The LOD Technical Journal: File #4 of 12 =--=--=--=--=--=--=--=--= Communications Technology (tm) Unequal Access LOD June 1993 The title of this article is that of communications technology. Not data communications or telephony but communications. The two have for all practical purposes become one in the same. Voice communications, wireless communication services etc. are now being transmitted by digital means. What was once a simple matter of drawing a line between the two is no more the case. This convergence together with new technologies radically changes the picture of communications. Many former concepts and systems will be obsolete in a few years. To examine the future of communications i'll cover: - ISDN and BISDN - ATM - SONET - Service Net-2000 - Other developments ISDN =--= A comprehensive description of ISDN would be to big to cram in here so a brief definition and update on the status of ISDN will be given. ISDN Defined ------------ ISDN is defined by the CCITT as: ...a network in general evolving from a telephony Integrated Digital Network (IDN), that provides end-to-end digital connectivity to support a wide range of services including voice and non-voice services, to which users have access by a limited set of standard multi-purpose user network interfaces... Basically ISDN is a network that carries voice and data over the same lines. All services exist in digital form and can be switched by one network. Much has been forecasted about how ISDN will change the world with interactive television, home banking, employees conducting business at home, new services etc. with AI systems controlling central databases. Technically defined it provides a digital interface, usually with 2 channel types - B channels for voice and data and D channels for signalling and control. This gives a dedicated channel for the subscribers information and one for control of the interface. The fundamental building block of ISDN is its 64 kbps digital channels. With two main interfaces - Basic Rate Interface (BRI) and Primary Rate Interface (PRI). BRI handles small scale services such as subscriber lines and PRI handles large scale services such as central databases. Each has both a D channel and X number of B channels. BRI has 2B + D channels and PRI has 23B + D channels. Each B channel is 64 kbps and the D channel is 64 kbps for the PRI and 16 kbps for the BRI. To plan for future increases 384 kbps has been allotted to the H0 channel, 1336 kbps to the H11 channel and 1920 kbps to the H12 channel. Integration ----------- ISDN will have one format, so various devices won't need their own dedicated lines. One common interface will accommodate all applications. By having one set of wires and protocols users won't need to bother with coaxial cables for television, X.25 protocols for packet switched networks (PSNs), telex lines, various leased lines etc. Misconceptions -------------- ISDN itself isn't going to provide anything. It is just the standard for network interface. Anything new will depend upon the services offered on it. The concept of digital switching is not a new one to begin with. Its been in use since the mid 60's. The real "upheaval" with ISDN is that Ma Bell is no longer going to provide just telephone calls but a whole range of services. This list of services along with speed requirements and channel type was taken from the IEEE. Service Speed Required Channel ------- -------------- ------- Voice 8,16,32,64 kbps B Alarms 10-100 bps D Smoke Fire Police Medical Utility metering 0.1-1 kbps D Energy Management 0.1-1 kbps D Interactive information 4.8-64 kbps B Electronic banking Electronic yellow pages Opinion polling High quality audio ~300-700 kbps Slow scan TV 56-64 kbps B Compressed video ~30 Mbps Compressed video conf. ~1.5 Mbps Broadcast video ~100 Mbps Switched video ~100 Mbps Interactive video ~100 Mbps Facsimile graphics 4.8-64 kbps B CCS --- Another vital part of ISDN is Common Channel Signalling (CCS). Which separates signalling information from user data. Rather than being an older form of in-band signalling where signals and data are on the same channel it is out of band, where signals travel on different channels. This allows more services and reduces circuit connection times. ISDN uses SS no.7 (SS7). The initial version SS6 used analog trunks of 2400 bps, SS7 uses digital trunks of 56/64 kbps. Well, you've most likely asking yourself what this all means for our underground activities. It will create a bonanza of new services and opportunities all unified in one network. Just as data and voice communications are merging so to will hacking, phreaking, cable fraud etc. Because ISDN has yet to be implemented on a mass scale in North America its not possible to say specifically how it may be abused. You should still be prepared for its arrival by understanding its design and purpose though. Many supplementary services have been approved for ISDN by the CCITT and more are being approved right now: Number Identification Services: - Direct Dialing In (DDI) - Multiple Subscriber Number (MSN) - Allows different numbers