Teleworker Connectivity

1. Teleworker Connectivity Adapted for Exploration 4, Chapter 6 by Donald W. Smith From CIS 186 ISCW and CIS 140 By Rick Graziani

2. Objectives • Describe the enterprise requirements for providing teleworker services • Explain how broadband services extend Enterprise Networks including DSL, cable, and wireless • Describe how VPN technology provides secure teleworker services in an Enterprise setting

3. Why Provide Teleworker Services

4. Remote Connection Options

5. Private versus Public networks • Describe the key differences between private and public network infrastructures

6. Broadband Services for Teleworkers

7. Cable Access Technologies

8. Cable Access Technologies • Cable access is one of the fastest growing technologies for home access to multiple services. • Community Antenna Television (CATV) a broad term referring to cable television in general – a form of transmission using shared TV signals. • Cable systems were originally built to extend the reach of TV signals and improve over-the-air TV reception. Rick Graziani graziani@cabrillo.edu

9. Early Days • Pennsylvania,1948 = John Walson, the owner of an appliance store in a small mountain town, needed to solve poor over-the-air reception problems experienced by customers trying to receive TV signals from Philadelphia through the mountains. • Walson erected an antenna on a utility pole on a local mountaintop that enabled him to demonstrate the televisions in his store with strong broadcasts coming from the three Philadelphia stations. • He connected the antenna to his appliance store via a cable and modified signal boosters. • He then connected several of his customers who were located along the cable path. • This was the first community antenna television (CATV) system in the United States. A typical cable operator now uses a satellite dish to gather TV signals. Rick Graziani graziani@cabrillo.edu

10. Early systems were one-way with cascading amplifiers placed in series along the network to compensate for signal loss. • Taps were used to couple video signals from the main trunks to subscriber homes via drop cables . • Modern cable systems provide two-way communication between subscribers and the cable operator. Transportation Network Rick Graziani graziani@cabrillo.edu

11. Comcast: TV, Internet and Voice • Cable access today is typically sold in in bundles offering: • Television • Internet • Voice Rick Graziani graziani@cabrillo.edu

12. What is a Cable System? • Cable Internet access has typical speeds of: • 2 Mbps to 6 Mbps downstream (Internet to home) • Less than 1 Mbps upstream (384 Kbps to 768 Kbps) • Asynchronous view of bandwidth allocation: • The bulk of traffic load are small outbound requests, returning large amounts of inbound data. • Note: More upstream speed was the #1 request by Comcast customers in an independent survey in 2006. #2 was lower prices. Rick Graziani graziani@cabrillo.edu

13. Terminology • Broadband: • (General) Data transmission using multiplexing methodology to provide more efficient use of the bandwidth. • (Cable) Frequency Division Multiplexing (FDM) of multiple signals in a wide radio frequency (RF) bandwidth over hybrid fiber-coaxial (HFC) network and the capability to handle large amounts of information. • Frequency Division Multiplexing: FDM is a means by which information from multiple channels or frequencies can be allocated bandwidth on a single wire. More in a moment! Rick Graziani graziani@cabrillo.edu

14. Terminology • Coaxial Cable • Carries radio frequency (RF) signals across the network. • Primary medium used to build cable TV systems. • Modern cable systems use: • fiber and • coaxial cable • Construction of the cable meant to minimize the effects of external electrical and RF interference. • CATV typically uses RG-6 or RG-59 Rick Graziani graziani@cabrillo.edu

15. Terminology • Amplifier: A device that magnifies an input signal, producing a larger output signal. • Problem with analog amplifiers is that they also amplify noise. • Tap: A device used to divide the input signal (RF) to support multiple outlets – typically 2, 4, or 8 ports. CATV Trunk Amplifier CATV Tap Rick Graziani graziani@cabrillo.edu

16. Terminology • Hybrid Fiber-Coaxial (HFC) – A mixed optical-coaxial network in which fiber optic cable is installed in place of some or all of the traditional trunk portion of the cable network. Transportation Network Rick Graziani graziani@cabrillo.edu

