Lecture 6 Data Communication Service Network Standardization Contents

Lecture #6: Data Communication Service. Network Standardization. Contents l Communication Services in Public 3 Networks 6 l Broadband Telecommunications 13 l Network Services l International Regulation: Service Providers 17 ' Standardization Instances 18 ª Standardization Documents 22 1

The Public Networks l Public networks - public services: l offered by network operators which own given subnet (phone companies, communication satellite owners, TV cable operators, etc. ) paid and used by subscriber (customer) Switched Multimegabit Data Service (SMDS) LANs “backbone” interconnection: 1/27 – – – broadband; switched, long distance network the connection between SMDS and LANs is usually DQDB MAN or short leased phone lines between LANs and SMDS subnet speed ~ 45 Mb/s; peak traffic tolerant and better 2 cost/performance ratio to leased phone lines

The Public Networks - SMDS Øconnectionless packet delivery service 1/28 Øvariable length packets up to 9 k. B user data and Ø 8 B source and destination addresses: 4 bit code + up to 15 decimal digits phone number (country code)+(city code)+(subscriber number) - worldwide identification Øoption: incoming and/or outcoming address screening for private secure communications Øspecial routing procedure for peak user traffic: system counter for each user accumulates unused time for communication and the user has priority for peak communications 3

The Public Networks - X. 25 l X. 25 networks: – interface between public packet-switching networks and the subscribers – connection oriented, based on telephone network: • switched virtual circuit (based on switched line) • permanent virtual circuit (based on leased line) – specified by CCITT – physical layer: X. 21 protocol (digital signaling) or analog interface (variation of RS-232) 4

The Public Networks - Frame Relay l Frame Relay Services: – “virtual” leased phone lines: lower cost than actual leased lines but limited longterm average bandwidth – connection oriented, low cost, high speed (1, 5 Mb/S, higher than X. 25), 1. 5 KB data packets – available virtual channels to multiple sites by 10 -bit address, time shared leased line – low level protocols: • bad frames are just discarded; • detection of transmission errors 5

Broadband Telecommunications l Broadband ISDN Integrated Services Digital Network – unifies all information transfer including existing: • circuit-switched phones • packet switched frame relay and SMDS services • DQDB • cable TV – and arising • multimedia (incl. CD-quality voice) • LAN interconnection • high-speed data transfer services etc. 6

Broadband Telecommunications ATM Asynchronous Transfer Mode l ATM – connection oriented transmission technology – short fixed-size packets - cells: 5 B Header and 48 B Payload 1/29 – cell switching instead of circuit switching provides: • up to Gb/S speed and • flexibility for real-time and non-real-time (but errorfree) communications • digital switching of cells replaces multiplexing 7

Broadband Telecommunications - ATM l l 2 standard speeds: -155 and 622 (4*155) Mb/S : Application: – TV/video – phone services – LAN backbones – client-server distributed processing l Multiple service providers over one communication media 8

Broadband Telecommunications - ATM l B-ISDN over ATM - reference model: 1/30 – 2 planes / 3 layers - user plane (for upper layers tasks) and control plane (connection management) – Physical layer - transparent to ATM cells, specifies the media timing and signaling (copper, fiber, waves etc. ) – ATM layer - specifies the cell header fields, provides cell transport, builds virtual circuits – Adaptation-to-ATM layer transforms upper layer data into ATM cells. Resume of the public 9 network services

Broadband Telecommunications - ATM l ATM sublayers: 1/31 – PMD (Physical Medium Dependent) specifies access and parameters of the transmission media – TC (Transmission Convergence) transformation of cells to bitstream and packing cells from the incoming bit stream – SR (Segmentation and Reassemble) transformation of packets to stream of cells and building packets from incoming cells – CS (Convergence Sublayer) - service interface support: high level data 10 structures, application timing, etc.

Networking Services - Summary 11

Access Network Comparisons Asymmetric Digital Subscriber Line Downstream Data Rate Narrowband Up to 56 Kbps dial-up modems Upstream Data Rate Access System Up to 56 Kbps Normal phone lines ISDN - BRI 56 Kbps to 128 Kbps Normal phone lines with ISDN Terminal Adapters ADSL (broadband) 1, 5 Mbps to 9 Mbps 16 Kbps to 500 Kbps Normal phone lines with ADSL modems Cable modems (broadband) 500 Kbps to 30 Mbps 99, 6 Kbps to 1 Mbps also planning to use 28, 8 Kbps (telecommunication return) Cable TV networks Satellite e. g. 400 Kbps Several possible starndards Wireless transmission 12

