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Ryerson University
Information Technology Management
ITM 301
Khalil Arbousa

ITM 301 Vocab Chapter 1: An Introduction to Networking  Network  Peer to peer network  Client/server network  NOS (network operating system) o Allows computer to function as a server  NIC (network interface card) o Connects workstation to network  LAN , MAN, WAN o Host o Node (connection point) o Connectivity device o Segment (group of nodes) o Backbone (network of networks) o Topology o Protocol (set of rules) o Packet (unit of data) o Addressing o Transmission media  Network services (printer, file, sharing, internet access)  File and print services (share data, applications, disk storage space)  Access services (remote users can access server)  Communication services  Internet services  Management o Traffic monitoring & control o Load balancing o Hardware diagnosis & failure alert o Asset management o License tracking o Security auditing o Software distribution o Address management o Backup & restore data Chapter 2: Network Standards Organizations  Standards  ANSI (American National Standards Institute) o Determine standards for electronics industry, chemical nuclear engineering, health/safety, construction  EIA & TIA o Electronics Industries Alliance (helps write ANSI standards) o Telecommunications Industry Association (info tech, wireless, satellite, fiber optics, telephone equipment)  IEEE (Institute of Electrical and Electronics Engineers) o Promotes development and education in engineering and com sci fields  ISO (International Organization for Standardization o Establish IT standards to facilitate global exchange of info and free trade  ITU (International Telecommunication Union) o Radio/tv frequencies, satellite/telephone specifications, network infrastructure  ISOC (Internet Society) o Accessible, info security, stable address services, open standards o IAB (Internet Architecture Board) (design & management) o IETF (Internet Engineering Task Force) (how systems communicate over the Internet  IANA & ICANN o Internet Assigned Numbers Authority (keeps records of available and reserved IP addresses o Internet Corp for Assigned Names and Numbers (IP addressing and domain name management)  ISP (Internet Service Provider) o A business that provides org and individuals with access to the internet  OSI model (Open Systems Interconnection) o Universal set of specifications that enables computer platforms across the world to communicate openly o Theoretical representation of what happens b/w 2 nodes communicating on a network  Application (provides interface b/w software apps and network for interpreting apps requests and requirements)  Presentation (allows hosts & apps to use a common language: data formatting, encryption, compression)  Session (establishes, maintains, terminates user connections)  Transport (ensures accurate delivery of data through flow control, segmentation and reassembly, error correction, acknowledgement)  Network (establishes network connections; translates network addresses into their physical counterparts and determines routing)  Data link (packages data in frames appropriate to network transmission method)  Physical (manages signaling to and from physical network connections) Week 3: Chapter 3: Transmission Basics and Networking Media  Transmit, transmission, transceiver  Analog (voltage varies continuously, wavy line) o Amplitude, frequency, wavelength, phase, wavelength o hertz  Volts, voltage  Noise  Digital (pulses of precise voltages, choppy) o Binary, bit, byte  Overhead (nondata info that accompanies data to be properly routed and interpreted)  Modem, modulation, demodulation (make suitable for carrying data) o AM (amplitude modulation) o FM (frequency modulation)  Simplex (signal travels one way direction)  Half-duplex (travel in both directions but one at a time)  Duplex (travel both directions)  Channel  Multi-plexing, subchannels o TDM (time division multiplexing) (divides channel into multiple time slots) o Statistical multiplexing (sorts slots to nodes according to priority) o FDM (frequency division multiplexing) (unique frequency band, multiplexed to travel over single channel) o WDM (wavelength division multiplexing) (fibre optic cable carries multiple light signals) o DWDM (dense wavelength division multiplexing)  Point to point transmission (one transmitter, one receiver)  Point to multipoint transmission (one transmitter, multiple receivers) o Broadcast (undefined receivers) o Nonbroadcast (defined recipients)  Throughput (measure of how much data is transmitted during a given period of time/capacity)  Bandwidth (diff b/w high/low frequencies)  Baseband (digital signals are sent through direct current pulses)  Broadband (modulated as radio frequency)  Noise o EMI (electromagnetic interference) o RFI (radio frequency interference) o Crosstalk o Attenuation (loss of signals strength)  Amplifier, regeneration  Latency (delay b/w transmission of signal and receipt)  RTT (Round trip time)  Throughput o Limitations: physics, multiplexing  Cost  Noise immunity  Size & Scalability  Connector cables o Coaxial, twisted pair, fiber optics, single mode fiber, multimode fiber,  Media converters o Fiber optic converters o Serial cables o Structured cabling Week 4: Chapter 4: TCP/IP Protocols  TCP/IP (Transmission Control Protocol/Internet Protocol) o A suite of specialized protocols o Open, flexible, routable o Four layers  Application, Transport, Internet, Network  Protocols o TCP (Transmission Control Protocol) o UDP (User Datagram P) o IP o IGMP (Internet Group Management P) o ARP (Address Resolution P) o ICMP (Internet Control Message P)  IPv4 Addressing  Binary & Dotted Decimal Notation  Subnet Mask  IPv6 Addressing  Assign IP Addresses (IANA, ICANN, RIRs) o Static, dynamic  DHCP (Dynamic Host Configuration P)  Private, Link-local addresses  Zero configuration  APIPA (Automatic private IP addressing)  Sockets  Ports  Host and DNS (Domain Name System) o Resolvers o Name servers o Namespace o Resource record  DDNS (Dynamic DNS)  Telnet  FTP (File Transfer P)  TFTP (Trivial FTP)  NTP (Network Time P)  PING (Packet Internet Groper) Week 5: Chapter 8: Wireless Networking  Wireless spectrum  Antennas o Radiation pattern  Directional  Omnidirectional o Range  Signal propagation o LOS (line of sight) o Reflection o Diffraction o Scattering o Multipath  Signal degradation o Fading  Attenuation  Noise  Frequency range (2.4-Ghz band) o LANs WANs use 5-Ghz band  Narrowband, broadband   Spread-spectrum o FHSS (frequency hopping spread spectrum) o DSSS (direct-sequence spread spectrum)  Fixed vs Mobile  WLAN architecture o Ad hoc o WAP (wireless access point)  IEEE 