Contemporary and Emerging Telecommunications Technologies

1. Contemporary and Emerging Telecommunications Technologies BAD 64046 29 January 2003

2. The Telecommunications Revolution • Development of telecommunications services have lagged development of the end devices • Improvements in connectivity are imperative because data has exceeded voice volume (end of 1990s) • Volume of traffic on the Internet doubles every 100 days

3. The Analog Network Must Go • Has been the staple technology for over 100 years • Huge investment in slow, analog, switched voice circuits • Present use of the analog network for data is a jury-rig • MODEMS are a gross way to adapt to the POTS voice network

4. Problems with the POTS Network • Analog only • Limited (without tricks) to 33.6 Kbps • Oriented toward connections that persist for a period of minutes • Inefficient for burst traffic patterns • All of the network intelligence is centralized at the switches • The local loop bottleneck

5. Incremental Workarounds to POTS • DSL -- uses existing Cu twisted pair, but sophisticated end electronics, to net much higher rates • Voice and data on cable TV coax network • Wireless local loop technologies

6. Evolution of Billing Methods • Historically by minute or call count • Unmetered flat rate • Long distance: time and distance • These old methods did not reflect accurate cost accounting • New techniques will include: • Bandwidth based • Traffic based • Timed usage • Flat rate

7. Telecommunications Service Offerings - Overview (1) • ATM (Asynchronous Transfer Mode) • Connection oriented, packet switching • 155Mbps - 2.5 Gbps • CLASS (Custom Area Local Signaling Services) • Enhanced POTS services • Caller ID, call waiting, call forwarding, conference calling

8. Telecommunications Service Offerings - Overview (2) • Frame Relay • Packet switched for city and wide area networking • 56/64 Kbps, T1 (1.544Mbps), T3 (44.736Mbps), E1 (2.048Mbps), E3 (34.368Mbps) • Personal Communication Services • Digital mobile wireless comm systems • Use the PCS spectrum allocation

9. Telecommunications Service Offerings - Overview (3) • POTS (Plain Old Telephone Service) • SMDS (Switched Megabit Data Service) • Connectionless, provided by LECs to interconnect metropolitan LANs • VoIP (Voice Over IP) • Digital voice on packet switched networks using the Internet Protocol

10. Bandwidth Definitions (1) • Broadband • Allows rates of 1.544 Mbps or higher • Circuits are usually multiplexed • Narrowband • 64 Kbps or less • Wideband • 64 Kbps < wideband < 1.5 Mbps

11. Bandwidth Definitions (2) • Downstream • Transmission away from the core network • Upstream • Transmission toward the core network

12. Network Terminology (1) • CO (Central Office) • The location at which all the circuits in the local loop are switched • Circuit Switched Network • Dedicated connection established from end to end for the duration of their ”call” • Connection-Oriented network • Pre-established connection is required • All data follows the same path • All data is received in same order as transmitted • (ATM, for example)

13. Network Terminology (2) • Digital Subscriber Line (DSL) • Uses traditional POTS Cu pairs • Voice over the data is sometimes supported • Local Loop • From the exchange switch (brick building) to your phone • Cu twisted pair

14. Network Terminology (3) • Packet Switched Network • Decomposes the bit stream into addressed packets • Packets transmitted independently • Bit stream is reassembled at the receiving end, into the proper order • Utilize bandwidth very efficiently

15. Network Terminology (4) • PSTN (Public Switched Telephone Network) • The existing worldwide circuit-switched telephone network • Underlying technology is switching to digital, but the architecture is unchanged • Router • Store and forward device • Connects multiple packet-switched networks running the same protocol

16. Network Terminology (5) • Switch • In packet-switched network: forwards packets to network segments based on hardware addresses of network interfaces • In circuit-switched network: establishes a network path between source and destination for the duration of call • In PSTN: the central office switch which contains all of the intelligence for the whole network

17. Network Terminology (6) • SONET (Synchronous Optical Network) • An interface standard • For fibre optic internetworking of transmission schemes from various vendors • Base rate for optical line is OC-1, 51.84 Mbps • OC-3 supports 155.52 Mbps

18. Network Terminology (7) • T-carrier System • Aggregates the bandwidth of voice circuits that have been converted for digital • Bandwidth is multiples of 64Kbps • T1, for example consists of 23 64Kbps channels); T3 has 672 channels • Virtual Circuit • Predefined path from node to node • Supported by a connection-oriented packet-switched network • Packets received in order sent

19. Telecom Industry Players (1) • CLEC (Competitive Local Exchange Carrier) • Compete against the incumbents • Sometimes have their own local loop infrastructure • ILEC (Incumbent Local Exchange Carrier) • Still service the majority of local users in the U.S.