to ring at one number. - Calling Line Identification Presentation (CLIP) - (ANI) - Calling Line Identification Restriction (CLIR) - blocks out an incoming ISDN number. - Connected Line Identification Presentation (CLOP) - Connected Line Identification Restriction (COLR) - Malicious Call Identification and Sub-Addressing (not yet defined by the CCITT). Call Offering Services: - Call Transfer - Lets a call be transferred to a third party. - Call Forwarding Busy (CFB) - Call Forwarding No Reply (CFNR) - Call Forwarding Unconditional (CFU) - Call Deflection Misc. Services: - Private Numbering Plan - Advice of Charge - Allows the caller to find out the cost of a call before, during or after. - Credit Card Calling and Reverse Charging - User-to-User Signalling (UUS) These supplementary services take advantage of SS7's full range of capabilites. ISDN Trials ----------- Since ISDN provides the "digital pipe" and the subscriber selects services; the network, circuits, trunks and customer premises equipment (CPE) are all being tested. Most of the early ISDN trials were quite basic and were intended only to prove the validity of ISDN concepts. The current status of ISDN is with more complex testing and actual implementations. A brief summary follows. Location Organization Date Details -------- ------------ ---- ------- Sweden Televerket/Ericsson 1981 Local network transmission Wisconsin Wisconsin Bell/ 1985 Customer acceptance trials, mobile Siemens unit Munich/Berlin DBP/Various 1984 BIGFON, local wideband ISDN dist. Tokyo NTT 1984 INS trial; 64/16/4/4, B/B/D/D access Venice SIP/Ericsson 1984 I.412 access London BT/Various 1985 IDA trial, commercial 64/8/8, B/B/D access Chicago Illinois Bell/AT&T 1986 I.412 access, fairly basic Phoenix Mountain Bell/NT 1986 I.412, DMS-100, 3 customers Phoenix Mountain Bell/GTE 1986 GTD5 EAX Phoenix Mountain Bell/NEC 1986 Digital adjunct to 1A ESS Portland PacBell/NT 1987 DMS-100, 32 kbps voice channels Atlanta Southern Bell/AT&T 1987 5ESS Boca Raton Southern Bell/ 1987 EWSD Siemens Ottawa Bell Canada/NT 1986 DMS-100, SS7 trials Ottawa Bell Canada/NT 1987 DMS-100, basic and primary access Belgium RTT/BTMC ? System 12, details unknown Germany DBP/Siemens/SEL 1986 EWSD System 12, comprehensive phased trials France CNET 1987 E 10, MT25, "Renan" project Florida Southern Bell/NT 1988 Fiber to home, POTS, ISDN, CATV transport US SWBT 1988 Internetwork 5ESS, DMS-100 and EWSD US MCI 1989 Test with Meridian SL-1 and SL-100s US Sprint 1990 All network switches support ISDN US AT&T 1990 Complete conversion to SS7 US MCI 1990 Complete conversion to SS7 Australia Telecom Australia 1990 ISDN commercially available Japan NTT 1990 ISDN in 200 cities US SWBT 1991 Internetworking of SWBT and IECs, ISDN and SS7 Brazil Telbras 1993 ISDN commercially available UK BT 1993 PRI in place Germany Deutsche Bundepost 1993 Nation wide ISDN, 3 million users Telekom Broadband ISDN (BISDN) ---------------------- Is designed to exploit ISDN's full broadband capabilities. With BISDN everything from alarm monitoring to live action video broadcasts can be handled. BISDN is designed to use optical transmissions and compress its data up to 15 times by using more sophisticated terminal equipment. Thus BISDN can handle video images which require refreshing 30 times a second and would require transfer rates of 100 Mbps with no compression. Because of its complexity BISDN will likely end up in commercial applications in the near future. Transfer Modes -------------- In the design of BISDN standards either the synchronous transfer mode (STM) or the asynchronous transfer mode (ATM) can be used. STM is the POTS way using time division multiplexing. Synchronous multiplexing uses a clock to assign windows for information to be transmitted, regardless of wether transmission takes place at all. Asynchronous multiplexing does without a clock to keep transmissions in place. ATM is virtually the same as this, with faster routines. In ATM windows for transmission are opened when needed and are not arbitrarily assigned. Information indicating the source is in each header. ATM is the more common method being CCITT approved. STM is still being debated as the use of highly accurate atomic clocks will ease multiplexing digital bit streams coming from multiple locations. ATM =-- Is a method of cell oriented switching and multiplexing giving high-speed, low error transmissions. Which combines the efficiency of packet technology with the reliability of circuit switching. It is made up of fixed, 53 character cells. Every cell has 48 characters and a 5 character header to keep track of its source. Incoming data is broken up into smaller uniform cells by ATM equipment, transmitted and reassembled upon reception. Since processing fixed sized cells is such a basic task, ATM is much faster at packet switching than say X.25 is. Giving ATM the ability to deal with such demanding applications as real-time video. ATM switches and transmits all forms of communications - voice, data, narrow and broadband, continuous and two-way dialogue traffic, in this uniform