802.11 WLANs  CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) o RTS/CTS (request to send/clear to send)  Association o Active Scanning  Probe o Passive scanning  Beacon frame o BSS (basic service set)  Group of stations that share an access point o BSSID (basic service set identifier)  ESS (extended service set)  ESSID o Roaming o Reassociation  Frames o Control  Medium access  Data delivery o Management  Association  reassociation o data  carry data sent b/w stations  4 address fields o Source address, transmitter, receiver, destination o Sequence control field (fragment large packets)  802.11b o 2.4-Ghz band o 22 Mhz channels o 11 mbps theoretical throughput o 5 mbps actual o 100 m node limit  802.11a o 5 Ghz band o 54 mbps theoretical o 11 and 18 mbps effective o 20 m node limit  802.11g o 2.4 Ghz band o 54 mbps theoretical o 20-25 mbps effective o 100 m node range  802.11n o Standard o 2.4 or 5 Ghz band o Actual 65 - 600 mbps throughput o MIMO (multiple input multiple output)  Phases of signals are adjusted and strength of multiple signals are summed o Channel bonding  2 20-MHz channels can be combined to make 40-MHz channel o Higher modulation rates  Simple channel divided into small channels o Frame aggregation  Combines multiple frames into one larger frame o Backward compatible (not all 802.11n features work o Recommendation  Use 802.11n-compatible devices  Implementing a WLAN o Home, small office o Formation of larger, enterprise wide WANs o Install + configure access points and clients o Implementation pitfalls  Determining the design o One access point  Combine w/ switching, routing functions  Connects wireless clients to LAN  Acts as internet gateway o Access WLAN placement considerations  Typical distances b/w access point + client  Obstacles  Type and number of b/w access point and clients o Larger WLANs  Systematic approach to access point placement o Site survey  Assesses client requirements, facility characteristics, coverage areas  Determines access point arrangement ensuring reliable wireless connectivity  Proposes access point testing o Install access points  Must belong to same ESS, share ESSID o Enterprise wide WLAN design considerations  How wireless LAN portions will integrate with wired portions  Configuring Wireless Connectivity Devices o Access point CD-ROM or DVD  Guides through setup process o Variables set during insttallationg  Admin pass  SSID  Whether or not DHCP is used  Whether or not SSID is broadcast  Security options  Configuring Wireless Clients o Configuration varies from one client type to another o Linus and UNIX clients wireless interface configuration  Use graphical interface  Iwconfig command-line function  View, set wireless interface parameters  Avoiding Pitfalls o Access point versus client configurations  SSID mismatch  Incorrect encryption  Incorrect channel, frequency  Standard mismatch (802.11 a/b/g/n) o Incorrect antenna placement  Verify client within 330 feet o Interference  Check for EMI sources  Wireless WANs o Wireless broadband  Latest wireless WAN technologies  Specifically designed for:  High throughput, long=distance digital data exchange  802.16 (WiMAX) o Worldwide Interoperability for Microwave Access  Most popular version: 802.16e (2005)  Improved WiMAX version: 802.16m (2011)  Functions in 2-11 or 11-66 GHz range  Licensed or nonlicensed frequencies o Ability to transmit and receive signals up to 30 miles  With fixed antennas  About 10 miles when antennas are mobile o 802.16m  Positioned to compete favorably with cellular data services  Backwards compatible with 802.16e equipment o Maximum throughput  Downlink: 120Mbps  Uplink: 60Mbps  Future improvements could take to 1Gbps  Cellular o Initially designed for analog telephone service  Today deliver data and voice o Cellular technology generations  1G: analog  2G: digital transmission up to 240Kbps  3G: data rates up to 384Kbps  Data communications use packet switching  4G: all-IP, packet switched network for data and voice o Network infrastructure  Cells served by antenna and base station  Controller assigns mobile clients frequencies o Cell size depends on:  Network’s access method  Region topology  Population  Amount of cellular traffic o Basic infrastructure  HSPA+ (High Speed Packet Access Plus)  3G technology o LTE (Long Term Evolution)  4G technology  Satellite o Used to deliver:  Digital television and radio signals  Voice and video signals  Cellular and paging signals  Data services to mobile clients in remote locations o Most popular satellite orbit  Geosynchronous Earth orbit (GEO)  Satellites orbit at same rate Earth turns o Downlink  Satellite transponder transmits signal to Earth-based receiver o Typical satellite  24 to 32 transponders  Unique downlink frequencies o Satellite frequency bands  L-band—1.5–2.7 GHz  S-band—2.7–3.5 GHz  C-band—3.4–6.7 GHz  Ku-band—12–18 GHz  Ka-band—18–40 GHz o Within bands  Uplink, downlink transmissions differ o Satellite Internet services  Subscriber uses small satellite dish antenna, receiver  Exchanges signals with provider’s satellite network  Typically asymmetrical  Bandwidth shared among many subscribers  Throughput controlled by service provider  Slower, more latency than other wireless WAN options MIDTERM Ch 6: Network Hardware, Switching, and Routing  NICs (Network interface cards) o Connectivity devices  Enable device transmission  Transceiver  Transmits and receives data o Physical layer and Data Link layer functions  Issue data signals  Assemble and disassemble data frames  Interpret physical addressing information  Determine right to transmit data o Smart hardware  Prioritization  Network management  Buffering  Traffic-filtering o Do not analyze information  Added by Layers 3 through 7 OSI model protocols o Importance  Common to every networking device, network  Types of NICs o Before ordering or installing NIC  Know device interface type o Types of NICs (NIC dependencies)  Access method  Network transmission speed  Connector interfaces  Compatible motherboard or device type  Manufacturer  Support for enhanced features o Bus  Circuit, signaling pathway  Motherboard uses to transmit data to computer’s components  Memory, processor, hard disk, NIC  Differ according to capacity  Defined by data path width and clock speed  Data path size  Parallel bits transmitting at any given time  Proportional to attached device’s speed o Expansion slots  Multiple electrical contacts on motherboard  Allow bus expansion o Expansion card (expansion board)  Circuit board for additional devices  Inserts into expansion slot, establishes electrical connection  Device connects to computer’s main circuit or bus  Computer centrally controls device o Multiple bus types  