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Hands-on Networking Fundamentals

Hands-on Networking Fundamentals. Chapter 9 Understanding WAN Connection Choices. X.25. WAN protocol that uses packet-switching techniques Used in public data networks (PDNs) from 1976 PDN: provides data communication services to public Current specifications

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Hands-on Networking Fundamentals

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  1. Hands-on Networking Fundamentals Chapter 9 Understanding WAN Connection Choices

  2. X.25 • WAN protocol that uses packet-switching techniques • Used in public data networks (PDNs) from 1976 • PDN: provides data communication services to public • Current specifications • Defines data transfer from DTE to DCE, then into PDN • DTE (Data terminal equipment) may be a computer • DCE (Data circuit equipment) may be a packet switch • Point-to-point connection-oriented communications • Includes transmission speeds up to 2.048 Mbps • Globally accepted due to reliability and adaptability • Links older LANs, mainframes, minicomputers to WANs Hands-on Networking Fundamentals

  3. X.25 and the OSI Model • ITU-T (Telecommunications Standardized Sector of the International Telecommunications Union) • Defines X.25 in layers like first three of OSI model • X.25 Physical Protocol layer (Layer 1) • Governs physical connectivity to adapters and cables • X.25 Link Access layer (Layer 2) • Equivalent to OSI Data Link layer's Mac sublayer • Handles data transfer, flow control, frame composition • X.25 Packet Protocol layer (Layer 3) • Like the OSI Network layer • Manages orderly exchange, reliability of connection Hands-on Networking Fundamentals

  4. Hands-on Networking Fundamentals

  5. X.25 Transmission Modes • Three modes for transmitting data packets • Switched virtual circuit (SVC) • Two-way channel between nodes based on X.25 switch • Logical connection maintained for transmission only • Example of packet switching • Permanent virtual circuit (PVC) • Logical channel remains connected at all times • Another example of packet switching • Datagrams • Packaged data sent without establishing channel • Reach destination using form of message switching Hands-on Networking Fundamentals

  6. Hands-on Networking Fundamentals

  7. X.25 Deployment • Reasons for popularity of X.25 networks • Provide worldwide connectivity between LANs • Release unused bandwidth from nodes not communicating • New technologies replacing X.25 networks • Frame relay • SMDS • SONET • Optical Ethernet Hands-on Networking Fundamentals

  8. Frame Relay • Meets demand of high-volume, high-bandwidth LANs • Current speeds up to 45 Mbps over DS-3 links • Defined via ITU-T I.451/Q.931 and Q.922 standards • Some transported protocols: IP, IPX, AppleTalk, PPP • Elements in common with X.25 • Both use packet switching over virtual circuits • Connections are switched (SVC) or permanent (PVC) • Frame relay specific elements • Uses frame relay assembler disassembler (FRAD) • Provides connectionless-oriented service • Does not perform extensive error checking Hands-on Networking Fundamentals

  9. Hands-on Networking Fundamentals

  10. Frame Relay Layered Communications • Differ from X.25 in number and some functionality • Two communication layers • Physical layer: corresponds to OSI Physical layer • Consists of interfaces similar to those in X.25 • Adapters connect to frame relay network • Telecommunication lines used for wire communications • Includes optional sublayer for reliability • Link Access Protocol for Frame Mode Bearer Services (LAPF): corresponds to OSI Data Link layer • Formats and validates frames • Performs switching • Checks for transmission errors and line congestion Hands-on Networking Fundamentals

  11. Vendor Services • Three types offered by frame relay service providers • Committed information rate (CIR) • Provides pledged minimum transmission rate • Problems: lines not monitored well, rate difficult to verify • Permanent virtual connection (PVC) • A continuous dedicated connection to a specific location • Appropriate for linking mission critical nodes • Port • Based on purchasing access to set of ports • Ports located on vendor’s telecommunications switch Hands-on Networking Fundamentals

  12. Integrated Services Digital Network (ISDN) • Digital-based standard with multiple applications • LAN-to-LAN connectivity • Home offices and telecommuting • Off-site backup and disaster recovery • Connecting private telephone system to a public telco • LAN-to-LAN video and multimedia applications • Benefits of ISDN • Provides voice, data, video services over one network • Layered protocol structure compatible with OSI model • Channels in multiples of 64 Kbps, 384 Kbps, 1536 Kbps • Has switched and non-switched connection services • Broadband ISDN capabilities of 155 Mbps and higher Hands-on Networking Fundamentals

  13. 1.200 Services for Networking • Divided into three parts • Bearer services • Circuit-mode: ISDN communication delivers service • Packet-mode: virtual call/permanent virtual call circuits • Teleservices • Provides for 3.1-KHz speech communications • Includes telex for interactive telecommunications, fax • Includes videotex to retrieve mailbox information • Supplementary services • Primarily for voice communications • Caller ID and conference calling Hands-on Networking Fundamentals

  14. Digital Communication Services • Two N-ISDN interfaces: basic rate and primary rate • Basic Rate Interface (BRI) ISDN • Uses form of time division multiple access (TDMA) • Has aggregate data transmission rate of 144 Kbps • Two 64-Kbps Bearer (B) channels: data, voice, graphics • One 16-Kbps Delta (D) channel: call setup and teardown • Multiple BRI channels can be "bonded" together • Many systems support bonding using Multilink PPP • Example: Bond two B channels for 128-Kbps throughput • Some telcos allow D channel to be used for downloads • Four-wire twisted pair connects BRI ISDN to customer Hands-on Networking Fundamentals