fashion. ATM transmits its data over a "virtual channel" when in connectionless mode. A virtual channel is the channel that connects points on the ATM network. A virtual connection moves a set of virtual channels with the same path identifier over the network. It has a cell header that consists of a virtual path and virtual channel identifier. To allow private networks, crossconnects or virtual path switches create a permanent link or virtual path between both ends of the network. Virtual path switches don't need signalling as ATM switches do. The adoption of a global ATM network will be at the earliest in 1995. Trials with ATM are already underway. The move toward BISDN will require the development of both this ATM network and crossconnects. SONET =--=- The Synchronous Optical Network (SONET) is the ANSI standard for the transmission of ATM frames on optical fiber networks. SONET vastly increases potential transmission rates. It far surpasses today's DS3 speed and has an OC-1 bandwith of 51.84 Mb/s. OC-48 is 2.5 Gb/s, the commercial version will be much slower at OC-3 or 155 Mb/s. In addition to providing greater data transfer rates it is a far more intelligent network, transmitting control directives in its synchronous stream. The subscriber's data is contained in the payload and the control directives in the overhead. Overhead is made up of its section, line and path components. Users can manipulate the network with messages placed in overhead. The section overhead covers frame and error monitoring and controls key equipment on the transmission line such as optical regenerators. Line overhead monitors performance. Path overhead monitors errors and controls the signalling between different points on the SONET network. SONET's synchronous bit streams give very reliable transmissions and multiplexing. SONET more or less integrates the functions of OA&M and as a result fewer systems will be needed to perform them. What this means is fewer access ports will be available to dial into. SONET (and for that matter ISDN, BISDN, SS7 and ATM) are more complicated and have a lot more to them than what's been presented here. Look for specialized files on them and what they can do for you in upcoming journals. Service Net-2000 =--=--=--=--=--= Service Net-2000 is designed to use the capabilites of the 5ESS Switch to provide a better public switched telephone network (PSTN). Improvements that are required by the advent of more technically demanding services such as HDTV, high speed data transmissions, speech recognition etc. These services require faster and faster communications and higher bandwiths. Service Net-2000, is designed to provide higher capacity switching and data networks using SONET technology. The goal being to provide an effective universal information service (UIS). In this Service Net-2000 is a kind of "follow up" to ISDN. Architecture ------------ SS7 is at the heard of this intelligent network. It provides 64 kb/s voice transmissions and 1.54 mb/s (T1) data transmissions, when over fiber optic or other high bandwith lines. The need for Service Net-2000 is high, once you consider the oncoming rush of optical transmissions measured in rates of gigabits/second. Nodes in Service Net-2000 are also "intelligent" being "self-aware", adapting to net changes, making corrections and self improving. The main goal to Service Net-2000 architecture is to provide unification. It combines basic functions such as switching, routing etc. with data transmissions just as ISDN does. The end result being a decentralized CO throughout the system. As individual functions disappear and are replaced by this integrated system. Service Node ------------ This integration is performed by the service node. Based on the 5ESS-2000 system (note that 5ESS is now 5ESS-2000 when used with Service Net-2000 and broadband network services-2000 (BNS2000)) The "2000" group that forms this is based on SONET. Using flexible mapping and frame switching rates at multiples of 51.84 mb/s are supported. The "2000" group consists of the: - Digital data multiplexer (DDM-2000) - Digital access and cross-connect systems IV-2000 (DACS IV-2000) - DACS III-2000 cross connect system - DACScan-2000 controllers - DACScan-2000 workstation - FT-2000 lightware The DACS IV-2000 is able to carry higher speed virtual tributary (VT) channels and not just today's, slower asynchronous ones. Both DACS IV-2000 and DACS III-2000 can support non-SONET hookups too, making them quite versatile. The DACS III-2000 differs from the IV-2000 in offering the DS3/Synchronous Transmission Signal-1 (STS-1) 5ESS-2000 --------- As I mentioned before 5ESS-2000 combines BNS-2000 with the other members of the "2000" group. This boosts the capacity of a 5ESS-2000 Switch to 250,000 lines on 64,000 trunks. Key to this is the improved switching module, the SM-2000. It handles everything associated with a call and can even be used as a stand alone remote office, in which case it's called a EXM-2000. To enable high-speed interfaces, 5ESS-2000 uses digital networking units (DNUs). All a DNU is, is a combination