PCIe bus: most popular expansion board NIC o PCIe (Peripheral Component Interconnect Express)  32-bit bus  Maximum data transfer rate: 1 Gbps  Introduced in 2004 o Determining bus type  Read documentation  Look inside PC case  If more than one expansion slot type:  Refer to NIC, PC manufacturers’ guidelines  Choose NIC matching most modern bus o Peripheral NICs  Attached externally  Simple installation into a variety of slots  PCMCIA (Personal Computer Memory Card International Association)  PCIe (Peripheral Component Interconnect Express)  USB (Universal Serial Bus)  CompactFlash  FireWire  Installing and configuring software may be required o On-Board NICs  Connect device directly to motherboard  On-board ports: mouse, keyboard o New computers, laptops  Use onboard NICs integrated into motherboard o Advantages  Saves space  Frees expansion slots  Installing and Configuring NICs o Installing NIC hardware  Read manufacturer’s documentation o Install expansion card NIC  Gather needed tools  Unplug computer, peripherals, and network cable  Ground yourself  Open computer case  Select slot, insert NIC, attach bracket, verify cables  Replace cover, turn on computer  Configure NIC software o Installing and configuring NIC software  Device driver  Software enabling device to communicate with operating system o Purchased computer with a peripheral  Drivers installed o Add hardware to computer  Must install drivers o Operating system built-in drivers  Automatically recognize hardware, install drivers o Drivers not available from operating system  Install and configure NIC software  Available at manufacturer’s Web site o Verifying NIC functionality  Check whether device can communicate with network o Diagnostic tools  Use manufacturer’s configuration utility  Loopback plug needed  Visual inspection of LEDs  Read manufacturer’s documentation  Use simple commands  Example: pinging the loopback address  Modular Interfaces o Hot-swappable components  Can be changed without disrupting operations o GBIC (Gigabit interface converter)  Standard type of modular interface  May contain RJ-45 or fiber-optic cable ports o SFPs (small form-factor pluggable)  Provide same form factor as GBIC  Allow more ports per inch  Repeaters and Hubs o Repeaters  Operate in Physical OSI model layer  No means to interpret data  Regenerate signal o Hub  Repeater with more than one output port  Typically contains multiple data ports  Patch cables connect printers, servers, and workstations  Most contain uplink port  Switching  Bridges o Devices that connect two network segments o Analyze incoming frames  Make decisions on where to direct them o Operate at Data Link OSI model layer o Single input and single output ports o Protocol independent o Filtering database  Contains known MAC addresses and network locations  Switches o Connectivity devices that subdivide a network  Segments o Traditional switches  Operate at Data Link OSI model layer o Modern switches  Can operate at Layer 3 or Layer 4 o Switches interpret MAC address information o Common switch components  Internal processor, operating system, memory, ports  Switch Installation o Follow manufacturer’s guidelines o General steps (assume Cat 5 or better UTP)  Verify switch placement  Turn on switch  Verify lights, self power tests  Configure (if necessary)  Connect NIC to a switch port (repeat for all nodes)  After all nodes connected, turn on nodes  Connect switch to larger network (optional)  Switching Methods o Four switching modes exist  Two basic methods discussed  Cut-through mode o Switch reads frame’s header o Forwarding decision made before receiving entire packet  Uses frame header: first 14 bytes contains destination MAC address o Cannot verify data integrity using frame check sequence o Can detect erroneously shortened packets (runts) o Runt detected: wait for integrity check o Cannot detect corrupt packets o Advantage: speed o Disadvantage  Data buffering (switch flooded with traffic) o Best use  Small workgroups needing speed  Low number of devices    Store-and-forward mode o Switch reads entire data frame into memory o Checks for accuracy before transmitting information o Transmit data more accurately than cut-through mode o Slower than cut-through mode o Best uses  Larger LAN environments; mixed environments o Can transfer data between segments running different transmission speeds    Fragment free  VLANs and Trunking o VLANs (virtual local area networks)  Logically separate networks within networks  Groups ports into broadcast domain o Broadcast domain  Port combination making a Layer 2 segment  Ports rely on Layer 2 device to forward broadcast frames o Collision domain  Ports in same broadcast domain  Do not share single channel  Advantage of VLANs o Flexible  Ports from multiple switches or segments  Use any end node type o Reasons for using VLAN  Separating user groups  Isolating connections  Identifying priority device groups  Grouping legacy protocol devices  Separating large network into smaller subnets  Switch typically preconfigured o One default VLAN o Cannot be deleted or renamed  Create additional VLANs o Indicate to which VLAN each port belongs o Additional specifications  Security parameters, filtering instructions, port performance requirements, network addressing and management options  Maintain VLAN using switch software  Potential problem o Cutting off group from rest of network  Correct by using router or Layer 3 switch  Trunking o Switch’s interface carries traffic of multiple VLANs  Trunk o Single physical connection between switches  VLAN data separation o Frame contains VLAN identifier in header  STP (Spanning Tree Protocol) o IEEE standard 802.1D o Operates in Data Link layer o Prevents traffic loops  Calculating paths avoiding potential loops  Artificially blocking links completing loop o Three steps  Select root bridge based on Bridge ID  Examine possible paths between network bridge and root bridge  Disables links not part of shortest path o History  Introduced in 1980s  Original STP too slow  RSTP (Rapid Spanning Tree Protocol)  Newer version  IEEE’s 802.1w standard o Cisco and Extreme Networks  Proprietary versions o No enabling or configuration needed  Included in switch operating software  Content and Multilayer Switches o Layer 3 switch (routing switch)  Interprets Layer 3 data o Layer 4 switch  Interprets Layer 4 data o Content switch (application switch)  Interprets Layer 4 through Layer 7 data o Advantages  Advanced filtering  Keeping statistics  Security functions o Distinguishing between Layer 3 and Layer 4 switch  Manufacturer dependent o Higher-layer switches  Cost more than Layer 2 switches  Used in network backbone  Routing  Routers o Multiport