ISDN - Iowa State University

What is ISDN! IntegratedServicesDigitalNetwork! InnovationSubscribersDon’t Need! Dr. Russell, CprE489 Fall, 99 Exam-1 1 Question 3! A Definition of ISDN! A network, in general evolving from a telephony IntegratedDigital Network (IDN), that provides end to end digitalconnectivity to support a wide range of services, includingvoice and non voice services, to which users have accessby a limited set of standard multi purpose user net workinterfaces. by CCITTDecember 7, 2000 Iowa State University 2

An Overview of ISDN! The ISDN is one of the hottest buzzwords, today! The ISDN is becoming a mainstreamtelecommunications network that will serves awide variety of users’ needs.! Experts call ISDN the telecommunicationsnetwork of the 21 st century, the foundation uponwhich to further build the information age.December 7, 2000 Iowa State University 3

N-ISDN and B-ISDNB! Two kinds of ISDN" N-ISDNprovides lower speed services (56Kbps - 2.0Mbps)" Narrowband ISDN as a means of switched WANaccess in data networks, it has fast call setup,flexibility in support different services and ability tosupport existing WAN protocols. Frame Relay &X.25" B-ISDNprovides high speed services(2 – 600 Mbps)" ATM (Asynchronous Transfer Mode technology) isthe basis for broadband ISDN, will be ideal forcarrying various types of multimedia traffic in thenext few years.December 7, 2000 Iowa State University 4

Why We Select ISDN! In a simple form, an ISDN is an enhancement tothe telephone local loop that allow both voice anddata to be carried over the same twisted pair.! In a more comprehensive view, an ISDN is anetwork that can provide a plenty of data andtelecommunications services.December 7, 2000 Iowa State University 5

Why We Select ISDN (cont…)! More cost-effectively than leased lines.! Dial-up ISDN links can replace leased-linelineconnections be used as supplemental bandwidthfor overflow and redundancy.! ISDN is a fully digital network, where all devicesand applications present themselves in a digitalform. All of the information can be switched &transported by the same network equipment.December 7, 2000 Iowa State University 6

ISDN Development History! The first service was introduced by BritishTelecom in June 1985.Another early pre-standard ISDN service wasproject Victoria, offered by Pacific Bell in 1986in Danvilll, , California.! ISDN availability is just over 70% in NorthAmerican.December 7, 2000 Iowa State University 7

How to Distinguish ISDN fromTraditional Telephone Network.! There are two key features distinguish ISDN fromtraditional telephone networks:" It is digital from one end of a connection to the other." It defines a small set of internationally standardizeduser/network interface protocols.December 7, 2000 Iowa State University 8

The Benefits of ISDN for Data-Intensive Application! ISDN offers many benefits for organizationswhere data applications use public switchedtelephone network facilities." ISDN provides clearer, quieter voice telephone service,with the built-in in security of digital transmission,managed by easy-toto-use call control features." ISDN can handle multiple devices on a single line." ISDN’s end-toto-end digital transmission delivers moreaccurate and reliable connectivity than analogtechnology, with lower error rates and fewer droppedconnections.December 7, 2000 Iowa State University 9

How ISDN Works! Review some concepts about digital transmission." Frequency Division MultiplexingIt is a scheme in which numerous signals are combined fortransmission on a single communications line or channel. Eachsignal is assigned a different frequency within the main channel." Time Division MultiplexingIt also is a scheme in which numerous signals are combined fortransmission on a single communications line or channel. Each signalis broken up into many segments,each having very short duration.! As digital networks and digital switching become morecommon, digital systems will be used extensively for highcapacity intercity interconnection of digital trafficDecember 7, 2000 Iowa State University 10

ISDN Logical Channels! In ISDN and other digital TDM environments, achannel generally refers to a time slot ontransmission facility and is full duplex.! ISDN defines two types of logical channnels" B (bearer) channel" D (data) channelDecember 7, 2000 Iowa State University 11

B - Channel! Transmit at 64 kbps and carry circuit-mode orpacket-mode user information such as voice, data,fax, and user-multiplexed information stream.! All network services are available through Bchannel.! The primary purpose of the B-channel, Bis to carrythe user’s voice, audio, image, data, and videosignals. No Service requests from the user are senton the B-channel. BDecember 7, 2000 Iowa State University 12