20. Telecom Industry Players (2) • LATA (Local Access and Transport Area) • Area around a major city where RBOCs are allowed to conduct business • Modified SMSAs • IXC (Interexchange Carrier) • AT&T, MCI WorldCom, Sprint • Carry traffic between telephone central exchanges

21. Telecom Industry Players (3) • IntraLATA • RBOCs restricted to selling only IntraLATA service unless they open their local service markets to competition • Only Bell Atlantic, now Verizon, has done so

22. Telecom Industry Players (4) • Long Distance Service • Generally, service across LATAs • Sometimes toll service within a large LATA • PTT (Post, Telegraph, and Telephone Administration) • Government agency responsible for providing postal and telecom services • Usually a monopoly • Privatized in most countries • See http://www.uts.an for example

23. Telecom Industry Players (6) • RBOC (Regional Bell Operating Company) • 1982 consent decree broke up AT&T • Seven parent companies formed for the then 22 existing Bell Operating Companies • Ours is SBC, formerly Ameritech

24. Data Communications Services (1) • Private Line Services • End to end non-switched persistent connection • Only appropriate when cheaper than a switched circuit • T1 is most common • Fractional T1 is possible • Pricing usually fixed monthly; distance sensitive but not usage sensitive

25. Data Communications Services (2) • ISDN (Integrated Services Digital Network) • Circuit switched narrowband or wideband service • Provides a digital local loop to the CO • Prices for residential service vary widely in U.S. ($30 to $200/month) • Usually two 64Kbps “B” channels and one 16Kbps “D” channel • The B channels can be multiplexed for faster throughput • Widely used for POS and credit card verification because of the persistent connection

26. Data Communications Services (3) • Frame Relay • Preferred by corporate data network users since mid 1990s • Packet switching system that builds variable length frames that are then relayed from node to node • Advantage is that it can handle many various protocols because of variable length frames • Handles delay sensitive data well, but not as well as ATM

27. More About Frame Relay • Typical connection speeds of 56Kbps up to 1.5Mbps for LAN to LAN connections • Up to 45Mbps is possible • CIR - Committed Information Rate can be exceeded in small bursts • Frame relay can be transported over SONET • Uses a combination of Permanent Virtual Circuits and Switched Virtual Circuits

28. Still More... • Frame Relay is standard in the U.S. for enterprise networks • Greatly reduces the need for in-house network engineers • Most of the network intelligence is at the vendor • Popularity is growing internationally because of the flexibility of the variable frame sizes

29. Frame Relay VPN Features • Data Services • Wide range of connectivity speeds supported • Integration of Voice Over Data • Service Separation • Facilitates coexistence of voice and data services • Integrated Billing

30. Frame Relay Standards • Developed by the Frame Relay Forum • Standards dictate how software will be used to combine low speed frame relay links into one faster link

31. Data Communications Services (4) • ATM • Developed in mid-1980s • Intended to be a carrier backbone technology • Uses fixed length packets called “cells” • Low latency supports synchronous demands • Can be implemented across backbones, WANs, LANs

32. ATM Details • Uses 53 byte cells • Can be switched by hardware very fast • Cell overhead is approximately 10% • Carrier ATM services are as fast as 622Mbps • MCI WorldCom, Sprint, AT&T, BT, France Telecom all have implemented high speed ATM backbones

33. ATM Advantages • Traffic integration • Isochronous traffic integrates easily with non delay-sensitive traffic • Supports very high bandwidths • Virtual networking capabilities ease network administration • Not widely used yet, as it is overkill except for high end applications such as CAD/CAM and videoconferencing

34. Service Level Agreements • Contract between vendor and customer • Defines measurement methods • Provides for penalties • Requires: • Baselining • Scope definition • Definition of measurement parameters • Mean Time to Install • Mean Time to Repair

35. ATM and LANs • ATM can be used to interconnect LANs • Ethernet and Token Ring packets are encapsulated in ATM packets • Standard is LANE 2.0 (“LAN Emulation”)

36. Data Communications Services (5) • POS (Packet Over SONET) • SONET uses time division multiplexing to transport data over fiber optics at very high speeds (~40Gbps) • POS allows packet data to be sent over a SONET link without the need for the intervening ATM switching layer • POS is 99.5% efficient versus only 88.4% for ATM

37. Data Communications Services (6) • SMDS (Switched Megabit Data Service) • Connectionless service • Every packet is sent independently of all others • No established virtual circuit is required • As fast as 45Mbps • Primarily used as a niche technique in companies that need multicasting capabilities

38. Data Communications Services (7) • Internet Based Virtual Private Networks • Used to make “tunnels” over private networks • The service provider’s network and intervening protocols are transparent to the VPN users • A key technology to support Virtual Corporations • Better SLAs are needed