connectivity device  Directs data between network nodes  Integrates LANs and WANs o Different transmission speeds, protocols  Operate at Network layer (Layer 3)  Directs data from one segment or network to another  Logical addressing  Protocol dependent o Slower than switches and bridges  Need to interpret Layers 3 and higher information o Traditional stand-alone LAN routers  Being replaced by Layer 3 routing switches o New niche  Specialized applications  Linking large Internet nodes  Completing digitized telephone calls  Router Characteristics and Functions o Intelligence  Tracks node location  Determine shortest, fastest path between two nodes  Connects dissimilar network types o Large LANs and WANs  Routers indispensable o Router components  Internal processor, operating system, memory, input and output jacks, management control interface o Multiprotocol routers  Multiple slots  Accommodate multiple network interfaces o Inexpensive routers  Home, small office use o Router capabilities  Connect dissimilar networks  Interpret Layer 3 addressing  Determine best data path  Reroute traffic o Optional router functions  Filter broadcast transmissions  Enable custom segregation, security  Support simultaneous connectivity  Provide fault tolerance  Monitor network traffic  Diagnose problems and trigger alarms o Interior router  Directs data between nodes on a LAN o Exterior router  Directs data between nodes external to a LAN o Border routers  Connect autonomous LAN with a WAN o Routing tables  Identify which routers serve which hosts o Static routing  Router configured to use specific path between nodes o Dynamic routing  Automatically calculates best path between nodes o Installation  Simple for small office or home office LANs  Web-based configuration  Challenging for sizable networks  Routing Protocols o Best path  Most efficient route from one node to another  Dependent on:  Hops between nodes  Current network activity  Unavailable link  Network transmission speed  Topology  Determined by routing protocol o Routing metric factors  Number of hops  Throughput on potential path  Delay on a potential path  Load (traffic)  Maximum transmission unit (MTU)  Cost  Reliability of potential path o Router convergence time  Time router takes to recognize best path  Change or network outage event o Distinguishing feature  Overhead; burden on network to support routing protocol o Distance-vector routing protocols  Determine best route based on distance to destination  Factors  Hops, latency, network traffic conditions o RIP (Routing Information Protocol)  Only factors in number of hops between nodes  Limits 15 hops  Type of IGP (Interior Gateway Protocol)  Can only route within internal network  Slower and less secure than other routing protocols o RIPv2 (Routing Information Protocol Version 2)  Generates less broadcast traffic, more secure  Cannot exceed 15 hops  Less commonly used o BGP (Border Gateway Protocol)  Communicates using BGP-specific messages  Many factors determine best paths  Configurable to follow policies  Type of EGP (Exterior Gateway Protocol)  Most complex (choice for Internet traffic) o Link-state routing protocol  Routers share information  Each router independently maps network, determines best path o OSPF (Open Shortest Path First)  Interior or border router use  No hop limit  Complex algorithm for determining best paths  Each OSPF router  Maintains database containing other routers’ links o IS-IS (Intermediate System to Intermediate System)  Codified by ISO  Interior routers only  Supports two Layer 3 protocols  IP  ISO-specific protocol  Less common than OSPF o Hybrid  Link-state and distance-vector characteristics  EIGRP (Enhanced Interior Gateway Routing Protocol)  Most popular  Cisco network routers only  EIGRP benefits  Fast convergence time, low network overhead  Easier to configure and less CPU-intensive than OSPF  Supports multiple protocols  Accommodates very large, heterogeneous networks o Path Vector Protocols  Border Gateway Protocol  the most scalable of all routing protocols.  BGP is the routing protocol of the global Internet, as well as for Service Provider private networks. B  GP has expanded upon its original purpose of carrying Internet reachability information, and can now carry routes for Multicast, IPv6, VPNs, and a variety of other data.  Gateways and Other Multifunction Devices o Gateway  Combination of networking hardware and software  Connects two systems using different formatting, communications protocols, architecture  Repackages information  Resides on servers, microcomputers, connectivity devices, mainframes o Popular gateways  E-mail gateway, Internet gateway, LAN gateway, voice/data gateway, firewall Ch 7: Wide Area Networks  WAN Essentials o WAN  Network traversing some distance, connecting LANs  Transmission methods depend on business needs o WAN and LAN common properties  Client-host resource sharing  Layer 3 and higher protocols  Packet-switched digitized data o WAN and LAN differences  Layers 1 and 2 access methods, topologies, media  LAN wiring: privately owned  WAN wiring: public through NSPs (network service providers)  Examples: AT&T, Verizon, Sprint o WAN site  Individual geographic locations connected by WAN o WAN link  WAN site to WAN site connection o Differences from LAN topologies  Distance covered, number of users, traffic  Connect sites via dedicated, high-speed links  Use different connectivity devices o WAN connections  Require Layer 3 devices  Routers  Cannot carry nonroutable protocols  Bus o Bus topology WAN  Each site connects serially to two sites maximum  Network site dependent on every other site to transmit and receive traffic  Different locations connected to another through point-to-point links o Best use  Organizations requiring small WAN, dedicated circuits o Drawback  Not scalable  Ring o Ring topology WAN  Each site connected to two other sites  Forms ring pattern  Connects locations  Relies on redundant rings  Data rerouted upon site failure o Expansion  Difficult, expensive o Best use  Connecting maximum five locations  Star o Star topology WAN  Single site central connection point  Separate data routes between any two sites o Advantages  Single connection failure affects one location  Shorter data paths between any two sites  Expansion: simple, less costly o Drawback  Central site failure can bring down entire WAN  Mesh o Mesh topology WAN  Incorporates many directly interconnected sites  Data travels directly from origin to destination  Routers can redirect data easily, quickly o Most fault-tolerant WAN type o Full-mesh WAN  Every WAN site directly connected to every other site  Drawback: cost o Partial-mesh WAN  Less costly  Tiered o Tiered