FCC, USA • Chaotic electronics in telecomm. Kennedy CRC press • Digital comm. Systems with sat. and fiber optics appln Kolimbiris, Addison wesley, 2001