Networking Fundamentals

Networking FundamentalsFiber-OpticCable

OSI ModelData unitLayerFunctionHostlayersData7.ApplicationNetwork process to application6.PresentationData representation, encryption and decryption, convert machine dependent data to machine independent data5.SessionInterhost communication, managing sessions between applicationsSegments4.TransportReliable delivery of packets between points on a network.MedialayersPacket/Datagram3.NetworkAddressing, routing and (not necessarily reliable) delivery of datagrams between points on a network.Bit/Frame2.Data linkA reliable direct point-to-point data connection.Bit1.PhysicalA (not necessarily reliable) direct point-to-point data connection.

Application (Layer 7)This layer supportsapplicationand end-user processes. Communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on datasyntaxare identified. Everything at this layer is application-specific. This layer provides application services forfile transfers,e-mail, and othernetworksoftwareservices.TelnetandFTPare applications that exist entirely in the application level. Tiered application architectures are part of this layer.Presentation (Layer 6)This layer provides independence from differences in data representation (e.g.,encryption) by translating from application to network format, and vice versa. The presentation layer works to transform data into the form that the application layer can accept. This layer formats and encrypts data to be sent across anetwork, providing freedom from compatibility problems. It is sometimes called the syntax layer.Mostly uselessSession (Layer 5)This layer establishes, manages and terminates connections betweenapplications. The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end. It deals with session and connection coordination.Mostly useless.Transport (Layer 4)This layer provides transparent transfer of data between end systems, orhosts, and is responsible for end-to-end error recovery andflow control. It ensures complete data transfer.Layer 4 data units are also called packets, but when you're talking about specific protocols, like TCP, they're "segments" or "datagrams" in UDP. This layer is responsible for getting the entire message, so it must keep track of fragmentation, out-of-order packets, and other perils. Layer 4 provides end-to-end management of communication. Some protocols, like TCP, do a very good job of making sure the communication is reliable. Some don't really care if a few packets are lost--UDP is the prime example.Network (Layer 3)This layer provides switching and routing technologies, creating logical paths, known asvirtual circuits, for transmitting data fromnodeto node. Routing and forwarding are functions of this layer, as well asaddressing,internetworking, error handling, congestioncontrol and packet sequencing.IP is part of layer 3, along with some routing protocols, and ARP (Address Resolution Protocol). Everything about routing is handled in layer 3. Addressing and routing is the main goal of this layer.Data Link (Layer 2)At this layer, data packets areencodedand decoded into bits. It furnishestransmission protocolknowledge and management and handles errors in the physical layer, flow control and frame synchronization. The data link layer is divided into two sub layers: The Media Access Control (MAC) layer and theLogical Link Control(LLC) layer. The MAC sub layer controls how a computer on the network gains access to the data and permission to transmit it. The LLC layer controls framesynchronization, flow control and error checking. Ethernet, among otherprotocols,lives on Layer 2.MAC address, switches, or network cardsPhysical (Layer 1)This layer conveys the bit stream - electrical impulse, light or radio signal -- through thenetworkat the electrical and mechanical level. It provides thehardwaremeans of sending and receiving data on a carrier, including defining cables, cards and physical aspects.Fast Ethernet,RS232, andATMareprotocolswith physical layer components.CharacteristicsFiber-OpticCableCharacteristics of Fiber-Optic CableSecurityImmunity to Electromagnetic InterferenceWeight and SizeSafetyBandwidthCorrosion and Water ResistanceGreater DistancesSecurityNo Vampire tapshard to eaves-dropI dont think its impossible just expensiveand requires specialized equipmentand know-how

Immune to EMP

Immunity to Electromagnetic InterferenceImmune to EMP

Motors and Generators do not cause interference

HAM/CB Garage Door Normal Computer Hair Dryer Weight and SizeLighter than copper (1/10)

Smaller diameter than copper (10/1)SafetyNo current means no sparks

Light transmission safer (and cheaper) than work lamps in some hazardous environments

BandwidthCompared to copper:higher frequency means greater bandwidthno impedance limitationsno inductive reactance (at high frequencies copper can lose conduction)

Corrosion and Water ResistanceGlass and plastic do not rust or corrode easily

No tarnish or verdigris (oxidation/rust)

Greater DistancesCopper networks segments mostly limited to 100 meters or less.fiber-optic can support distances over 20 kilometers.FDDI applications can be 200 km (124 mi).The Nature of Lightlight energy waves - electromagneticelectromagnetic waves need no carrier (can travel through a vacuum) unlike sound wavesinstead of frequency wavelengthvisible light roughly 400 - 800 nmnano meter is meter/billionfiber-optic commonly use 850nm - 1550nm

Constructionglass or plastic core serves as medium for light wavescladding surrounds the core traps light in the corebuffer physically protects core/claddingwater proofing may be addedoil or water resistant sheath coversallloose tube gel filled greater protectiontight buffer less space more fragile

TransmissionAttenuation can be through scattering, dispersion, Fresnel reflection, or extrinsic loss due to bends splices and connectorsScattering due to impurities in the core, cumulative over distance. Glass is better than plastic.Dispersion distortion from cladding reflection. primary limiter on distanceFresnel reflection occurs at connectors

SpecificationsMultimode fiber optic cable - large core diameterSingle-mode fiber optic cable - small core diameter - matched to wavelength to control dispersion - allows greater distancesMicrometers - um - meter/millionCable identified as core/cladding multimode eg 50/125 65.5/125single-mode eg 8.3/125802.3 StandardsFiber-OpticCable802.3 StandardsGigabit Ethernet1000Base___

10 Gigabit Ethernet10GBase ___

10GBaseW 10GBase___WW=WANW=Wavelength

Gigabit EthernetIEEE 802.3z

1000BaseSX - multimode fiber

1000BaseLX single (5km) or multimode fiber (550m)

1000BaseCX - copper core 25m10 Gigabit EthernetIEEE 802.3aefiber only

10GBaseSR (short range) 26m-82m10GBaseLR (long range) 10km single-mode10GBaseER (extended range) 40km single-mode10GBaseWWide area networks and SONET10GBaseSW Short Wavelength (850nm)connect dist.= 33m10GBaseLW Long Wavelength (1310nm)connect dist.= 10km10GBaseEW Extended Wavelength (1550nm)connect dist.= 40km (25mi)FDDIFiber Distributed Data Interference40km100MbpsBackbone for MAN or WANStructured as dual rings (primary, secondary)Fault tolerant two waysRings transmit in opposite directionsToken ringFiber-Optic Cable ConnectorsProprietary designs aboundSC ST FC LC and MTRJ are most commonST round insert like BNC (push and twist)SC square plugFC screw threads like coaxial connectorLC new small single or duplex dev. by LucentTechnologies (formerly Bell Labs)MTRJ - another small duplex designSee page 135

Installation and TroubleshootingFiber-OpticCableInstallation and TroubleshootingInstalling ConnectorsMaking a Fusion SpliceUsing Fiber-Optic Cable Metersnot usually prepared in the fieldrequires expertise to apply, certifications (BICSI, FOA, Nortel Networks, Beldon )cleaved not cutInstalling ConnectorsDesign/measure prior to installation/supplySplicing difficulties include dirt and alignmentGlass cores must be cleaved carefullyPlastic cores must be cut carefully

Making a Fusion SpliceFusion Splicetwo ends melted/welded/fused together Mechanical splicingends clamped with gel to mitigate Fresnel effects

Using Fiber-Optic Cable MetersPower meter and light source

OTDR optical time Domain Reflectometercan locate faults (distance to)rent dont buy