topology WAN  Sites connected in star or ring formations  Interconnected at different levels  Interconnection points organized into layers  Form hierarchical groupings o Flexibility  Allows many variations, practicality  Requires careful considerations  Geography, usage patterns, growth potential  PSTN o PSTN (Public Switched Telephone Network)  Network of lines, carrier equipment providing telephone service  POTS (plain old telephone service)  Encompasses entire telephone system  Originally: analog traffic  Today: digital data, computer controlled switching o Dial-up connection  Modem connects computer to distant network  Uses PSTN line o PSTN elements  Cannot handle digital transmission  Requires modem o Signal travels path between modems  Over carrier’s network  Includes CO (central office), remote switching facility  Signal converts back to digital pulses o CO (central office)  Where telephone company terminates lines  Switches calls between different locations o Local loop (last mile)  Portion connecting residence, business to nearest CO  May be digital or analog o Digital local loop  Fiber to the home (fiber to the premises) o Passive optical network (PON)  Carrier uses fiber-optic cabling to connect with multiple endpoints o Optical line terminal  Single endpoint at carrier’s central office in a PON  Device with multiple optical ports o Optical network unit  Distributes signals to multiple endpoints using fiber-optic cable  Or copper or coax cable  X.25 and Frame Relay o X.25 ITU standard  Analog, packet-switching technology  Designed for long distance  Original standard: mid 1970s  Mainframe to remote computers: 64 Kbps throughput  Update: 1992  2.048 Mbps throughput  Client, servers over WANs  Verifies transmission at every node  Excellent flow control, ensures data reliability  Slow, unreliable for time-sensitive applications o Frame relay  Updated X.25: digital, packet-switching  Protocols operate at Data Link layer  Supports multiple Network, Transport layer protocols o Both perform error checking  Frame relay: no reliable data delivery guarantee  X.25: errors fixed or retransmitted o Throughput  X.25: 64 Kbps to 45 Mbps  Frame relay: customer chooses o Both use virtual circuits  Node connections with disparate physical links  Logically appear direct  Advantage: efficient bandwidth use o Both configurable as SVCs (switched virtual circuits)  Connection established for transmission, terminated when complete o Both configurable as PVCs (permanent virtual circuits)  Connection established before transmission, remains after transmission o PVCs  Not dedicated, individual links o X.25 or frame relay lease contract  Specify endpoints, bandwidth  CIR (committed information rate)  Minimum bandwidth guaranteed by carrier o PVC lease  Share bandwidth with other X.25, frame relay users o Frame relay lease advantage  Pay for bandwidth required  Less expensive technology  Long-established worldwide standard o Frame relay and X.25 disadvantage  Throughput variability on shared lines o Frame relay and X.25 easily upgrade to T-carrier dedicated lines  Same connectivity equipment  ISDN o Standard for transmitting digital data over PSTN o Gained popularity: 1990s  Connecting WAN locations  Exchanges data, voice signals o Protocols at Physical, Data Link, Transport layers  Signaling, framing, connection setup and termination, routing, flow control, error detection and correction o Relies on PSTN for transmission medium o Dial-up or dedicated connections  Dial-up relies exclusively on digital transmission o Capability: two voice calls, one data connection on a single line o Two channel types  B channel: “bearer”  Circuit switching for voice, video, audio: 64 Kbps  D channel: “data”  Packet-switching for call information: 16 or 64 Kbps o BRI (Basic Rate Interface) connection o PRI (Primary Rate Interface) connection o BRI: two B channels, one D channel (2B+D)  B channels treated as separate connections  Carry voice and data o Bonding  Two 64-Kbps B channels combined  Achieve 128 Kbps o PRI: 23 B channels, one 64-Kbps D channel (23B+D)  Separate B channels independently carry voice, data  Maximum throughput: 1.544 Mbps o PRI and BRI may interconnect  T-Carriers o T1s, fractional T1s, T3s o Physical layer operation o Single channel divided into multiple channels  Uses TDM (time division multiplexing) over two wire pairs o Medium  Telephone wire, fiber-optic cable, wireless links o Many available, most common: T1 and T3 o  Types of T-Carriers o T1: 24 voice or data channels  Maximum data throughput: 1.544 Mbps o T3: 672 voice or data channels  Maximum data throughput: 44.736 Mbps (45 Mbps) o T-carrier speed dependent on signal level  Physical layer electrical signaling characteristics  DS0 (digital signal, level 0)  One data, voice channel  T-Carrier Connectivity o T-carrier line requires connectivity hardware  Customer site, switching facility  Purchased or leased  Cannot be used with other WAN transmission methods o T-carrier line requires different media  Throughput dependent o Wiring  Plain telephone wire  UTP or STP copper wiring  STP preferred for clean connection o Coaxial cable, microwave, fiber-optic cable o T1s using STP require repeater every 6000 feet o Multiple T1s or T3  Fiber-optic cabling o o o CSU/DSU (Channel Service Unit/Data Service Unit)  Two separate devices  Combined into single stand-alone device  Interface card  T1 line connection point o CSU  Provides digital signal termination  Ensures connection integrity o DSU  Converts T-carrier frames into frames LAN can interpret (and vice versa)  Connects T-carrier lines with terminating equipment  Incorporates multiplexer o Smart jack  Terminate T-carrier wire pairs  Customer’s demarc (demarcation point)  Inside or outside building o Connection monitoring point o Incoming T-carrier line  Multiplexer separates combined channels o Outgoing T-carrier line  Multiplexer combines multiple LAN signals o Terminal equipment  Switches, routers  Best option: router, Layer 3 or higher switch  Accepts incoming CSU/DSU signals  Translates Network layer protocols  Directs data to destination o CSU/DSU may be integrated with router, switch  Expansion card  Faster signal processing, better performance  Less expensive, lower maintenance solution  DSL (Digital Subscriber Line) o Operates over PSTN o Directly competes with ISDN, T1 services o Requires repeaters for longer distances o Best suited for WAN local loop o Supports multiple data, voice channels  Over single line  Higher, inaudible telephone line frequencies o Uses advanced data modulation techniques  Data signal alters carrier signal properties  Amplitude or phase modulation  Types of DSL o xDSL refers to all DSL varieties  