D - Channel! Transmits at 16 Kbps for BRI and 64 Kbps for PRI. Itcarries call signaling and setup information to establish anetwork connection, request network services, route dataover B channels, and teardown the call when complete.! The network and user equipment exchange all servicerequests and other signaling messages over the ISDN D-Dchannel.! The D-channel’s Dprimary function is for user-networksignaling, the transport of packet mode data is thesecondary function of the D-channel. DDecember 7, 2000 Iowa State University 13

Other Channel- H Channel! A user application requesting a bit rate higher than 64Kbpsmay be obtained by using wideband channels, or H-channel, which provide the bandwidth equivalent of agroup of B-channels." H0 channel, the first designated higher-rate channel, which has adata rate of 384 Kbps. This is equivalent to logically grouping sixB-channel together." H1 channel, it comprises all available time slots at a single userinterface employing a T1 or E1 carrier. An H1 channel operates at1.536Mbps and is equivalent to 24 time slots (24 B-Channels) forcompatibility with the T1 carrier.December 7, 2000 Iowa State University 14

ISDN User Interface Standards! Basic Rate Interface (BRI)! It consists of two 64 Kbps B channel and one 16Kbps D channel for a total of 144 Kbps. (2B+D)! Primary Rate Interface (PRI)! PRI is intended for users with greater capacityrequirements. Typically, the channel structure is23B channels plus one 64 Kbps D channel for atotal of 1536 Kbps! In Europe, PRI is 30B+64 KbpsDecember 7, 2000 Iowa State University 15

BRI and PRI User/NetworkInterfaceDecember 7, 2000 Iowa State University 16

ISDN Devices! Different types of functional devices that connecta customer site to ISDN services at the telephonecarrier central office.12345TE (Terminal equipment)TA (Terminal adapters)NT1, NT2 unitT, U and other interfaceConnectorsRJ11, RJ12, RJ45December 7, 2000 Iowa State University 17

Physical Connection to ISDNDecember 7, 2000 Iowa State University 18

ISDN Protocol Architecture! Like other telecommunication networks, ISDNemploys a number of protocols. Message betweenthe user and the network as well as end-user dataall flow simultaneously over the ISDN accesschannels. End-user data and user-networksignaling information use different sets ofprotocols, although they share the same physicalmedium.! Layer 2 Q.921 & Layer 3 Q.931December 7, 2000 Iowa State University 19

Layer 2 Q.921! Describes the procedures to ensure error-freecommunication over the physical link and definesthe logical connection between user and network! Layer 2 Frame FormatFlag Address Control Information FCS Flag" Flag –Start of frame(end of previous frame)" Address-logical address including Terminal endpoint identifier" Control- Identifies type of frame" Information Layer 3 Information" FCS-Frame Frame Check Sequence" Flag-End of frame (start next frame)December 7, 2000 Iowa State University 20

Layer Q.931# Defines the signaling messages used to requestservices form the networkDecember 7, 2000 Iowa State University 21

Relationship of Layer 1,2,3! The ISDN Layer 1 protocol defines the physicalconnection between TE (TE1 or TA) and networktermination equipment (NT2 or NT1).! The ISDN Layer2 and 3 protocols define thelogical link and signaling protocols, respectively,between ISDN TE (TE1 or TA) or customer-premises switching equipment.December 7, 2000 Iowa State University 22

Establishing the Link Layer! The Layer 2 establishment procedure1. The TE (Terminal Endpoint) and the Network initially exchangeReceive Ready (RR) frames, listening for someone to initiate aconnection2. The TE sends an Unnumbered Information (UI) frame with a SAPIof 63 (management procedure, query network) and TEI of 127(broadcast)3. The Network assigns an available TEI (in the range 64-126)4. The TE sends a Set Asynchronous Balanced Mode (SABME) framewith a SAPI of 0 (call control, used to initiate a SETUP) and a TEIof the value assigned by the network5. The network responds with an Unnumbered Acknowledgement(UA), SAPI=0, TEI=assigned.6. The connection is ready for a Layer 3 setup.December 7, 2000 Iowa State University 23

Establishing the Link Layer! These are the steps that occurs when an ISDN call isestablished.1. Caller sends a SETUP to the Switch.2. If the SETUP is OK, the switch sends a CALL PROCeeding to the Caller,and then a SETUP to the Receiver.3. The Receiver gets the SETUP. If it is OK, then it rings the phone e and sendsan ALERTING message to the Switch.4. The Switch forwards the ALERTING message to the Caller.5. When the receiver answers the call, is sends a CONNECT message to theSwitch6. The Switch forwards the CONNECT message to the Caller.7. The Caller sends a CONNECT ACKnowledge message to the Switch8. The Switch forwards the CONNECT ACK message to the Receiver.9. Done. The connection is now up.December 7, 2000 Iowa State University 24