17. Cable System Standards • National Television Standards Committee (NTSC) • Defines technical standards for analog television systems in North America using a 6 MHz modulated signal. • Phase Alternating Line (PAL) • A color coding system used in broadcast television throughout Europe, Asia, Africa, Brazil and Argentina using a 6, 7 o r 8 MHz modulated signal. • Systeme Electronic Caouleur avev Memoire (SECAM) • An analog color television system used in France and some Eastern European countries using 8 MHz modulated signal. Rick Graziani graziani@cabrillo.edu

18. Cable System Components • Depending upon the provider the implementation of these components may differ. • Antenna site: • Cable provider’s main receiving and satellite dish facilities. • Location chosen for optimum reception of over-the-air, satellite, and sometimes point-to-point signals. • Headend • Master facility where signals are first received, processed, formatted, and then distributed downstream to the cable network: the transportation and distribution network. • Usually unmanned (“lights-out”) and inside security fencing. Transportation Network Rick Graziani graziani@cabrillo.edu

19. Cable System Components • Transportation network (Feeder network): • A transportation network links a remote antenna site to a headend or a remote headend to the distribution network. • The transportation network can be: • microwave • coaxial supertrunk • fiber-optic Transportation Network Rick Graziani graziani@cabrillo.edu

20. Cable System Components • Distribution network: • In a traditional (classic) cable system called a tree-and-branch cable system, the distribution network consists of trunk and feeder cables. • Trunk is the backbone that distributes signals throughout the community service area to the feeder • Typically uses 0.750-inch (19-mm) diameter coaxial cable. • Feeder branches flow from a trunk and reach all of the subscribers in the service area via coaxial cables. • Usually a 0.50-inch (13-mm) diameter coaxial cable. Transportation Network Rick Graziani graziani@cabrillo.edu

21. Cable System Components • Node: • Performs optical to RF conversion. • Subscriber drop: • A subscriber drop connects the subscriber to the cable services. • The subscriber drop is a connection between the feeder part of a distribution network and the subscriber terminal device (for example, TV set, videocassette recorder [VCR], High Definition TV set-top box, or cable modem). • A subscriber drop consists of: • radio grade (RG) coaxial cabling (usually 59-series or 6-series) • grounding and attachment hardware, passive devices • set-top box. Transportation Network Rick Graziani graziani@cabrillo.edu

22. Cable System Benefits • Cost-effective solution for densely populated areas. • Issue with non-residential areas. • Cable systems support: • telephony • data services • analog and digital video services • Larger cable operators adopted a common practice of keeping various equipment, (telephone switches and Cable Modem Termination Systems (CMTS)) in the same facility. • This integrates all types of services—telephony, data, and analog and digital video services. Rick Graziani graziani@cabrillo.edu

23. CMTS • Cable Modem Termination Systems (CMTS) • CMTS usually resides at the headend. • CMTS modulates and demodulates the signal to and from the cable modem (CM). • More later Rick Graziani graziani@cabrillo.edu

24. Radio Frequency Signals • Much of the RF spectrum is reserved for radio communications and therefore cannot be used for TV signals. • In the over-the-air TV broadcast environment: • VHF: 30 MHz – 300 MHz • UHF: 300 MHz – 3 GHz • In cable systems, the signal is transmitted across the cable rather than in the air. Rick Graziani graziani@cabrillo.edu

25. Radio Frequency Signals • Cable television industry defines the television spectrum for the downstream path only. • The following frequency scope is used: • Downstream: From the cable operator to the subscriber, the outgoing frequencies are in the range of 50 to 860 MHz. • Upstream: Reverse path from the subscriber to the cable operator, the incoming frequencies are in the range of 5 to 42 MHz. • The downstream frequency range is divided into channels (6 MHz channels in North America and 7 to 8 MHz for Europe). Rick Graziani graziani@cabrillo.edu

26. Digital Signals over RF Channels • DOCSIS: Data-over-Cable Service Interface Specification • An international standard developed by CableLabs, a nonprofit research and development consortium for cable-related technologies. • CableLabs tests and certifies cable equipment vendor devices (cable modem [CM] and cable modem termination systems [CMTS]) and grants DOCSIS-certified or Qualified status. • http://www.eurocablelabs.com • Defines the manner in which the individual components communicate in the cable network. • Cable operators use DOCSIS to implement Internet access over their existing HFC infrastructure. Rick Graziani graziani@cabrillo.edu