  15. Hands-on Networking Fundamentals

  16. Broadband ISDN • Supports transfer rates of 155 Mbps to 1 Gbps (fiber) • Uses cells instead of packets • Cell has three parts: header, control data, data payload • Compatible with two other technologies • Asynchronous Transfer Mode (ATM) • Synchronous optical network (SONET) • Has not yet gained widespread acceptance Hands-on Networking Fundamentals

  17. Hands-on Networking Fundamentals

  18. ISDN Considerations • Two reasons to choose ISDN • Faster WAN solutions not available • Need to operate multiple devices over connection • Local availability depends on two factors • Whether service is offered by telco • Whether city infrastructure supports ISDN • Most commonly used protocols • National ISDN-1 (NI-1): RBOCs, long distance carriers • National ISDN-2 (NI-2): later version of NI-1 • Cabling: twisted-pair copper wire or fiber-optic cable Hands-on Networking Fundamentals

  19. Asynchronous Transfer Mode • High-speed network transport used in WANs or LANs • Carries data, voice, video, and multimedia applications • Many possible transmission speeds (up to 40 Gbps) • Easily scalable: as traffic grows, add more switches • Physical links operate over many cable types • Cell switching for communications over ATM channel • Adds virtual channel identifier to front of TDM time slot • Enables device to place bit onto channel asynchronously • Gives Quality of Service (QoS) for time-sensitive traffic • Supported by ANSI, the IETF, the ETSI, and the ITU-T • Compatible with B-ISDN, DSL, FDDI, and others Hands-on Networking Fundamentals

  20. Hands-on Networking Fundamentals

  21. How ATM Works • Sets up virtual circuits as pathway between nodes • Three types of virtual circuits employed • ATM permanent virtual circuit (ATM PVC) • Dedicated circuit with preassigned path • Eliminates delays caused by circuit setup and teardown • ATM switched virtual circuit (ATM SVC) • Set up and tear down as needed (transparent to user) • Temporary connection active during communication only • ATM smart permanent virtual circuit (ATM SPVC) • Manually configured like PVCs (but only at end devices) • Provides a dedicated bandwidth like a PVC • Defined path to switch and fault tolerance similar to SVC Hands-on Networking Fundamentals

  22. Hands-on Networking Fundamentals

  23. Digital Subscriber Line (DSL) • High-speed networking between subscriber and telco • Transmits data, voice, and video communications • Useful applications of DSL • Internet access, especially file downloads and uploads • Residential lines for home use and telecommuting • Office and small business WAN access • Accessing multimedia over a network • Quickly transmitting a large image file • Taking an interactive class or seminar • Implementing a distributed client/server application Hands-on Networking Fundamentals

  24. DSL Service Types • Asymmetric Digital Subscriber Line (ADSL) • Supports traditional data, multimedia, distance learning • Allows simultaneous transfer of voice and data • G.lite Asymmetric Digital Subscriber Line (G.lite ADSL) • Variation of ADSL compatible with Plug and Play (PnP) • Integrated Services Digital Network Digital Subscriber Line (IDSL) • Enables DSL in networks with Digital Loop Carrier • Rate Adaptive Asymmetric Digital Subscriber Line (RADSL) • Transmission rate adapted to data, multimedia, or voice Hands-on Networking Fundamentals

  25. DSL Service Types (continued) • High Bit-Rate Digital Subscriber Line (HDSL) • Full-duplex communications at fixed transfer rates • Does not support voice as well as ADSL and RADSL • Symmetric High Bit-Rate Digital Subscriber Line (SHDSL) • Can be used over one or two wires • Use of two wires improves range over other DSL types • Digital Subscriber Line (VDSL) • High-bandwidth alternative to coaxial or fiber-optic based networks • Symmetric Digital Subscriber Line (SDSL) • Symmetrical bandwidth useful with interactive media Hands-on Networking Fundamentals

  26. SONET • Synchronous optical network • Open, affordable fiber-optic transmission standard • Connects to interfaces for ATM, ISDN, and routers • Transmits data faster than 1 Gbps (up to 9.953 Gbps) • Five applications for SONET • Very high-speed data connectivity over long distances • Video conferencing between distant sites • Long-distance teaching • High-quality sound and video reproduction • High-speed transmission of complex graphics Hands-on Networking Fundamentals

  27. Communications Media and Characteristics • Uses single-mode fiber-optic cable, T-carrier lines • Main transport method occurs at Physical layer • Compatible with technologies using fixed cell lengths • SONET transmission speeds: 51.84 to 9953.28 Mbps • Designated by optical carrier (OC) and Synchronous Transport Signal Level (STS) • Common options: OC-3, OC-12, OC-48, and OC-192 • Synchronous Digital Hierarchy (SDH) • SONET-like standard developed by ITU-T • Synchronous Transport Model Level (STM) • Designation for various speeds Hands-on Networking Fundamentals

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  30. Ethernet-Based MANs And WANs (Optical Ethernet) • High-speed alternative to SONET and frame relay • Networks consist of three basic elements • Gigabit or 10 Gigabit Ethernet MAN or WAN backbone • Multimode fiber-optic cable connections up to six miles • Single-mode fiber-optic cable connections up to 43.4 miles • Ethernet backbone links three types of LANs • Fast Ethernet • Gigabit Ethernet • 10 Gigabit Ethernet Hands-on Networking Fundamentals

  31. Hands-on Networking Fundamentals

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