ADSL, G.Lite, HDSL, SDSL, VDSL, SHDSL o Two DSL categories  Asymmetrical and symmetrical o Downstream  Data travels from carrier’s switching facility to customer o Upstream  Data travels from customer to carrier’s switching facility o Downstream, upstream throughput rates may differ  Asymmetrical  More throughput in one direction  Downstream throughput higher than upstream throughput  Best use: video conferencing, web surfing o Symmetrical  Equal capacity for upstream, downstream data  Examples: HDSL, SDSL, SHDSL  Best use: uploading, downloading significant data amounts o DSL types vary  Data modulation techniques  Capacity  Distance limitations  PSTN use o  DSL Connectivity o ADSL: common example on home computer o Establish TCP connection o Transmit through DSL modem  Internal or external  Splitter separates incoming voice, data signals  May connect to switch or router o DSL modem forwards modulated signal to local loop  Signal continues over four-pair UTP wire  Distance less than 18,000 feet: signal combined with other modulated signals in telephone switch o Carrier’s remote switching facility  Splitter separates data signal from voice signals  Request sent to DSLAM (DSL access multiplexer)  Request issued from carrier’s network to Internet backbone o DSL competition  T1, ISDN, broadband cable o DSL installation  Hardware, monthly access costs  Slightly less than ISDN; significantly less than T1s o DSL drawbacks  Throughput lower than broadband cable  Broadband Cable o Cable companies connectivity option o Based on TV signals coaxial cable wiring  Theoretical transmission speeds  150 Mbps downstream; 10 Mbps upstream  Real transmission  10 Mbps downstream; 2 Mbps upstream  Transmission limited ( throttled)  Shared physical connections o Best uses  Web surfing  Network data download o Cable modem  Modulates, demodulates transmission, reception signals via cable wiring  Operates at Physical and Data Link layer  May connect to connectivity device o Infrastructure required  HFC (hybrid fiber-coax)  Expensive fiber-optic link supporting high frequencies  Connects cable company’s offices to node o Cable drop  Connects node to customer’s business or residence  Fiber-optic or coaxial cable  Connects to head end o Provides dedicated connection o Many subscribers share same local line, throughput  BPL (Broadband Over Powerline) o High-speed Internet access over the electrical grid  Began around 2000 o Advantages  Potential for reaching remote users o Roadblocks to development  Opposition from telecommunications groups  Costly infrastructure upgrades  Signals subject to more noise than DSL, cable  Signals interfere with amateur radio  ATM (Asynchronous Transfer Mode) o Functions in Data Link layer o Asynchronous communications method  Nodes do not conform to predetermined schemes  Specifying data transmissions timing  Each character transmitted  Start and stop bits o Specifies Data Link layer framing techniques o Fixed packet size  Packet (cell)  48 data bytes plus 5-byte header o Smaller packet size requires more overhead  Decrease potential throughput  Cell efficiency compensates for loss o ATM relies on virtual circuits  ATM considered packet-switching technology  Virtual circuits provide circuit switching advantage  Reliable connection o Allows specific QoS (quality of service) guarantee  Important for time-sensitive applications o Compatibility  Other leading network technologies  Cells support multiple higher-layer protocol  LANE (LAN Emulation)  Allows integration with Ethernet, token ring network  Encapsulates incoming Ethernet or token ring frames  Converts to ATM cells for transmission o Throughput: 25 Mbps to 622 Mbps o Cost: relatively expensive  SONET (Synchronous Optical Network) o Key strengths  WAN technology integration  Fast data transfer rates  Simple link additions, removals  High degree of fault tolerance o Synchronous  Data transmitted and received by nodes must conform to timing scheme o Advantage  Interoperability o Fault tolerance  Double-ring topology over fiber-optic cable o SONET ring  Begins, ends at telecommunications carrier’s facility  Connects organization’s multiple WAN sites in ring fashion  Connect with multiple carrier facilities  Additional fault tolerance  Terminates at multiplexer  Easy SONET ring connection additions, removals  Data rate indicated by OC (Optical Carrier) level  o Implementation  Large companies  Long-distance companies  Linking metropolitan areas and countries o ISPs  Guarantying fast, reliable Internet access o Telephone companies  Connecting Cos o Best uses: audio, video, imaging data transmission o Expensive to implement o WAN Technologies Compared  Chapter 14: Ensuring Integrity and Availability  Integrity o Soundness of network’s programs, data, services, devices, connections  Availability o How consistently and reliably a file or system can be accessed  Uptime o Measure of time functioning normally between failures o Often expressed as percent uptime    Integrity and availability compromised by: o Security breaches o Natural disasters o Malicious intruders o Power flaws o Human error  Follow guidelines to keep network highly available o See Pages 646-647 of text  Availability and Integrity Controls o Define and implement a security policy. o Allow only network administrator to create or modify NOSs. o Monitor the network for unauthorized access or changes. o Record authorized system changes in change management system. o Install redundant components. o Perform regular health checks on the network. o Check system performance, error logs, and the system log regulary o Keep Backups, system images, and emergency repair disks current and available. o Implement and enforce security and disaster recovery policies.  Malware o Malicious software o Program designed to intrude upon or harm system, resources  Examples: viruses, Trojan horses, worms, bots o Virus  Replicating program intent to infect more computers  Copied to system without user knowledge  Replicates through network connections or exchange of external storage devices o Trojan horse (Trojan)  Program that disguises itself as something useful  Actually harms your system  Malware Types and Characteristics o Malware categorized by location and propagation method  Boot sector viruses  Macro viruses  File-infector viruses  Worms  Trojan horses  Network viruses  Bots o o o Malware characteristics  Encryption is deployed to prevent detection.  