27. DOCSIS • Defines the OSI Layer 1 and Layer 2 requirements for connectivity between cable devices. • Physical layer: • For data signals that the cable operator can use, DOCSIS specifies the channel widths (bandwidths of each channel) as 200 kHz, 400 kHz, 800 kHz, 1.6 MHz, 3.2 MHz, and 6.4 MHz. DOCSIS also specifies modulation techniques (the way to use the RF signal to convey digital data). • MAC layer: • Defines a deterministic access method (time-division multiple access [TDMA] or synchronous code division multiple access [S-CDMA]). Rick Graziani graziani@cabrillo.edu

28. Digital Signals over RF Channels • DOCSIS • 1.0 April, 1997 • 1.1 April, 1999 • 2.0 January, 2002: QoS and IP Telephony • 3.0 August 2006: IPv6 and Channel Bonding • Channel Bonding allows the use of multiple downstream and upstream channels at the same time. • Reaching speeds of 160 Mbps downstream and 120 Mbps upstream • Current services based on cable architecture and provisioning practices – the typical range is 256 Kbps to 6 Mbps Rick Graziani graziani@cabrillo.edu

29. Describing DSL Technology

30. What is DSL • Several years ago, research by Bell Labs identified that a typical voice conversation over a local loop only required the use of bandwidth of 300 Hz to 3 kHz. • This was enough of a frequency range for normal voice conversation – low to high. • For many years, the telephone networks did not use the bandwidth beyond 3 kHz. Rick Graziani graziani@cabrillo.edu

31. What is DSL • Service providers deploy DSL connections in the last step of a local telephone network, the local loop. • The connection is set up between a pair of modems on either end of a copper wire that extends between the customer premises equipment (CPE) and the DSL access multiplexer (DSLAM). • A DSLAM is the device located at the central office (CO) of the provider and concentrates connections from multiple DSL subscribers. Rick Graziani graziani@cabrillo.edu

32. DSL Modem • The DSL modem or transceiver connects the teleworker’s computer to the DSL line. • USB or Ethernet cable • Can be built into small routers with 10/100 switch ports • The DSLAM is at the central office and combines individual DSL connections from users into one high capacity link to the Internet. • The advantage that DSL has over cable technology is that DSL is not a shared medium. • Each user has a separate direct connection to the DSLAM. Rick Graziani graziani@cabrillo.edu

33. DSL • DSL types fall into two major categories, taking into account downstream and upstream speeds: • Symmetrical DSL: Upstream and downstream speeds are the same. • Asymmetrical DSL: Upstream and downstream speeds are different. Downstream speed is typically higher than upstream speed. • Term xDSL covers a number of DSL variations. • Data rate that DSL service can provide depends on the distance between the subscriber and the CO. • The shorter the distance: the higher the bandwidth available. Rick Graziani graziani@cabrillo.edu

34. DSL Variants Rick Graziani graziani@cabrillo.edu

35. Asymmetric DSL TypesADSL • Most commonly deployed. • Supports data and voice simultaneously over existing copper lines. • The downstream rate ranges from 256 kbps (1.5 Mbps more common) to 8 Mbps • Upstream rates 16 Kbps 1 Mbps • Local loop range 18,000 feet • ITU-T Recommendation G992.1 and ANSI Standard T1.413-1998 specify full rate ADSL. Rick Graziani graziani@cabrillo.edu

36. Symmetric DSL TypesSDSL • Downstream and upstream rates from 128 Kbps to 2.32 Mbps • Most typical implementation is 768 Kbps • SDSL general term for various vendor implementations, proprietary and non-standardized • Data only, no voice (POTS) • Distances up to 21,000 feet • Symmetrical nature of SDSL makes it ideal for commercial use when the end user must send large amounts of data by applications such as e-mail messaging to customers with large attachments, uploading data to corporate servers, or updating web pages. • Note: Symmetric DSL is not as common as asymmetric DSL. Rick Graziani graziani@cabrillo.edu

37. Symmetric DSL TypesG.SHDSL (Symmetric high-data-rate DSL) • Industry-standard SDSL – ITU G.991.2 • Distances up to 26,000 feet • Downstream and upstream rates from 192 Kbps to 2.3 Mbps • Data only, no voice (POTS) Rick Graziani graziani@cabrillo.edu