of a 5ESS Switch with say a DACS switch. The DNU-IV is a derivative of the DACS IV-2000 and gives additional high speed possibilities. Due to its high operating speed it can greatly speed up CO operations that are slowed down by older copper wirings. With the DNS-2000 cell switch, the broadband integrated services digital network (BISDN) will be created. Point-to-point packet frame relays can be provided even to those lacking T-1s. As well as offering switched multimegabit data services (SMDS) with up to T3 capabilities. The cell switch is made up of low speed port carriers running at 8 mb/s and high-speed switching systems running in excess of 200 mb/s. BNS-2000 handles both frame relays that require connections and SMDSs which don't. Service Net-2000 has the ability to redirect calls between different areas effortlessly. The service control point (SCP) provides the information for the service circuit node based on call screening options, the date/time etc. Allowing the 5ESS-2000 switch to offer a whole range of options such as call waiting, forwarding, blocking etc. Basically the idea behind Service Net-2000 is to add intelligence to the 5ESS switching system and to drastically improve its speed and call handling abilities. With the purpose of creating a more powerful UIS. Other Developments =--=--=--=--=--=-- Intelligent Network (IN) ------------------------ IN is just distributing AI throughout the network. A trend which pops up numerous times throughout this issue of the journal with Expert Systems, Service-Net 2000 etc. The idea behind IN is to have large and fast central databases connected with the rest of the network with protocols such as X.25, SS7 etc. IN allows global service to be introduced easier with good flexibility. IN is comprised of service switching points (SSPs) and service control points (SCPs). SSP takes calls and sends them to an SCP. SCPs contain the databases themselves such as calling card verification data. Telecommunication Management Network (TMN) ------------------------------------------ TMN as the name implies manages the network. TMN performs OA&M on a CCITT standardized structure. Gigabit Testbeds ---------------- Are now being implemented for experimental purposes by DARPA, NSF and others. Several are being conducted by the Corporation for National Research Initiatives (NRI). They involve telcos, academic, commercial and government researchers for the future National Research and Education Network (NREN) Internet. NREN promises a good deal of services, such as real-time transmission of high-speed data streams, huge automated electronic libraries and Gb/s transmission rates taking us away from ascii into full motion video. One experimental net is Vistanet with ATM and SONET capabilities and 622 Mb/s speed. Another one is Aurora. Bellcore is providing an experimental Sunshine switch and IBM a Planet Packet Transfer Mode (PTM). Unlike ATM, PTM packets have no fixed size being as large as 2k. PTM is not a recognized standard but may end up in commercial use, with ATM serving the network itself from the CO. NT is providing a SONET Digital Multiplex System (S/DMS) that takes up to 16 SONET inputs of 155 Mb/s and multiplexes them to 2.4 Gb/s for Casa a co- operative venture of several organizations in California. The main component of Casa is a high-performance parallel interface (Hippi) gateway for SONET. A European group called RACE (R&D in advanced communications technologies in Europe) is designing Integrated Broadband Communications (IBC) within a BISDN. RACE is also working on Code-Division Multiple Access (CDMA), optical networks, teleshopping, electronic funds transfer over a ATM BISDN, mobile network architecture and the universal mobile telecommunications system (UMTS). The Future ---------- Compared to the last century of relatively stagnant copper wiring the impact of higher bandwiths and optical technologies will - eventually - be monumental. All of this does however depend on the introduction of optical fibers. Because of the narrow-band copper wires that are the last link to the subscriber, evolution to better technology is stunted (in the US at least). The cost of overhauling these copper wires in the US with fiber ones is on the order of 200 billion US. In other nations however, the use of fibers linking residential homes is more than 50%. Fiber technology is however, constantly growing and its price dropping. As an aside to all this, look at what's been done in the last 10 years of communications compared to the last 100 years. We are constantly lessening the doubling time of communications technology. In the next 3 years we will equal the last 10 years of progress. Soon it will drop down to a year and then to a matter of months. Since International standards take 15 + years to work out bureaucracy may become an impediment. --------------------------------------------------------------------------- Sources IEEE 0018-9235/93 Telecommunications Journal April 1993 Various books and articles on ISDN ---------------------------------------------------------------------------