Networking Technologies - Cramsession 
Computing ModelsCentralized - Mainframe provides data storage and terminals are used for remote data input/output.Distributed - Multiple computers individually perform tasks and computations.Collaborative - Multiple computers share tasks and processing abilities.Local Area Network (LAN) - Uses one transmission medium; contained within campus.Metropolitan Area Network (MAN) - Uses different transission mediums; contained within city.Wide Area Network (WAN) - Interconnects LANs and MANs and can extend around the world.
Standard TopologiesBus - A single cable that connects all computers in a single line.Star - Computers connect to a centralized hub via cable segments.Ring - Connects all computers on a single cable. Ends are not terminated, but form a full loop connecting the last computer to the first computer.Mesh - Commonly used in WAN configurations. Routers are connected to multiple links for redundancy and to give the ability to determine the quickest route to a destination.
Bus
Ring
Star
Mesh
Signal TransmissionsBaseband - Uses digital signaling over a single frequency. Transmits birectionally.Broadband - Uses analog signaling over a range of frequencies. Transmits unidirectionally. Uses amplifiers for signal regeneration.Bit Synchronization - Uses clock to measure time for signals and bit extraction.
Access MethodsCSMA/CD - Collision Detection; listens to cable prior to sending data. (EtherNet)CSMA/CA - Collision Avoidance; Announces intention to send data. (Appletalk)Token-Passing - Token revolves around ring, computer which has token is permitted to data. (TokenRing)One device designated media administrator. Secondary device waits to be polled by primary device to check if it has data to be sent.
CablesAttenuation - The degrading of a signal as it travels farther from its origination.Crosstalk - Signal overflow from one wire to another adjacent wire.Jitter - Instability in a signal wave; Caused by signal interference or an unbalanced FDDI ring or Token Ring.
Coaxial
Thick Ethernet 50 ohm RG-8 and RG-11
Thin Ethernet 50 ohm RG-58
Cable TV 75 ohm RG-59
ARCnet 93 ohm RG-62
Unshielded Twisted Pair - Twisted pair wiring that is susceptible to crosstalk.Shielded Twisted Pair - Twisted pair wiring that has foil or braided jacket around wiring to help reduce crosstalk and to prevent electromagnetic interference.Fiber-Optic - Cable in which the center core, a glass cladding composed of varying layers of reflective glass, refracts light back into the core.
Cables
Type Connection Type Max Length Speeds Cost
ThinNet Coaxial BNC T Connector 185 meters (607 ft) Up to 10Mbps Inexpensive
ThickNet Coaxial DIX/AUI 500 meters (1640 ft) Up to 10Mbps Moderately Expensive
UTP RJ-11, RJ-45, RS-232, RS-449 100 meters (328 ft) Up to 100Mbps Moderately Inexpensive
STP RJ-11, RJ-45, RS-232, RS-449 100 meters (328 ft) Up to 500Mbps Moderate
Fiber-Optic 25 kilometers Up to 2Gbps Expensive
UTP/STP Category
Speeds
Cat 2 4 mbps
Cat 3 10 mpbs
Cat 4 16 mbps
Cat 5 100 mbps
Data Transmission DevicesDevices that connect one system to another system: Devices that connect network segments to form one large network:
Component Function
Transmission Media Adapter Adapter used to connect dissimilar NIC and cable connections (i.e. RJ-45 to RS-232 adapter).
Modem Converts digital signals to analog for communications over telephone lines.
Repeater Regenerates signals for retransmission. Moves packets from one physical media to another. Will pass broadcast storms. Cannot connect different network topologies or access methods.
Bridge Bridges are used to segment networks. They forward packets based on address of destination node. Uses RAM to build a routing table based on hardware addresses. Will connect dissimilar network topologies. Will forward all protocols. Regenerates the signal at the packet level.
Remote Bridge Same as bridge, but used for telephone communications. Uses STA (Spanning Tree Algorithm). 
Router Routes packets across multiple networks. Uses RAM to build a routing table based on network addresses (i.e. TCP address). Shares status and routing information to other routers to provide better traffic management and bypass slow connections. Will not pass broadcast traffic. Are slower than bridges due to complex functions. Strips off Data Link Layer source and destination addresses and then recreates them for packets. Routers can accomodate multiple active paths between LAN segments. Will not pass unroutable protocols.
Brouter Will act as a router for specified protocols and as a bridge for other specified protocols. 
Gateway Used for communications between different NOS's (i.e. Windows NT and IBM SNA). Takes the packet, strips off the old protocol and repackages it for the receiving network.
Multiplexer Device that can divide transmissions into two or more channels.
Switches Hub with bridging capabilities. Switch filters traffic through MAC addresses. Creates sessions on ports within the hub.
Hubs - Point of connection between segments.
OSI Model
OSI Layers
Application Layer Allows applications to use the network. Handles network access, flow control and error recovery.