Some viruses, worms, Trojan horses  Stealth  Hidden to prevent detection  Disguised as legitimate programs  Polymorphism  Change characteristics every time they transfer to new system  Use complicated algorithms; incorporate nonsensical commands  Time dependence (Time Bomb)  Programmed to activate on particular date  Can remain dormant and harmless until date arrives  Logic bombs: programs designed to start when certain conditions met o Malware can exhibit more than one characteristic  Malware Protection o Effective malware protection requires:  Choosing appropriate anti-malware program  Monitoring network  Continually updating anti-malware program  Educating users o Malware leaves evidence  Some detectable only by anti-malware software  User symptoms  Unexplained file size increases  Significant, unexplained system performance decline  Unusual error messages  Significant, unexpected system memory loss  Periodic, unexpected rebooting  Display quality fluctuations o Malware often discovered after damage done o Anti-malware key software functions  Signature scanning  Compares file’s content with known malware signatures  Integrity checking  Compares current file characteristics against archived version o Monitoring unexpected file changes o Receive regular updates from central network console o Consistently report valid instances of malware o Anti-malware software implementation  Dependent upon environment’s needs o Key: deciding where to install software  Desktop machines  Server o Balance protection with performance impact o Anti-malware policies  Rules for using anti-malware software  Rules for installing programs, sharing files, using external disks o Management should authorize and support policy o Anti-malware policy guidelines  See Pages 651-652 of text o Measures designed to protect network from damage, downtime  Fault Tolerance o Capacity for system to continue performing  Despite unexpected hardware, software malfunction o Failure  Deviation from specified system performance level  Given time period o Fault  Malfunction of one system component  Can result in failure o Fault-tolerant system goal  Prevent faults from progressing to failures o Degrees of fault tolerance  Optimal level depends on file or service criticality  Highest level  System remains unaffected by most drastic problem  Environment o Consider network device environment o Protect devices from:  Excessive heat, moisture  Use temperature, humidity monitors o Break-ins o Natural disasters  Power o Blackout  Complete power loss o Brownout  Temporary dimming of lights o Causes  Forces of nature  Utility company maintenance, construction o Solution  Alternate power sources o Power flaws not tolerated by networks o Types of power flaws that create damage  Surge  Momentary increase in voltage  Noise  Fluctuation in voltage levels  Brownout  Momentary voltage decrease  Blackout  Complete power loss o Uninterruptible power supplies (UPSs)  Battery-operated power source  Directly attached to one or more devices  Attached to a power supply  Prevents harm to device, service interruption o UPS categories  Standby  Online o Standby UPS (offline UPS)  Provides continuous voltage  Switches instantaneously to battery upon power loss  Restores power  Problems  Time to detect power loss  Device may have shut down or restarted o Online UPS  A/C power continuously charges battery  No momentary service loss risk  Handles noise, surges, sags  Before power reaches attached device  More expensive than standby UPSs o Factors to consider when choosing UPS  Amount of power needed  Period of time to keep device running  Line conditioning o Generators  Powered by diesel, liquid propane, gas, natural gas, or steam  Do not provide surge protection  Provide electricity free from noise  Used in highly available environments o Generator choice  Calculate organization’s crucial electrical demands  Determine generator’s optimal size  Network Design o Supply multiple paths for data travel o Topology  LAN: star topology and parallel backbone provide greatest fault tolerance  WAN: full-mesh topology  SONET technology  Uses two fiber rings for every connection  Can easily recover from fault in one of its links o Review PayNTime example on Pages 657-658 o Possible solutions: supply duplicate connection  Use different service carriers  Use two different routes  Critical data transactions follow more than one path o Network redundancy advantages  Reduces network fault risk  Lost functionality, profits o Disadvantage: cost o Scenario: two critical links  Capacity, scalability concerns  Solution  Partner with ISP  Establish secure VPNs o See Figure 14-4 o Scenario  Devices connect one LAN, WAN segment to another  Experience a fault  VPN agreement with national ISP  Single T1 link supports five customers o o Problem with arrangement of Figure 14-5  Many single points of failure  T1 link failure  Firewall, router, CSU/DSU, multiplexer, or switch o Solution  Redundant devices with automatic failover  Hot swappable devices  Immediately assume identical component duties o Cold spare  Duplicate device on hand, not installed o o Failover capable or hot swappable components  Desired for switches or routers supporting critical links  Adds to device cost o Link aggregation (bonding)  Combination of multiple network interfaces to act as one logical interface  Example: NIC teaming o Load balancing  Automatic traffic distribution over multiple components or links o o Naming and addressing services  Failure causes nearly all traffic to come to a halt o Solution: maintain redundant name servers o DNS caching servers  Allows local name resolution  Faster performance  Reduces burden on master name serve  o DNS can point to redundant locations for each host name  Use different IP addresses that all point to identical Web servers o Round-robin DNS  Use each IP address sequentially o Load balancer  Dedicated device for intelligent traffic distribution  Considers traffic levels when forwarding requests  o CARP (Common Address Redundancy Protocol)  Allows pool of computers to share IP addresses  Master computer receives request  Parcels out request to one of several group computers  Servers o Critical servers  Contain redundant components  Provide fault tolerance, load balancing o Server mirroring  Fault-tolerance technique  One device, component duplicates another's activities  Uses identical servers, components  High-speed link between servers  Synchronization software  Form of replication  Dynamic copying of data from one location to another o Server mirroring advantage  Flexibility in server location o Disadvantages  Time delay for mirrored server to assume functionality  Toll on network as data copied between sites o Hardware and software costs  May be justifiable o Clustering  Links multiple servers together  Act as single server o Clustered servers share processing duties  Appear as single server to users o Failure of one server  Others take over o More cost-effective than mirroring  