Relationship of B-and BD-channel DProtocol ArchitecturesDecember 7, 2000 Iowa State University 25

ISDN Services and Applications! Bear service :allow the users to send information from onedevice on the network to another.! Teleservices are a VAS (value added service) provided bythe network, above and beyond the mere transport of bits.! Two other types of servicesare associated with the bearerand teleservies" Supplementary service" B-ISDN serviceDecember 7, 2000 Iowa State University 26

ISDN Applications! A key of the successful deployment of ISDN is theapplication for the new technology and services." Geographic coverage" Bandwidth usage" Closed user group" 7 x 24 accessDecember 7, 2000 Iowa State University 27

Interconnecting LANs and ISDN! ISDN's high throughput capacity with dynamicbandwidth allocation features, signal quality,reliability, flexibility, fast call setup, and attractivetariffs make ISDN an excellent, cost-effectivemedium for the networking applications." Remote LAN-toto-LAN & LAN-toto-host internetworking" Remotenode-toto-LAN & terminal-toto-hostinternetworking" Internet and on-line services accessDecember 7, 2000 Iowa State University 28

Remote LAN-toto-LAN and LAN-to-host internetworking! ISDN are well suited for on-demand remote LAN-to-LAN configurations since they provide atelephone circuit only when information needs tobe transferred.December 7, 2000 Iowa State University 29

Remote node-toto-LAN andterminal-toto-host internetworking! Remote node-toto-LAN internetworking can beextended to a single user in a remote location.December 7, 2000 Iowa State University 30

Internet and on-line servicesaccess! ISDN’s high-speed service solves the bandwidthaccess problem for these remote users, as well asfor Internet users on an enterprise LAN.December 7, 2000 Iowa State University 31

ISDN Services deliver! Telco service providers deliver ISDN servicesfrom the central office ISDN digital switch in oneof three ways.! Through a direct BRI (2B+D) connection! Through an ISDN Centrex service! Through a PRI (23B+D) connectionDecember 7, 2000 Iowa State University 32

ISDN Customer PremisesEquipment Requirements! Bridge/routers to provide remote LAN-toto-LAN or node-toto-LAN ISDN connections to the central site LAN.! Terminal adapters (TAs) to be used in T2 (nonnativeISDN) bridge/routers and other devices to provide ISDNinterface connections.! Aggregation devices, specialized TAs that aggregate orbond the B channels into a single higher-speed connectionwhen needed! Access servers, the central site connection devices thatprovide dial-up access to users of remote node-toto-LANapplications.December 7, 2000 Iowa State University 33

The Conclusion of ISDN! With ISDN you are equipped for the future sinceall advances in telecommunications are based onthis standard. It is already the standard throughoutEurope and North American, it will soon becomethe worldwide standard. Only ISDN allows you totake part in all the coming rapid developments.December 7, 2000 Iowa State University 34

References[1]. John M. Griffiths. “ISDN explained” Second Edition[2]. Peter Bocker. “ISDN,The Integrated Services Digital Network, Concepts, Methods,Systems”[3] Jay Ranade. “Guide to Integrating Digital Services” Consulting Editor[4] Dervis Z.DenizDeniz. “ISDN and Its Application to LAN Interconnection”[5] Michael J. Miller, Syed V. Ahamed. “Digital Transmission Systems and Networks”[6] James Y. Bryce. “Using ISDN” Second Edition[7] Gary C. Kessler, Peter V. Southwick “ISDN, Concepts, Facilities and Services” ThreeEdition[8] Andrew S. Tanenbaum. “Computer Networks” Third Edition[9] U.KillatKillat. “Access to B-ISDN Bvia PONS, ATM Communication in Practice”[10] J.C.BicBic, , D.DupontielDupontiel and J.C.ImbeauxImbeaux. “Elements of Digital communication”[11] http://www.3com.com/nsc1/500606.html[12] http://www.alumni.caltechcaltech.edu/~dank/isdn/[13] http://www.ralphbralphb.net/ISDN/[14] http://www.whatiswhatis.comDecember 7, 2000 Iowa State University 35

Questions?