Presentation Layer Translates data into a form usable by the application layer. The redirector operates here. Responsible for protocol conversion, translating and encrypting data, and managing data compression.
Session Layer Allows applications on connecting systems to establish a session. Provides synchronization between communicating computers.
Transport Layer Responsible for packet handling. Ensures error-free delivery. Repackages messages, divides messages into smaller packets, and handles error handling.
Network Layer Translates system names into addresses. Responsible for addressing, determining routes for sending, managing network traffic problems, packet switching, routing, data congestion, and reassembling data.
Data Link Layer Sends data from network layer to physical layer. Manages physical layer communications between connecting systems.
  • LLC - (802.2) Manages link control and defines SAP's (Service Access Points). 
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  • MAC - (802.3, 802.4, 802.5, 802.12) Communicates with adapter card. 
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    Physical Layer Transmits data over a physical medium. Defines cables, cards, and physical aspects.
    Component
    Which OSI layer it resides on
    Repeater Physical
    Bridge Data Link (MAC Sublayer)
    Remote Bridge Data Link (MAC Sublayer)
    Router Network
    Brouter Data Link and Network
    Gateway Transport, Session, Presentation and Application
    Mulitplexer Physical
    Switch Data Link
    OSI Model Chart
    (Contributed Mr. Perry's Class, Network Engineering and Management Program, Computer Learning Center, Schaumburg, IL.)
    IEEE 802 Specifications
    802.2 LLC (Logical Link Control) Adds header fields to identify upper-layer protocols.
    802.3 CSMA/CD - Ethernet Provides physical layer options including different topologies, media types, data rates and signaling modes.
    802.4 Token Bus LAN Uses bus topology, token-passing access method, and both baseband and broadband medias.
    802.5 Token Ring LAN Uses token-passing access method and differential Manchester encoding to provide data rates.
    802.6 MAN (Metropolitan Area Network) Distributed Queue Dual Bus dynamically allocates bandwidth through time-division access.
    802.9 Integrated Voice/Data Networks Isochronous Ethernet that transports bursty as well as time-sensitive traffic.
    802.11 Wireless Networks Standard for wireless network implementations.
    802.12 Demand Priority Access Lan, 100 Base VG - AnyLAN Based on a physical start topology contention-based network.
    Protocols
    OSI layer
    Protocols residing here
    Application SMB, NCP
    Presentation NCP
    Session N/A
    Transport TCP, SPX, UDP, NetBEUI
    Network IP, IPX, NetBEUI, DLC, DecNET
    Data Link HDLC
    Physical None
    IPX - Performs addressing and routing functions. Resides in Network Layer.SPX - Extension of IPX. Resides on Transport Layer - ensures error-free packet delivery.NCP - NetWare Core Protocol; Used for NetWare application, file and print services.SAP - Service Advertising Protocol; Used by NetWare servers to broadcast status communications.RIP - Routing Information Protocol; Routers use this to communicate with each other to determine the least busy and shortest (number of hops) network routes.IP - Performs addressing and routing functions. Resides in Network Layer.ICMP - Internet Control Message Protocol; Provides error and flow control information for IP.TCP - Transport service, ensures error-free packet delivery.UDP - Connectionless transport service.ARP - Relates network addresses to hardware addresses.NFS - Network File System; Allows dissimlar O/S's to access remote file systems.HDLC - High-level Data Link Control; Supports asynchronous and synchronous transmissions. Uses LLC flow control.SLIP - Provides dial-up communications, but is unable to simultaneously transfer multiple protocols.PPP - Performs dynamic IP addressing, multi-protocol support, password login and error control.
    Packet Switching NetworksPacket Switching - Packets are relayed across network along the best route available.
    Type
    Function
    X.25 Designed to connect remote terminals to mainframe host systems. Is very slow due to constant error-checking.
    Frame Relay Point-to-point system which uses digital leased lines. Will provide bandwidth as needed. Requires frame relay capable bridge or router for transmission.
    ATM Advanced implementation of packet switching. Transmits at speeds of 155Mbps to 622Mbps with capabilities of higher speeds. Transmits data in 53 byte (48 application, 5 header) cells. Uses switches as multiplexers to permit several computers to simultaneously trasmit data on a network. Great for voice and video communications.
    ISDN Transmits at 128k/sec. Has three data channels - 2 B channels @ 64k/sec & 1 D channel @ 16k/sec. The B channels carry data while the D channel performs link management and signaling.
    FDDI 100 Mbps token-passing ring network which uses fiber-optic media. Uses a dual-ring topology for redundancy and in case of ring failure. Each ring is capable of connecting 500 computers over 100 kilometers (62 miles). Can be used as a network backbone. Uses beaconing for ring troubleshooting.
    Beaconing - Computers are used to detect network faults, then transmit the fault signal to the server.