38. Symmetric DSL TypesHDSL (High-data-rate DSL) • Downstream and upstream rates up to768 Kbps (Total 1.544 Mbps) for T1 • Available for T1 (1.544 Mbps) or E1 (2.048 Mbps) of symmetrical bandwidth • HDSL as a substitute for T1 and E1 • HDSL only carries data only (No POTS) and uses only two wires! Rick Graziani graziani@cabrillo.edu

39. Symmetric DSL TypesHDSL2 (Second Generation HDSL) • Downstream and upstream rates up to1.5 Mbps • HDSL only carries data only (No POTS) • Uses only two wires! Rick Graziani graziani@cabrillo.edu

40. Factors Affecting DSL Performance • All DSL types are limited in: • Distance • speed. • Speed is inversely proportional to distance. • Longer distance in the local loop means a lower maximum speed • Various impairments in the local loop that attenuate or distort the signal also affect the maximum speed of certain DSL connections Rick Graziani graziani@cabrillo.edu

41. Factors Affecting DSL Performance • Signal attenuation: • Attenuation means signal loss over distance and is determined by the distance between a subscriber and the CO. • The longer the distance between the two, the more attenuation occurs and therefore the lower the speed. Rick Graziani graziani@cabrillo.edu

42. Factors Affecting DSL PerformanceBridge Tap • Bridge tap: • An extra telephone wire with an un-terminated cable end connected to the local loop. • Common problem • Phone company runs a cable down the street the cable may extend a mile or so passed your house. • No other house or device is using your specific copper pair. • Installer takes the wires that come from your demarc, and "Taps" the wires coming from your house on to a copper pair. • (continued) Rick Graziani graziani@cabrillo.edu

43. Factors Affecting DSL PerformanceBridge Tap • Bridge tap (continued): • They do not cut the cable pair at the junction box. • In order not to drastically reduce the amplitude and of the signal coming from your telephone they do not to terminate the extended cable end either. • Your telephone line is simply tapped into the middle of it. • It's sort of like having an additional half-mile antenna picking up all the garbage in the air and feeding it to your telephone equipment. • Such an un-terminated tap can cause noise and reflections and can radiate power that reduces signal strength and, consequently speed. • DSL providers should remove bridge taps before installing a DSL. Rick Graziani graziani@cabrillo.edu

44. ADSL Deployment • Service providers deploy ADSL service between ADSL modems at the subscriber and the CO locations with an ADSL modem at each end: • An ADSL Transmission Unit-Remote (ATU-R) located at the subscriber end • An ADSL Transmission Unit-central office (ATU-C) located at the service provider end; a DSLAM at the central office encompasses multiple ATU-Cs Rick Graziani graziani@cabrillo.edu

45. DMT (Discrete Multi-Tone) • The main difference is that DMTdoes not use only two wide channels for upstream and downstream data traffic. • DMT divides the frequency band into 256 separate 4 kHz-wide channels. • Implementing DMT modulation is more complex than implementing CAP modulation because DMT modulation uses a large number of channels. • However, DMT modulation offers more flexibilitywhen traversing lines of differing quality. Rick Graziani graziani@cabrillo.edu

46. Types of Broadband Wireless • Municipal Wi-Fi • City-wide coverage with meshed repeaters… • Often not secure 802.11x networks • WiMAX • 802.16 • Antenna must have Line-of-Sight to tower • Satellite Internet • One –way multicast • One-way terrestrial return (dial-up for upstream) • Two-Way Satellite Internet Rick Graziani graziani@cabrillo.edu

47. WiMAX Protocols • Uses licensed 2.5 and 3.5 Ghz bands • Much ‘cleaner’ than 2.4Ghz public Rick Graziani graziani@cabrillo.edu

48. Markets for WiMAX • Example: ClearWire (merged with Sprint Nextel wireless) Rick Graziani graziani@cabrillo.edu

49. Introducing VPN Technology

50. Traditional WANs • Traditional wide-area network (WAN) connections between branch offices was accomplished with point-to-point (p2p) circuits: • X.25 • ATM • Frame Relay • Due to the “open” nature of the Internet, it is not considered secure • IPsec is used as a means of safeguarding IP data • Note that IPsec can be used on any type of connectivity—not just Internet links. • Predominantly used on data that traverses insecure or untrusted networks, such as the Internet. Rick Graziani graziani@cabrillo.edu