For large networks o Clustering advantages over mirroring  Each clustered server  Performs data processing  Always ready to take over  Reduces ownership costs  Improves performance  Storage o Data storage  Issues of availability and fault tolerance apply o Various methods available  Ensure shared data and applications never lost or irretrievable o RAID (Redundant Array of Independent [or Inexpensive] Disks)  Collection of disks  Provide shared data, application fault tolerance o Disk array (drive)  Group of hard disks o RAID drive (RAID array)  Collection of disks working in a RAID configuration  Single logical drive o Hardware RAID  Set of disks, separate disk controller  RAID array managed exclusively by RAID disk controller  Attached to server through server’s controller interface o Software RAID  Software implements and controls RAID techniques  Any hard disk type  Less expensive (no controller, disk array)  Performance rivals hardware RAID o Several different types of RAID available o NAS (Network Attached Storage)  Specialized storage device, storage device group  Provides centralized fault-tolerant data storage o Difference from RAID  Maintains own interface to LAN o Advantages  NAS device contains own file system  Optimized for saving, serving files o Easily expandable o No service interruption o Disadvantage  No direct communication with network clients o NAS use  Enterprises requiring fault tolerance, fast data access o SANs (Storage Area Networks)  Distinct networks of storage devices  Communicate directly with each other, other networks o Typical SAN contains multiple storage devices  Connected to multiple, identical servers o SAN advantages  Fault tolerant  Extremely fast  Special transmission method  Fiber-optic media, proprietary protocols  Example: Fibre Channel o Install in location separate from LAN served  Provides added fault tolerance o Highly scalable o Faster, more efficient method of writing data o SAN disadvantages  High cost  Small SAN: $100,000  Large SAN: several million dollars o More complex than NAS, RAID  Training, administration efforts required o Use  Environments with huge data quantities requiring quick availability  Data Backup o Backup  Copies of data or program files  Created for archiving, safekeeping  Store off site o Without backup: risk losing everything o Many backup options available  Performed by different software and hardware  Use different storage media types o Can be controlled by NOS utilities, third-party software  Backup Media and Methods o Approach to selecting backup media, methods  Ask questions to select appropriate solution o Optical media  Media storing digitized data  Uses laser to write data, read data  Examples: CDs, DVDs o Backup requirements  Recordable CD or DVD drive, software utility o Blu-ray  Optical storage format o DVD and Blu-ray DVD disadvantages  Writing data takes longer than other media  Requires more human intervention than other backup methods o Tape backups  Copying data to magnetic tape o Requirements  Tape drive connected to network  Management software  Backup media o Small network tape backups  Stand-alone tape drives attached to each server o Large network tape backups  One large, centralized tape backup device  Manages all subsystems’ backups o Extremely large environments  Robots retrieve, circulate tapes from tape storage library o External disk drives (removable disk drives)  Storage device attached temporarily to computer  USB, PCMCIA, FireWire, CompactFlash port  Simple to use, save, share data  Temporary drive appears like any other drive o Large data amount requirements  Backup control features, higher storage capacity, faster read-write access o Network backups  Save data to another place on network  Different server, another WAN location  SAN, NAS storage device o Online backup (cloud backup)  Saves data to another company’s storage array using Internet  Implement strict security measures  Automated backup, restoration processes o Evaluate online back up provider  Test speed, accuracy, security, recovery  Backup Strategy o Devise a strategy to perform reliable backups o Document in accessible area o Address various questions o Archive bit  File attribute  Set to on or off  On indicates file must be archived o Used by various backup methods o Full backup  All data copied  Uncheck archive bits o Incremental backup  Copy data changed since last full, incremental backup  Uncheck archive bits o Differential backup  Copy only data changed since last backup  All data marked for subsequent backup  Does not uncheck archive bits o Determine best backup rotation scheme  Plan specifies when and how often backups occur  Goal  Provide excellent data reliability without overtaxing network, requiring intervention o Grandfather-Father-Son strategy  Uses backup sets  Daily (son)  Weekly (father)  Monthly (grandfather) o Ensure backup activity recorded in backup log  Backup date  Media identification  Type of data backed up  Type of backup  Files backed up  Backup location o Establish regular verification schedule  Attempt to recover files periodically  Disaster Recovery o Disaster recovery  Restoring critical functionality, data  After enterprise-wide outage  Affecting more than single system, limited group o Consider possible extremes  Not relatively minor outages, failures, security breaches, data corruption  Disaster Recovery Planning o Account for worst-case scenarios o Identify disaster recovery team o Provide contingency plans  Restore and replace:  Computer systems  Power  Telephony systems  Paper-based files o Plan contains various sections o Lessen critical data loss risk  Disaster Recovery Contingencies o Cold site  Components necessary to rebuild network exist  Not appropriately configured, updated, or connected o Warm site  Components necessary to rebuild network exist  Some appropriately configured, updated, and connected o Hot site  Components exist and match network’s current state  All appropriately configured, updated, and connected Chapter 10: Virtual Networks and Remote Access • Virtualization o Emulation of a computer, operating system environment, or application:  On a physical system o Virtual machines (VMs)  Virtual workstations  Virtual servers  Can be configured to use different types of:  CPU  Storage drive  NIC o VM appears to user no different than physical computer:  Running the same software o Host  Physical computer o Guest  Virtual machines o Hypervisor  Manages virtual machines o Advantages of virtualization  Efficient use of resources  Cost and energy savings  Fault and threat isolation  Simple backups, recovery, and replication o Disadvantages  Compromised
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