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Chapter Seven

Chapter Seven. WANs and Remote Connectivity. Objectives. Describe a variety of WAN transmission and connection methods Identify criteria for selecting an appropriate WAN topology, transmission method, and operating system

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Chapter Seven

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  1. Chapter Seven WANs and Remote Connectivity

  2. Objectives • Describe a variety of WAN transmission and connection methods • Identify criteria for selecting an appropriate WAN topology, transmission method, and operating system • Understand the hardware and software requirements for connecting to a network via modem • Install and configure simple remote connectivity for a telecommunicating client

  3. WAN Essentials • WAN link • Connection between one WAN site and another site • A WAN link is typically described as point-to-point • Dedicated line • Continuously available link that is leased through another carrier

  4. PSTN • Public Switched Telephone Network • Refers to the network of typical telephone lines and carrier equipment. • Also called plain old telephone service (POTS) • Usually use a serial protocol such as PPP, SLIP or even HDLC to connect.

  5. PSTN Figure 7-2: A typical PSTN connection to the Internet

  6. X.25 and Frame Relay • X.25 • Analog, packet-switched LAN technology optimized for long-distance data transmission • Frame Relay • Updated, digital version of X.25 that also relies on packet switching

  7. X.25 and Frame Relay • SVC (switched virtual circuit) • A dynamic circuit set up and torn down for each call. No one really uses them. • PVCs (permanent virtual circuit) • A static connection that does not require set-up or tear-down. This is what is used in industry. • CIR (committed information rate) • Guaranteed minimum amount of bandwidth selected when leasing a frame relay circuit

  8. Packet Switched vs. Circuit Switched

  9. ISDN (Integrated Services Digital Network) • All ISDN connections comprise two types of channels: • The B channel is the “bearer” channel • The D channel is the “delta” channel (some call it data) • ISDN Can be had in two flavours: • PRI – Primary Rate interface (23B +1D) x 64kbps • BRI – (Basic Rate interface) 2 64k B + 1 16k D

  10. BRI (Basic Rate Interface) • A variety of ISDN using two 64-Kbps bearer (B) channels and one 16-Kbps data (D) channel, as indicated by the following notation: • 2B+D • Through bonding, the two 64-Kbps channels can be combined to achieve an effective throughput of 128-Kbps

  11. BRI (Basic Rate Interface) • The Network Termination 1 (NT1) device connects twisted-pair wiring at customer’s building with ISDN terminal equipment (TE) via RJ-11 or RJ-45 data jacks • A terminal adapter (TA) converts digital signals into analog signals for use with ISDN phones and other analog devices Figure 7-4: A BRI link

  12. PRI (Primary Rate Interface) • A variety of ISDN using 23 B channels and one 64-Kbps D channel, as represented by the following notation: • 23B+D • PRI links use same kind of equipment as BRI links, but require the services of an extra network termination device—called a Network Termination 2 (NT2)—to handle multiple ISDN lines

  13. PRI (Primary Rate Interface) • It is only feasible to use ISDN for the local loop portion of a WAN link Figure 7-5: A PRI link

  14. T-Carriers • Broadband • Group of network connection types or transmission technologies generally capable of exceeding 1.544 Mbps throughput • T-carriers • Term for any kind of leased line that follows the standards for T1s, fractional T1s, T1Cs, T2s, T3s, or T4s

  15. Types of T-Carriers • The most common T-carrier implementations are T1 and T3 • Signal level • ANSI standard for T-carrier technology that refers to its Physical layer electrical signaling characteristics • DSO (digital signal, level 0) • Equivalent of one data or voice channel • Fractional T1 • Arrangement allowing an organization to use only some channels on a T1 line, paying for what they use

  16. Types of T-Carriers Figure 7-1: Carrier specifications

  17. T-Carrier Connectivity • Wiring • Can use unshielded or shielded twisted-pair copper wiring • CSU/DSU (Channel Service Unit/Data Service Unit) • CSU provides termination for the digital signal and ensures connection integrity through error correction and line monitoring • DSU converts the digital signal used by bridges, routers, and multiplexers into the digital signal sent via the cabling Figure 7-6: A CSU/DSU connecting a T1

  18. T-Carrier Connectivity • Multiplexer • Device that combines multiple voice or data channels on one line Figure 7-7: Typical use of a multiplexer on a T1-connected data network

  19. T-Carrier Connectivity • Routers and bridges • On a typical T1-connected data network, terminal equipment will consist of bridges, routers or a combination of the two Figure 7-8: A router on a T1-connected network

  20. DSL • Digital Subscriber Lines • Uses advanced data modulation techniques to achieve extraordinary throughput over regular phone lines • Like ISDN, DSL can span only limited distances without the help of repeaters

  21. Types of DSL • Term xDSL refers to all DSL varieties, of which at least eight currently exist • DSL types can be divided into two categories: • Asymmetrical • Symmetrical • To understand the difference between these two categories, you must understand the concept of downstream and upstream data transmission

  22. Types of DSL Table 7-2: Comparison of DSL types

  23. DSL Connectivity • DSL connectivity, like ISDN, depends on the PSTN • Inside carrier’s POP, a device called a DSL access multiplexer (DSLAM) aggregates multiple DSL subscriber lines and connects them to a larger carrier or to the Internet backbone Figure 7-9: A DSL connection

  24. Cable • Cable connections require that the customer use a special cable modem, a device that modulates and demodulates signals for transmission and reception via cable wiring Figure 7-11: A cable modem

  25. Cable • Hybrid fiber-coax (HFC) • Very expensive fiber-optic link that can support high frequencies • HFC upgrades to existing cable wiring are required before current TV cable systems can serve as WAN links • Cable drop • Fiber-optic or coaxial cable connecting a neighborhood cable node to a customer’s house • Head-end • Cable company’s central office, which connects cable wiring to many nodes before it reaches customers’ sites

  26. Cable Figure 7-12: Cable infrastructure

  27. SONET (Synchronous Optical Network) • Can provide data transfer rates from 64 Kbps to 39.8 Gbps using the same TDM technique used by T-carriers • Known internationally as SDH (Synchronous Digital Hierarchy) • SONET is self-healing

  28. Sonet Network

  29. SONET (Synchronous Optical Network) Table 7-3: SONET OC levels

  30. WAN Implementation:Speed Table 7-4a: A comparison of WAN technology transmission speeds

  31. WAN Implementation:Speed Table 7-4b: A comparison of WAN technology transmission speeds

  32. Summary • WANs are distinguished from LANs by the fact that the former networks traverse a wider geographical area • WAN transmissions can be provided by: • Frame Relay • X.25 • ATM • Dedicated Lines (T1, T3) • Sonet of X.25 • WANS can be $$$$

  33. Housekeeping • Test on Chapter 7 on Monday Nov 8th • Assignment Due Wednesday Nov 10th: • Please research and describe the differences between ATM, SONET and Frame Relay. • The paper should be in the following format: • 1.5 spacing, 11 pt. Times New Roman font. • Approx 2 – 3 pages per topic. • Include a proper works cited page, cover page. • Time Due: 8:15 am

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