* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Hands-on Networking Fundamentals
Survey
Document related concepts
Network tap wikipedia , lookup
Passive optical network wikipedia , lookup
Point-to-Point Protocol over Ethernet wikipedia , lookup
Low-voltage differential signaling wikipedia , lookup
Computer network wikipedia , lookup
Deep packet inspection wikipedia , lookup
Multiprotocol Label Switching wikipedia , lookup
List of wireless community networks by region wikipedia , lookup
Serial digital interface wikipedia , lookup
Internet protocol suite wikipedia , lookup
Recursive InterNetwork Architecture (RINA) wikipedia , lookup
Airborne Networking wikipedia , lookup
Synchronous optical networking wikipedia , lookup
Transcript
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 – 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 2 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 3 Hands-on Networking Fundamentals 4 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 5 Hands-on Networking Fundamentals 6 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 7 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 8 Hands-on Networking Fundamentals 9 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 10 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 11 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 12 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 13 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 14 Hands-on Networking Fundamentals 15 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 16 Hands-on Networking Fundamentals 17 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 18 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 19 Hands-on Networking Fundamentals 20 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 21 Hands-on Networking Fundamentals 22 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 23 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 24 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 25 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 26 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 27 Hands-on Networking Fundamentals 28 Hands-on Networking Fundamentals 29 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 30 Hands-on Networking Fundamentals 31