Network Services Networks provide communication connections between users and services. Services implement the logical behavior seen by users. Services are mainly Service Logic software situating in the networks elements themselves (embedded services) or in special service nodes (overlay services). l Embedded services are implemented as integral parts in switches, routers and mobile exchanges. Examples of these are Plain Old Telephone Services (POTS), ISDN connectivity and supplementary services, Mobile connectivity services and Intelligent Network services in SSCP network elements. l Overlay services are implemented in external switches or computers which are connected to the existing access or basic networks. Examples of these are Voice and Multimedia services, GSM messaging services and overlay Intelligent Networks. 13 l

Network Services delay (S) 10 10 Electronic Mail Batch Processing Transaction Processing 1 (S) 10 10 ONLINE 10 (m. S) RPC 10 k File Transfer Interactive Multimedia TV HDTVAnimation Voice Compressed VIDEO 100 k 1 M 100 M Virtual Reality speed 1 G 10 G b/S 14

Networks and Services The service provision through networks is usually divided vertically into infrastructure, (value added) services and contents. l – Infrastructure services mean selling generic point to point or multipoint connections “pipes” to the customers. This is a typical product of a public network operator. – Value Added Networks (VAN) are products that provide more complex behavior (called service logic) on the network than simple “pipes”. Electronic mail, WWW and Intelligent Network voice services are value added. Mobile network voice services are often considered generic, but here we would like to consider mobility as a strong added value component. – Content Services are digital information available or sold through networks. The digital (also called multimedia) 15 contents are usually combined with some service logic

Networks and Services The increasing role of value added services and digital contents available through networks will introduce new players: l – Network Operators are the traditional players owning public networks and selling infrastructure and value added services. They may have also content services available e. g. in their Cable TV networks. – Service Providers create and sell value added services on top of the existing networks. Service providers do not usually own complete networks, but may own and operate certain network parts such as base stations. – Content Providers which own digital contents and sell them using also networks as their distribution channels. 16

International Network Regulation - Service Providers l l Common carriers (USA, >2200 approved by Federal Communication Commission: AT&T, Bell, GTE. . . ) National PTTs (government monopoly) ISPs (Internet Service Providers) mostly private Satellite Communication Services Providers - usually divisions of National PTTs (big countries, KPN (the Netherlands), India, etc. ) – TV/Radio broadcasting, – Military/Navy area, – Data Communications • example: Intersat (geostationary orbit) • terrestrial receivers: VSATs (Very Small Aperture Terminals) (“dishes”) • Sat-To-Sat communications 17

International Network Regulation Main Standardization Instances l l l CCITT (after 1993 ITU-T) - International consultative committee for telegraphs and telephones intergovernmental organization (US presented by the Department of States) ISO - Union of the national standardization instances (ANSI, DIN, SFS, БДС …) divided in TCs (for computers TC 97, now JTC 1 and subcommittees: for telecommunications JTC 1/SC 6) IEEE, ACM 18

Organizations in international standardization l ITU-International Telecommunication Union l JTCI-ISO/IEC Joint Technical Committee 1 l ISO-International Organization for Standardization l IEC-International Electronical Committee l ISOC-Internet Society l ATM Forum 19

Organizations in regional standardization l l l ETSI - European Telecommunications Standards Institute T 1 - Committee for telecommunications Industry Association (USA) TIA - Telecommunications Industry Association (USA) IEEE - Institute of Electrical and Electronics Engineer (USA) TTC- Telecommunications Technology Council (Japan) RCR - Research & Development Center for Radio Systems (Japan) 20

Main Standardization Instances of the Internet l IAB (Internet Activity Board, 1983 ARPANET; later Internet Architecture Board) split in 1989 into l IRTF (Internet Research Task Force), l IETF (Internet Engineering Task Force) l + ISOC (Internet SOCiety) 21

Standardization Documents l ISO adoption procedure passes: – – – l l Committee Draft International Standard ISO issued >5000 standards incl. OSI IAB (Internet standardization) – RFCs: series of technical reports (>2500 up to now e. g. RFC 2022: about PGP with MIME coding, RFC 2694: about DNS algorithm extensions) – formal process: • RFC (professional interest to the RFC) • Proposed Standard (working implementation independently tested by several different institutions) 22 • Draft Standard

Switched Multimegabit Data Service (SMDS) SMDS - LANs “backbone” interconnection 23

The Public Networks – SMDS packet 24

ATM packet 25

ATM - reference model 26

ATM sublayers 27